Synthesis and structure of nitrile-solvated rare earth metallocene cations [Cp2Ln(NCR)3][BPh4] (Cp = C5Me5, C5H4SiMe3; R = Me, tBu, Ph)

The coordination chemistry of MeCN, tBuCN, and PhCN with the cationic rare earth metallocene complexes [(C5Me5)2Ln][(μ-Ph)2BPh2], 1-Ln (Ln = Y, La, Gd), has been examined to determine how nitrile coordination will affect the metallocene geometry. Crystallographic determination of geometry was possible for [(C5Me5)2Ln(NCMe)3][BPh4] (2-Y, 2-Gd), [(C5Me5)2Y(NCtBu)3][BPh4] (3-Y), and [(C5Me5)2Ln(NCPh)3][BPh4] (4-La, 4-Gd). In each case, only three nitriles are found to coordinate and the metallocenes are bent with (C5Me5 ring centroid)–metal–(C5Me5 ring centroid) angles of 137–140°. The THF adduct, [(C5Me5)2La(NCMe)2(THF)][BPh4], 5-La, was also crystallographically characterized. A similar result was observed with the yttrium metallocene of the trimethylsilyl-containing ligand (C5H4SiMe3)1−: coordination of only three nitriles is found in [(C5H4SiMe3)2Y(NCMe)3][BPh4], 6-Y, which has a 136.8° (C5Me5 ring centroid)–Y–(C5Me5 ring centroid) angle.

In the presence of excess amounts of MeCN, tBuCN, and PhCN, the cationic rare earth tetraphenylborate complexes [(C5Me5)2Ln][(μ-Ph)2BPh2] form complexes containing just three nitriles [(C5Me5)2Ln(NCR)3][BPh4], which have bent metallocene geometries with 137–140° (C5Me5 ring centroid)–metal–(C5Me5 ring centroid) angles.Figure optionsDownload as PowerPoint slide