The influence of phosphine ligands on the stoichiometry of mixed-ligand hexacoordinate iron(II) complexes with isocyanides and phosphines

The synthesis and characterization of complexes of the type [FeX(4-CH3-C6H4NC)nL5−n]ClO4 (X  Cl, Br, or I; n = 2, 3 or 4; L  PhPMe2, PhPEt2, Ph2PMe, Ph2PEt, or Ph2P(OEt) are described. The steric hindrance by the phosphine ligand is tentatively correlated with the influence of the π-acidity of phosphine and isocyanide ligands in determining the composition of these compounds. Their structures have been postulated on the basis of infrared and PMR spectra. Mossbauer parameters have also been determined at liquid nitrogen temperature by a treatment of the data by the point-charge model.