Isolated CH stretching frequencies, methyl group geometry, and methyl CH bond lengths and strengths in tricarbonyl(η5-cyclopentadienyl)methyl-chromium(II), -molybdenum(II), and -tungsten(II)
- 1 January 1985
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 6,p. 1207-1212
- https://doi.org/10.1039/dt9850001207
Abstract
‘Isolated’ methyl CH stretching frequencies, ν(CHis), are reported for [M(CHD2)(η5-C5H5)(CO)3](M = Cr, Mo, or W) and are used to predict CH bond lengths, bond-dissociation energies, and mean HCH angles. The methyl groups are subject to appreciable internal rotation energy barriers and each contain two different types of CH bond, with non-equivalent orientations in the molecule and with significantly different bond lengths and strengths. The CH bond strengths decrease in the order Cr > Mo > W, reflecting a corresponding increase in metal–carbon bond strength estimated to be of the order of 55–70% from Cr to W. The methyl groups in [Cr(CHD2)(η5-C5H5)(CO)3] and [Cr(CD3)(η5-C5H5)(CO)3] are affected by extensive H/D exchange, probably with the 1,2-dimethoxyethane solvent used in the preparative reaction.Keywords
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