Compounds of the Pentamethylcyclopentadienyl Ligand CsMes Cp

Evidence from UV-visible spectra (Cm and Am compounds) and Mossbauer spectra (Np compounds) indicates that these compounds have probably rather more covalent contributions to their bonding than do the corresponding lanthanide compounds, but are largely ionic compared with cyclopentadienyls in the +4 state. 

Analogous compounds AnCps exist for other actinides, e.g. Th, Np ( ), Pu, Am, Bk, Cf, Cm. The thorium(iii) compound is especially noteworthy, on account of the rarity of this oxidation state the structure of the similar Th C5H3(SiMe3)2 3 is known to have trigonal planar geometry around thorium. 

3Th C5H3(SiMe3)2 2Cl2 - -Na/K(alloy) Th - -2Th C5H3(SiMc3)2 3 + 6Na/KCl 

These Th compounds are EPR-active spectra indicate a 6d ground state for Th C5H3(SiMc3)2 3, despite the fact that the free Th + ion has a 5f configuration. 

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