Synthesis and characterization of new hydrotri(3,5-dimethyl-1-pyrazolyl)borate vanadium halfsandwich complexes

Paramagnetic vanadium(III) complexes of the type Tp*VCl2(L) were prepared by replacing the dimethylformamide ligand in Tp*VCl2(dmf) (1) by various N-containing heterocycles. The new compounds Tp*VCl2(L) (L=4 substituted pyridine NC5H4-R(4) (R = H (3a), CH3 (3b), C2H5 (3c), Ph (3d)), pyridazine (4), pyrimidine (5), pyrazine (6), imidazole (7a), 1-methylimidazole (7b), 1,2-dimethylimidazole (7c), and 4,4'-bipyridine (8)) were characterized by IR and mass spectroscopy, and the molecular structure of 3b was determined by X-ray crystallography. A binuclear product, [Tp*Cl2V](2)(L-L) (9),containing 4,4'-bipyridine (L-L) as bridging ligand, and the dimethyl sulfoxide complex, Tp*Cl-2(O=SMe2) (10), were also investigated. Reactions of 1 with phenol and triethylamine in the presence of air gave Tp*V(O)(OPh)(2) (11). Other diamagnetic vanadium(V) complexes such as Tp*V((NBu)-Bu-t)(SR)(2) (R = Et (12a), Ph (12b) and Tp*V((NBu)-Bu-t)(S2C6H4) (12c)) were obtained from the tert-butylimido compound Tp*V((NBu)-Bu-t)Cl-2 (2) and the appropriate thiol in the presence of the base triethylamine. The H-1, C-13 and V-51 NMR spectra of 2, 11 and 12a-c are reported. (C) 1998 Elsevier Science S.A.