Phosphine oxides, infrared spectra

The intermediate cyclooctene complex appears to be more reactive with respect to CS coordination and more sensitive to oxidation when the arene ring bears electron-withdrawing groups (e.g., C02CH3). Dicarbonyl(methyl rj6-benzoate)-thiocarbonyl)chromium is air stable in the solid state and reasonably stable in solution.9 The infrared spectrum exhibits metal carbonyl absorptions at 1980 and 1935 cm"1 and a metal thiocarbonyl stretch at 1215 cm"1 (Nujol) (these occur at 1978, 1932, and 1912 cm"1 in CH2C12 solution).10 Irradiation of the compound in the presence of phosphite or phosphine leads to slow substitution of CO by these ligands, whereas the CS ligand remains inert to substitution. The crystal structure has been published."... 

The carbonyls are disposed trans to each other, which is deduced from the single carbonyl in the infrared spectrum. A similar cation may be formed by mild oxidation of the chromium dicarbonyl phosphine, Cr(CO)2QP [QP = tris(o-diphcnylphosphinophenyl)phosphine]. 

Hydridonitrosyltris(triphenylphosphine)ruthenium(I) is stable in air in the solid state, but slowly oxidizes in solution. The infrared spectrum of the complex shows absorptions at 1965 cm-1 [v(Ru—H)] and 1640 cm-1 [v(N—O)]. The H nmr spectrum (which is temperature-independent) shows a high-field quartet at t16.6 (2Jph = 30 Hz), consistent with a trigonal bipyramidal structure with axial hydride and equatorial phosphines.1 This structure has been confirmed in the solid state by x-ray crystallography,3 which reveals a slightly distorted trigonal bipyramid. The axial nitrosyl is coordinated in a linear fashion (Ru—N—O angle = 176°). 

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