Cyclopentadienyl complexes, dimeric

Although carbonyl and cyclopentadienyl complexes are well known for Tc(I) and Tc(III), none appear to have been reported for Tc(II). This may be ascribed to the tendency to follow the 18-electron rule, which, due to the odd number of electrons, would require dimer formation for compliance. Similarly, no Tc(II) cyano or isonitrile complexes appear to have been isolated. 

These can be made by various routes, including hydrogenolysis of Ln-C bonds thermolysis of alkyls and substitution of halide. Thus hydrogenolysis of the dimeric methyl-bridge cyclopentadienyl complexes (Ln, e.g., Y, Er, Yb, Lu) in THE affords [Cp2Ln(thf)(/u,-H)]2 ... 

In solution, the cyclopentadienyl tricarbonyl dimers [CpMo(CO)3]2 and [CpW(CO)3]2 react to form the heterobimetallic complex Cp(CO)3Mo-W(CO)3Cp. However, the reaction does not go to completion a mixture results in which the [CpMo(CO)3]2 and [CpW(CO)3]2 are in equilibrium with the mixed metal compound. The abundance of the three organometallic complexes is governed statistically by the number of CpMo(CO)3 and CpW(CO)3 fragments present. If 0.00100 mmol of [CpMo(CO)3]2 and 0.00200 mmol of [CpW(CO)3]2 are dissolved in toluene until equilibrium is achieved, calculate the amounts of the three organometallic complexes in the equilibrium solution. (Reference T. Madach and H. Vahrenkamp, Z. Naturforsch., 1979, 34b, 573.)... 

Cyclopentadienyl Complexes Cyano, Isonitrile, and Thiocyanate Complexes Aqua, Halide, and Related Dimeric Complexes Carboxylato and /3-Diketonato Complexes... 

Cyclopentadienyl complexes are often prepared as dimeric species, but less frequently as higher clusters. Several techniques are used to prepare cyclopentadienyl dimers. A generally useful reaction is of a mononuclear carbonyl with dicyclopentadiene. The proper conditions for preparation of Cp2Fe2(CO)4 have been studied . ... 

Several catalytic systems including iridium hydride, oxo-phosphoranyl, N-heterocyclic carbene, cyclooctadiene, and dimeric cyclopentadienyl complexes have been successfully employed in alkyne hydrosilylation to afford selectively j0-(Z)-alkenylsilanes in high 3delds (4). 

The nickel cyclopentadienyl carbonyl dimer [NiCp (CO)]2, where Cp is iV,7V-(dimethylamino)ethylcyclopenta-dienyl, was reacted with Ga2Cl4 to give a heterodinuclear complex (Equation (20)). 

The vinylidene/acetyhdo interconversions carried out in this experiment are similar to those seen for other metal complexes" and are relevant to the known ability of (q -C5H5)RuCl(PPh3)2 to catalyze the dimerization of phenylacetylene to a mixture of Z- and -l,4-diphenyl-l-buten-3-yne. The chemistry of ruthenium cyclopentadienyl complexes has been reviewed. ... 

Ruthenium.— The oxidative addition of quinones to d and to metal centres is well documented. Now the oxidative addition of u-quinones to the d complex RuCl2(PPh3)3 has been reported. The reactions of ruthenium and iron cyclopentadienyl carbonyl dimers with azobenzene are described later (see manganese and rhenium). 

Cyclopentadienyl complexes, [CpMo(CO)2(S2CNR2)], have been prepared via addition of thiuram disulfides to the triple-bonded dimers, [CpMo(CO)2l2 (900,901), and from the thermal reaction of [CpMo(CO)3]2 and diethylamine in the presence of carbon disulfide (902). Two examples of complexes of this type, namely, [CpMo(CO)2(S2CNMc2)] and [CpMo(CO)2(S2CN—i-Pr2)] have been crystallographically characterized (900,901). Brunner and Wachter (903) also isolated some unusual examples, namely, [CpMo(CO)2(S2CNRH)]... 

Treating pentacarbonyliron with dicyclopentadiene affords the dicarbonyl (ri -cyclopentadienyl)iron dimer [Cp(CO)2pe]2. Reduction of the latter with sodium amalgam provides the nucleophilic dicarbonyl(r -cyclopentadienyl)iron anion [Cp(CO)2Fe]. Allylic halides or tosylates can be reacted with this Fe(0) complex to afford ri -allyl-Fp-iron complexes (Fp = Fe(CO)2Cp, Scheme... 

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