Activation of transition metalalkyl bonds in methyl titanium, trichloride, dialkyl(bipyridine)nickel and other transition metal alkyls by interaction with organoaluminum compounds

Abstract

Metalcarbon bonds of various alkyl-transition metal compounds including TiCH 3Cl 3, NiR 2Bipy, Cr(C 2H 5)Cl 2Py 3, FeR 2Bipy 2, CuCH 3(PPh 3) 3(C 6H 5CH 3) are activated and split on interaction with organoaluminum compounds [AlR′ 3 and AlR′ 2(OC 2H 5), where R′ = CH 3, C 2H 5, and n-C 3H 7]. Kinetics of the cleavage of the TiCH 3 bond in TiCH 3Cl 3 and NiR bonds in NiR 2Bipy in solutions containing the organoaluminum compounds were studied by volumetric and spectroscopic methods, respectively. In both cases the reactions were first order with respect to the concentrations of the alkyltransition metal compounds. The pseudo first order rate constants for the decomposition of NiR 2Bipy in THF solution on addition of AlR′ 3 were proportional to [AlR′ 3] for low concentrations of AlR′ 3 and to 1/[AlR′ 3] for high concentrations. Based on the kinetics, a mechanism is proposed which involves coordination of AlR′ 3 with NiR 2Bipy, and splitting the NiR bonds of the binuclear adduct thus formed. The decrease of the rate constants at higher concentrations of AlR′ 3 is attributed to displacement of the complexed organoaluminum component by interaction wit AlR′ 3·THF.