Properties of CH bonds in cobalt, tin and zinc alkyl compounds

• Main Author: Jack, J. James
• Published: University of Aberdeen 1997
• Subjects: 547; Organic chemistry
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287607

This thesis describes the results of a detailed vibrational study on a series of mainly methyl, but also certain ethyl containing organometallic compounds. The primary objective of the work is to show that 'isolated CD' frequencies, v^isCD measured from a CH₂D group, can be used to provide predictions of CH bond parameters (CH bond length (<I>r</I>_oCH), HCH bond angle (αHCH) etc.) equally as well as 'isolated CH' frequencies, v^isCH measured from a CHD₂ group. From a review of spectroscopic data in the literature it is apparent that v^isCD, can be linearly related to v^isCH. The 98% correlation coefficient for the v^isCD versus v^isCH plot illustrates the existence of a workable linear relationship. Clearly the existence of such a relationship seems to suggest that the isotopic substitution CH₂D removes Fermi and other resonance effects almost as well as the CHD₂ isotopic substitution. Moreover, correcting the v^isCD frequency for the effects of anharmonicity using a variable R correction factor with a maximum variation 0.5% from 1.011 gives a much improved fit. Making use of existing linear correlations between v^isCH and fundamental CH bond parameters (r_oCH and αHCH), it has been shown that the determination of the v^isCD frequency can be used to provide useful predictions of r_oCH and αHCH. All this can be achieved without the need for deuteration of ligand CH sites, even in complex systems, previously necessary in the determination of v^isCH frequencies. The CH/CD stretching regions for a series of eight methylpyridinatocobaloxime isotopomers have been studied, frequencies assigned and the geometry of the methyl group determined.