Spectroscopic characterization of primary and secondary phosphine ligation on ruthenium(II) complexes

Ruthenium(II) complexes of the primary phosphines PH2Fc and PH2CH2Fc and the secondary phosphine PH(CH2Fc)2, including [(p-cymene)RuCl(L)2](PF6) (p-cymene = p-iPrC6H4Me, L = PH2CH2Fc and PH(CH2Fc)2, 2b and 2c, respectively) and trans-[RuCl2(L)4] (L = PH2Fc, PH2CH2Fc, and PH(CH2Fc)2, 3a-c, respectively) were prepared and characterized by IR, 1H NMR, and 31P NMR spectroscopy. 3b was additionally characterized by X-ray crystallography. The spectroscopic effects of phosphine ligation were determined. Characteristic downfield shifts of the 31P NMR resonances and increases in energy of the nu(P-H) modes were observed in all cases. Iterative fitting of coupling constants to second-order NMR spectra also resulted in a complete elucidation of 31P-1H and 31P-31P couplings. This analysis provides a basis for considering the influence of coordinate bonding on the observed 1J(PH) and 2J(PP) constants.