Notes. Synthesis and crystal structure of tris[bis(trimethylsilyl)amido]oxoniobium(V): a four-co-ordinated oxo niobium precursor

Abstract

The reaction between [NbCl₄(thf)₂](thf = tetrahydrofuran) and LiN(SiMe₃)₂ affords, by oxygen abstraction of the thf ligand, the first non-chlorine oxoamido derivative of niobium, [NbO{N(SiMe₃)₂}₃], (1). This novel compound could also be obtained directly from (NbOCl₃)_n, although in poor yield. Its monomeric nature was confirmed by X-ray analysis. The crystals are monoclinic, space group P2₁/n, with a= 12.352(12), b= 18.107(3), c= 15.036(14)Å, β= 101.83(5)°, and Z= 4. The structure was solved and refined on the basis of 4 585 significant counter data to a final R of 0.034. The steric hindrance of the bis(trimethylsilyl) amido ligand stabilizes a low co-ordination number, with a terminal NbO bond. Compound (1) also represents the first authentic four-co-ordinate niobium compound structurally characterized.