Cyclopentadienyl organometallic chemistry

Indeed, it is the cyclopentadienyls which provide the major part of the organometallic chemistry of this group and they are known for metal oxidation states of IV, III and II though III... 

Bis(cyclopentadienyl) complexes are central to the organometallic chemistry of the early transition metals and feature in applications such as alkene polymerization chemistry. Parallels can be drawn between a porphyrin ligand and two cyclopentadienyl ligands, in that they both contribute a 2— formal charge and exert a considerable steric influence on other ligands in the same molecule. Several of the metalloporphyrin complexes discussed below have bis(cyclopentadienyl) counterparts, and authors in some ca.ses have drawn quite detailed comparisons, although these discussions will not be repeated here. 

No attempt to cover the coordination chemistry of unsaturated cyclic anions such as cyclopentadienyl is made here, due to their coverage in the companion series on Comprehensive Organometallic Chemistry. The only example to be mentioned here, because it is the first example of a high-spin Co11 organometallic complex, is Co(Cp)(Tp).196... 

All these properties but the first and the last are also typical for cyclopentadienyl ligands, which are used extensively in organometallic chemistry. In organosilicon chemistry, the first stable monomeric silicon(II) derivative could be isolated with the aid of these ligands [3], It therefore seemed challenging to investigate the interaction of phosphinomethanides I with silicon centers. 

Despite a common perception that organometallic chemistry essentially belongs in the province of catalysis rather than in vivo applications because of high reactivity of metal carbon bonds, certain organometallic species have very high kinetic stability. Indeed, this point is highlighted by the present wide application of the isonitrile complex Tc(ses-tamibi), [Tc(2-methoxyisobutylisonitrile)6]+, in myocardial imaging. Rhenium tricarbonyl and cyclopentadienyl complexes offer further ex-... 

Of course, it is not without precedence as there are already various reviews and textbooks in the area. Most closely related to this work are the reviews by Setzer and Schleyer and by Weiss °. A textbook edited by Sapse and Schleyer contains chapters on various topics of lithium chemistry. Three reviews by StaUce, Harder and by Jutzi and Burford concentrate on cyclopentadienyl organometallic derivatives, containing also the s-block derivatives. Two reviews deal with the heavier alkali metal organics, the first written by Schade and Schleyer , the second by Smith . There are several chapters on lithium organics within more general metal organic publications ... 

The original concepts of metal-ligand bonding were essentially related to the dative covalent bond the development of organometallic chemistry has revealed a further way in which ligands can supply more than one electron pair to a central atom. This is exemplified by the classical cases of bis(benzene)chromium and bis(cyclopentadienyl)iron, trivial name ferrocene. These molecules are characterised by the bonding of a formally unsaturated system (in the organic chemistry sense, but expanded to include aromatic systems) to a central atom, usually a metal atom. 

The discovery and structural elucidation of ferrocene in 1951 and the subsequent development of metal-cyclopentadienyl chemistry started a new era in organometallic chemistry . 

The organometallic chemistry of the first-row transition metals generally starts with the binary metal carbonyl organometallic complexes. Noncarbonyl organometallic complexes starting with other easily accessible binary compounds provide entries to a broader spectrum of complexes. In this context, we describe the synthesis of the mixed sandwich complex (tj5-pentamethylcyclopentadienyl) ( j5-cyclopentadienyl) iron as an example of the synthetic utility of the solution-stable derivative (>j5-pentamethyl-cyclopentadienyl) (2,4-pentanedionate) iron. 

In view of the ubiquity of the 5-cyclopentadienyl ligand in organometallic chemistry, and the reports in the literature of perchlorocyclopentadienyl analogues (56), it is both curious and unfortunate that attempts (85) to prepare complexes of the /5-pentafluorocyclopentadienyl ligand from the known C5F j anion (87,88) have failed. 

Fluxional and Nonrigid Behavior of Transition Metal Organometallic ir-Complexes, 16, 211 Free Radicals in Organometallic Chemistry, 14, 345 Functionally Substituted Cyclopentadienyl Metal Compounds, 21,1... 

Cyclopentadienide (Cp) 1 is well known as one of the most frequently used ligands in organometallic chemistry. In addition, the cyclopentadienide anion 1 has always been quoted as a classic example of Hiickel aromaticity, to demonstrate along with benzene and the cydoheptatrienyl cation the validity of the (4n + 2) -electron rule. In contrast, a simple and stable cyclopentadienyl cation of the type 1+ remains to be elusive [5]. With the highly unstable neutral cyclobutadiene and the cydoheptatrienyl anion, 1+ shares the character-... 

Arene ruthenium and osmium complexes play an increasingly important role in organometallic chemistry. They appear to be good starting materials for access to reactive arene metal hydrides or 16-electron metal(O) intermediates that have been used recently for carbon-hydrogen bond activation. Various methods of access to cyclopentadienyl, borane, and carborane arene ruthenium and osmium complexes have been reported. 

The organometallic chemistry of halocarbonyl complexes of molybde-num(II) and tungsten(II) has been extensively studied since the early report in 1956 by Piper and Wilkinson1 of the cyclopentadienyl halocarbonyl complexes [MoX(CO)3Cp] (X = Cl, Br, I). More than 700 references of relevance to the review were collected up to June 1995, and hence some selection had to be made. The review is concerned with molybde-num(II) and tungsten(II) complexes containing both carbon monoxide and at least one halide ligand. The review is mainly restricted to the formation of complexes with those ligands as the final products of reactions, and not reactions of this type of complex. 

Cyclopentadiene (1), a simple organic compound first found in the volatile parts of coal tar, has become one of the most important ligands used in organometallic chemistry. More than 80% of all known organometallic complexes of the transition metals contain the cyclopentadienyl fragment or a derivative thereof. 

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