Small molecule activation by plutonium(III) and uranium(III) organometallic complexes

The activation of small molecules by organometallic complexes across the periodic table, as far as uranium, have transformed our understanding of electronic structure and bonding. Here, we report the transuranic PuIII cyclopenta-dienyl complex, [PuIII(CpMe4)3] (1-Pu), and demonstrate its differences in small molecule reactivity compared to the known UIII analogue, [UIII(CpMe4)3] (1-U). Complex 1-Pu reductively cleaves the small molecule diphenyldisulfide, (PhS)2 through a mechanistic pathway different to complex 1-U, and does not react with 1,2-diphenylhydrazine, (PhHN)2, whereas 1-U reductively cleaves both (PhS)2 and (PhHN)2. The (PhS)2 cleavage by 1-Pu and 1-U affords the new bimetallic, phenylsulfido-bridged PuIII complex, [{PuIII(CpMe4)2}2(mu-SPh)2] (2-Pu) via {CpMe4}1- elimination, and the UIV terminal sulfido complex, [U(Cp Me4)3(SPh)] (3-U) from oxidation of the UIII ion, respectively. The reductive cleavage of (PhHN)2 by 1-U forms an analogous UIV terminal amido complex, [U(CpMe4)3(NHPh)] (4-U). Combined experimental data and DFT calculations suggest the reductive transformations are enabled through sterically in-duced reduction (SIR) and metal-promoted reductive cleavage pathways for Pu and U, respectively.