Chemistry of <i>C-</i>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 <i>closo-exo</i>-4,5-Li(THF)<sub>2</sub>-1-Li(THF)<sub>2</sub>-2,3-(SiMe<sub>3</sub>)<sub>2</sub>C<sub>2</sub>B<sub>4</sub>H<sub>4</sub> with anhydrous LnCl<sub>3</sub> (Ln = Sm, Gd, Tb, Dy, Ho), in a molar ratio of 2:1 in dry benzene (C<sub>6</sub>H<sub>6</sub>), produced the sandwiched paramagnetic species {[η<sup>5</sup>-1-Ln-2,3-(SiMe<sub>3</sub>)<sub>2</sub>-2,3-C<sub>2</sub>B<sub>4</sub>H<sub>4</sub>]<sub>3</sub>[(μ<sub>2</sub>-1-Li-2,3-(SiMe<sub>3</sub>)<sub>2</sub>-2,3-C<sub>2</sub>B<sub>4</sub>H<sub>4</sub>)<sub>3</sub>(μ<sub>3</sub>-OMe)][μ<sub>2</sub>-Li(C<sub>4</sub>H<sub>8</sub>O)]<sub>3</sub>(μ<sub>3</sub>-O)} (Ln = Sm (<b>1</b>), Gd (<b>2</b>), Tb (<b>3</b>), Dy (<b>4</b>), Ho (<b>5</b>)) 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 <b>1</b> was also characterized by <sup>1</sup>H, <sup>11</sup>B, and <sup>13</sup>C NMR spectroscopy. Compounds <b>1</b>−<b>5</b> 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 <b>2 </b>with MnCl<sub>2</sub> in benzene, followed by the addition of TMEDA, gave a dinuclear manganacarborane sandwich complex, 4,4‘,5,5‘-Mn(TMEDA)-1,1‘-<i>commo-</i>Mn[2,3-(SiMe<sub>3</sub>)<sub>2</sub>-2,3-C<sub>2</sub>B<sub>4</sub>H<sub>4</sub>]<sub>2</sub> (<b>6</b>). Compound <b>6 </b>was characterized on the basis of its elemental analysis and IR spectrum and also by X-ray diffraction. The reaction of <b>1 </b>with CoCl<sub>2 </sub>in dry benzene, followed by the addition of TMEDA, gave the cobalt(III) sandwich complex, Li(TMEDA)<sub>2</sub>{1,1‘-<i>commo-</i>Co[2,3-(SiMe<sub>3</sub>)<sub>2</sub>-2,3-C<sub>2</sub>B<sub>4</sub>H<sub>4</sub>]<sub>2</sub>} (<b>7</b>). Complex <b>7</b> was characterized on the basis of <sup>1</sup>H, <sup>7</sup>Li,<sup>11</sup>B, and <sup>13</sup>C NMR spectra and IR spectra and also by X-ray diffraction.