ch# 17 coordination chemistry. transition metals transition metals show similarities within a...

CH# 17CH# 17Coordination

ChemistryCoordination

Chemistry

Transition MetalsTransition Metals Transition metals show similarities within a period

and a group, different than representative elements Differences can be attributed to the fact that

when electrons are added across a period the valence electrons are not effected.

Therefore group designations are not important here

Behave as metals, strong metallic character

Transition metals show similarities within a period and a group, different than representative elements Differences can be attributed to the fact that

when electrons are added across a period the valence electrons are not effected.

Therefore group designations are not important here

Behave as metals, strong metallic character

Transition MetalsTransition Metals• Some differences– Melting point, Tungsten melts 3400°, while mercury -

39°C– Some soft, like sodium that can be cut with a butter

knife– Reactivity• Some spontaneously react with oxygen like iron,

which flakes off• Others react with oxygen to make a colorless tight

fitting oxide, such as chromium, thus protecting the surface• Some metals are inert to oxygen such as gold, silver

and platinum

• Some differences– Melting point, Tungsten melts 3400°, while mercury -

39°C– Some soft, like sodium that can be cut with a butter

knife– Reactivity• Some spontaneously react with oxygen like iron,

which flakes off• Others react with oxygen to make a colorless tight

fitting oxide, such as chromium, thus protecting the surface• Some metals are inert to oxygen such as gold, silver

and platinum

Transition MetalsTransition MetalsIonic compound formation

More than one oxidation state is often observed

Cations, often are complexes, which we will discuss later in this chapter

Most compounds are colored, since complexes absorb visible light

Many compounds are paramagneticThis chapter will deal specifically the first row transition elements

Ionic compound formation More than one oxidation state is often

observed Cations, often are complexes, which

we will discuss later in this chapter Most compounds are colored, since

complexes absorb visible light Many compounds are paramagneticThis chapter will deal specifically the first row transition elements

Transition ElementsTransition Elements

Electron ConfigurationsElectron ConfigurationsExceptions to the AUFBAU principle

Cr prefers a half full d as opposed to a full 4s, thus 4s13d5

Copper prefers a full 3d as opposed to a full 4s, thus 4s13d10

This half filled, or filled d orbital, is used most of the time to explain this, but other transition metals do not follow this trend.

Exceptions to the AUFBAU principle Cr prefers a half full d as opposed to a full 4s,

thus 4s13d5

Copper prefers a full 3d as opposed to a full 4s, thus 4s13d10

This half filled, or filled d orbital, is used most of the time to explain this, but other transition metals do not follow this trend.

Electron ConfigurationsElectron Configurations

Many texts explain AUFBAU exceptions of chromium and copper as a half full sublevel are more stable than a full 4 s sublevel, or for copper that a full d-sublevel is more stable than a half full 4s

Why is this not the case in periods below?The 4 s and the 3 d orbitals are of about

the same energy or nearly degenerate. Perhaps there is a larger repulsive force in the 4s than in 3d orbitals.

I do not think any one knows, but it is good to think and create right?

Many texts explain AUFBAU exceptions of chromium and copper as a half full sublevel are more stable than a full 4 s sublevel, or for copper that a full d-sublevel is more stable than a half full 4s

Why is this not the case in periods below?The 4 s and the 3 d orbitals are of about

the same energy or nearly degenerate. Perhaps there is a larger repulsive force in the 4s than in 3d orbitals.

I do not think any one knows, but it is good to think and create right?

Electron ConfigurationsElectron Configurations4d and 5d Transition Series– See the size relation on next slide• Decrease in size as we go from left to right, stopping when the d is half full• Significant drop in size going from 3d to 4d, but 4d and 5d remain about the same size–Called Lanthanide contraction–Adding f electrons below the d and the valence shell shel electrons (shielding)–Thus the effect of the increasing size by adding another shell of electrons, which is normally in transition and representative elements, is offset by the shielding of the added f electrons

4d and 5d Transition Series– See the size relation on next slide• Decrease in size as we go from left to right, stopping when the d is half full• Significant drop in size going from 3d to 4d, but 4d and 5d remain about the same size–Called Lanthanide contraction–Adding f electrons below the d and the valence shell shel electrons (shielding)–Thus the effect of the increasing size by adding another shell of electrons, which is normally in transition and representative elements, is offset by the shielding of the added f electrons

Transition Element Sizes

Transition Element Sizes

Oxidation States and IEOxidation States and IE

See common oxidation states on Next slide

The maximum oxidation state for each transition element going across the row is what we would get by losing both 4s and 3d electrons, toward the end only 2+ is observed, the explanation is that as the effective charge increases thus holding the d electrons tighter.

Reducing ability, decreases from left to right

See common oxidation states on Next slide

The maximum oxidation state for each transition element going across the row is what we would get by losing both 4s and 3d electrons, toward the end only 2+ is observed, the explanation is that as the effective charge increases thus holding the d electrons tighter.

Reducing ability, decreases from left to right

Transition Metal Oxidations #’s

Transition Metal Oxidations #’s

Sc V Ti CrMn

Fe Co Ni Cu Zn

3 2 2 2 2 2 2 2 1 2

3 3 3 3 3 3 3 2

4 4 4 3

4 5

5 6 6 6

7

Ionization Energies Ionization Energies

Red dot- First ionization energy

(removing 4s e)

Blue dot-third ionization energy removing 3d electron, closer to nucleus, thus more tightly held

First-row Transition Metals


Scandium Rare element most always +3 oxidation

state, ie ScCl3, Sc2O3

Chemistry of scandium resembles the lanthanides

Colorless compounds Diamagnetic Color and magnetic properties are due to d

electron, Sc has no d electrons

Scandium Rare element most always +3 oxidation

state, ie ScCl3, Sc2O3

Chemistry of scandium resembles the lanthanides

Colorless compounds Diamagnetic Color and magnetic properties are due to d

electron, Sc has no d electrons

First-row Transition MetalsFirst-row Transition Metals

Titanium Found in the earths crust (0.6%) Low density and high strength Fairly inert, and is used in pipes TiO2 is a very common white pigment Common oxidation state is +4

Titanium Found in the earths crust (0.6%) Low density and high strength Fairly inert, and is used in pipes TiO2 is a very common white pigment Common oxidation state is +4



Vanadium Found in the earth’s crust about 0.02% Common oxidation state is +5 Since vanadium contains d electrons solutions

are coloredVO2

+ is yellow with V in the +5 oxidation stateVO2+ is blue with V in the +4 oxidation stateV3+ is blue-green with V in +3 oxidation stateV2+ is violet with V in +2 oxidation state

Vanadium Found in the earth’s crust about 0.02% Common oxidation state is +5 Since vanadium contains d electrons solutions

are coloredVO2

+ is yellow with V in the +5 oxidation stateVO2+ is blue with V in the +4 oxidation stateV3+ is blue-green with V in +3 oxidation stateV2+ is violet with V in +2 oxidation state



Chromium– Rare, but important industrial chemical– Chromium oxide is colorless, tuff, and holds to

the metal strongly, almost invisible– Chromium compounds in solution are also

colored since they contain d electrons– Common oxidation states are +2, +3 and +6– Chromium VI is an excellent oxidizing agent!

