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Theoretical Predictions of the Structures and Energetics of ClF n +/- (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
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Background Small d-orbital contribution to the bondings in SF 3 to SF 6 1, 2 d-hybridization model un-suitable Mostly 3s and 3p orbitals for bonding Oscillating trend of the bond energies of SF n-1 +F SF n was observed experimentally 3 1.Reed & Weinhold, JACS, 108,3586,1986; 2.Cooper et al, JACS, 116, 4414,1994; 3. Kiang & Zare, JACS, 102,4024,1980 StructuresEnergetics Ground States Excited States New Model: Prediction
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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 1 st RPB2 nd RPB weak long R e strong short R e X( 3 P) XF( 4 - ) XF 2 ( 3 B 1 ) Excited States X=S, Cl +
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New Model: Recoupled Pair Bond (RPB) B. Bonding will rearrange to maximize the stability. Rearrange XF 3 ( 2 A ’ ) RPB two RPBs one covalent bond. one RPB two covalent bond s X=S, Cl +
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Applications of the Recoupled Pair Bonding 1. Oscillating Bond Energies in SF n and ClF n 1.Woon & Dunning, JPCA, 113, 7915, 2009; 2. Chen, Woon & Dunning, JPCA, 113, 12645, 2009 Cl-F ClF-F ClF 2 -F ClF 3 -F ClF 4 -F S-F SF-F SF 2 -F SF 3 -F SF 4 -F SF 5 -F Energy /eV RCCSD(T)/AVTZ without Zero Point Energy Correction SF n, n 2. The formation of molecules with normal valence (e.g. CX 2, X=H,F, n=1,2; TI13) Decouple the 1 st 3p 2 Decouple the 2 nd 3p 2 Decouple the 3s 2
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Objectives Predict unknown states of ClF n +/-. 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.
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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
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XF n (X=S, Cl + ): Prediction I (n=1-3) XF ( 2 ) XF( 4 XF 2 ( 1 A 1 ) XF 2 ( 3 B 1 ) XF 3 ( 2 A ’ ) covalent w/antibonding e - hypervalent w/rearrangement XF 2 ( 3 A 2 )
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SF n : Results I (n=1-3) 2.37 4.50 3.69 SF 3 ( 2 A’)SF 2 ( 1 A 1 ) 3.84 4.48 3.68 SF 2 ( 3 B 1 ) SF 2 ( 3 A 2 ) 1.31 0.81 1.96 SF( 4 – ) SF( 2 ) 3.49 1.53 covalent w/antibonding e - hypervalent w/rearrangement 1.72 S S SS S S RCCSD(T)/AVTZ results without ZPE correction Bond energies in eV
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ClF n + : Results I (n=1-3) F F F Cl F F 2.48 0.29 2.77 3.23 2.53 1.97 0.20 FF Cl FF 1.78 22 1A11A1 3B13B1 2A’2A’ RCCSD(T)/AVTZ results without ZPE correction Bond energies in eV 44 covalent w/antibonding e - hypervalent w/rearrangement 3A23A2 Not Stable
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XF n (X=S, Cl + ), (n=4-6) covalent w/antibonding e - hypervalent w/rearrangement XF 4 ( 1 A 1 )XF 5 ( 2 A 1 ) XF 6 ( 1 A 1g ) XF 3 ( 2 A 1 ) SF 3 ( 2 A’) 4.17 1.714.64 ClF 3 + ( 2 A 1 ) 2.040.10 2.53 Cl RCCSD(T)/AVTZ results without ZPE correction; Bond energies in eV SS S
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Mulliken Populations of ClF n + and SF n StateSpeciesQ(X)Q(F equatorial )Q(F axial ) 22 SF0.475-0.475 ClF + 1.179-0.179 4-4- SF0.585-0.585 ClF + 0.9600.040 1A11A1 SF 2 0.948-0.474 ClF 2 + 1.406-0.203 3B13B1 SF 2 1.098-0.548 ClF 2 + 1.444-0.222 3A23A2 SF 2 0.962-0.481 2 A’SF 3 1.477-0.421-0.528 ClF 3 + 1.642-0.180-0.231 1A11A1 SF 4 1.816-0.398-0.510 ClF 4 + 1.949-0.174-0.300 2A12A1 SF 5 2.314-0.374-0.485 ClF 5 + 2.257-0.224-0.258 1 A 1g SF 6 2.754-0.459 ClF 6 + 2.643-0.274 1. F axial draws more electron density than F equatorial does 2. F atoms in SF n draw more electron density than those in ClF n + XF 3 ( 2 A ’ ) F equatorial F axial F axial RPB F equatorial CB
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Bond Energies of the Ground state ClF n + in Comparison with SF n (n=1-6) 1. The bond energies of ClF n + also exhibit the oscillating trend as seen in SF n. 2. The formation of ClF 3 + and ClF 5 + involves the recoupled pair bond. Both species are weakly bound with respect to ClF n-1 + + F. Energy/eV n RCCSD(T)/AVTZ, Zero Point Energy Correction B3LYP/AVTZ Decouple the 3p 2 Decouple the 3s 2
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Summary I Because Cl has larger nuclear charge than S, it holds the electrons more tightly than S. In the case of the ClF n +, 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.
