Cyclopentadienyl ligand synthesis

Semproni SP, Milsmann C, Chirik PJ. Side-on dinitrogen complexes of titanocenes with disubstituted cyclopentadienyl ligands synthesis, structure, and spectroscopic characterization. Organometallics. 2012 31 3672-3682. 

Two commonly used synthetic methodologies for the synthesis of transition metal complexes with substituted cyclopentadienyl ligands are important. One is based on the functionalization at the ring periphery of Cp or Cp metal complexes and the other consists of the classical reaction of a suitable substituted cyclopentadienyl anion equivalent and a transition metal halide or carbonyl complex. However, a third strategy of creating a specifically substituted cyclopentadienyl ligand from smaller carbon units such as alkylidynes and alkynes within the coordination sphere is emerging and will probably find wider application [22]. 

Phenyl-Substituted Cyclopentadienyl Ligand 3.1 Ligand Synthesis... 

Bis(amido) phosphine-donor complexes, with Zr(IV), 4, 816 Bis(amido) pyridines, with Zr(IV) and Hf(IV), 4, 790 Bis(aminoalkylidyne) complexes, diiron carbonyl complexes with cyclopentadienyl ligands, 6, 248-251 Bisaminosilylenes, in molybdenum carbonyls, 5, 406 Bis(tj-arc nc) complexes, as metal vapor synthesis milestone, 1, 236... 

Cyclopentadienyl rings, in chromocenes with heteroatom substitutions, 5, 330 with pentalene rings, 5, 331 with substitutions, 5, 329 Cyclopentadienyl ruthenocenes, synthesis, 6, 639 Cyclopentadienyl—silylamido complexes, with Zr(IV) and Hf(IV) and monodentate ligands, 4, 852 Cyclopentadienyl—silylamido dienes, with Zr(IV) and Hf(IV),... 

Diiridium(I) complexes, dihydrogen uptake, 7, 289 Diiridium(III) polyhydrides, synthesis and reactivity, 7, 410 Diiron carbonyl complexes with cyclopentadienyl ligands... 

Scheme 2. Synthesis of chiral chelating cyclopentadienyl ligands...

Some half-sandwich titanium compounds with cyclopentadienyl ligands have been shown to be the most active catalysts for synthesis of these polymers. Fluorinated half-sandwich metallocenes, synthesized by Roesky et al. (263), have activities of up to a factor of 30 greater than those of chlorinated compounds. Polymerization has been carried out within a temperature range of 10-70°C (264). 

A. R. Kudinov, M. I. Rybinskaya, Yu. T. Struchkov, A. I. Yanovskii, and P. V. Petrovskii, Synthesis of the First 30-Electron Triple-Decker Complexes of the Iron Group Metals with Cyclopentadienyl Ligands. X-Ray Structure of [(/ -C5H5)Ru (p,jy-C5Me5)Ru(jy-C5Me5)]PF6, J. Organomet. Chem. 336, 187-197 (1987). 

A. R. Kudinov, A. A. Filchikov, P. V. Petrovskii, and M. I. Rybinskaya, 30-Electron Cationic Iron- and Cobalt-containing Triple-Decker Complexes with a Central Cyclopentadienyl Ligand. The First Synthesis of the Parent Triple-Decker Iron Complex with Cyclopentadienyl Ligands, [( 5-C5H5)Fe(p-jy jy-C5H5)Fe(jy5-C5H5)]PFg, Russ. Chem. Bull. 48, 1352-1355(1999). 

By introducing substituents into cyclopentadienyl ligands, steric hindrance takes place which might reduce the number of ligands bonded to the metal. The synthesis of Cp Ln consists of the reaction... 

As noted earlier, pentamethyl substitution in the cyclopentadienyl ligand confers some stability allowing ligand redistribution and the synthesis of chloride complexes of lanthanides. Stabilization also occurs by coordination with Lewis bases or alkali halides. 

Previously, we synthesized and studied various Group 4 complexes with different ligations as alternatives to the cyclopentadienyl ligand. Here we present an overview of the synthesis, structure, and catalytic properties in the polymerization of a-olefins of several zirconium octahedral complexes. We show how the stereoregular polymerization of a-olefins using these octahedral zirconium complexes can be modulated by pressure. These results raise conceptual questions regarding the general applicability of ds-octahedral C2-sym-metry complexes to the stereospecific polymerization of a-olefins. 

Considerable effort has been directed to the stereoselective synthesis of aimulated cyclopentadienyl complexes of the group 4 transition metals. Ci asymmetric and C2 synunetric aimulated cyclopentadienyl ligands have been used to prepare chiral organotitanium complexes, which are now being actively studied as catalysts for asymmetric synthesis and olefin polymerization see Asymmetric Synthesis by Homogeneous Catalysis). 

Recent developments in the chemistry of divalent lanthanide complexes of simple cyclopentadienyl ligands have involved new syntheses and structural characterization. As described in Section VII, by using the 5Mes ligand, advances in reactivity as well as synthesis and structure have been made. 

An elegant use of the chirality and the leaving group ability of the camphorsulfonate ester has been reported in the synthesis of a chiral C2 symmetric cyclopentadienyl ligand (eq 6), ... 

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