Why?• Strength increases as acidity increases• Chromerge very good glassware cleaning agent

– What would we predict for Cr metal?– Cr6+ in the form of dichromate ion usually

reduces to the +3 state

Chromium– Rare, but important industrial chemical– Chromium oxide is colorless, tuff, and holds to

the metal strongly, almost invisible– Chromium compounds in solution are also

colored since they contain d electrons– Common oxidation states are +2, +3 and +6– Chromium VI is an excellent oxidizing agent!

Why?• Strength increases as acidity increases• Chromerge very good glassware cleaning agent

– What would we predict for Cr metal?– Cr6+ in the form of dichromate ion usually

reduces to the +3 state


First-row Transition Metals• Iron

– Is the most abundant heavy metal (4.7%) in earth’s crust, Why?

– Common oxidation states +2 and +3– Iron solutions are colored since they contain

d electrons

• Cobalt– Relatively rare– Hard bluish-white metal– Common oxidation states are +2 and +3– Oxidation states +1 and +4 are also known• Typical color is rose color

• Iron– Is the most abundant heavy metal (4.7%) in

earth’s crust, Why?– Common oxidation states +2 and +3– Iron solutions are colored since they contain

d electrons

• Cobalt– Relatively rare– Hard bluish-white metal– Common oxidation states are +2 and +3– Oxidation states +1 and +4 are also known• Typical color is rose color



Nickel Most always the +2 oxidation state Sometimes +3 oxidation state Emerald green colored solutions

Nickel Most always the +2 oxidation state Sometimes +3 oxidation state Emerald green colored solutions


First-row Transition Metals• Copper

– Quite common, as sulfides, arsenides, chlorides and carbonates

– Great electrical conductor second only to silver– Widely used in plumbing– Found in bronze and brass– Not highly reactive will not reduce H+

– Slowly oxides in air, producing a green oxide– Common oxidation state +2, +1 is also known– Aqueous solution are bright Royal blue– Quite toxic, used to kill bacteria– Paint often contains copper so algae do not

grow on the paint

• Copper– Quite common, as sulfides, arsenides, chlorides

and carbonates– Great electrical conductor second only to silver– Widely used in plumbing– Found in bronze and brass– Not highly reactive will not reduce H+

– Slowly oxides in air, producing a green oxide– Common oxidation state +2, +1 is also known– Aqueous solution are bright Royal blue– Quite toxic, used to kill bacteria– Paint often contains copper so algae do not

grow on the paint



Zinc Quite common in earths crust, usually as ZnS Great reducing agent, quite reactive Oxidation state of +2 Used to galvanize steel

Zinc Quite common in earths crust, usually as ZnS Great reducing agent, quite reactive Oxidation state of +2 Used to galvanize steel

Coordination compounds

Coordination compounds

Transition metals form coordination compounds

Transition metals contain a complex ion attached to ligands via coordinate covalent bonds

Coordination compounds are usually colored and paramagnetic

Transition metals form coordination compounds

Transition metals contain a complex ion attached to ligands via coordinate covalent bonds

Coordination compounds are usually colored and paramagnetic

Coordination compoundsCoordination compounds Complex ions, usually inside [ ]

Transition coordinately bonded to Lewis bases, the metal is acting as a Lewis acid

Example [CoCl(NH3)5]2+ this cation can combine with anions to balance the charge, thus forming a salt

Ligands are the groups of atoms bonded with a coordinate covalent bond to a transition metal, or a transition metal ion.

Complex ions, usually inside [ ] Transition coordinately bonded to

Lewis bases, the metal is acting as a Lewis acid

Example [CoCl(NH3)5]2+ this cation can combine with anions to balance the charge, thus forming a salt

Ligands are the groups of atoms bonded with a coordinate covalent bond to a transition metal, or a transition metal ion.

Coordinate Covalent Bonding

Coordination compoundsCoordination compounds Alfred Werner was the father of

coordination chemistry Alfred Werner called the salt formation

the primary valence The secondary valence is the formation

of the complex ion itself The compound above has a secondary

valence of 6, since it combines with 6 ligands

The primary valence is +2 since that is what needs to be neutralized with anions.

Now days the secondary valence is called the coordination number and the primary valence is called the oxidation state

Alfred Werner was the father of coordination chemistry

Alfred Werner called the salt formation the primary valence

The secondary valence is the formation of the complex ion itself

The compound above has a secondary valence of 6, since it combines with 6 ligands

The primary valence is +2 since that is what needs to be neutralized with anions.

Now days the secondary valence is called the coordination number and the primary valence is called the oxidation state

Aqueous Solutions of Metal Ions

Aqueous Solutions of Metal Ions

Coordination CompoundsCoordination Compounds The number of coordinate covalent

bonds formed by the metal ion and the ligands

Variance of 2-8, with 6 being most common.

Geometrical Shape Ligands = 2, then linear

Rare for most metals Common for d-10 systems (Cu+, Ag+, Au+, Hg2+)

Ligands = 3, Trigonal planar Rare for most metals Is known for d-10 systems (example HgI3

‑)

The number of coordinate covalent bonds formed by the metal ion and the ligands

Variance of 2-8, with 6 being most common.

Geometrical Shape Ligands = 2, then linear

Rare for most metals Common for d-10 systems (Cu+, Ag+, Au+, Hg2+)

Ligands = 3, Trigonal planar Rare for most metals Is known for d-10 systems (example HgI3

‑)

Coordination CompoundsCoordination Compounds• Geometrical Shape

Ligands = 4, then tetrahedral, or square planar Tetrahedral structure is observed for

nontransition metals, BeF42- and d-10 inons

such as ZnCl42-, FeCl4-, FeCl42-

Square planar is found with second and third row transition metals with d-8 Rh+, Pd2+

-Ligands = 5 trigonal bipyramid square pyramidal

• Geometrical Shape Ligands = 4, then tetrahedral, or square planar Tetrahedral structure is observed for

nontransition metals, BeF42- and d-10 inons

such as ZnCl42-, FeCl4-, FeCl42-

Square planar is found with second and third row transition metals with d-8 Rh+, Pd2+

-Ligands = 5 trigonal bipyramid square pyramidal

Coordination compoundsCoordination compounds• Geometrical Shape

− Ligands = 6, then octahedral and prismatic (rare)

− Ligands = 7 Relatively uncommon, pentagonalSecond and third row transition metals,

lanthanides , and actinides− Lignads = 8, relatively common for larger

metal ions, common geometry antiprism and dodecahedron

− Lignads = 9 larger metal ions, geometry tricapped trigonal prism [Nd(H2O)9]3+

The Ligand Arrangements for Coordination Numbers 2, 4, and 6

The Ligand Arrangements for Coordination Numbers 2, 4, and 6

LigandsLigands Atoms attached to a transition metal via

coordinate covalent bonds They are Lewis bases, since they donate

a pair of electrons to the transition metal. Ligands are classified relative to how

many attachments to the metal Monodentate forms one bond to a transition

metal Lignads forming more than bond are called

chelating ligands, or chelates

Atoms attached to a transition metal via coordinate covalent bonds

They are Lewis bases, since they donate a pair of electrons to the transition metal.

