Synthesis and characterization of two novel cobalt (II) phosphine complexes: crystal structures of [CoCl3(Cy2PCH2PCy2H)] and [Co(NO3)2(Cy2PCH2PCy2O)]. Cy = cyclohexyl, C6H11

The complexes [(Cy2PCH2PCy2H)CoCl3] (1) and [(Cy2PCH2PCy2O)Co(NO3)2] (2), Cy = cyclohexyl (C6H11), have been prepared and characterized by EPR, UV–Vis, microanalysis and X-ray crystallography. The reaction CoCl2 · 6H2O and dcpm, dcpm = bis(dicyclohexylphosphino)methane, was found to form the monomeric, four coordinate, thermochromic and paramagnetic complex [(Cy2PCH2PCy2H)CoCl3] (1). Of particular interest is the formation of a zwitterion, or inner salt, in which the dangling phosphine adds a hydrogen atom, giving the phosphorus a +1 formal charge. The molecule adopts a pseudo-tetrahedral geometry around the central cobalt atom to which the cyclohexyl groups bind in an equatorial fashion to the phosphine. The reaction of Co(NO3)2 · 6H2O and dcpm in a toluene/methanol/methylene chloride mixture yields the pseudo-octahedral complex [(Cy2PCH2PCy2O)Co(NO3)2] (2). The cobalt is in the +2 oxidation state with one of the phosphorus atoms again having a +1 formal charge. The complex adopts a pseudo-octahedral geometry around the central cobalt atom with the cyclohexyl groups binding in an equatorial fashion to the phosphine similar to [(Cy2PCH2PCy2H)CoCl3].