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IR and Raman Characterization of the Zincocenes (η5-C5Me5)2Zn2 and (η5-C5Me5)(η1-C5Me5)Zn

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journal contribution
posted on 23.10.2008, 00:00 authored by Diego del Rio, Irene Resa, Amor Rodriguez, Luis Sánchez, Ralf Köppe, Anthony J. Downs, Christina Y. Tang, Ernesto Carmona
The measured Raman and IR spectra of solid, polycrystalline bis(pentamethylcyclopentadienyl)dizinc, (η5-C5Me5)2Zn2, 1, and bis(pentamethylcyclopentadienyl)monozinc, (η5-C5Me5)(η1-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 68Zn-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 68Zn 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 68Zn substitution. A stretching force constant of 1.42 mdyne Å−1 has been estimated for the Zn−Zn bond of 1.