Metallkomplexe der Phosphinsäuren. XVIII. Ansa- und Oligokomplexe bifunktioneller Dithiophosphinsäuren

Metal Complexes of Phosphinic Acids. XVIII. Ansa- and Oligo-Complexes of Bifunctional Dithiophosphinic Acids The influence of R′ in the bifunctionell chelate ligands ^?S(S)P(R)? R′? (R)P(S)S^? on the association of their planar Ni^II and tetrahedral Co^II complexes is investigated by vapour pressure osmometry and in the case of diamagnetic Ni^II compounds also by ³¹P-NMR spectroscopy. While insoluble coordination polymers S₂P(R)? R′? (R)PS₂M]_x (M = Ni^II, Co^II) are formed with R′ = p-(C₂H₄)₂C₆H₄ it can be shown, that in solutions of the complexes with R′ = o-(C₂H₄)₂C₆H₄ and R′ = o-(C₃H₆)₂C₆H₄ there exists an association equilibrium comprehending oligomers with n ? x. Above all in the latter case steric conditions seem to favour intramolecular chelating and thus formation of ansa-type complexes. Synthesis of the ligands and the complexes is described.