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IR and Raman Characterization of the Zincocenes (η 5 -C 5 Me 5 ) 2 Zn 2 and (η 5 -C 5 Me 5 )(η 1 -C 5 Me 5 )Zn

2008; American Chemical Society; Volume: 112; Issue: 42 Linguagem: Inglês

10.1021/jp805291e

1520-5215

Diego del Rı́o, I. Resa, Amor Rodríguez, Luis Sánchez, Ralf Köppe, Anthony J. Downs, Christina Y. Tang, Ernesto Carmona,

Organoboron and organosilicon chemistry

The measured Raman and IR spectra of solid, polycrystalline bis(pentamethylcyclopentadienyl)dizinc, (eta(5)-C5Me5)2Zn2, 1, and bis(pentamethylcyclopentadienyl)monozinc, (eta(5)-C5Me5)(eta(1)-C5Me5)Zn, 8, are reported in some detail. The IR spectra of the vapors of 1 and 8 each trapped in a solid Ar matrix at 12 K confirm the essentially molecular character of the solids. The experimental results have been interpreted with particular reference (i) to the corresponding spectra of (68)Zn-enriched samples of the compounds, and (ii) to the spectra simulated by density functional theory (DFT) calculations at the B3LYP level. The marked differences of structure of 1 and 8 contrast with the relatively close similarity of their vibrational spectra, disparities being revealed only on detailed scrutiny, including the effects of (68)Zn enrichment, and primarily at wavenumbers below 1000 cm(-1). The Zn-Zn stretching motion of 1 features not as a single, well-defined mode identifiable with intense Raman scattering but in several normal modes which respond in varying degrees to (68)Zn substitution. A stretching force constant of 1.42 mdyne A(-1) has been estimated for the Zn-Zn bond of 1.