2012 intro organologam

Mekanisme Reaksi Kimia Anorganik Reaksi Organologam

Referensi:

James E.Huheey, Ellen A.Keither, Richard L. Keiter. 1993. Inorganic Chemistry: Principles of Structure and Reactivity Fourth Edition. Harper

Collins College, New York (Bab 13, 15)

Miessler, Tarr, Inorganic Chemistry, 2nd Edition, 1999.

Shriver, Atkins, Inorganic Chemistry, 3rd Edition, 1999.

RH Crabtree, The Organometallic Chemistry of the Transition Metals, Wiley 2001

Online : http://www.chem.ox.ac.uk/icl/dermot.html

Lecture Notes online: www.ocw.mit.edu

Lecture Note yang telah dibagikan (Mencakup 2/3 materi, bahasa Indonesia)

Help : ruang dosen, e-mail, phone

Pertemuan I- tugas terstruktur

2

Kimia Organologam

Definisi Kimia Organologam

Aturan 18 elektron: Electron Counting (pertemuan I)

Ligan Organometal (pertemuan II)

Reaksi Kompleks Organologam (pertemuan III-V)

Adisi Oksidatif

Eliminasi Reduktif

Proses Substitusi

Reaksi Insersi

Eliminasi Alfa-Hidrida dan Abstraksi

Eliminasi Beta-Hidrida

Aplikasi dalam reaksi katalitik (pertemuan 5-7) (Dengan Luasnya Kajian Kimia Organologam-hanya ada 7 pertemuan,

Bahasan per minggu dan slide power point dapat sedikit berubah

dari rencana pembelajaran)

3

Mekanisme Reaksi Kimia Anorganik Reaksi Organologam

Organometallic compounds are compounds wherein the metal is bonded through carbon to an organic molecule, radical or ion.

senyawaan yang mengandung ikatan LOGAM KARBON

Dari yang telah anda pelajari:Cr(CO)6 Hingga: senyawa sandwich dengan sistem ligan organik tak jenuh pi terdelokalisasi

4

BASED ON ORGANOMETALLICS JOURNAL:

"organometallic" compound will be defined as one in which there is a bonding interaction (ionic or covalent, localized or delocalized) between one or more carbon atoms of an organic group or molecule and a main group, transition, lanthanide, or actinide metal atom (or atoms).

organic derivatives of the metalloids (boron, silicon, germanium, arsenic, and tellurium) will be included in this definition.

metal-containing compounds which do not contain metal-carbon bonds will be considered as well. Such compounds may include, inter alia, representatives from the following classes: molecular metal hydrides; metal alkoxides, thiolates, amides, and phosphides; metal complexes containing organo-group 15 and 16 ligands; metal nitrosyls...."

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Historical Perspective

1827 Zeises Salt Na[PtCl3C2H4]-seny org.logam pertama

1847 Frankland, Zn(Et)2, first metal alkyl

1900 Grignard, organomagnesium halides

1907 Pope and Peachey, PtMe3I, first transition metal s-alkyl

1917. Schenk, lithium alkyls

1931 Heiber, Fe(CO)4H2 first transition metal hydride

1951. Pauson and Miller, ferrocene

1955 Fisher, bis arene metal complex

1973. Fisher, Cr(CO)4(CR), first carbyne complex

1983. Bergman, Graham, C-H bond activation

1983 Green, Brookhart, agostic metal-hydrogen interaction

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The Nobel Prize in Chemistry 2010

Richard F. Heck, Ei-ichi Negishi, Akira Suzuki

Richard

F. Heck

American

citizen.

Born

1931

Ei-ichi

Negishi

Japanese

citizen.

Born

1935

Akira

Suzuki

Japanese

citizen.

Born

1930

Why the Heck Bother with the Heck Reaction: Applications in Industry and Total Synthesis

Non-Steroidal

Anti-inflammatory drugs

Sunscreen Agents

Flavourings

Cosmetic Additives

Key Steps in Total Synthesis O

O O

ACB

L.F. Tietze and T. Grote,

J. Org. Chem., 1994, 59, 192

J.J. Masters, D.K. Jung,

W.G. Bornmann and

S.J. Danishefsky,

Tetrahedron Lett., 1993, 34, 7253

O

NH

NSO2Ph

Taxol

Skeleton

CC-1065

Skeleton

MeO

O

O

2-Ethylhexyl trans-4-methoxycinnamate

MeO

O

O

Isoamyltrans-4-methoxycinnamate

COOH

CH3

MeO(s)-Naproxen

Br

MeO

MeO

Heck reaction

The Nobel Prize in Chemistry 2010

The Suzuki reaction

Suzuki reaction to

develop organic

polymers that emit

light when a current

runs through them.

