Cyclopentadienyl complexes anionic

Another route to complexes with a,/i-unsaturated acyl ligands involves reaction of the dicar-bonyl(r/5-cyclopentadienyl)iron anion of 12 with a,/ -unsaturated acyl halides38. 

Electrochemical oxidation of the M(IV) bis-cyclopentadienyl complexes such as [Mo( j -C5H5)2X2], where X is an anionic ligand, have been widely studied. Invariably, such complexes undergo reversible oxidation to the M(V) species... 

This review deals with metal-hydrocarbon complexes under the following headings (1) the nature of the metal-olefin and -acetylene bond (2) olefin complexes (3) acetylene complexes (4) rr-allylic complexes and (5) complexes in which the ligand is not the original olefin or acetylene, but a molecule produced from it during complex formation. ir-Cyclopentadienyl complexes, formed by reaction of cyclopentadiene or its derivatives with metal salts or carbonyls (78, 217), are not discussed in this review, neither are complexes derived from aromatic systems, e.g., benzene, the cyclo-pentadienyl anion, and the cycloheptatrienyl cation (74, 78, 217), and from acetylides (169, 170), which have been reviewed elsewhere. 

Germyl metallocene derivatives of the early transition metals, Ti, Zr and Hf (M) have been synthesized by the combination of metallocene halides and germyl anions (equations 4 and 5)38-40. The cyclopentadienyl complexes Cp2M(GePh3)Cl39 are difficult to purify due to their instability in solution however, use of the pentamethylcyclopen-tadienyl group(Cp ) enhances both the solubility and stability of these complexes40,41. 

Neodymium cyclopentadienyl complexes are also obtained in-situ by the addition of Cp-derivatives (e.g. indene, cyclopentadiene, pentamethyl-cyclopentadiene, tetramethylcyclopentadiene, di-tert-butylcyclopentadiene, methylcyclopentadiene and fluorene) to standard Nd-catalyst systems such as NdV/MAO. It can be assumed that the respective cyclopentadienyl-anions are formed by proton abstraction from the Cp-derivatives. In the homopolymerization of BD the addition of Cp-derivatives results in an increase of the 1,2-content of about 4-10%. In addition, the in-situ formed Nd Cp-derivatives... 

This volume also gives a description of the evolution in Nd-catalyzed polymerization of dienes from the early works to the current state of the art. The authors highlight the tremendous variety of investigated catalyst systems and both articles order the catalyst systems according to the type of anions carboxylates, alcoholates, halides, hydrides, phosphates, phosphonates, allyls, tetraalkylaluminates, cyclopentadienyl complexes, amides, acetylacetonates,... 

The tripyrazolylborate anion (RB(pz)3, 58) acts as a tridentate ligand, and frequently results in complexes which are analogous to cyclopentadienyl complexes. The first Rhin-RB(pz)3 complexes were prepared by the oxidative addition of I2 to [Rh2 RB(pz)3 (CO)3], and resulted in octahedral, monomeric complexes [Rh RB(pz)3 (CO)I2] (R = H, and, in low yield, for R = pz).892 For the tetrapyrazolyl species (R = pz) the NMR spectrum showed two, non-interconverting pyrazole environments in a 3/1 ratio, consistent with a tridentate configuration for the borate. The C—O stretch is very high (2090 cm-1), consistent with the formal Rhni designation.892... 

The methylcyclopentadienylmolybdenum tricarbonyl synthesis illustrates how a cyclopentadienylpotassium solution can be prepared and then used to prepare a typical transition metal-cyclopentadienyl complex. By analogous procedures, one can prepare a wide variety of metal complexes of the anions of cyclopentadiene, indene, etc. The ferrocene and nickelocene syntheses illustrate how the procedure can be adapted to the... 

The first group 5 cyclopentadienyl complexes with a pendant phosphane ligand were reported very recently by Fryzuk. Ligands 35 and 36 were treated with NbCl3(DME) to give niobium bischelates 207 and 208 in 80% yield (Scheme 35). Carbonylation gave 209 and 210 in 80% yield both were characterized by X-ray structure analyses. Oxidation with PbCL resulted in formation of trichlorides 211 and 212, which can also be obtained from the anionic ligands by treatment with Nb(0)Cl3(THF)2 (Scheme 36). 211 was structurally characterized. ... 

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