Divergent uranium- phosphorus-based reduction of MeSiN with steric modification of phosphido ligands.

We describe an example of a two-electron metal- and ligand-based reduction of MeSiN using uranium(iv) complexes with varying steric properties. Reaction of (CMe)U(CH)[P(SiMe)(Ph)] with MeSiN produces the imidophosphorane complex, (CMe)U(CH)[N[double bond, length as m-dash]P(SiMe)(Ph)] through oxidation of phosphorus. However, a similar reaction with a more sterically encumbering phosphido ligand, (CMe)U(CH)[P(SiMe)(Mes)] forms the U(iv) complex, (CMe)U[ -(,)-N(SiMe)P(Mes)N(SiMe)]. In probing the mechanism of this reaction, a U(vi) bis(imido) complex, (CMe)U([double bond, length as m-dash]NSiMe){[double bond, length as m-dash]N[P(SiMe)(Mes)]} was isolated. DFT calculations show an intramolecular reductive cycloaddition reaction leads to the formation of the U(iv) bis(amido)phosphane from the U(vi) bis(imido) complex. This is a rare example of the isolation of a reaction intermediate in element chemistry.