Mono- and Homobimetallic Vanadium Complexes: Borane Adducts of Vanada(IV)azirine Complexes

The reaction between [VCp2], BPh3, or BCl3 and the nitrile F3CC6H4C⋮N gives the borane
adduct of vanada(IV)azirine complex [VCp2{η2:C,N-F3CC6H4CN·BR3}] (R = Ph (2), Cl (3)).
Using B(C6F5)3 and dicyano compounds such as 1,4-benzene dicarbonitrile N⋮C(C6H4)C⋮N
and adiponitrile N⋮C(CH2)4C⋮N, an access to homobimetallic vanadium complexes was
obtained and complexes [(VCp2)2{η2:C,N-(C6F5)3B·NC(C6H4)CN·B(C6F5)3}] (6) and [(VCp2)2{η2:C,N-(C6F5)3B·NC(CH2)4CN·B(C6F5)3}] (8) are formed. Malononitrile N⋮CCH2C⋮N in
the presence of 2 equiv of B(C6F5)3 and 1 or 2 equiv of [VCp2] gave the monometallic complex
[(VCp2){η2:C,N-(C6F5)3B·NCCH2C⋮N·B(C6F5)3}] (7). Complexes 2, 3, 7, and 8 were
characterized by X-ray structure determination. All these complexes are paramagnetic to
one electron per vanadium.