Abstract Complexes of the type Co(NO)(CO) x(PF 3) 3−x readily undergo partial or complete solvolysis with methanol or, with greater facility react with sodium methoxide in methanol with replacements of –F by –OCH 3. The complexes with a lower degree of solvolysis are isolated by gas-liquid chromatography and identified. The volatility of the complexes decreases rapidly as the degree of solvolysis increases. The stretching frequencies of the characteristic carbonyl and nitrosyl bands shift to progressively lower values as the degree of solvolysis increases. This solvolysis reaction appears to be the simplest procedure to prepare complexes of the type PF 2(OCH 3) and PF(OCH 3) 2. The end product of solvolysis are trimethylphosphite complexes.