Synthesis and characterization of Ru(II) and Ru(III) complexes of diphenylphosphinoacetic acid and their interaction with small molecules

Abstract

Complexes of Ru(II) and Ru(III) with the bidentate ligand diphenylphosphinoacetic acid (POH) are reported. The ligand POH reacts with RuCl 2(PPh 3) 3 in a 1:3 ratio to give a five-coordinate complex of composition Ru(PO) 2(POH) with complete displacement of PPh 3. In a 1:2 ratio however the complex Ru(PO) 2(PPh 3) is formed. The reaction of POH with RuCl 2(DMSO) 4 in a 2:1 ratio afforded a yellow complex of composition HRu(PO) 2Cl(DMSO). In a 3:1 ratio of POH to RuCl 2(DMSO) 4 however, the complex HRu(PO) 3 was obtained. Neutral complexes of the composition Ru(PO) 2Cl(AsPh 3) and Ru(PO) 3 were obtained by the reaction of RuCl 3(AsPh 3) 2·MeOH with POH in 1:2 and 1:3 mole ratios in acetone solution, respectively. A dimeric chloro bridged complex of composition [Ru(PO) 2Cl] 2 was obtained on reaction of RuCl 33H 2O with POH in methanol. The complexes have been characterized on the basis of elemental analysis 1H, 13C{ 1H} and 31P{ 1H} NMR, EPR and electrochemical studies. The square pyramidal complexes 1 and 2 undergo facile addition reactions with CO, H 2, PPh 3 and DMSO to form octahedral species. The redox potentials Ru III/Ru II of the complexes become more positive with an increase in the π-acidity of the ligand coordinated to the metal ion.