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Abstract
The otherwise very fast CO substitution of Co4(CO)12 by P(OMe)3 and P(OEt)3 in aprotic solvents, affording phosphite-monosubstituted products was retarded by the use of CHCI3 as solvent. This made it possible to investigate these reactions by conventional methods. Kinetic data were obtained by following changes in IR spectra during reaction. The rates show predominantly a ligand-dependent pathway, with the usual two-term rate law, rate = (k1 + k2 [P(OR)3])C4(CO)12. It is suggested that the rates are retarded in protonic solvents by decreasing the nucleophilicity of phosphites due to a hydrogen bonding interaction between the H atom of CHCI3 and the O atoms of the ligands.