Cyclopentadienyl anion ligand structure

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. ... 

Here we have discussed only very few of the many ligands that have been studied. Many variations of substituents at the cyclopentadienyl ligand have been studied, and there are more to come as well as variation in the structure of the bridge, the anions, and the central metal. In summary, the toolbox is quite extensive prediction of properties of new polymers to be made can guide the catalysis research in the design of new catalysts. 

Alike metallocomplex anion-radicals, cation-radicals of odd-electron structure exhibit enforced reactivity. Thus, the 17-electron cyclopentadienyl dicarbonyl cobalt cation-radical [CoCp(CO)2] undergoes an unusual organometallic chemical reaction with the neutral parent complex. The reaction leads to [Co2Cp2(CO)4]. This dimeric cation-radical contains a metal-metal bond unsupported by bridging ligands. The Co—Co bond happens to be robust and persists in all further transformations of the binuclear cation-radical (Nafady et al. 2006). 

Yb(5d)(H20)3]Cl, and [Yb(5d)(CoP] (fig. 12) where CoP is the cyclopentadienyl-tris(dieth-ylphosphito)cobaltate(I) anion (see fig. 13) for which the luminescence intensity increases in the proportions 1 22 36 62 271, upon excitation at 512 nm (Meng et al., 2000). The effect of coordinated water molecules on the metal-centered fluorescence intensity is clearly seen in the more than four-fold enhancement obtained by replacing the three water molecules in [Yb(5d)(H20)3 ]C1 by CoP the 2F5/2 lifetime of the latter complex (40 ps) is also much longer than lifetimes reported for other Ybm porphyrinates. In addition, the cobaltate anion rigidities the molecule, which results in a much finer structure of the ligand-field split electronic levels. 

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