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)­AriPr6}2 [AriPr6 = C6H3-2,6-(C6H2-2,4,6-iPr3)2] (1) was synthesized via the reaction
of LiN­(H)­AriPr6 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)­ArMe6 with [V2Cl3(THF)6]+I– afforded
V­{N­(H)­ArMe6}2 [ArMe6 = C6H3-2,6-(C6H2-2,4,6-Me3)2] (2), which has a
nonlinear [N–V–N = 123.47(9)°] vanadium coordination.
Magnetometry studies showed that V­{N­(H)­AriPr6}2 and V­{N­(H)­ArMe6}2 have ambient temperature magnetic moments of 3.41 and 2.77
μB, 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 μB. 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 2 to
dry O2 resulted in the formation of the diamagnetic V­(V)
oxocluster [V­{N­(H)­ArMe6}2]2(μ-O–Li–O)2 (3).