New Molecular Niobium(IV) Complexes NbX4(OPPh3)2 (X = Cl, Br): Synthesis, Crystal and Electronic Structure

Abstract

New molecular niobium(IV) complexes NbCl₄(OPPh₃)₂(1) and NbBr₄(OPPh₃)₂(2) are synthesized by heating respective niobium pentahalide with a mixture of triphenylphosphine and triphenylphosphine oxide. For the obtained compounds the crystal structure is solved: 1P-1, a = 13.3540(5) Å, b = 9.4461(3) Å, c = 9.5635(3) Å, α = 93.084(1)°, β = 121.263(1)°, γ = 115.058(1)°, Z = 1, R₁ = 0.0194; 2P-1, a = 13.308(2) Å, b = 9.5934(8) Å, c = 9.5556(9) Å, α = 93.975(3),°, β = 119.391(4)°, γ = 114.740(4)°, Z = 1, R₁ = 0.0184. The unpaired electron is mainly located on the niobium atom, which is supported by quantum chemical calculations and EPR spectroscopic results.