Theoretical Predictions of the Structures and Energetics of ClFn

+/- (n =1-6) Ions: Extended Studies of Hypervalent Species Using the

Recoupled Pair Bonding Model

Lina Chen, David E. Woon, Thom. H. Dunning, Jr.

Department of Chemistry University of Illinois, Urbana-Champaign

Columbus , Ohio June 24 2010

Background Small d-orbital contribution to the bondings in SF3 to SF6

1, 2

d-hybridization model un-suitable

Mostly 3s and 3p orbitals for bonding

Oscillating trend of the bond energies of SFn-1+FSFn was observed experimentally3

1.Reed & Weinhold, JACS, 108,3586,1986; 2.Cooper et al , JACS, 116, 4414,1994; 3. Kiang & Zare, JACS, 102,4024,1980

New Model: Recoupled Pair Bond (RPB)A. RPB involves decoupling a lone pair of electrons on the

central atom

recoupling them with singly occupied ligand orbitals

+F F

1st RPB 2nd RPB

weaklong Re

strongshort Re

X(3P)

FF

XF(4-) XF2(3B1)

Excited States

X=S, Cl+

New Model: Recoupled Pair Bond (RPB)B. Bonding will rearrange to maximize the stability.

FF

FF

F Rearrange

F

XF3(2A’)

RPB

F

F

F

two RPBs one covalent bond.

one RPBtwo covalent bonds

X=S, Cl+

Applications of the Recoupled Pair Bonding 1. Oscillating Bond Energies in SFn and ClFn

1.Woon & Dunning, JPCA, 113, 7915, 2009; 2. Chen, Woon & Dunning, JPCA, 113, 12645, 2009

Cl-F

ClF-F

ClF2-F

ClF3-F

ClF4-F

S-FSF-F

SF2-F

SF3-F

SF4-F

SF5-F

Ener

gy /

eV

RCCSD(T)/AVTZ without Zero Point Energy Correction

SFn, n

2. The formation of molecules with normal valence (e.g. CX2, X=H,F, n=1,2; TI13)

Decouple the 1st 3p2

Decouple the 2nd 3p2

Decouple the 3s2

Objectives

Predict unknown states of ClFn+/-.

Compute ionization energies and electron affinities for experimental detection.

Cl+ and S are isoelectronic, as are Cl- and Ar. Identify factors that influence the strength of the RPB.

Methodology

High level ab initio methods which account for dynamical correlations. Coupled Cluster Methods: CCSD(T) and RCCSD(T) Molpro

Augmented correlation consistent basis sets: F: aug-cc-pVXZ

Cl: aug-cc-pV(X+d)Z

Generalized Valence Bond (GVB) Diagrams

X=T, Q

XFn (X=S, Cl+): Prediction I (n=1-3)

XF (2)

XF(4

XF2(1A1)

XF2(3B1)

XF3(2A’)

covalent

covalent w/antibonding e-

hypervalent

hypervalent w/rearrangement

XF2(3A2)

SFn: Results I (n=1-3)

2.37

4.50

3.69

SF3(2A’)SF2(1A1)3.84

4.48

3.68

SF2(3B1)

SF2(3A2)

1.31

0.81

1.96

SF(4–)

SF(2)3.49

1.53

covalent

covalent w/antibonding e-

hypervalent

hypervalent w/rearrangement

1.72

SS

S S

S

S

RCCSD(T)/AVTZ results without ZPE correctionBond energies in eV

ClFn+: Results I (n=1-3)

F

F FClFCl

FCl

2.48

0.29

2.77

3.23

2.53

1.97

0.20

F F

Cl

F F

Cl

1.782

1A1

3B1

2A’

RCCSD(T)/AVTZ results without ZPE correctionBond energies in eV

4

covalent

covalent w/antibonding e-

hypervalent

hypervalent w/rearrangement

3A2

Not Stable

XFn (X=S, Cl+), (n=4-6)

covalent covalent w/antibonding e-

hypervalent hypervalent w/rearrangement

XF4(1A1) XF5(2A1) XF6(1A1g)

XF3(2A1)

SF3(2A’)4.17 1.71 4.64

ClF3+ (2A1)

2.04 0.10 2.53Cl

ClCl

RCCSD(T)/AVTZ results without ZPE correction; Bond energies in eV

SSS

Mulliken Populations of ClFn+ and SFn

State

Species

Q(X) Q(F equatorial)

Q(F axial)

2 SF 0.475 -0.475

ClF+ 1.179 -0.1794- SF 0.585 -0.585

ClF+ 0.960 0.0401A1 SF2 0.948 -0.474

ClF2+ 1.406 -0.203

3B1 SF2 1.098 -0.548

ClF2+ 1.444 -0.222

3A2 SF2 0.962 -0.481

2A’ SF3 1.477 -0.421 -0.528

ClF3+ 1.642 -0.180 -0.231

1A1 SF4 1.816 -0.398 -0.510

ClF4+ 1.949 -0.174 -0.300

2A1 SF5 2.314 -0.374 -0.485

ClF5+ 2.257 -0.224 -0.258

1A1g SF6 2.754 -0.459

ClF6+ 2.643 -0.274

1. Faxial draws more electrondensity than Fequatorial does

2. F atoms in SFn draw more electron density than those in ClFn

+

XF3(2A’) Fequatorial

Faxial Faxial

FaxialRPBFequatorialCB

Bond Energies of the Ground state ClFn+ in

Comparison with SFn (n=1-6)

1. The bond energies of ClFn+ also exhibit the oscillating trend as seen in SFn.

2. The formation of ClF3+ and ClF5

+ involves the recoupled pair bond. Both species are weakly bound with respect to ClFn-1

+ + F.

