[6] The synthesis of 5 will be described elsewhere.[7] Crystal structure analyses: 3a¥ Li (Et2O) 3: A colorless crystal (0.45 î 0.35 î 0.25 mm3) was measured at 193 K on an IPDS area detector system (Stoe) with MoKα radiation. C40H76B3LiO3Si2, monoclinic, space group P21/c, Z= 4, a= 1183.4 (1), b= 2277.6 (2), c= 1756.7 (1) pm, b= 98.32 (1) 8, V= 4685.0 (6) î10À30 m3, 1calcd= 0.993 MgmÀ3, 50384 reflections up to q= 25.848, 8557 independent (Rint= 0.1160), 3910 with I> 2s (I). The structure was solved with direct methods and refined against F2 with full matrix. Hydrogen atoms were considered as riding at calculated positions, wR2= 0.1527 for all reflections, R= 0.0691 for observed reflections. Limited accuracy due to the disorder of the diethyl ether in the Li (Et2O) 3 cation. 4: Pale yellow crystal (0.30 î 0.15 î 0.05 mm3) C28H46B3ClSi2, monoclinic, space group C2/c, Z= 8, a= 3031.1 (2), b= 988.1 (1), c= 2217.6 (1) pm, b= 111.06 (1) 8, V= 6198.1 (8) î10À30 m3, 1ber= 1.086 MgmÀ3, measurement as for 3a¥ Li (Et2O) 3, 12475 reflections up to q= 24.08, 4627 independent (Rint= 0.1414), 1857 with I> 2s (I)(only very thin platelets available). The structure was solved analogously to that of 3a, resulting in wR2= 0.1144 for all reflections, and R= 0.0539 for the observed reflections. CCDC-187178 (3a¥ Li-(Et2O) 3) and CCDC-187179 (4) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www. ccdc. can. ac. uk/conts/retrieving. html (or from the Cambridge Crystallographic Centre, 12 Union Road,