Polyhydride complexes of rhenium with the chelating ligand 1,2-bis(diphenylphosphinite)ethane

Abstract

The reaction of [ReOCl 3(AsPh 3) 2] with Ph 2POCH 2CH 2OPPh 2 (L) in refluxing THF yielded the complex [ReOCl 3L] ( 1). The new polyhydride [ReH 7L] ( 2) was obtained by treating 1 with NaBH 4 in absolute ethanol. The heptahydride 2 is stable in the solid state but in solution dimerises, giving [Re 2H 8L 2] ( 3). Polyhydrides 2 and 3 were characterised as classical species by variable-temperature NMR spectroscopy ( 1H and 31P) and T 1 measurements. The protonation of [ReH 7L] and [Re 2H 8L 2] in CH 2Cl 2-d 2 with HBF 4·Et 2O gave the hydride cations [ReH 6(η-H 2)L] + and [Re 2H 9L 2] +, which were characterised as non-classical and classical, respectively, on the basis of T 1(min) measurements. The reaction of 1 with PPh n (OR) 3− n (L′; n=1, 2; R=Me, Et) in refluxing THF gave [ReCl 3LL′] ( 4) in excellent yield. The complex [ReCl 3L{PPh(OEt) 2}] was converted to the pentahydride [ReH 5L{PPh(OEt) 2}] by treatment with NaBH 4 at room temperature.