Rhenium complexes of P,P,P′,P′-tetrakis(o-hydroxyphenyl)diphosphinoethane

Preparation of the hydrochloride salt of a new potentially hexadentate ligand precursor P,P,P′,P′-tetrakis(o-hydroxyphenyl)diphosphinoethane dihydrochloride (abbreviated H4P2O4•2HCl) is described. From H4P2O4•2HCl, neutral [Re2O2Cl2(PPh3)2(μ-P2O4)] and dianionic [Re2O2Br4(μ-P2O4)]2− dinuclear rhenium(V) complexes were synthesized. The complexes have been characterized by elemental analysis, infrared spectroscopy, mass spectrometry, and 1H/31P{1H} NMR spectra. 31P{1H} NMR revealed that only one isomer, presumably the anti, was present for [Re2O2Cl2(PPh3)2(μ-P2O4)], and that two isomers, both anti and syn isomers, were observed for [Re2O2Br4(μ-P2O4)]2−. The coligands (PPh3 for the former, Br− for the latter) of both complexes underwent ligand exchange with pyridine.