The goal is to

improve super-thin

OLED (organic light-

emitting diode)

displays.

Suzuki reaction to

develop new light-

capturing

molecules. These

can be spray-

painted onto a

surface and could

become a part of

future flat solar cell

The Suzuki reaction

has been used to

develop variants of the

antibiotic vancomycin.

These variants are

effective against

strains of bacteria that

are otherwise resistant

(MRSA)

Ligan Organik tidak jenuh

Dapat berikatan dengan logam melalui lebih dari 1 cara Contoh Allyl

* Sbg alkil berikatan dgn logam melalui satu atom karbon

* melalui sistem elektron , ketiga atom karbonnya

berikatan dengan logam (hapticity, h)

M

M

12

Hapto (h) Number

Jumlah atom terkonjugasi pada ligan yang terikat ke logam

h5-C5H5 pentahaptosiklopentadienil

Sebagai ligan C5H5 disebut siklopentadienil (Cp)

13

eta-x was originally developed to indicate how many contiguous donor atoms of a -system were coordinated to a metal center. Hapticity is another word

used to describe the bonding mode of a ligand to a metal center. An h5-

cyclopentadienyl ligand, for example, has all five carbons of the ring bonding to the

transition metal center.

hx values for all-carbon based ligands where the x value is odd usually

indicate anionic carbon ligands (e.g., h5-Cp, h1-CH3, h1-allyl or h3-allyl, h1-

CH=CH2). The # of electrons donated (ionic method of electron counting) by the

ligand is usually equal to x + 1. Even hx values usually indicate neutral carbon -

system ligands (e.g., h6-C6H6, h2-CH2=CH2, h4-butadiene, h4-cyclooctadiene).

The # of electrons donated by the ligand in the even (neutral) case is usually just

equal to x.

hx

14

mu-x is the nomenclature used to indicate the presence of a bridging ligand between two or more metal centers. The x refers to the number of metal

centers being bridged by the ligand. Usually most authors omit x = 2 and just use

m to indicate that the ligand is bridging the simplest case of two metals.

mx

There are two different general classes of bridging ligands:

1) Single atom bridges

2) Two donor atoms separated by a bridging group (typically organic)

Ta2 (m-t-Bu-CC-t-Bu) (m-Cl)2Cl2(THF)2 Mo2(m-CH2P(Me)2CH2)4

Ordering Inorganic/organometallic chemists generally do NOT use IUPAC naming rules.

There are some qualitative rules that most authors seem to use in American

Chemical Society (ACS) publications:

in formulas with Cp (cyclopentadienyl) ligands, the Cp usually comes first, followed by the metal center: Cp2TiCl2

other anionic multi-electron donating ligands are also often listed in front of the metal, e.g., trispyrazolylborate anion (Tp)

in formulas with hydride ligands, the hydride is sometimes listed first. Rules # 1 & 2, however, take precedence over this rule: HRh(CO)(PPh3)2 and

Cp2TiH2

bridging ligands are usually placed next to the metals in question, then followed by the other ligands (note that rules 1 & 2 take precedence):

Co2(m-CO)2(CO)6 , Rh2(m-Cl)2(CO)4 , Cp2Fe2(m-CO)2(CO)2

anionic ligands are often listed before neutral ligands: RhCl(PPh3)3, CpRuCl(=CHCO2Et)(PPh3) (neutral carbene ligand), PtIMe2(CCR)(bipy).

Problem: Sketch structures for the following:

a) CpRuCl(=CHCO2Et)(PPh3)

b) Co2(m-CO)2(CO)6 (Co-Co bond, several possible structures)

c) trans-HRh(CO)(PPh3)2 [Rh(+1) = d8]

d) Ir2(m-Cl)2(CO)4 [Ir(+1) = d8]

e) Cp2TiCl2

Aturan 18 elektron

Mirip dengan aturan Oktet, analogi s2p6d10

Sering dilanggar

Berguna untuk penghitungan dan perkiraan reaktivitas

Terdapat dua cara: ionik dan kovalen

Yang harus diketahui : muatan formal, d electron count

Metode ionik: menghilangkan ligan daril ogam dan jika perlu menambah elektron ke tiap ligan adar terbentuk kulit valensi tertutup (closed valence shell).