Ener

gy/

eV

n

RCCSD(T)/AVTZ, Zero Point Energy Correction B3LYP/AVTZ

Decouple the 3p2

Decouple the 3s2

Summary I Because Cl has larger nuclear charge than S, it holds the

electrons more tightly than S. In the case of the ClFn+, the

positive charge on Cl is even larger. Thus the central atom holds the electrons even more tightly. This makes it even harder for F to withdraw electron density from Cl.

ClFn-: Predictions and Results

ClF- (2+) ClF2- (2A1) ClF3

- (2A1) ClF4- (1A1) ClF5

- (2A1) ClF6- (1A1)

ClF- (2+) ClF2- (2A1) ClF3

- (2A1) ClF4- (1A1) ClF5

- (2A1) ClF6- (1A1)

ClF- ClF2- ClF3

- ClF4- ClF5

- ClF6-

Rax 2.180 1.868 2.093 1.806 2.136 1.792Req 1.816 1.775A1 91.12 90.00 89.60 90.00T1 180.00

Bond Energies (BDE) of ClFn- (n=1-6)

Ener

gy/

eV

n

RCCSD(T)/AVTZZero Point Energy Correction B3LYP/AVTZ

Decouple the 3p2

Again, the oscillating trend can be explained by RPB

Ionization Energies (IE) and Electron Affinities (EA) of ClFn species (n=0-6)

Ener

gy/

eV

n

1. The IE of F is much higher than the ones of the ClFn species.2. The EA of F, however, is lower than the ones of the open shell species ClF2, ClF4, and ClF6, as well as the close shell ClF5.

Summary II

Recoupled pair bonding is capable to predict the structures and energetics of the ground states as well as the excited states of

SFn and ClFn+/0/-.

Because of the positive charge, the lone pair electrons in Cl are much harder to be decoupled than the ones in the S. The bond

energies of ClFn+ are much smaller than the analogous SFn species.

(ClFn- should be similar to ArFn. Research on ArFn is in progress.)

IE and EA of the ClFn species also exhibit oscillating trends as seen in the bond energies of ClFn and SFn.

Acknowledgment Funded by the Distinguished Chair for Research Excellence in

Chemistry at the University of Illinois at Urbana-Champaign. Dunning Group: Thom. H. Dunning, Jr., David E. Woon,

Jeff Leiding, Beth Lindquist, Lu Xu and Tyler Takeshita

SFn: Results I (n=1-3)

2.37

4.50

3.69

SF3(2A’)SF2(1A1)3.84

4.48

3.68

SF2(3B1)

SF2(3A2)

1.31

0.81

1.96

SF(4–)

SF(2)3.49

1.53

RCCSD(T)/AVTZ results without ZPE correctionBond lengths in Å; Bond Energy in eV

covalent

covalent w/antibonding e-

hypervalent

hypervalent w/rearrangement

1.72F

F F1.663

1.57287.6SF

1.608

S

F 1.893

S

1.559

1.673

97.8

F FS

F FS

163.4

163.5

1.665

83.0F F

S

ClFn+: Results I (n=1-3)

F3

F1 F21.613

1.55390.53

ClF

1.541

Cl

F

2.320

Cl

2.48

0.29

2.77

3.23

2.53

1.97

0.20

1.552

1.602

101.7

F F

Cl

F F

Cl

41.02

1A1

3B1

2A’

154.9

152.84

RCCSD(T)/AVTZ results without ZPE correctionBond lengths in Å; Bond Energy in eV

4

covalent

covalent w/antibonding e-

hypervalent

hypervalent w/rearrangement

The structures and states of ClFn+ are similar to the structure of the corresponding

isoelectronic SFn species, except for ClF2+, no stable 3A2 state was found.

3A2

Not Stable

XFn (X=S, Cl+), (n=4-6)

covalent covalent w/antibonding e-

hypervalent hypervalent w/rearrangement

XF4(1A1) XF5(2A1) XF6(1A1g)

XF3(2A1)

SF5(2A1)

SF3(2A’)

SF4(1A1) SF6(1A1g)4.17 1.71 4.64

ClF3+ (2A1)

1.540 1.602

105.56

1.538

1.592

92.361.552

F F

F F

1A12A1 1A1g2.04 0.10 2.53Cl

Cl

F F

F F

F

Cl

F F

F F

F

F

173.84

RCCSD(T)/AVTZ results without ZPE correction, Bond lengths in Å; Bond Energy in eV/mol

1.565

1.546

1.600

91.6

1.554

1.651172.2

101.3

Bond Energies (BDE) of ClFn- (n=1-6)

n 0 1 2 3 4 5

BE Difference 0.19 -1.08 1.41 -0.01 2.12 0.53

EA(ClFn)-EA(F) 0.19 -1.11 1.41 -0.08 2.08 0.42

1. The difference ≈ the difference of electron affinities between the ClFn and F.2. For n=2 and 4, the anions tend to dissociate to the close shell ClF or ClF3

species because EA(ClF,ClF3).< EA(F).

Ener

gy/

eV

n

RCCSD(T)/AVTZZero Point Energy Correction B3LYP/AVTZ

Ionization Energy of ClF

ClF+ (2)

ClF+(4

12.58eV

10.21eV

12.69eV

MRCI+Q/AVTZ results without ZPE correction

Ionization Energy of ClF2

ClF2+(1A1)

ClF2+(3B1)

10.65eV

12.43eV

12.26eV

9.90eV

RCCSD(T)/AVTZ results without ZPE correction