Ligands are classified relative to how many attachments to the metal Monodentate forms one bond to a transition

metal Lignads forming more than bond are called

chelating ligands, or chelates

LigandsLigands Ligands are classified relative to how

many attachments to the metal Bidentate, a chelating agent, forms two

bonds, examples:OxalateEthylenediamine

Polydentate forms more than two bonds.DiethylenetriamineEthylenediaminetetraacetic acid

Ligands are classified relative to how many attachments to the metal Bidentate, a chelating agent, forms two

bonds, examples:OxalateEthylenediamine

Polydentate forms more than two bonds.DiethylenetriamineEthylenediaminetetraacetic acid

LigandsLigands EDTA is used to remove lead from

animals More complicated ligands are found in

biological compounds EDTA is used as a preservative to tie up

substances that could catalyze decomposition of food products

EDTA is used to remove lead from animals

More complicated ligands are found in biological compounds

EDTA is used as a preservative to tie up substances that could catalyze decomposition of food products

EthylenediamineEthylenediamine

Ethylenediamminetetracidic acid

Coordination of EDTA with a 2+ Metal Ion

Coordination of EDTA with a 2+ Metal Ion

NomenclatureNomenclature Cationic species named before anionic species Within a complex, the ligands are named first in

alphabetical order followed by the metal atom the names of anionic lignads end in the suffix -o-

chloride ----->chloro cyanide ----->cyano oxide ----->oxo Hydroxide -->hydroxo Oxalate------>oxalato Sulfate ------>Sulfato Nitrate ------>Nitrato

Cationic species named before anionic species Within a complex, the ligands are named first in

alphabetical order followed by the metal atom the names of anionic lignads end in the suffix -o-

chloride ----->chloro cyanide ----->cyano oxide ----->oxo Hydroxide -->hydroxo Oxalate------>oxalato Sulfate ------>Sulfato Nitrate ------>Nitrato

NomenclatureNomenclature lignads whose names end in -ite or ate

become -ito and ato respectively carbonate ----> carbonato oxalate-----> oxalato thiosulfate ----> thiosulfato Sulfite -----> sulfito

neutral lignads are given the same names as the neutral molecule exceptions, ammonia (ammine), water

(aqua), carbon monoxide (Carbonyl), and NO (nitrosyl)

lignads whose names end in -ite or ate become -ito and ato respectively carbonate ----> carbonato oxalate-----> oxalato thiosulfate ----> thiosulfato Sulfite -----> sulfito

neutral lignads are given the same names as the neutral molecule exceptions, ammonia (ammine), water

(aqua), carbon monoxide (Carbonyl), and NO (nitrosyl)

NomenclatureNomenclature When there is more than one of a particular

ligand, number is specified by di, tri, tetra, penta, hexa, and so forth. when confusion might result, the prefixes bis, tris and tetrakis are employed e.g. bis(ethylenediaminne) negative (anionic) complex ions always end

in the suffix -atealuminum -----> aluminate chromium -----> chromatemanganese ------> manganatecoblat ------> cobaltate

For some metals the -ate is appended to the Latin stem always appears with

When there is more than one of a particular ligand, number is specified by di, tri, tetra, penta, hexa, and so forth. when confusion might result, the prefixes bis, tris and tetrakis are employed e.g. bis(ethylenediaminne) negative (anionic) complex ions always end

in the suffix -atealuminum -----> aluminate chromium -----> chromatemanganese ------> manganatecoblat ------> cobaltate

For some metals the -ate is appended to the Latin stem always appears with

NomenclatureNomenclature the common English name for the element

iron ----> ferr ------> ferrate copper ---> cupra -----> cuprate lead ----> plumb -----> plumbate silver ---> argent ----> argentate gold ---> aur ----> aurate tin ----> stann -----> stannate

the oxidation number of the metal in the complex is written in roman numerals within parentheses following the name of the metal

the common English name for the element iron ----> ferr ------> ferrate copper ---> cupra -----> cuprate lead ----> plumb -----> plumbate silver ---> argent ----> argentate gold ---> aur ----> aurate tin ----> stann -----> stannate

the oxidation number of the metal in the complex is written in roman numerals within parentheses following the name of the metal

NomenclatureNomenclature Formula writing

Metal is first, followed by anions, then neutral molecules

If two or more anions or neutral molecules are present, then use alphabetical order.

Nomenclature Examples tetracyanonickelate(II) ion tetramminedichlorocobalt(III) ionsodium hexanitratochromate(III)diamminesilver(I) ion

Formula writing Metal is first, followed by anions, then neutral

molecules If two or more anions or neutral molecules

are present, then use alphabetical order. Nomenclature Examples

tetracyanonickelate(II) ion tetramminedichlorocobalt(III) ionsodium hexanitratochromate(III)diamminesilver(I) ion




Nomenclature Examples tetracyanonickelate(II) ion [Ni(CN)4]2-

tetramminedichlorocobalt(III) ion sodium hexanitratochromate(III) diamminesilver(I) ion




tetracyanonickelate(II) ion [Ni(CN)4]2-

tetramminedichlorocobalt(III) ion sodium hexanitratochromate(III) diamminesilver(I) ion





tetramminedichlorocobalt(III) ion [CoCl2(NH3)4]+

sodium hexanitratochromate(III) diamminesilver(I) ion






sodium hexanitratochromate(III) diamminesilver(I) ion





tetramminedichlorocobalt(III) ion [Co(NH3)4Cl2]+

sodium hexanitratochromate(III) Na3[Cr(NO3)6] diamminesilver(I) ion





tetramminedichlorocobalt(III) ion [Co(NH3)4Cl2]+

sodium hexanitratochromate(III) Na3[Cr(NO3)6] diamminesilver(I) ion





tetramminedichlorocobalt(III) ion [CoCl2 NH3)4]+

sodium hexanitratochromate(III) Na3[Cr(NO3)6]

diamminesilver(I) ion [Ag(NH3)2]+





tetramminedichlorocobalt(III) ion [CoCl2 NH3)4]+



NomenclatureNomenclatureName the following:

[Ni(H2O)6]Cl2 hexaaquanickel(II) chloride

[Cr(en)3](ClO3)3

K4[Mn(CN)6]

K[PtCl5 (NH3)]

[Cu(en)(NH3)2][Co(en)Cl4]

[Pt(en)2Br2](ClO4)2

Name the following: [Ni(H2O)6]Cl2 hexaaquanickel(II)

chloride [Cr(en)3](ClO3)3

K4[Mn(CN)6]

K[PtCl5 (NH3)]


[Pt(en)2Br2](ClO4)2



[Cr(en)3](ClO3)3

tris(ethylenediamene)chromium(III) chlorate

K4[Mn(CN)6]

K[PtCl5(NH3)]


[Pt(en)2Br2](ClO4)2

Name the following: [Ni(H2O)6]Cl2 hexaaquanickel(II)

chloride [Cr(en)3](ClO3)3

tris(ethylenediamene)chromium(III) chlorate

K4[Mn(CN)6]

K[PtCl5(NH3)]


[Pt(en)2Br2](ClO4)2



[Cr(en)3](ClO3)3

trisethylenediamenechromium(III) chlorate

K4[Mn(CN)6] Potassium hexacyanomanganate(IV)

K[PtCl5(NH3)]


[Pt(en)2Br2](ClO4)2

Name the following: [Ni(H2O)6]Cl2 hexaaquanickel(II) chloride

[Cr(en)3](ClO3)3



K[PtCl5(NH3)]


