Organometallic compounds metal olefin complexes

Although much of the chemistry of organometallics is of recent development, such compounds have been known for many years. Zeise s salt, a metal olefin complex having the formula K[Pt(C2H4)Cl3], was prepared in 1825. The first metal alkyl has been known since 1849 when Frankland prepared diethyl zinc by the reaction... 

In essence the active centers for catalytic polymerization of olefins are organometallic complexes of transition metals. For this reason a search for individual organometallic compounds that would possess catalytic activity in olefin polymerization is of great interest. The first attempts to use organometallic compounds of transition metals as catalysts for olefin polymerization were made long ago [e.g. CH3TiCl3 as a catalyst for polymerization of ethylene 116). However, only in recent years as a result of the application of relatively stable organometallic compounds of transition... 

Some attempts which I had made in 1946 to obtain PtPh2 or [PtPhJ from the reaction of phenylmagnesium bromide with [ PtCl2(C2H4)2 2] in ether had yielded biphenyl as the only pure solid product, and this served to confirm in my mind the belief that transition metals had no normal organometallic chemistry. I decided then to concentrate on the platinum(II)-olefin complexes. The first question was whether the olefin-metal bond used the d electrons normally involved in the oxidation of platinum(II) to platinum(IV) (valence d electrons) to bind the olefin, as required by such structures as (I), or whether, as was then generally believed, they were olefin coordination compounds formed independently of the presence of d electrons, even by Main Group element ions. 

Recent Developments in Theoretical Organometallic Chemistry, 15, 1 Redistribution Equilibria of Organometallic Compounds, 6, 171 Redistribution Reactions of Transition Metal Organometallic Complexes, 23, 9S Redistribution Reactions on Silicon Catalyzed by Transition Metal Complexes, 19, 213 Remarkable Features of (t) -Conjugated Diene) zirconocene and -hafnocene Complexes, 24, 1 Selectivity Control in Nickel-Catalyzed Olefin Oligomerization, 17, lOS Silyl, Germyl, and Stannyl Derivatives of Azenes, N H Part I. Derivatives of Diazene, N3H2, 23, 131... 

Apparently, the reactivity of organometallic compounds in the addition of olefins to Mt—C bonds is determined by the capability of these compounds to coordinate olefins. The formation of intermediate n-complexes ensures further insertion of olefin by a concerted mechanism with a low activation energy. Thus, a high reactivity of active centers, containing a transition metal, comparable to the reactivity of the radical active centers, is achieved. The activation energy of the propagation in olefin polymerization on catalysts containing transition metals (2-6 kcal/mol) does not exceed its value for the radical polymerization (Table 10). 

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