Preparation and solid-state characterization of nickel(II) complexes with 1′-(diphenylphosphino)ferrocenecarboxylic acid

1'-(Diphenylphosphino)ferrocenecarboxylic acid (Hdpf) reacts with nickel(II) halides and nickel(II) thiocyanate to give the paramagnetic complexes [NiX2(Hdpf-kappaP)(2)] (X = Cl, 1; Br, 2; I, 3) and the diamagnetic planar isothiocyanato complex [Ni(SCN-kappaN)(2)(Hdpf-kappaP)(2)] (4), respectively. In situ neutralization of Hdpf followed by reaction with nickel(II) sulfate affords the salt [Ni(dpf)(2)] (5). The halide complexes 1-3 easily undergo dissociative decomposition in polar donor solvents; compound 5 is insoluble in all common solvents. All compounds were characterized by IR and UV/vis spectroscopies and magnetic measurements in the solid state. The solid-state structure of the solvate 4 . 2CHCl(3) was determined by single-crystal X-ray diffraction. A series of complexes, including the ligand Hdpf and its Ca salt (6) as reference compounds, were further studied by X-ray photoelectron spectroscopy. Spectral data and magnetic measurements indicate compound 5 contains the dpf(-) anion as a P,O-coordinated ligand.