Metallomethanes: XII. Vibrational spectra and force fields of methylmercurimethanes

Abstract

The vibrational spectra data, the assignments, and the results of normal coordinate calculations for CH 4 − n (HgCH 3) n molecules (2 ⩽ n ⩽ 4) are reported. The central CHg valence force constants are 1.870, 1.653, and 1.582 N cm −1 while the terminal ones are 2.121, 2,101, and 2.160 N cm −1 for n = 2, 3 and 4, respectively. The latter values are 12, 21, and 27% higher than the central CHg force constants, but all of them are substantially lower than those in dimethylmercury (2.379 N cm −1). These findings can be accounted for in terms of increasing shift of electron density towards the periphery of these molecules and increasing non-bonded metal-metal interaction. The nature of the normal modes is discussed.