Contoh jika kompleks memenuhi oktet, mengambil NH3 berarti mengambil NH3-

gugus metil sebagai 2 elektron donor., berhubung logam bermuatan positif maka

nantinya d-electron countnya harus dikurangi satu. Lihat contoh

Metode kovalen: menghilangkan seluruh ligan dalam bentuk netral. Misal amonia dihilangkan sebagai molekul netral dengan sepasang elektron bebas. Mana amonia

adalah 2 elektron donor netral. Jika ligannya NH3 maka yang diambil berbentuk NH3

radikal, sebagai satu donor elektron, kemana yang satunya pergi? Dihitung pada

logam, kedudukan logam dihitung sebagai d-electron terisi penuh, misal Fe selalu 8.

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ATURAN 18 ELEKTRON, WHY?

Contoh Cr(CO)6. interaksi d orbital Cr Ligan CO merupakan ligan s-

donor (HOMO) dan -akseptor (LUMO)

28

Penambahan 1 elektron akan memberikan populasi pada orbital eg-antibonding-destabilisasi

Pengurangan 1 el akan mengurangi t2g (bonding karena pengaruh CO sebagai - akseptor )-destabilisasi, maka 18e paling stabil

Sifat s-donor CO meninggikan energi eg

Sifat - akseptor CO menurunkan t2g

Selain s-donor - akseptor bisa jadi tidak mematuhi aturan 18 elektron

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Perkecualian untuk Zn(en)32+ (spesies dgn 22 elektron)

* orbital t2g dan eg terisi.

* en merupakan s-donor yg tdk sekuat ligan CO maka elektron

pada orbital eg tidak cukup antibonding, dan bisa ditempati dengan

stabil dengan penambahan 4 elektron

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TiF62- (Spesies dengan 12 elektron)

Ligan F- merupakan ligan dengan -donor sebaik s-donor.

-donor pada F- mendestabilisasi orbital t2g sehingga agak antibonding

Spesie TiF62- mempunyai 12 elektron pada orbital s bonding dan tidak ada

elektron pada orbital antibonding t2g dan eg

Konfigurasi 18 elektron kompleks stabil dengan ligan -akseptor yang kuat .

Termasuk utk geometri trigonal bipyramida (Fe(CO)5) dan geometri

tetragonal (Ni(CO)4).

Untuk geometri square planar, konfigurasi yg stabil adalah 16 elektron.

Khususnya utk kompleks logam d8

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Kompleks dengan aturan 16 e

Biasanya unsur blok d diseb. kanan khususnya group 9 dan 10

Tabel senyawaan organologam dgn aturan 16 dan 18

Biasanya < 18 e Biasanya 18 e 16 atau 18 e

Sc

Y

La

Ti

Zr

Hf

V

Nb

Ta

Cr

Mo

W

Mn

Tc

Re

Fe

Ru

Os

Co

Rh

Ir

Ni

Pd

Pt

32

PERHITUNGAN ELEKTRON DLM KOMPLEKS

Cr(CO)6

Fe(CO)4PPh3

Cr

6 CO

Total

Fe

4CO

PPh3

Total

6 e

12 e

18 e

8 e

8 e

2 e

18 e

36

.

Ni(PF3)4

[Mn(CO)5]-

[Co(CO)4]-

Mn2(CO)10

Ni

4 PF3

Total

Mn

5 CO

Muatan

Total

Co

4 CO

Muatan

2 Mn

10 CO

Mn Mn

Total

10 e

8 e

18 e

7 e

10 e

1 e

18 e

9 e

8 e

1 e

14 e

20 e

2 e

36 e

Co2(CO)8

[PtCl4]2-

HMn(CO)5

2 Co

8 CO

Co Co

Total

Pt

4 Cl

Muatan

Total

Mn

5 CO

H

Total

18 e

16 e

2 e

36 e

10 e

4 e

2 e

16 e

7 e

10 e

1 e

18 e

37

Tentukan electron counts dengan kedua metode untuk

a. [Fe(CO)42-

b. [(5-C5H5)2Co]+

c. (3-C5H5)(5-C5H-5-)Fe(CO)

d. Co2(CO)8 (satu ikatan bridging Co-Co)

e. IrCl(CO)(PPh3)2

dengan membandingkan beda hasil kedua metode perhitungan

electron tentukan logam transisi deret pertama untuk kompleks 18

elektron (kecuali e. 16 elektron)berikut

a. [M(CO)3PPh3]-

b. HM(CO)5

c. (4-C8H8)M(CO)3

d. [(5-C5H5)2(Co)3]2

e. [M(CN)4]2-

40

Aturan 18 Elektron

Q : Ngapain repot-repot ngitung elektron?

