Synthesis and Molecular Structure of (C5Me5)2U(OtBu)(SePh): A Mixed-Ligand Alkoxide-Selenide Uranium(IV) Metallocene Complex Resulting from tert-Butoxy-Trimethylsilane Elimination

The title compound (C5Me5)(2)U((OBu)-Bu-t)(SePh) (1) was synthesized and characterized by NMR spectroscopy, elemental analysis, and X-ray crystallography. This system represents a unique example of an actinide complex with two different group 16 elements coordinated to the metal center and the first mixed-ligand actinide alkoxide-selenide complex. The complex crystallizes in the orthorhombic space group Pbca with unit cell parameters a = 17.830(7) , b = 14.973(6) , c = 21.254(8) , V = 5674(4) (3), Z = 8, D (calc) = 1.727 Mg/m(3). The uranium(IV) mixed-ligand alkoxide-selenide complex adopts a pseudo-tetrahedral geometry, with the tert-butoxide and phenylselenide ligands occupying the plane bisecting the metallocene unit. Structural comparisons of the complex (C5Me5)(2)U((OBu)-Bu-t)(SePh) (1) are made with related selenide and alkoxide uranium(IV) complexes. Reaction of (C5Me5)(2)U((OBu)-Bu-t)(2) with Me3Si-SePh affords the unusual alkoxide-selenide uranium(IV) complex (C5Me5)(2)U((OBu)-Bu-t)(SePh), which has been characterized by a combination of NMR spectroscopy, elemental analysis, and X-ray crystallography.