Actinide hydride complexes as multielectron reductants:: Analogous reduction chemistry from [(C5Me5)2UH]2, [(C5Me5)2UH2]2, and [(C5Me5)2ThH2]2

Methods to separate the components of the equilibrium mixture of [(C5Me5)(2)UH](2) and [(C5Me5)(2)UH2](2) have been developed that allow their reductive chemistry to be studied. These actinide hydrides can act as four-, six-, and eight-electron reductants depending on the substrate with H-2 as the byproduct of a H- -> e(-) + (1)/(2) H-2 redox couple. This hydride reduction chemistry allows complexes of redox-inactive Th4+ such as [(C5Me5)(2)ThH2](2) to be four- and six-electron reductants. [(C5Me5)(2)UH](2) and [(C5Me5)(2)UH2](2) cleanly reduce 2 equiv of PhEEPh (E = S, Se) to form 2 equiv of (C5Me5)(2)U(SPh)(2) and (C5Me5)(2)U(SePh)(2) in an overall four-electron reduction in each case. [(C5Me5)(2)UH](2) and [(C5Me5)(2)UH2](2) also effect a six-electron reduction of 3 equiv of 1,3,5,7-cyclooctatetraene to [(C5Me5)(C8H8)U](2)(C8H8) and an eight-electron reduction of 2 equiv of PhNNPh to form 2 equiv of the U6+ imido complex (C5Me5)(2)U(NPh)(2). In each reaction, H-2 is a byproduct. This hydride-based reduction is also successful with the tetravalent thorium hydride [(C5Me5)(2)ThH2](2), which reduces 2 equiv of PhSSPh to (C5Me5)(2)Th(SPh)(2) and 3 equiv of C8H8 to [(C5Me5)(C8H8)Th](2)(C8H8) with concomitant formation of H-2. X-ray crystallographic data are reported on [(C5Me5)(2)UH](2), [(C5Me5)(2)UH2](2), and (C5Me5)(2)U(SePh)(2) as well as the thorium reduction products (C5Me5)(2)Th(SPh)(2) and [(C5Me5)(C8H8)Th](2)(C8H8).