A : Dasar untuk mempelajari struktur dan reaktivitas reaksi organologam.

Tidak beda jauh dari struktur Lewis.

Maka,perhitungan seharusnya otomatis, perhitungan seharusnya bukan dengan menghapal ligan tapi memahami karakteristik sharing elektron dalam kompleks

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Perkiraan Reaktivitas

(C2H4)2PdCl2 (C2H4)(CO)PdCl2

(C2H4)PdCl2

(C2H4)2(CO)PdCl2

?

CO- C2H4

- C2H4CO

dissociative

associative

Most likely associative:

16-e PdII

18-e PdII

16-e PdII

42

43

Cr(CO)6 Cr(CO)5(MeCN)

Cr(CO)5

Cr(CO)6(MeCN)

?

MeCN- CO

- COMeCN

dissociative

associative

Perkiraan Reaktivitas

Almost certainly dissociative:

18-e Cr(0)

16-e Cr(0)

18-e Cr(0)

Electron counting Q : Terus kalo saya ngitung elektron hasilnya 16

atau 14 artinya apa?

A : Struktur dengan elektron count dibawah ideal disebut kekurangan elektron (electron-deficient )atau tidak jenuh (coordinatively unsaturated).

Mempunyai valence orbitals(orbital kosong) .

Membuatnya bersifat elektrofilik, bisa diserang nukleofilik.

Bisa sangat reaktif, menyerang hidrokarbon atau mengikat gas mulia

44

Reactivity of electron-deficient compounds

Fe(CO)5h

- COFe(CO)4

THF Fe(CO)4(THF)

18-e Fe(0)

unreactive

16-e Fe(0)

very reactive 18-e Fe(0)

45

Q : Trus kalo electron counting ketemunya lebih dari 18, terlalu banyak maksudnya apa?

A : Jumlah net kovalen bonds kecil valenceorbital tidak cukup tersedia untuk elektron ini

An ionic model is required to explain part of the bonding.

Ikatan bersifat lemah Relatif jarang untuk logam transisi, biasanyaterjadi

karena reduksi (= penambahan elektron).

Elektron bisa berada pada L-M bonding orbitals atau pada metal-centered lone pairs.

Metal-centered orbitals punya energi tinggi atom metal dengan suatu lone pair adalah s-donor

(nucleophile).

46

Belajar mengenal muatan dan donor untuk ligan umum

Cationic 2e- donor: NO+ (nitrosil)

Neutral 2e- donors: PR3 (phosphines), CO (carbonyl), R2C=CR2 (alkenes), RCCR (alkynes, can also donate 4 e-), NCR (nitriles)

Anionic 2e- donors: Cl- (chloride), Br- (bromide), I- (iodide), CH3

- (methyl), CR3- (alkyl), Ph- (phenyl), H-

(hydride) bisa donor 4 e- tapi untuk perhitungan awal hitung sebagai2e- donors (kecuali jadi bridging ligands): OR- (alkoxide), SR- (thiolate), NR2

- (inorganic amide), PR2-

(phosphide)

Anionic 4e- donors: C3H5- (allyl), O2

- (oxide), S2- (sulfide), NR2

- (imido), CR2

2- (alkylidene) and from the previous list: OR- (alkoxide), SR- (thiolate), NR2

- (inorganic amide), PR2-

Anionic 6e- donors: Cp- (cyclopentadienyl), N3- (nitride)

Cara Mempercepat Electron Counting

47

Ligands, Charges, and Donor #s

48

Ligands, Charges, and Donor #s

49

Lewis Base Ligands -- Halides

X

XX X

F , , , Cl Br I

Increasing polarizability

Primary Halides

Strongest nucleophilefor low oxidation statemetals centers

MM

M

MM

M

2e- terminal 4e- -bridgingm 6e- -bridgingm3

Common Misconception: The halides are anionic ligands, so they are NOT

electron-withdrawing ligands. In organic chemistry the halogens can be

considered neutral ligands and do drain electron density from whatever they are

attached to. But here they are anionic and are perfectly happy with that charge.

Their electronegativity makes the halides poor donor ligands. As one moves from F- to I-, the donor ability increases as the electro-negativity drops.

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2012 intro organologam

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