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A convenient synthesis of several ‘phosphomide’ ligands (P adjacent to carbonyl group) from secondary phosphines is reported. The new anisoyl substituted phosphines are considerable more stable to hydrolysis, and are stronger σ-donor ligands than P-acetyl-diphenylphosphine as determined by the measurement of ν(CO) for the corresponding rhodium carbonyl complexes trans-[RhL2(CO)Cl]. In contrast, a new phosphomide derived from perfluoro-octanoyl chloride was found to be a highly unstable, electron poor π-acceptor ligand. The crystal structure of [RhCp*Cl2{Ph2PC(O)CH3}] showed a normal pseudo-octahedral piano-stool molecular geometry with a Rh&z.sbnd;P bond length of 2.3186(5) A˚. The extra stability observed for the P-anisoyl phosphomides has led us to apply this class of ligand in rhodium catalysed hydroformylation for the first time. [Copyright &y& Elsevier]