[Pt(en)2Br2](ClO4)2

NomenclatureNomenclatureName the following:[Ni(H2O)6]Cl2 hexaaquanickel(II) chloride

[Cr(en)3](ClO3)3



K[PtCl5(NH3)] Potassium monoaminepentachloroplatinate(IV)


[PtBr2(en)2](ClO4)2

Name the following:[Ni(H2O)6]Cl2 hexaaquanickel(II) chloride

[Cr(en)3](ClO3)3



K[PtCl5(NH3)] Potassium monoaminepentachloroplatinate(IV)


[PtBr2(en)2](ClO4)2


[Cr(en)3](ClO3)3 trisethylenediamenechromium(III) chlorate


K[PtCl5(NH3)] Potassium triaminpentachloroplatinate(IV)

[Cu(en)(NH3)2][Co(en)Cl4] ethylenediaminediaminecopper(II) tetrachloroethylenediaminecobaltate(II)

[Pt(Br2en)2](ClO4)2


[Cr(en)3](ClO3)3 trisethylenediamenechromium(III) chlorate


K[PtCl5(NH3)] Potassium triaminpentachloroplatinate(IV)

[Cu(en)(NH3)2][Co(en)Cl4] ethylenediaminediaminecopper(II) tetrachloroethylenediaminecobaltate(II)

[Pt(Br2en)2](ClO4)2


[Cr(en)3](ClO3)3 tris(ethylenediamene)chromium(III) chlorate


K[PtCl5 (NH3)] Potassium monoaminpentachloroplatinate(IV)

[Cu(en)(NH3)2][Co(en)Cl4] ethylenediaminediamincopper(II) tetrachloroethylenediaminecobaltate(II)

[Pt(en)2Br2](ClO4)2

bis(ethylenediamine)dibromoplatinum(IV) perchlorate


[Cr(en)3](ClO3)3 tris(ethylenediamene)chromium(III) chlorate


K[PtCl5 (NH3)] Potassium monoaminpentachloroplatinate(IV)

[Cu(en)(NH3)2][Co(en)Cl4] ethylenediaminediamincopper(II) tetrachloroethylenediaminecobaltate(II)

[Pt(en)2Br2](ClO4)2

bis(ethylenediamine)dibromoplatinum(IV) perchlorate

Some Classes of IsomersSome Classes of Isomers

Coordination IsomersCoordination Isomers Structural (constitutional) isomers

Definition- Different compounds of the same formula.

Types of structural (constitutional) isomers Ionization isomerism

[Cr(NH3)SO4]Cl ppts AgCl when silver nitrate is added [Cr(NH3Cl)]SO4 ppts barium sulfate when barium is added

Hydrate isomers differ in the placement of water Coordination isomers differ in the placement of

ligands between the metal atoms [CuBr4][PtCl4] or [CuCl4][PtBr4]

Structural (constitutional) isomers Definition- Different compounds of the same

formula. Types of structural (constitutional) isomers

Ionization isomerism [Cr(NH3)SO4]Cl ppts AgCl when silver nitrate is added

[Cr(NH3Cl)]SO4 ppts barium sulfate when barium is added

Hydrate isomers differ in the placement of water Coordination isomers differ in the placement of

ligands between the metal atoms [CuBr4][PtCl4] or [CuCl4][PtBr4]

Coordination IsomersCoordination Isomers Types of structural (constitutional) isomers

Linkage isomers differ by the atom that is coordinated to the metal O-N-O-M O2N-M, bond to oxygen, or bond to nitrogen

Stereoisomerism (octahedral use models) Definition, Same formula, same attachment of

atoms, but atoms are in different volumes of space geometrical isomers (cis and trans)

cis-[Co(NH3)4Cl2]+ chlorides on same side trans- chlorides on the opposite side

Types of structural (constitutional) isomers Linkage isomers differ by the atom that is

coordinated to the metal O-N-O-M O2N-M, bond to oxygen, or bond to nitrogen

Stereoisomerism (octahedral use models) Definition, Same formula, same attachment of

atoms, but atoms are in different volumes of space geometrical isomers (cis and trans)

cis-[Co(NH3)4Cl2]+ chlorides on same side trans- chlorides on the opposite side

As a Ligand, NO2

- can Bond to a Metal Ion (a) Through a Lone Pair on the Nitrogen Atom or (b) Through a Lone Pair on One of the Oxygen Atoms

As a Ligand, NO2

- can Bond to a Metal Ion (a) Through a Lone Pair on the Nitrogen Atom or (b) Through a Lone Pair on One of the Oxygen Atoms

(a) The cis Isomer of Pt(NH3)2Cl2

(b) The trans Isomer of Pt(NH3)2Cl

2

(a) The cis Isomer of Pt(NH3)2Cl2

(b) The trans Isomer of Pt(NH3)2Cl

2

The Compound [Co(NH3)4Cl2]Cl has cis and trans Isomers

The Compound [Co(NH3)4Cl2]Cl has cis and trans Isomers

Optical IsomersOptical IsomersOptical isomers(nonsuperimposable mirror images)

Chiral molecule-nonsuperimposable on it’s mirror image

Enantiomers-a pair of nonsuperimposable mirror images

Ploarimeter-an instrument that measures the rotation of polarized light by an optically active compound

Dextrorotatory-rotation of polarized light clockwise

Levorotatory-rotation of polarized light counterclockwise

Racemates- a 50/50 mixture of enantiomers (no rotation of polarized light)

Optical isomers(nonsuperimposable mirror images)

Chiral molecule-nonsuperimposable on it’s mirror image

Enantiomers-a pair of nonsuperimposable mirror images

Ploarimeter-an instrument that measures the rotation of polarized light by an optically active compound

Dextrorotatory-rotation of polarized light clockwise

Levorotatory-rotation of polarized light counterclockwise

Racemates- a 50/50 mixture of enantiomers (no rotation of polarized light)

A human hand exhibits a nonsuperimposable mirror image. Note that the mirror image of the right hand (while identical to the left hand) cannot be turned in any way to make it identical to (superimposable on) the actual right hand.

A human hand exhibits a nonsuperimposable mirror image. Note that the mirror image of the right hand (while identical to the left hand) cannot be turned in any way to make it identical to (superimposable on) the actual right hand.

Optical Isomers

Isomers I and II of CO(en)33+ are Mirror Images

that Cannot be SuperimposedIsomers I and II of CO(en)3

3+ are Mirror Images that Cannot be Superimposed

Optical Isomers

(a) Superimposable. (b) Not Superimposable

(a) Superimposable. (b) Not Superimposable

Optical Isomers

Polarized LightPolarized Light

Rotating the Plane of Polarization of Light Rotating the Plane of Polarization of Light

Polarized Light

Valence Bond ModelValence Bond Model

Valence bond (VB) approach (Localized Model) relative to octahedral systems

Overlay of the atomic orbitals of the metal and the ligands

Since the ligands normally do not possess single electrons, then a pair of electrons from the ligand, must overlap with the empty orbitals of the metal

Valence bond (VB) approach (Localized Model) relative to octahedral systems

Overlay of the atomic orbitals of the metal and the ligands

Since the ligands normally do not possess single electrons, then a pair of electrons from the ligand, must overlap with the empty orbitals of the metal


Consider for example the blue-violet [Cr(H2O)6]3+ complex

This is a 3d3 system, thus the 6 electron pairs from the water will occupy the d2sp3 hybrid (note the 4s and 4p orbitals are used here)

The 4d orbitals are not used in this case, since the 3d orbitals are lower in energy, and the bonds formed are stronger

The orbital notation shows three single electrons, verified by Gouy Balance measurements.

