Alkylvanadium and Alkylniobium Reagents, IIItlI. 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 and 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 VCl,, CrCl,, or MnCl, 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 (allyl),M + MC1, (M = VC1, CrC1, Mn) lies 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 VC13 and corresponds with the observation that by chromation of allylMgBr with 1 equivalent of CrC1, ca. 50% of the CrC1, remain unaffected although the allylMgBr is completely consumed. Conversely, according to the results of the "Competition Constant Method" vanadation of 1, 2, or 3 equivalents of allylMgBr with VOC1, gives three different allyl complexes which are believed to be allylVOClz (5), (allyl),VOCl (6), and (allyl),VO (7). Vanadation of 1 or 2 equivalents of crotylMgBr with 1 or 2 equivalents of VCl, gives analogous results to the corresponding reactions with allylMgBr.
