Rhenium-(III) and -(V) hydride complexes with modified poly(pyrazolyl)borates

The hydrides [ReH2{kappa(3)-(OR)(mu-OR)B(pz)2}(PPh3)(2)] (R = Me 1 or Et 2) and [ReH4{kappa(3)-(H)(mu-OR)B(3,5-Me(2)pz)(2)}(PPh3)] (R = Me 3 or Et 4) have been obtained by treating [ReOCl3(PPh3)(2)] with Na[H2B(pz)(2)] or Na[ H2B(3,5-Me(2)pz)(2)] in alcohols (ROH, R = Me or Et) at room temperature. T he same type of reaction with Na[Ph2B(pz)(2)], using methanol as solvent, g ave [ReO(OMe){kappa(2)-Ph2B(OMe)(pz)}(2)] 5, although in a very low yield. The characterization of the new compounds involved IR and H-1 NMR spectrosc opies, (31)p-{H-1} NMR, variable temperature H-1 and P-31 NMR studies, T-1 and J(H-D) measurements. The crystal structures of the complexes 1, 4 and 5 were also determined. The structural parameters of the hydride ligands in 1 and 4 have not been obtained, but were tentatively assigned by X-ray diff raction associated with molecular orbital calculations of ab initio and ext ended Huckel type.