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 ([2ox]­X, where
X– = BPh4 or PF6) and [CoVL]­BPh4 ([3ox]­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, 2ox, and 3ox, double in 3, and dative
(Ni → V) in 4. The (d–d)10 species, 2 and 3ox, are diamagnetic
and exhibit large diamagnetic anisotropies of −4700 ×
10–36 m3/molecule. Complexes 2 and 3ox 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 2ox and (d–d)11 3, while (d–d)12 4 is S = 1 based on Evans’ method.