The reaction of hexacarbonylvanadium with aromatic compounds. Part 4. Properties of tetracarbonylvanadium arene cations and the crystal and molecular structure of tetracarbonyl(1,2,4,5-tetramethylbenzene)vanadium(I) hexacarbonylvanadate(1—)

Abstract

Improved syntheses of the cationic arene complexes of vanadium(I), [V(CO)₄(C₆H_6-nMe_n)]⁺, are reported together with their ¹H n.m.r. spectra. An X-ray crystal and molecular structure determination of the title compound has been carried out. Crystals are monoclinic, space group P2₁/a, a= 18.135(5), b= 12.746(4), c= 10.025(4)Å, β= 93.03(2)°, and Z= 4. R= 0.072 for 1 007 observed reflections (Mo-K_α radiation). In the cation the vanadium atom is half-sandwiched between the arene ligand and the four carbonyl groups, the latter being oriented in such a way as to become eclipsed with respect to two of the methyl groups. The [V(CO)₆]^– anion is a nearly regular octahedron with a mean V–C distance of 1.93 Å and two sets of C–V–C angles, thus leading to a slight trigonal elongation of the octahedron.