Portal de Periódicos da CAPES

Binuclear cyclopentadienylvanadium carbonyl thiocarbonyls: Vanadium–vanadium bonding and four-electron donor bridging thiocarbonyl groups

2011; Elsevier BV; Volume: 31; Issue: 1 Linguagem: Inglês

10.1016/j.poly.2011.03.001

1873-3719

Zhong Zhang, Qian‐Shu Li, Yaoming Xie, R. Bruce King,

Organic and Molecular Conductors Research

Abstract Theoretical studies on the cyclopentadienylvanadium carbonyl thiocarbonyls Cp 2 V 2 (CS) 2 (CO) n ( n = 5, 4, 3, 2, 1, 0) indicate the energetic preference for structures with four-electron donor bridging CS groups. Thus the lowest energy Cp 2 V 2 (CS) 2 (CO) 5 structures have an “end-on” four-electron donor CE (E = O, S) bridge and no vanadium–vanadium bond. The lowest energy Cp 2 V 2 (CS) 2 (CO) 4 structure has a four-electron donor bridging η 2 -μ-CS group and a V–V distance of ∼3.0 A corresponding to a formal single bond. The lowest energy Cp 2 V 2 (CS) 2 (CO) 3 structures also have a single bridging η 2 -μ-CS group. Both Cp 2 V 2 (CS) 2 (CO) n ( n = 4 and 3) are predicted to lie energetically above the disproportionation products Cp 2 V 2 (CS) 2 (CO) n +1 + Cp 2 V 2 (CS) 2 (CO) n −1 . This contrasts with the stable carbonyl analog Cp 2 V 2 (CO) 5 , which has been synthesized and characterized structurally by X-ray diffraction. The lowest energy structures for the highly unsaturated Cp 2 V 2 (CS) 2 (CO) and Cp 2 V 2 (CS) 2 have two four-electron bridging η 2 -μ-CS groups. The distances corresponding to V–V single bonds, V V double bonds, and V V triple bonds in the Cp 2 V 2 (CS) 2 (CO) n structures ( n = 4, 3, 2, 1, 0) are predicted to fall in the ranges 2.98 ± 0.07, 2.77 ± 0.21, and 2.52 ± 0.06 A, respectively. The thermodynamics of the Cp 2 V 2 (CS) 2 (CO) n system suggest Cp 2 V 2 (CS) 2 (CO) 2 as the most promising synthetic objective.