Heterobimetallic Complexes That Bond Vanadium to Iron, Cobalt, and Nickel

Zero-valent iron, cobalt, and nickel were installed into the metalloligand V[N(o-(NCH₂P(ⁱPr)₂)C₆H₄)₃] (1, VL), generating the heterobimetallic trio FeVL (2), CoVL (3), and NiVL (4), respectively. In addition, the one-electron-oxidized analogues [FeVL]X ([2^ox]X, where X^- = BPh₄ or PF₆) and [CoVL]BPh₄ ([3^ox]BPh₄) were prepared. The complexes were characterized by a host of physical methods, including cyclic voltammetry, X-ray crystallography, magnetic susceptibility, electronic absorption, NMR, electron paramagnetic resonance (EPR), and Mössbauer spectroscopies. The CoV and FeV heterobimetallic compounds have short M-V bond lengths that are consistent with M-M multiple bonding. As revealed by theoretical calculations, the M-V bond is triple in 2, 2^ox, and 3^ox, double in 3, and dative (Ni → V) in 4. The (d-d)¹⁰ species, 2 and 3^ox, are diamagnetic and exhibit large diamagnetic anisotropies of '4700 × 10^-36 m³/molecule. Complexes 2 and 3^ox are also characterized by intense visible bands at 760 and 610 nm (ε > 1000 M^-1 cm^-1), respectively, which correspond to an intermetal (M → V) charge-transfer transition. Magnetic susceptibility measurements and EPR characterization establish S = ¹/₂ ground states for (d-d)⁹ 2^ox and (d-d)¹¹ 3, while (d-d)¹² 4 is S = 1 based on Evans' method.