Iron-57 Mössbauer spectroscopic studies on 1,1′-bis(diphenylphosphino)ferrocene metal complexes. The influence of metal-ion geometry on the hyperfine interactions

57 Fe Mössbauer spectroscopic data for a series of 1,1′-bis(diphenylphosphino)ferrocene metal complexes [Fe(η-C5H4PPh2)2MXn](X = halide or CO, n= 2 or 4) are reported. An approximately linear correlation was found between the isomer shift (δ) and the quadrupole splitting (Δ). Moreover, complexes of like co-ordination geometry fell within exclusive domains on a plot of δvs.Δ. The results of an analysis of available crystal-structure data are consistent with these observations. The Mössbauer hyperfine interactions are discussed in relation to the geometry of the co-ordinated metal.