Samarium complexes alkyl compounds

The first lanthanide-NHC complexes were isolated by Arduengo and coworkers in 1994.62 A stable carbene displaces THF in bis(pentamethylcy-clopentadienyl)-samarium-THF to form the samarium(II)-NHC complex 55 (Scheme 29). The addition of a second equivalent of NHC resulted in the isolation of the bis(NHC) adduct 56. Compound 56 was characterised in the solid state by single crystal X-ray diffraction and exhibits samarium-NHC bond distances of 2.837(7) A and 2.845(7) A, which are longer than the M-C bond in a-bonded alkyl lanthanide complexes. 

A novel synthesis (Evans et al. 1985b) of Cp2Sm(THF)2 has been devised by reacting Sml2 with KCp (1 2). When the stoichiometry of the reaction is 1 1 the iodine derivative [Cp Sm(p-l)(THF)2]2 is formed. The latter, with the reactive side of the halide ligand, is suitable for enlarging the series of novel samarium compounds, particularly alkyl complexes. 

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