Resumen de Synthesis, spectroscopic studies and structural systematics of phosphine oxide complexes with Group II metal (beryllium¿barium) nitrates

W. Levason, M. F. Davis

• Complexes of the nitrates of beryllium, magnesium, calcium, strontium and barium with the phosphine oxides OPPh3, Ph2P(O)CH2P(O)Ph2, and o-C6H4(P(O)Ph2)2 have been prepared and characterised by analysis and IR spectroscopy and the structures of [Be(OPPh3)2(NO3)2], [Mg(OPPh3)2(NO3)2], [Ca{Ph2P(O)CH2P(O)Ph2}2(NO3)2] and [Ca{o-C6H4(P(O)Ph2)2}2(NO3)2] have been determined. The solution speciation has been probed by a combination of 1H, 31P{1H} and 9Be NMR spectroscopy and conductance measurements. The variation in speciation and stability from Be–Ba is interpreted in terms of changes in the charge/radius ratio of the cations—thus whilst Be and Mg interact strongly with the phosphinoyl ligands, strontium and especially barium have very limited affinity for these ligands, and the complexes are extensively dissociated in solution.