Synthesis and Structural Features of Boratabenzene Rare-Earth Metal Alkyl Complexes

A series of solvent-free boratabenzene rare-earth metal alkyl complexes (C5H5BR)2LnCH(SiMe3)2 (9: R = NEt2, Ln = Y; 10: R = NPh2, Ln = Y; 11: R = CH3, Ln = Y; 12: R = NPh2, Ln = Sm; 13: R = NPh2, Ln = Dy; 14: R = NEt2, Ln = Lu; 15: R = NPh2, Ln = Lu; 16: R = Me, Ln = Lu) were synthesized. The solid-state structures of 10, 13, and 15 were determined by single-crystal X-ray diffraction. The crystal structures of 10, 13, and 15 feature highly unsymmetrical coordination of the alkyl ligands and short Ln−C(alkyl) distances. The diamagnetic yttrium and lutetium alkyl complexes, 9−11 and 14−16, were characterized by (1H, 13C, 11B) NMR spectroscopy. The Ln−CαHα (1H NMR: δ 0.68−0.99 ppm) and Ln−CαHα (13C NMR: δ 33.9−39.1 ppm) resonances of these boratabenzene rare-earth metal alkyl complexes are rather downfield in comparison with those of the bis-Cp rare-earth metal alkyl complexes. 89Y NMR spectra of the boratabenzene yttrium alkyl complexes 9−11 and the Cp complex (C5H4Me)2YCH(SiMe3)2 were recorded. The 89Y NMR chemical shifts for 9, 10, and 11 are 176.1, 170.0, and 162.2 ppm, respectively, which are significantly downfield in comparison with that of (C5H4Me)2YCH(SiMe3)2 (44.0 ppm).