ALKYLVANADIUM AND ALKYLNIOBIUM REAGENTS . 3. 2 UNCONVENTIONAL CHEMICAL METHODS FOR THE CHARACTERIZATION OF LABILE TRANSITION-METAL COMPLEXES - APPLICATION TO ALLYL DERIVATIVES OF V(III), V(V), CR(III), AND MN(II)

Two little known chemical methods, the ''Competition Constant Method'' and the production of ''Ligand Concentration/Product Yield Diagrams'' , are suitable for the characterisation and identification of allyl an d crotyl transition metal species prepared in solution. These methods (Figures 1-6) gave the following results: by transmetallation of 1 or 2 equivalents of allylMgBr with 1 equivalent of VCl3, CrCl3, or MnCl2 and subsequent reaction with ketones, a diallyl (2, 23, 25) and not a monoallyl derivative of the transition metal reacts with the ketones, suggesting that the equilibrium: 2 allylMCl half arrow pointing right over half arrow pointing left (allyl)2M + MCl2 (M = VCl, CrCl, Mn) lie s far to the right hand side. This assumption was confirmed by the IR spectrum in the case of vanadation of 1 and 2 equivalents of allylMgBr with VCl3 and corresponds with the observation that by chromation of allylMgBr with 1 equivalent of CrCl3 ca. 50% of the CrCl3 remain unaff ected although the allylMgBr is completely consumed. Conversely, accor ding to the results of the ''Competition Constant Method'' vanadation of 1, 2, or 3 equivalents of allylMgBr with VOCl3 gives three differen t allyl complexes which are believed to be allylVOCl2 (5), (allyl)2VOC l (6), and (allyl)3VO (7). Vanadation of 1 or 2 equivalents of crotylM gBr with 1 or 2 equivalents of VCl3 gives analogous results to the cor responding reactions with allylMgBr.