A contribution to the chemistry of organotransition metal halides

Abstract

Transition metal halides are often converted into more or less well-defined reduction products by Grignard reagents. organolithium and organoaluminium compounds. By means of less polar alkylating or arylating agents. such as zinc dialkyls. tin tetraalkyls and boron trialkyls. definite organotransition metal halides can be obtained. Alkyl and aryltitanium trihalides. alkyltungsten pentachlorides and complexes of alkylzirconium trihalides, dialkyizirconium dihalides and dialkylvanadium dichlorides. prepared in this way. are described and discussed. The chemistry of cs-transition metal compounds has been greatly developed in the last 10—15 years. The new compounds of this class of substances are predominantly such in which, besides cs-bonded organo-groups, ligands capable of forming it-bonds, such as carbon monoxide molecules or cyclopentadienyl groups are attached to the metal atoms. In this case, the it-bonded ligands ordinarily cause a rise in the stability of the cs-metal—carbon bonds. According to the kind of reflection, the conditions of the bonds at the transition metal atoms are more simple or more complicated if, except for the cs-bonded alkyl or aryl groups, only halogen atoms are attached to the metal atoms. However, it is not yet possible to give universal statements concerning this part of the chemistry of organotransition metals since the number of known and more precisely characterized organotransition metal halides is still very small. This is still a very undeveloped area of' organometallic chemistry, the treatment of which, however, requires a considerable amount of experimental work. Experiments to alkylate or arylate different transition metal halides were carried out even in the second half of' the last century. Zinc and mercury dialkyls or aryls and Grignard reagents and later organolithium compounds, were used predominantly, as alkylating agents. In many of these experiments the sensitivity of the expected compounds to air and moisture was not sufficiently taken into account. However, more important in all these former experiments was th fact that the small thermal stability of many organotransition metal compounds, which is well known today, was not expected at that time, and therefore, only more or less well-defined reduction products of the transition metal halides were obtained. However, the decomposition temperature of the desired organotransition metal halides