Cydopentadienyl Ligands

Allyl Complexes. Allyl complexes of uranium are known and are usually stabilized by cydopentadienyl ligands. Allyl complexes can be accessed via the interaction of a uranium halide and an allyl grignard reagent. This synthetic method was utilized to obtain a rare example of a "naked" homoleptic allyl complex, U(r 3-C3H5)4 [12701-96-1], which decomposes at 0°C. Other examples, which are more stable than the homoleptic allyl complex have been synthesized, ie, U(allyl)2(OR)2 (R = alkyl), U(allyl)3X (X = halide), and U(allyl)(bipy)3-... 

Common abbreviations for cydopentadienyl ligands include Cp = C5H5, Cp = C5Me5, and Cp = C5EtMe4. 

Okuda J (1991) Transition Metal Complexes of Sterically Demanding Cydopentadienyl Ligands. 160 97-146... 

With the cydopentadienyl ligand, vanadium forms the simple sandwich compound, "vanadocene , [V( - -C5Hj)2] which is dark violet, paramagnetic (3 unpaired electrons) and extremely air-sensitive. Oxidative addition reactions are possible and provide compounds such as [V()9 -CjH5)2C1 ] (n = 1,2,3) and LV(rj -C5H5)2R2], while it.s reaction with dithioacetic acid produces the dark-brown tetramer [V4(fj -C H5)4( 3-S4), Fig. 22.11. " With four V " atoms, eight electrons are available for six V-V bonds and the implied bond order of 2/3... 

Fig. 15.37 Some known triple deckers containing cydopentadienyl ligands.

Symbols B and S. There are two established and well-used systems for chirality symbols and these differ in fundamental ways. The first, the convention for chiral carbon atoms is equally appropriate to metal complexes and is most often used in conjunction with ligand chirality. However, it can be applied to metal centers and has been useful for pseudotetrahedral organometallic complexes when, for example, cydopentadienyl ligands are treated as if they were monodentate ligands of high priority. 

The general synthesis for this class of metallocene compounds is illustrated in Scheme 32 for the preparation of 110. Ferrocene undergoes ri -cydopentadienyl ligand replacement with the aromatic hydrocarbon in the presence of aluminum, aluminum chloride, and titanium tetrachloride to afford the desired Ti -cyclopentadienyl(isopropylbenzene)iron (II) chloride. Anion exchange with KPFg in aqueous solution gives the PFe" salt 110. 

The dediazotation reaction of various diazoalkanes (reaction 8.34) was successfully applied in the preparation of stable dinuclear cobalt carbene complexes (16) containing Tj -cydopentadienyl ligands [66-71]. 

Tj -cydopentadienyl ligand. Additionally, the nitrogen atom of the Ti(IV) catalyst species. Moreover, a theoretical study of the... 

Electronic structure. In the 7r-cydopentadienyl ligand, the normal or-bonded system for the carbon and hydrogen atoms may be assumed to be unaffected by the ligand metal bonding. 

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