Organolanthanide chemistry with bis(trimethylsilyl)methyl- and tert-butyldimethylsilyl-substituted cyclopentadienyl ligands.: Synthesis and characterisation of tris(cyclopentadienyl)lanthanide(III) complexes, including crystal structures of [Ln{η5-C5H4CH(SiMe3)2}3] (Ln = Nd or Tm) and [Ce{η5-C5H3(SiMe2But)2-1,3}3]

The homoleptic tris(substituted cyclopentadienyl)lanthanide(III) complexes [LnCp(3)(R)] (Ln = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Gd (6), Tb (7), Dy (8), Er (9), Tm (10) and Yb (11)], [NdCp3t] (12), [CeCp3tt] (13) and [NdCp3tt] (14) [Cp-R = eta(5)-C5H4{CH(SiMe3)(2), Cp-t = eta(5)-C5H4(SiMe2But), Cp-tt = eta(5)-C5H3(SiMe2But)(2)-1,3], have been synthesised by the reaction of the anhydrous lanthanide(III) halide with the appropriate sodium or potassium cyclopentadienide in THF. The characterisation of these complexes was established by H-1-, C-13- and Si-29-NMR spectroscopy (for 1-5 and 12-14), elemental analysis and mass spectrometry. The early paramagnetic lanthanide complexes 2-5, and 12-14 had very sharp H-1-NMR spectral signals, and the paramagnetic shifts were temperature-dependent. The molecular structures of 4, 10 and 13 have been determined by single crystal X-ray diffraction studies. The attempted syntheses of organoneodymium(II) and organothulium(II) complexes are also described. (C) 1999 Elsevier Science S.A. All rights reserved.