BETA-DIIMINATO COMPLEXES OF V-III AND TI-III - FORMATION AND STRUCTURE OF STABLE PARAMAGNETIC DIALKYLMETAL COMPOUNDS

(Mono-beta-diiminato)titanium(III) and -vanadium(III) dichlorides LMCl 2 [L = ArNC(R)CHC(R)NAr-] are easily accessible from the metal trichlo rides and LLi in THF. The crystal structures of LVCl2 (Ar = 2,6-iPr(2) C(6)H(3), R = Me) and LTiCl2 (Ar = 2,4,6-Me3C6H2, R = Me and Ar = 2,4, 6-Me3C6H2, R = tBu) reveal tetrahedral metal environments. Treatment o f LVCl2 with alkyllithium reagents affords surprisingly stable dialkyl vanadium(III) compounds; the structure of LV(nBu)(2) (Ar = 2,6-iPr(2)C (6)H(3), R = Me) is similar to that of the dichloride. The correspondi ng dialkyltitanium(III) compounds are less stable; only the dimethyl d erivatives could be obtained in pure form (from LTiCl2 and MeMgI), and only for ligands bearing 2,6-disubstituted aryl groups. The structure of LTiMe2 (Ar = 2,4,6-Me3C6H2, R = Me) is also similar to that of the dichloride. Reaction of LTiMe2 with B(C6F5)(3) produces a catalyst fo r alpha-olefin polymerization, but the corresponding V-III derivatives are inactive.