FORMATION AND CHARACTERIZATION OF THE UNSYMMETRICAL DIRHENIUM POLYHYDRIDES RE2H6(PME3)5 AND RE2H6(SBPH3)5 AND OBSERVATIONS CONCERNING THE MECHANISM OF THE CONVERSION OF RE2H8(PME3)4 TO [RE2H5(PME3)6]+

The reaction of Re2H8(PMe3)4with PMe3in methanol proceeds to give [Re2H5(PMe3)6]+via the intermediacy of Re2H6(P Me3)5and [Re2H7(PMe3)5]+, both of which have been isolated and characterized on the basis of their ’H and 3IP NMR spectra and their electrochemical properties. Measurements of the 1H NMR spectrum of Re2H6(PMe3)5in C7D8over the temperature range +50 to − 100 ° C show that this complex possesses the unsymmetrical structure (Me3P)3HRe(μ -H)3ReH2(PMe3)2, at least at low temperatures. A similar type of structure has been found in the solid state for Re2H6(SbPh3)5, a complex that is formed by the reaction of (n-Bu4N)2Re2Cl8with an excess of SbPh3and NaBH4in ethanol. A single-crystal X-ray structure determination on Re2H6(SbPh3)5has been carried out with the data collected at − 100 ° C. Crystal data are as follows: monoclinic space group P21/n, a = 13.287 (5) Â, b = 40.137 (8) Â, c = 14.392 (5) Â, β = 92.55 (2)°, V= 7667 (7) Â 3, and Z = 4. The structure was refined to R = 0.030 (Rw= 0.037) for 7182 data with / > 3.0 = r(I). The Re-Re distance is 2.5340 (6) Â, and all six hydride ligands (three terminal, three bridging) have be en located and refined. © 1990, American Chemical Society. All rights reserved.