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ClF n - : Predictions and Results ClF - ( 2 + ) ClF 2 - ( 2 A 1 )ClF 3 - ( 2 A 1 )ClF 4 - ( 1 A 1 )ClF 5 - ( 2 A 1 )ClF 6 - ( 1 A 1 ) ClF - ( 2 + ) ClF 2 - ( 2 A 1 )ClF 3 - ( 2 A 1 )ClF 4 - ( 1 A 1 )ClF 5 - ( 2 A 1 )ClF 6 - ( 1 A 1 ) ClF - ClF 2 - ClF 3 - ClF 4 - ClF 5 - ClF 6 - R ax 2.1801.8682.0931.8062.1361.792 R eq 1.8161.775 A191.1290.0089.6090.00 T1180.00
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Bond Energies (BDE) of ClF n - (n=1-6) Energy/eV n RCCSD(T)/AVTZ Zero Point Energy Correction B3LYP/AVTZ Decouple the 3p 2 Again, the oscillating trend can be explained by RPB
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Ionization Energies (IE) and Electron Affinities (EA) of ClF n species (n=0-6) Energy/eV n 1. The IE of F is much higher than the ones of the ClF n species. 2. The EA of F, however, is lower than the ones of the open shell species ClF 2, ClF 4, and ClF 6, as well as the close shell ClF 5.
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Summary II Recoupled pair bonding is capable to predict the structures and energetics of the ground states as well as the excited states of SF n and ClF n +/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 ClF n + are much smaller than the analogous SF n species. (ClF n - should be similar to ArF n. Research on ArF n is in progress.) IE and EA of the ClF n species also exhibit oscillating trends as seen in the bond energies of ClF n and SF n.
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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
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SF n : Results I (n=1-3) 2.37 4.50 3.69 SF 3 ( 2 A’)SF 2 ( 1 A 1 ) 3.84 4.48 3.68 SF 2 ( 3 B 1 ) SF 2 ( 3 A 2 ) 1.31 0.81 1.96 SF( 4 – ) SF( 2 ) 3.49 1.53 RCCSD(T)/AVTZ results without ZPE correction Bond lengths in Å; Bond Energy in eV covalent w/antibonding e - hypervalent w/rearrangement 1.72 F FF 1.663 1.572 87.6 S F 1.608 S F 1.893 S 1.559 1.673 97.8 FF S FF S 163.4 163.5 1.665 83.0 F F S
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ClF n + : Results I (n=1-3) F3 F1 F2 1.613 1.553 90.53 Cl F 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 FF Cl FF 41.0 22 1A11A1 3B13B1 2A’2A’ 154.9 152.84 RCCSD(T)/AVTZ results without ZPE correction Bond lengths in Å; Bond Energy in eV 44 covalent w/antibonding e - hypervalent w/rearrangement The structures and states of ClF n + are similar to the structure of the corresponding isoelectronic SF n species, except for ClF 2 +, no stable 3 A 2 state was found. 3A23A2 Not Stable
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XF n (X=S, Cl + ), (n=4-6) covalent w/antibonding e - hypervalent w/rearrangement XF 4 ( 1 A 1 )XF 5 ( 2 A 1 ) XF 6 ( 1 A 1g ) XF 3 ( 2 A 1 ) SF 5 ( 2 A 1 ) SF 3 ( 2 A’) SF 4 ( 1 A 1 ) SF 6 ( 1 A 1g ) 4.17 1.714.64 ClF 3 + ( 2 A 1 ) 1.540 1.602 105.56 1.538 1.592 92.36 1.552 FF FF 1A11A1 2A12A1 1 A 1g 2.040.10 2.53 Cl FF FF F FF FF 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 1.651 172.2 101.3
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Bond Energies (BDE) of ClF n - (n=1-6) n012345 BE Difference0.19-1.081.41-0.012.120.53 EA(ClF n )-EA(F)0.19-1.111.41-0.082.080.42 1. The difference ≈ the difference of electron affinities between the ClF n and F. 2. For n=2 and 4, the anions tend to dissociate to the close shell ClF or ClF 3 species because EA(ClF,ClF 3 ).< EA(F). Energy/eV n RCCSD(T)/AVTZ Zero Point Energy Correction B3LYP/AVTZ
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Ionization Energy of ClF ClF + ( 2 ) ClF + ( 4 12.58eV 10.21eV 12.69eV MRCI+Q/AVTZ results without ZPE correction
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Ionization Energy of ClF 2 ClF 2 + ( 1 A 1 ) ClF 2 + ( 3 B 1 ) 10.65eV 12.43eV 12.26eV 9.90eV RCCSD(T)/AVTZ results without ZPE correction
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