PREPARATION AND CHARACTERIZATION BY P-31-NMR SPECTROSCOPY OF MIXED DISUBSTITUTED [FE(CO)3LL'] COMPLEXES

The disubstituted complexes [Fe(CO)3LL′], where L and L′ are different phosphine ligands have been prepared by reaction of the hydrosilyl derivatives [Fe(CO)3L(H)SiPh3] with L′. Good results were obtained for L = PMe3 and L′ = PPh3, P(OPh)3, P(OEt)3 or P(O-i-Pr)3 but with L′ = PMe2Ph, PMePh2, PEt3, a mixture of homo and mixed disubstituted derivatives were obtained. The results can be interpreted in terms of exchange of the L ligand in [Fe(CO)3L(H)SiPh]3 with L′. The variations in the 31P{1H} NMR chemical shifts and 2JPP coupling constants are discussed in the light of the properties of the ligands, and good correlations are revealed with the cone angle and the pKa, respectively. © 1990.