Consider for example the blue-violet [Cr(H2O)6]3+ complex

This is a 3d3 system, thus the 6 electron pairs from the water will occupy the d2sp3 hybrid (note the 4s and 4p orbitals are used here)

The 4d orbitals are not used in this case, since the 3d orbitals are lower in energy, and the bonds formed are stronger

The orbital notation shows three single electrons, verified by Gouy Balance measurements.

4s 4p3d

Gouy BalanceGouy Balance

Valence Bond ModelValence Bond ModelConsider next the [Ni(H2O)6]2+

This is a d8 system, there are no empty 3d orbitals

The 6 ligands, then will occupy the 4th energy shell sp3d2

The orbital notation shows two unpaired electrons, verified by experiment

Consider next the [Ni(H2O)6]2+

This is a d8 system, there are no empty 3d orbitals

The 6 ligands, then will occupy the 4th energy shell sp3d2

The orbital notation shows two unpaired electrons, verified by experiment

4s 4p3d 4d


When 3d orbitals are employed, the system is referred to as an inner orbital complex; where if the 4d orbitals are used, then the system is referred to as an outer orbital complex.

In the two previous examples there was no choice where the electrons are placed.

When 3d orbitals are employed, the system is referred to as an inner orbital complex; where if the 4d orbitals are used, then the system is referred to as an outer orbital complex.

In the two previous examples there was no choice where the electrons are placed.

Coordination Compound Bonding

Coordination Compound Bonding

Co3+ is an ion that can show either inner orbital, or an outer orbital complexes

Co3+ is d 6 system Pairing up the 6 electrons, will

produce an inner orbital d2sp3, which is diamagnetic

If the d electrons are not paired, then an outer orbital sp3d2 complex is formed, with 4 unpaired electrons and paramagnetic

Co3+ is an ion that can show either inner orbital, or an outer orbital complexes

Co3+ is d 6 system Pairing up the 6 electrons, will

produce an inner orbital d2sp3, which is diamagnetic

If the d electrons are not paired, then an outer orbital sp3d2 complex is formed, with 4 unpaired electrons and paramagnetic

Valence Bond ModelValence Bond ModelTo pair, or not to pair, that is the question

This question arises for d 4,5,6 systems Failure to pair produces outer orbital

systems Two factors to consider

Stronger bonds are formed from 3d orbitals, than 4d orbitals

Pairing means putting two electrons in the same orbital. A higher energy system for sure (electron repulsion), but the outer orbital system does not require pairing electrons

To pair, or not to pair, that is the question This question arises for d 4,5,6 systems Failure to pair produces outer orbital

systems Two factors to consider

Stronger bonds are formed from 3d orbitals, than 4d orbitals

Pairing means putting two electrons in the same orbital. A higher energy system for sure (electron repulsion), but the outer orbital system does not require pairing electrons


If the formation of bonds releases more energy than the pairing energy, then the inner orbital complex is preferred; if not, then the outer orbital complex is favored

Most first row transition elements when combined with ligands tend to favor inner orbital complexes for d4 or d6 systems, with the exception of the ligands H2O and F-, which usually prefer outer orbital complexes

If the formation of bonds releases more energy than the pairing energy, then the inner orbital complex is preferred; if not, then the outer orbital complex is favored

Most first row transition elements when combined with ligands tend to favor inner orbital complexes for d4 or d6 systems, with the exception of the ligands H2O and F-, which usually prefer outer orbital complexes


The d-5 system produced the half filled system (chromium), which is weird.

It is hard to disturb this stability, thus paring usually does not happen, thus these systems prefer outer orbital complexes with most complexes, but CN- is an exception

The d-5 system produced the half filled system (chromium), which is weird.

It is hard to disturb this stability, thus paring usually does not happen, thus these systems prefer outer orbital complexes with most complexes, but CN- is an exception

Valence Bond ModelValence Bond ModelValence bond approach and other geometries

Consider [Ni(CN)4]2- which is square planar and diamagnetic

Here Ni2+ is a d-8 system Here pairing will create an empty d orbital, thus

allowing the dsp2 hybrid orbital system to form Cyanide, is a strong ligand, as it was in the

octahedral system

The [CoCl4]2- complex forms the tetrahedral geometry

This is a d-7 system Tetrahedral here and sp3

Valence bond approach and other geometries Consider [Ni(CN)4]2- which is square planar

and diamagnetic Here Ni2+ is a d-8 system Here pairing will create an empty d orbital, thus

allowing the dsp2 hybrid orbital system to form Cyanide, is a strong ligand, as it was in the

octahedral system

The [CoCl4]2- complex forms the tetrahedral geometry

This is a d-7 system Tetrahedral here and sp3

Valence Bond ModelValence Bond ModelOne of the most striking physical properties of the coordination compounds is their color, and the valence bond theory does little to explain color.

One of the most striking physical properties of the coordination compounds is their color, and the valence bond theory does little to explain color.

Crystal Field Splitting Theory


Crystal field splitting theory (CF) Developed by physics to explain impurities

in crystal lattices Electrostatic bonds no coordinate

covalent bonds Ligands are anions or polar particles

Crystal field splitting theory (CF) Developed by physics to explain impurities

in crystal lattices Electrostatic bonds no coordinate

covalent bonds Ligands are anions or polar particles


Crystal Field Splitting Theory Another modified version of molecular

orbital theory Organizes the d orbitals in order of increasing

energy Organization of energy depends on the

geometry of the complex ion Consider the geometry of the d orbitals page

967 As a ligand approaches in an octahedral

complex, the nonbonding electrons will repel electrons found in the dz2 and dx2-y2, thus splitting the potential energy of the 5 d orbitals, this is where the name Crystal Field Splitting theory comes from

Another modified version of molecular orbital theory

Organizes the d orbitals in order of increasing energy

Organization of energy depends on the geometry of the complex ion

Consider the geometry of the d orbitals page 967

As a ligand approaches in an octahedral complex, the nonbonding electrons will repel electrons found in the dz2 and dx2-y2, thus splitting the potential energy of the 5 d orbitals, this is where the name Crystal Field Splitting theory comes from



The average energy of the d orbitals is not altered

The energy difference is called Δo where the o means octahedral

The two d orbitals of higher energy are called eg while the three lower energy orbitals are called t2g

The eg increases in energy by 0.6, and the t2g decreases in energy by 0.4, thus total energy change is zero

The average energy of the d orbitals is not altered


The two d orbitals of higher energy are called eg while the three lower energy orbitals are called t2g

The eg increases in energy by 0.6, and the t2g decreases in energy by 0.4, thus total energy change is zero

Crystal Field SplittingCrystal Field Splitting

CF Energy DiagramCF Energy Diagram

Octahedral and Tetrahedral Splits

Octahedral and Tetrahedral Splits

Some d SystemsSome d Systems



Referred to as the crystal field splitting Absorption of light corresponds to delta, the

greater the difference the more blue in color light is absorbed, all other colors are reflected

