Ligand cyclopentadienyl isonitrile

The six-coordinate tris(benzamidinates) [PhC(NSiMe3)2]3Ln also form 1 1 adducts with donor ligands such as THF, MeCN, or PhCN. In the case of ben-zonitrile, it was possible to isolate and structurally characterize two of these seven-coordinated nitrile-adducts. They are most readily isolated when the original preparation is directly carried out in the presence of one equivalent of benzonitrile (Scheme 15). The facile adduct formation with small donor molecules is yet another analogy between the tris(amidinates) and the tris(cyclopentadienyl) complexes, for which similar adducts with, for example, THF, nitriles or isonitriles are well established [6,7,17]. 

The cyclohexyl isonitrile complexes of the tris(methylcyclopentadienyl) cerium, praseodymium, and neodymium compounds have been mentioned in a discussion of the NMR spectra of these and the corresponding tricyclopentadienyl rare earth complexes, which showed that the AG values of the fluxionality of the cyclohexyl ligands decreased in contrast to those of the unsubstituted cyclopentadienyl derivatives (R.D. Fischer, 1979). 

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