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 [(C 5 Me 5 ) 2 UH] 2 and [(C 5 Me 5 ) 2 UH 2 ] 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 Th 4+ such as [(C 5 Me 5 ) 2 ThH 2 ] 2 to be four- and six-electron reductants. [(C 5 Me 5 ) 2 UH] 2 and [(C 5 Me 5 ) 2 UH 2 ] 2 cleanly reduce 2 equiv of PhEEPh (E = S, Se) to form 2 equiv of (C 5 Me 5 ) 2 U(SPh) 2 and (C 5 Me 5 ) 2 U(SePh) 2 in an overall four-electron reduction in each case. [(C 5 Me 5 ) 2 UH] 2 and [(C 5 Me 5 ) 2 UH 2 ] 2 also effect a six-electron reduction of 3 equiv of 1,3,5,7-cyclooctatetraene to [(C 5 Me 5 )(C 8 H 8 )U] 2 (C 8 H 8 ) and an eight-electron reduction of 2 equiv of PhN NPh to form 2 equiv of the U 6+ imido complex (C 5 Me 5 ) 2 U( NPh) 2 . In each reaction, H 2 is a byproduct. This hydride-based reduction is also successful with the tetravalent thorium hydride [(C 5 Me 5 ) 2 ThH 2 ] 2, which reduces 2 equiv of PhSSPh to (C 5 Me 5 ) 2 Th(SPh) 2 and 3 equiv of C 8 H 8 to [(C 5 Me 5 )(C 8 H 8 )Th] 2 (C 8 H 8 ) with concomitant formation of H 2 . X-ray crystallographic data are reported on [(C 5 Me 5 ) 2 UH] 2, [(C 5 Me 5 ) 2 UH 2 ] 2, and (C 5 Me 5 ) 2 U(SePh) 2 as well as the thorium reduction products (C 5 Me 5 ) 2 Th(SPh) 2 and [(C 5 Me 5 )(C 8 H 8 )Th] 2 (C 8 H 8 ).