Formation of Alkyl and Aryl Titanium-Carbon Bond Compounds

Abstract

The first compound synthesized and isolated, contain ing a titanium-carbon bond was phenyltitanium triisopropoxide. Much information was accumulated related to the preparation and properties of organotitanium compounds of the type R n TiX 4-n , where R could be alkyl or aryl groups and X could be alkoxy groups or halogen. The organotitanium compounds can exist at various valence levels. Compounds of the type R n TiX m can exist when the sum of n and m is 2 or 3. These materials, although more stable than quadrivalent organotitanium compounds, exhibit some thermal instability and act as catalysts for polymerization. Reduction of titanium com pounds by organometallic reagents takes place through the intermediate formation of an organo titanium compound. Reduction proceeds only to the extent of giving a mixture of bi-and trivalent compounds even in the presence of excess Grignard reagent. Reaction of the lower valent titanium com pounds with the solvent may account for this.Alkyl and aryl organometallic compounds containing direct carbon to titanium bonds are discussed. These carbon-metal bonds are of at least partial covalent character. New work is described which further elucidates the nature of the organotitanium com pounds formed on reaction of organometallic reagents with titanium esters or chlorides at varying molar ratios. Conclusions or proposed structures are based upon diagnostic tests and chemical analyses similar to those by Herman and Nelson (8).Although most of the compounds described are diffcult to handle and even more difficult to isolate in purified state, they are increasingly important as catalysts in heterogeneous polymerization. This field has grown rapidly since Ziegler's announce ment (18) of the low pressure polymerization of ethylene by means of catalysts formed by the interaction of organometallic reagents, such as org a no aluminum compounds, with various derivatives of titanium.The initial attempt to prepare a stable and isolatable organotitanium compound was made in 1861 by Cahours (3). Many further attempts were also unsuccessful (1,2,4,7,(10)(11)(12)(13)(14)16)· Under some circumstances, organotitanium products of a transi tory nature may have been formed in solution, especially in the reactions of titanium 265Downloaded by MICHIGAN STATE UNIV on February 18, 2015 |

A contribution to the chemistry of organotransition metal halides

“…The most important reactions by which methyltitanium trichloride can be prepared are represented by the following equations. TiCl4 + Al(CH3h~e;~n~ (CH3h TiCl2 + CH3AICI2 (6) After Beermann and Bestian 1 had given the tirst report ab out the preparation of methyltitanium trichloride from titanium tetrachloride and diethylaluminium chloride in 1959, another method of the preparation, the reaction of titanium tetrachloride with dimethylzinc, was found in 1961 by de Vries 2 .…”