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

The reaction of [ReOCl3(AsPh3)2] with Ph2POCH2CH2OPPh2 (L) in refluxing THF yielded the complex [ReOCl3L] (1). The new polyhydride [ReH7L] (2) was obtained by treating 1 with NaBH4 in absolute ethanol. The heptahydride 2 is stable in the solid state but in solution dimerises, giving [Re2H8L2] (3). Polyhydrides 2 and 3 were characterised as classical species by variable-temperature NMR spectroscopy (1H and 31P) and T1 measurements. The protonation of [ReH7L] and [Re2H8L2] in CH2Cl2-d2 with HBF4·Et2O gave the hydride cations [ReH6(η-H2)L]+ and [Re2H9L2]+, which were characterised as non-classical and classical, respectively, on the basis of T1(min) measurements. The reaction of 1 with PPhn(OR)3−n (L′; n=1, 2; R=Me, Et) in refluxing THF gave [ReCl3LL′] (4) in excellent yield. The complex [ReCl3L{PPh(OEt)2}] was converted to the pentahydride [ReH5L{PPh(OEt)2}] by treatment with NaBH4 at room temperature.