Cyclopentadienyl and arene complexes

Cyclopentadienyl and Arene Complexes Cyano and Isonitrile Complexes... 

COMC(6)447R P M. Maitlis, P Espinet, and M. J. H. Russell, Comp. Organomet. Chem., 1982, 6, 447 54. Cyclopentadienyl and Arene Complexes of Palladium(II). II... 

The organisation of this Report is similar to that of Volume 13. Cyclopentadienyl and arene complexes that contain metal-metal bonds, carbene, carbyne, or hydrocarbyl ligands, and reactions that involve replacement or elaboration of other ligands present, generally are not included (see Chapters 9-13). Only those metalla-borane and -carbaborane complexes that also incorporate a Cp or arene ligand are described, and crystal-structure determinations are included only where results of particular significance or solutions to structural problems are provided. 

R. Pettit and G. F. Emerson, Advances in Organometallic Chemistry 1, 1964, 1. Cyclopentadienyl and arene complexes. Reviews of early work... 

Wigley, David E., Organoimido Complexes of the Transition Metals Wilkinson, G. and Cotton, F. A., Cyclopentadienyl and Arene Metal 42 239... 

Several cyclopentadienyl- and arene-substituted allyl complexes of the group-VIA metals are made by treating halo complexes with organomagnesium halides or tetrallyl-tin, e.g. ... 

By 1957, a variety of both 7r-cyclopentadienyl and arene-metal complexes was known, and it was interesting to determine whether mixed-sandwich complexes containing both of these ligands around the same could be produced. Two early examples of such complexes are given below ... 

A modern series of new plastics are based on transition metals (e.g. Fe, Ti, Cr, Zn, V) to form polymers and possess unusual properties such as variable oxidation states, and ligand exchange on the metal atom. They have reduced UV absorption and visible radiation and exhibit electrical conductivity. Examples include cyclopentadienyl and arene metal n polymeric complexes that act as electron rich aromatic system and are very reactive to a range of monomers to form polymers. 

Contrary to organometallic complexes bearing cyclopentadienyl and arene ligand, there are few reports concerning this class of second-sphere coordination adducts. In 1986, Harada and Takahashi reported that /3-CD and 7-CD can... 

Transition metal complexes self-assembled via Tc-interactions are not large in number, although some very interesting examples have been reported. This area of organometallic chemistry is far from being systematically investigated and it is quite difficult to make any predictions concerning possible supramolecular structures of particular compounds. With the exception of several polymeric olefin and arene complexes, the majority of the complexes described in this section are cyclopentadienyl derivatives. 

The complexation of unsaturated hydrocarbons by transition metals is a powerful activation method that plays a fundamental role in their stoichiometric and catalytic transformation. The bonds formed are governed by jt backbonding. Olefins, dienes and arenes are usually 2-electron L, 4-electron L2, and 6-electron L3 ligands respectively, and alkynes are 2-electron L or 4-electron L2 depending on the needs of the metal. The odd-electron ligands are the 3-electron LX allyl radical and 5-electron L2X dienyl radicals. Cyclopentadienyl and arene sandwich complexes will be examined in Chap. 11. 

Cyclopentadienyl-metal-arene complexes are mostly known with Fe and Ru. The CpM group (M = Fe or Ru) activates many aromatic syntheses (nucleophilic addition and substitution, benzylic deprotonation, etc.). With Fe, they are stable in the 17, 18 and 19e forms with perme-thylated rings, which provides electron-reservoir properties (stoichiometric and catalytic) and proton-reservoir functions (perfunctionalization of polymethylbenzene ligands). 

The classification of metal 7r-complexes has customarily been based on the types of organic 7c-ligands rather than on the metal elements in the TT-complex. In accordance with this classification, the three major groups of olefin, Ti-cyclopentadienyl, and arene metal Tc-complexes as well as their subgroups are described in the following by illustration of typical 7c-complexes. 

The reaction of the appropriate Grignard reagent with selected transition metal halides provides a very useful method for the preparation of many cyclopentadienyl and arene Tc-complexes. The reaction of cyclopentadienyl-magnesium bromide with ferric chloride constituted the original method for the preparation of ferrocene (2-26). 

R. L. Pruett, in Preparative Inorganic Reactions , Volume 2, edited by W. L. Jolly (Intersdence, New York, 1965), p. 187. Preparation of cyclopentadienyl and arene metal complexes. 

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