The energy absorbed is related to the wave length


Referred to as the crystal field splitting Absorption of light corresponds to delta, the

greater the difference the more blue in color light is absorbed, all other colors are reflected

The energy absorbed is related to the wave length

Crystal Field SplittingCrystal Field Splitting Placement of electrons into these

5 psudo-molecular orbitals depends on the magnitude of Δo and the pairing energy P

If Δo < P, then the next electron goes into the eg orbital, creating a high spin case

If Δo > P, then the next electron goes into t2g creating low spin case

Placement of electrons into these 5 psudo-molecular orbitals depends on the magnitude of Δo and the pairing energy P

If Δo < P, then the next electron goes into the eg orbital, creating a high spin case

If Δo > P, then the next electron goes into t2g creating low spin case

Examples With Pairing Energy

Examples With Pairing Energy

Crystal Field SplittingCrystal Field SplittingFactors affecting magnitude of Δo

Charge on metal ion Increasing charge causes radius to decrease,

thus ligands are more strongly attached, thus increasing Δo

The Δo for a tripositive ion is about 50% when compared to a dipositive ion

Principle quantum number With the same charge and same ligands, then

as we travel down a group then Δo increases This effect is due to the larger radius of the

metal ion Repulsive ligand forces are important in

smaller metal ions

Factors affecting magnitude of Δo

Charge on metal ion Increasing charge causes radius to decrease,

thus ligands are more strongly attached, thus increasing Δo

The Δo for a tripositive ion is about 50% when compared to a dipositive ion

Principle quantum number With the same charge and same ligands, then

as we travel down a group then Δo increases This effect is due to the larger radius of the

metal ion Repulsive ligand forces are important in

smaller metal ions

Crystal Field SplittingCrystal Field SplittingNature of the ligands

For ligands of the same group, the Δo decreases as the size of the ligand increases

Smaller more localized charges interact more strongly with the d orbitals of the metal ion.

Small neutral ligands with a localized pair of electrons, i.e. NH3, gives larger than expected Δo, when compared to a spherical ligand such as F-, that has unlocalized electrons

Nature of the ligands For ligands of the same group, the Δo

decreases as the size of the ligand increases

Smaller more localized charges interact more strongly with the d orbitals of the metal ion.

Small neutral ligands with a localized pair of electrons, i.e. NH3, gives larger than expected Δo, when compared to a spherical ligand such as F-, that has unlocalized electrons

Crystal Field SplittingCrystal Field Splitting If the ligands cause a large splitting

(large value of Δ) then the electrons will fill the lower t2g orbital first, thus minimizing the single electrons (strong field case) (low spin)

If the ligands cause a small splitting (low value of Δ) then the electrons will fill the t2g one at a time and then fill the eg orbitals one at a time (Weak field case) (high spin)

If the ligands cause a large splitting (large value of Δ) then the electrons will fill the lower t2g orbital first, thus minimizing the single electrons (strong field case) (low spin)

If the ligands cause a small splitting (low value of Δ) then the electrons will fill the t2g one at a time and then fill the eg orbitals one at a time (Weak field case) (high spin)

Low Spin d-4 SystemLow Spin d-4 System

High Spin d-4 SystemHigh Spin d-4 System

Crystal Field SplittingCrystal Field Splitting Only d 4,5,6,7 have a choice of high

spin, or low spin This model explains magnetic and

color properties of complexes. Color chart or color wheel

Only d 4,5,6,7 have a choice of high spin, or low spin

This model explains magnetic and color properties of complexes.

Color chart or color wheel

Color WheelColor Wheel

Visible SpectrumVisible Spectrum


Magnitude of splitting Magnitude of ΔO depends on the charge of

the central metal, the higher the greater ΔO

For example NH3 is weak field with Co 2+ and strong field with Co 3+

As charge increases the ligands are drawn closer to the metal, thus the closer the greater the splitting

Magnitude of splitting Magnitude of ΔO depends on the charge of

the central metal, the higher the greater ΔO

For example NH3 is weak field with Co 2+ and strong field with Co 3+

As charge increases the ligands are drawn closer to the metal, thus the closer the greater the splitting

Crystal Field SplittingCrystal Field Splitting Depends on polarity, size, etc. I-<Br-<Cl-<acetate<F-<OH-

<oxalate<H2O<SCN-<NH3<en<NO2-

<CN-≈CO Iodine is the smallest splitting

Depends on polarity, size, etc. I-<Br-<Cl-<acetate<F-<OH-

<oxalate<H2O<SCN-<NH3<en<NO2-

<CN-≈CO Iodine is the smallest splitting

Crystal Field SplittingCrystal Field Splitting Cobalt here can have two

possibilities Depends what the ligands are High spin same as outer Low spin same as inner If iodine is used we have high spin

Because delta is not large

Cobalt here can have two possibilities

Depends what the ligands are High spin same as outer Low spin same as inner If iodine is used we have high spin

Because delta is not large

Crystal Field SplittingCrystal Field Splitting Bond formation overcomes small

delta If aqua is used we have the low spin

case All paired Diamagnetic Different colors because delta is different

The possibility of high spin or low spin exists when

D=4,5,6 or 7, Choice between High and Low spin

d 0,1,2,3,8,9,10 High spin only

Bond formation overcomes small delta

If aqua is used we have the low spin case

All paired Diamagnetic Different colors because delta is different

The possibility of high spin or low spin exists when

D=4,5,6 or 7, Choice between High and Low spin

d 0,1,2,3,8,9,10 High spin only

Crystal Field SplittingCrystal Field Splitting Crystal Field Stabilization Energies

If the t2g populated, then stability is increased, since it is lower potential energy

Stabilization can be calculated by multiplying the number of electrons in the t2g orbital by 0.4Δ

If a combination occupied by t2g and eg then subtract 0.4 t2g from 0.6 eg for stabilization energy

Wave numbers Energies obtained by spectroscopic measurements

are oftern given in units of wave numbers (cm-1) Wave number is the reciprocal of the wavelength of

the corresponding electromagnetic radiation expressed in cm

cm-1 = 11.96 j

Crystal Field Stabilization Energies If the t2g populated, then stability is increased, since

it is lower potential energy Stabilization can be calculated by multiplying the

number of electrons in the t2g orbital by 0.4Δ

If a combination occupied by t2g and eg then subtract 0.4 t2g from 0.6 eg for stabilization energy

Wave numbers Energies obtained by spectroscopic measurements

are oftern given in units of wave numbers (cm-1) Wave number is the reciprocal of the wavelength of

the corresponding electromagnetic radiation expressed in cm

cm-1 = 11.96 j

Color and the Colors of ComplexesColor and the Colors of Complexes

Two types of mixing colors Additive, occurs when colored lights

are superimposed on each other Subtractive, occurs when colored

paints are mixed with each other

Two types of mixing colors Additive, occurs when colored lights

are superimposed on each other Subtractive, occurs when colored

paints are mixed with each other

Crystal Field Splitting

Additive Mixing (light beams)Additive Mixing (light beams) For additive mixing a primary

color is defined as any three colors that produce white light Examples:

R + G + B = W

Secondary colors are those that are produced by combining two primary colors Examples:

R + G = YR + B = M

For additive mixing a primary color is defined as any three colors that produce white light Examples:

R + G + B = W

Secondary colors are those that are produced by combining two primary colors Examples:

R + G = YR + B = M


Additive and Subtractive MixingAdditive and Subtractive Mixing


Complex SolutionsComplex Solutions

Subtractive MixingSubtractive Mixing Some wave lengths of white light are

removed from absorption (promoting electrons to higher levels)

The reflected light, does not contained the absorbed colors, thus has a color due to the absence of another color.

