Linear and Nonlinear Two-Coordinate Vanadium Complexes: Synthesis, Characterization, and Magnetic Properties of V(II) Amides

The synthesis and characterization of the first stable two-coordinate vanadium complexes are described. The vanadium­(II) primary amido derivative V­{N­(H)­Ar^{<i>i</i>Pr₆}}₂ [Ar^{<i>i</i>Pr₆} = C₆H₃-2,6-(C₆H₂-2,4,6-<i>i</i>Pr₃)₂] (<b>1</b>) was synthesized via the reaction of LiN­(H)­Ar^{<i>i</i>Pr₆} with the V­(III) complex VCl₃·2NMe₃ or the V­(II) salt [V₂Cl₃(THF)₆]⁺I^– in a 2:1 and 4:1 stoichiometry, respectively. Reaction of the less crowded LiN­(H)­Ar^Me₆ with [V₂Cl₃(THF)₆]⁺I^– afforded V­{N­(H)­Ar^Me₆}₂ [Ar^Me₆ = C₆H₃-2,6-(C₆H₂-2,4,6-Me₃)₂] (<b>2</b>), which has a nonlinear [N–V–N = 123.47(9)°] vanadium coordination. Magnetometry studies showed that V­{N­(H)­Ar^{<i>i</i>Pr₆}}₂ and V­{N­(H)­Ar^Me₆}₂ have ambient temperature magnetic moments of 3.41 and 2.77 μ_B, respectively, which are consistent with a high-spin d³ electron configuration. These values suggest a significant spin orbital angular momentum contribution that leads to a magnetic moment that is lower than their spin-only value of 3.87 μ_B. DFT calculations showed that the major absorptions in their UV–vis spectra were due to ligand to metal charge transfer transitions. Exposure of the reaction mixture for <b>2</b> to dry O₂ resulted in the formation of the diamagnetic V­(V) oxocluster [V­{N­(H)­Ar^Me₆}₂]₂(μ-O–Li–O)₂ (<b>3</b>)