Chemistry of C-Trimethylsilyl-Substituted Heterocarboranes. 19. Synthetic and Structural Studies on Trinuclear Ln(III) Carborane Clusters [Ln(III) = Sm, Gd, Tb, Dy, Ho]. I. Conversion to Sandwiched Manganese(II) and Cobalt(III) Carborane Complexes

The reaction of closo-exo-4,5-Li(THF)2-1-Li(THF)2-2,3-(SiMe3)2C2B4H4 with anhydrous LnCl3 (Ln = Sm, Gd, Tb, Dy, Ho), in a molar ratio of 2:1 in dry benzene (C6H6), produced the sandwiched paramagnetic species {[η5-1-Ln-2,3-(SiMe3)2-2,3-C2B4H4]3[(μ2-1-Li-2,3-(SiMe3)2-2,3-C2B4H4)33-OMe)][μ2-Li(C4H8O)]33-O)} (Ln = Sm (1), Gd (2), Tb (3), Dy (4), Ho (5)) in 59%, 58%, 49%, 52%, and 59% yields, respectively. All compounds were characterized by IR spectroscopy and by single-crystal X-ray diffraction studies; compound 1 was also characterized by 1H, 11B, and 13C NMR spectroscopy. Compounds 15 are isostructural clusters consisting of three half-sandwich lanthanacarboranes, three lithiacarboranes, three bridging lithium atoms, and three THF molecules of solvation. Their structures are such that the nine metal atoms form a tricapped trigonal prism with the lanthanide metals at the capping positions. The reaction of 2 with MnCl2 in benzene, followed by the addition of TMEDA, gave a dinuclear manganacarborane sandwich complex, 4,4‘,5,5‘-Mn(TMEDA)-1,1‘-commo-Mn[2,3-(SiMe3)2-2,3-C2B4H4]2 (6). Compound 6 was characterized on the basis of its elemental analysis and IR spectrum and also by X-ray diffraction. The reaction of 1 with CoCl2 in dry benzene, followed by the addition of TMEDA, gave the cobalt(III) sandwich complex, Li(TMEDA)2{1,1‘-commo-Co[2,3-(SiMe3)2-2,3-C2B4H4]2} (7). Complex 7 was characterized on the basis of 1H, 7Li,11B, and 13C NMR spectra and IR spectra and also by X-ray diffraction.