Here primary colors are M,Y, and BG; while secondary colors are G, B, and R.

If a material absorbs all three primary colors, then there in no light left to be reflected, thus black.

Some wave lengths of white light are removed from absorption (promoting electrons to higher levels)

The reflected light, does not contained the absorbed colors, thus has a color due to the absence of another color.

Here primary colors are M,Y, and BG; while secondary colors are G, B, and R.

If a material absorbs all three primary colors, then there in no light left to be reflected, thus black.

Subtractive MixingSubtractive Mixing

If a material absorbs one color, primary or secondary, the reflected or transmitted color is the complimentary color.

Thus a magenta shirt has that color because the dye it contains strongly absorbs green light and reflects the magenta, the compliment of green (see color wheel)

If a material absorbs one color, primary or secondary, the reflected or transmitted color is the complimentary color.

Thus a magenta shirt has that color because the dye it contains strongly absorbs green light and reflects the magenta, the compliment of green (see color wheel)

Color WheelColor Wheel

Colored SolutionsColored Solutions

Colored solutions absorb photons of white light to promote electrons to higher energy levels.

White light, minus the absorbed color, is no longer white, but appears as the compliment of the color that was absorbed

Ions having noble gas configurations do not have energy absorptions in the visible range, thus they appear colorless; likd NaCl (aq)

Colored solutions absorb photons of white light to promote electrons to higher energy levels.

White light, minus the absorbed color, is no longer white, but appears as the compliment of the color that was absorbed

Ions having noble gas configurations do not have energy absorptions in the visible range, thus they appear colorless; likd NaCl (aq)

Colored SolutionsColored Solutions Crystal field splitting deals with d-electrons

and not Noble gas structures. The do absorb in the visible spectrum and

we see the color of the light that is complimentary to the color absorbed

A solution containing [Cu(H2O)4]2+ absorbs most strongly in the yellow region of the spectrum (about 580 nm)

The wavelength of the transmitted light is violet

Crystal field splitting deals with d-electrons and not Noble gas structures.

The do absorb in the visible spectrum and we see the color of the light that is complimentary to the color absorbed

A solution containing [Cu(H2O)4]2+ absorbs most strongly in the yellow region of the spectrum (about 580 nm)

The wavelength of the transmitted light is violet

Acidity of Coordination Compounds

Acidity of Coordination Compounds

Water molecules coordinately bonded to a metal ion can lose a proton, thus causing the hydrate to act as an acid


Acidic HydratesAcidic HydratesWater molecules coordinately bonded to a metal ion can lose a proton, thus causing the hydrate to act as an acid


Cr(H2O)63+

Cr(H2O)5(OH)2+ + H+ ka = 1 X 10-4



Cr(H2O)63+

Cr(H2O)5(OH)2+ + H+ ka = 1 X 10-4

Ka =[Cr(H2O)5(OH)2+][H+]

[Cr(H2O)63+]

The hydroxide ion is bonded to the transition metal cation. The greater the charge of the metal ion and the smaller it is produces a stronger attraction to the hydroxide thus making the complex more stable and more acidic.



Cr(H2O)63+

Cr(H2O)5(OH)2+ + H+ ka = 1 X 10-4

Ka =[Cr(H2O)5(OH)2+][H+]

[Cr(H2O)63+]

Calculate the pH of a 1.00 M solution of Cr3+

Ka =(x)(x)1.0-x = 1.00 X 10-4



Cr(H2O)63+

Cr(H2O)5(OH)2+ + H+ ka = 1 X 10-4

Ka =[Cr(H2O)5(OH)2+][H+]

[Cr(H2O)63+]

Calculate the pH of a 1.00 M solution of Cr3+

Ka =(x)(x)1.0-x = 1.00 X 10-4

[H+] = 10-4

pH = - log10-

4

pH = 4

Solubility of Ionic Compounds

Solubility of Ionic Compounds

When a precipitate forms the solution is said to be saturatedSaturated solutions can also be formed by adding to much soluteAn equilibrium exists between ions forming solid and the solid dissolving to form ions.From the equilibrium constant we can determine the molar solubility

When a precipitate forms the solution is said to be saturatedSaturated solutions can also be formed by adding to much soluteAn equilibrium exists between ions forming solid and the solid dissolving to form ions.From the equilibrium constant we can determine the molar solubility

Silver Chloride Solubility


Silver chloride is known to be insoluble according to our solubility rules, but some does dissolve.


AgCl(s) Ag+(aq) + Cl-(aq) Ksp= 1.8X10 -10






Ksp = [Products]

[Reactants]= ?






Ksp = [Ag+][Cl-]






Ksp = [Ag+][Cl-] = [X][X] X2 = 1.8 X 10-10

X = 1.34 X 10-5 M






Ksp = [Ag+][Cl-] = [X][X] X2 = 1.8 X 10-10

X = 1.34 X 10-5 M

1.34 X 10-5 mole Ag+

mole Ag+mole AgCl

L

142 g AgClmole AgCl

1.91 X 10-3 g AgCl will dissolve in a liter of water

Sample ProblemSample ProblemDetermine the molar solubility of magnesium hydroxide.Determine the molar solubility of magnesium hydroxide.


Mg(OH)2 (s) Mg2+ + 2 OH- ksp= 1.8 X 10-11


Mg(OH)2 (s) Mg2+ + 2 OH- ksp= 1.8 X 10-11

Ksp = [Mg2+][OH-]2

x 2x


Mg(OH)2 (s) Mg2+ + 2 OH- ksp= 1.8 X 10-11

Ksp = [Mg2+][OH-]2 = x(2x)2 = 1.8 X 10-11

x 2x

x = 1.65 X 10-4 M


Mg(OH)2 (s) Mg2+ + 2 OH- ksp= 1.8 X 10-11

Ksp = [Mg2+][OH-]2 = x(2x)2 = 1.8 X 10-11

x 2x

x = 1.65 X 10-4 M

[OH-] = 2(1.65x10-4) = 3.3x10--4

Sample ProblemSample ProblemDetermine the additional mass of magnesium hydroxide dissolved, after the addition of 125 mL of 1.00 X 10-4 M HCl.

Determine the additional mass of magnesium hydroxide dissolved, after the addition of 125 mL of 1.00 X 10-4 M HCl.Mg(OH)2 (s) Mg2+ + 2 OH- ksp= 1.8 X 10-11

Which way will the equilibrium shift?



Which way will the equilibrium shift? Right



Which way will the equilibrium shift? Right

What is the hydroxide ion concentration after addition of the HCl?



