Synthesis cyclopentadienyl

Zirconocene complexes containing two indenyl or tetrahydroindenyl groups bridged with short links such as —CH2—CH2— or —Si(CH3)— can produce isotactic polymers of higher a-olefins (32). To synthesize syndiotactic PO, bridged zirconocene complexes with rings of two different types are required, one example of which is isopropyl(cyclopentadienyl)(l-fluorenyl)zirconocene. These complexes are used for the synthesis of syndiotactic PB... 

CyclopentadienylthaHium and its alkylated derivatives are used in the synthesis of metallocenes (qv) and other transition-metal cyclopentadienyl complexes (29). 

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... 

In the context of pyridin synthesis from alkynes and nitriles homogeneously catalyzed by (cyclopentadienyl)cobalt complexes (Eq. 13), it was found that electron-withdrawing groups on the cyclopentadienyl ring significantly increase the activity [63]. During the screening of various cobalt half-sandwich complexes... 

In a related study the synthesis of half-sandwich cyclopentadienyl titanium f-butylimido complexes containing pendant-arm-functionalized amidinate ligands... 

The chemistry of cyclopentadienyltin compounds is reviewed in references (267) and (26S). The ready disproportionation of (CsH5)4Sn with SnCU (269), and the sensitivity of the cyclopentadienyl-tin bond to acidolysis and to photolysis (270) suggests that these compounds may find application in synthesis. 

It was shown that planar-chiral cyclopentadienyl-phosphine ligands were excellent chirality inducers during the synthesis of chiral-at-metal tetrahedral Ru-phosphine or -phosphite complexes (99% de). 

The story of the heavy analogs of 6jt-electron cyclopentadienyl anions has culminated in the latest synthesis of a compound containing three heavier group 14 elements (two Si and one Ge) in the ring. This aifionic species 69 Li+ was prepared by the reduction of the disilagermacyclopentadiene precursor 70 with potassium graphite KCg followed by the exchange of countercation from K+ to Li+ by treatment with LiBr (Scheme 2.66). ... 

An alternative synthesis of a thermally stable cyclopentadienyl functionalized polymer involved ring bromination of poly(oxy-2,6-diphenyl-l,4-phenylene), followed by lithiation with butyl lithium to produce an aryllithium polymer. Arylation of 2-norbornen-7-one with the metalated polymer yielded the corresponding 2-norbornen-7-ol derivative. Conversion of the 7-ol to 7-chloro followed by treatment with butyl lithium generated the benzyl anion which undergoes a retro Diels-Alder reaction with the evolution of ethylene to produce the desired aryl cyclopentadiene polymer, 6. 

Reaction of the same neutral borabenzene-ligand adduct, C5H5B-PMe3, with a transition, rather than an alkali, metal alkyl or amide can furnish r 6-boratabenzene complexes in a single step (Scheme 8).17 This efficient transformation presumably proceeds through initial ir-coordination of CsHsB-PMes to the transition metal, followedby an intramolecular substitution reaction. In contrast to other approaches to the synthesis of T 6-boratabenzene complexes, this synthetic route does not have a parallel in if-cyclopentadienyl chemistry. 

While the chemistry of metal carbonyl complexes has enjoyed a rather long and colorful history, being extensively studied and widely reviewed (7-3), the synthesis and reactivity of the group 4B (Ti, Zr, Hf) metal carbonyls have developed relatively slowly. Although the first well-characterized group 4B metal carbonyl complex, bis(i7-cyclopentadienyl)-dicarbonyltitanium (1), was reported by Murray of Monsanto Co. in... 

To complete the synthesis of the diazofluorene, the cyclization product 126 is treated with diisopropylethylamine and triflyl azide [50], to afford the diazofluorene 127 in 81 % yield. Under these conditions, the hydroxyfulvene is likely deprotonated to generate a cyclopentadienyl anion. Attack of this anion on the trifyl azide reagent... 

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