Preparation, characterisation and reactivity of a series of classical and non-classical rhenium hydride complexes

Hydride complexes [ReH(CO)(4)L] 1, [ReH(CO)(3)L-2] 2, [ReH(CO)(2)L-3] 3 and [ReH(CO)L-4] 4 [L = P(OEt)(3) a, PPh(OEt)(2) b, PPh2(OEt) c or PPh2(OMe) d] were prepared by treating [ReH(CO)(5)] with the appropriate phosphite under UV irradiation or reflux. The complexes were characterised by IR, H-1, C-13 and P-31 NMR spectroscopy and by crystal structure determinations of Id and 2d. Protonation of the monocarbonyls I [ReH(CO)L-4] 4 in CD2Cl2 with HBF4.Et2O resulted in an equilibrium mixture of the classical dihydride complexes [ReH2(CO)L-4]+BF4- and their non-classical tautomers [Re(eta(2)-H-2)(CO)L-4]+BF4-. The dihydride [ReH2(CO){PPh(OEt)(2)}(4)]BPh4 was also isolated as a solid by protonation of [ReH(CO){PPh(OEt)(2)}(4)] in ethanol. Thermally unstable [Re(eta(2)-H-2)(CO)(4)L](+), [Re(eta(2)-H-2)(CO)(3)L-2](+) and [Re(eta(2)-H-2)(CO)(2)L-3](+) 7 cations were also prepared by protonation of the corresponding monohydrides 1, 2 and 3 and fully characterised in solution. The unsaturated complexes [Re(CO)(2)L-3]BPh4 and [Re(CO)L-4]BPh4 11 and the triflate [Re(eta(1)-OSO2CF3)(CO)(3)L-2] were obtained from the eta(2)-H-2, derivatives by evolution of H-2,. The new complexes [Re(C=CPh)(CO)(3)L-2], [Re(C=CPh)(CO)L-4] 13, [Re(4-MeC6H4CN)(CO)(2)L-3]BPh4, [Re(4-MeC6H4NC)(CO)(2)L-3]BPh4 and [Re(4-MeC6H4NC)(CO)L-3]BPh4 were prepared by treating the triflate compounds or the unsaturated compounds [Re(CO)(2)L-3]BPh4 and [Re(CO)L-4]BPh4 with Li+C=CPh- or with the appropriate ligand.