Which way will the equilibrium shift? RightWhat is the hydroxide ion concentration after addition of the HCl?1.00 X 10-4 mole HCl

L

0.125 L= 1.25 X10-5 mole HCl

3.3x10-4 – 1.25x10-5 = 3.176 x 10-4 mole OH-

3.176x10-4 mole OH-

1.125 L = 2.822X104 M OH-

Sample ProblemSample ProblemWhat additional mass of Mg is dissolved

Ksp = [Mg2+][OH-]2 = 1.8 X 10-11

[Mg2+][OH-]2 = 1.8 X 10-11

[Mg2+][2.2822X10-4]2 = 1.8 X 10-11

[Mg2+] = 2.26X10-4M Mg2+

2.26X10-4M Mg2+ - 1.65X10 -4 Mg2+ (original) = 6.1 X10-5 moles Mg2+

6.1 X 10-5 moles Mg2+

moles Mg2+

24.3 g Mg2+

= 1.5 X 10-3 g Mg2+

About Dissolving Precipitates

About Dissolving Precipitates

Precipitates form when the product of the ion concentration Q>Ksp. Since precipitates are in equilibrium with the ions that form the LeChatelier’s Principle will control the solution process. The previous sample problem demonstrated how solubility is controlled by Ph. Clearly pH is dependent upon solubility and this is a very important consideration in qualitative analysis, which is always emphasized in prelab lectures. If the procedure states acidic or basic, use litmus paper. If the procedure states just basic, then use pH paper and adjust the pH to 8. If the procedure requires a specific pH, then use pH paper.

Solubility Controlling Factors

Solubility Controlling Factors

Since precipitate formation is related to solubility, then the following factors control precipitation also. These factors control the process, by adding or removing ions from the equilibrium mixture according to leChateliers principle.

The pH of the solutionremoving H+ or OH- by adding acid or base

Formation of a complexAdding a substance to form a coordination compound

Formation of a gasAdding a substance to convert one of the ions to a gas.

Since precipitate formation is related to solubility, then the following factors control precipitation also. These factors control the process, by adding or removing ions from the equilibrium mixture according to leChateliers principle.

The pH of the solutionremoving H+ or OH- by adding acid or base

Formation of a complexAdding a substance to form a coordination compound

Formation of a gasAdding a substance to convert one of the ions to a gas.

Dissolving AgCl (s)Dissolving AgCl (s)One of the most common applications of precipitate control by complex formation involves the insoluble silver chloride precipitate.

AgCl(s) Ag+(aq) + Cl-(aq) Ammonia will complex with silver ion to from the diamminosilver(I) complex, thus removing silver ion from solution. According to LeChatelier’s principle, silver chloride produces more silver ions which are then complexed with ammonia until all of the silver chloride solid is dissolved. The following slide illustrates this process quantitatively.

One of the most common applications of precipitate control by complex formation involves the insoluble silver chloride precipitate.

AgCl(s) Ag+(aq) + Cl-(aq) Ammonia will complex with silver ion to from the diamminosilver(I) complex, thus removing silver ion from solution. According to LeChatelier’s principle, silver chloride produces more silver ions which are then complexed with ammonia until all of the silver chloride solid is dissolved. The following slide illustrates this process quantitatively.

Complex FormationComplex FormationConsider silver complex formation with ammonia

Ag+ + NH3 ⇄ Ag(NH3)+ K1 = 2.1x103

Ag(NH3)+ + NH3 ⇄ Ag(NH3)2 K2 = 8.2x103

When using a large excess of NH3 and since the formation constants are large, the reaction can be considered to be complete, since the overall constant is 1.72x107.

Consider silver complex formation with ammonia

Ag+ + NH3 ⇄ Ag(NH3)+ K1 = 2.1x103

Ag(NH3)+ + NH3 ⇄ Ag(NH3)2 K2 = 8.2x103

When using a large excess of NH3 and since the formation constants are large, the reaction can be considered to be complete, since the overall constant is 1.72x107.

Ag+ + 2NH3 → Ag(NH3)2+ Kf = K1 x K2

Kf =1.72x107

Complex FormationComplex Formation Ag+ + 2NH3 → Ag(NH3)2

+

Given: [Ag+]i = 5x10-4 and [NH3]I = 1.0

Then [Ag+]f = 0 and [NH3]f = 1.0- 2(5x10-4), and [Ag(NH3)2

+]=5x10-4

Ag+ + 2NH3 → Ag(NH3)2+

Given: [Ag+]i = 5x10-4 and [NH3]I = 1.0

Then [Ag+]f = 0 and [NH3]f = 1.0- 2(5x10-4), and [Ag(NH3)2

+]=5x10-4

Yes, but there is a small amount of Ag+ so then how can we calculate this concentration? Next slide!

Complex FormationComplex FormationHow much [Ag(NH3)+] is present can be calculated using the K2

K2= [Ag(NH3)2+]/[NH3][ Ag(NH3)+]

Solving for [Ag(NH3)+] = [Ag(NH3)2+]/[NH3][ K2]

[Ag(NH3)+]=6.1x10-8, using 1.0 for ammonia

In a similar way, using K1, [Ag+] can be determined to be 2.9x10-11

How much [Ag(NH3)+] is present can be calculated using the K2

K2= [Ag(NH3)2+]/[NH3][ Ag(NH3)+]

Solving for [Ag(NH3)+] = [Ag(NH3)2+]/[NH3][ K2]

[Ag(NH3)+]=6.1x10-8, using 1.0 for ammonia

In a similar way, using K1, [Ag+] can be determined to be 2.9x10-11

Complex FormationComplex Formation

How do you dissolve and insoluble salt? For example AgCl

The equilibrium is AgCl ⇄ Ag+ + Cl-

Need to shift the equilibrium to the right to dissolve the solid AgCl

Consider the following process

AgCl ⇄ Ag+ + Cl- Ksp=1.6x10-10

Ag+ + NH3 ⇄ Ag(NH3) K1 = 2.1x103

Ag(NH3)+ + NH3 ⇄ Ag(NH3)2+ K2 = 8.2x103

AgCl (s) + 2NH3 ⇄ Ag(NH3)2+ + Cl- K1xK2x Ksp

How do you dissolve and insoluble salt? For example AgCl

The equilibrium is AgCl ⇄ Ag+ + Cl-

Need to shift the equilibrium to the right to dissolve the solid AgCl

Consider the following process

AgCl ⇄ Ag+ + Cl- Ksp=1.6x10-10

Ag+ + NH3 ⇄ Ag(NH3) K1 = 2.1x103

Ag(NH3)+ + NH3 ⇄ Ag(NH3)2+ K2 = 8.2x103

AgCl (s) + 2NH3 ⇄ Ag(NH3)2+ + Cl- K1xK2x Ksp

Complex FormationComplex Formation

AgCl (s) + 2NH3 ⇄ Ag(NH3)2+ + Cl- K =2.8x103

Use the equilibria expression above to calculate the solubility of AgCl in a 10.0 M ammonia solution

K = [Ag(NH3)2+][Cl-]/[NH3]2 → 2.8x10-3 = x2/ (10-2x)2

X=0.48 M

AgCl (s) + 2NH3 ⇄ Ag(NH3)2+ + Cl- K =2.8x103

Use the equilibria expression above to calculate the solubility of AgCl in a 10.0 M ammonia solution

K = [Ag(NH3)2+][Cl-]/[NH3]2 → 2.8x10-3 = x2/ (10-2x)2

X=0.48 M

10.0 0 0 initial

10-2x x x

The EndThe End

ch# 17 coordination chemistry. transition metals transition metals show similarities within a...

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d sublevel

s sublevel

d orbitals

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coordination chemistry

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group designations

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