Alkylvanadium‐ und Alkylniob‐Reagenzien, III. über zwei unkonventionelle Methoden zur Charakterisierung labiler Organoübergangsmetall‐Komplexe; Anwendungen auf Allylderivate von V III , V V , Cr III und Mn II

Alkylvanadium and Alkylniobium Reagents, III [1] . – Two Unconventional Chemical Methods for the Characterisation 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 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 3 , CrCl 3 , or MnCl 2 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 allylMCI (allyl) 2 M + MCl 2 (M = VCl, CrCl, 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 VCl 3 and corresponds with the observation that by chromation of allylMgBr with 1 equivalent of CrCl 3 ca. 50% of the CrCl 3 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 VOCl 3 gives three different allyl complexes which are believed to be allylVOCl 2 ( 5 ), (allyl) 2 VOCl ( 6 ), and (allyl) 3 VO ( 7 ). Vanadation of 1 or 2 equivalents of crotylMgBr with 1 or 2 equivalents of VCl 3 gives analogous results to the corresponding reactions with allylMgBr.