Monomeric, Divalent Vanadium Bis(arylamido) Complexes: Linkage Isomerism and Reactivity

Divalent complexes of vanadium were synthesized employing bulky silyl­(aryl)­amido ligands −N­(SiiPr3)­DIPP and −N­(SitBu2Me)­DIPP (DIPP = 2,6-iPr2C6H3). Solid-state structural characterization revealed that although the ligand −N­(SiiPr3)­DIPP supports a monomeric, bis­(amido) complex of vanadium, its constitutional isomer −N­(SitBu2Me)­DIPP affords a homoleptic complex in which the vanadium center is sandwiched between the arene rings, an unusual binding mode for arylamido ligands. Magnetometry studies indicate that V­[N­(SiiPr3)­DIPP]2 and V­[(η5-DIPP)­N­(SitBu2Me)]2 have similar high-spin d3 electron configurations. However, spectroscopic methods, including electron paramagnetic resonance, nuclear magnetic resonance, infrared, and UV–visible spectroscopies, in addition to cyclic voltammetry and reactivity studies, suggest that V­[N­(SiiPr3)­DIPP]2 is stereochemically nonrigid in solution, while V­[(η5-DIPP)­N­(SitBu2Me)]2 is not. This nonrigidity explicitly impacts the reactivity of V­[N­(SiiPr3)­DIPP]2, which can be used to access both amido-bound and arene-bound complexes. Moreover, treatment of V­[N­(SiiPr3)­DIPP]2 with single and multielectron oxidants reveals a range of transformations including an intramolecular sp3 C–H bond activation.