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Reaction of GeCl 2 ‚dioxane with 2 equiv of Li(THF) 2.5 Ge(SiMe 3 ) 3 in hexane afforded moderate yields of two cyclopolygermanes. A cyclotrigermane, (Ge(SiMe 3 ) 2 ) 3 , was characterized by NMR spectra, elemental analyses, and an X-ray crystal structure determination. It crystallized from pentane in the R3 hc space group (rhombohedral) with a ) 19.294(3) Å, R ) 31.89(1)°, V ) 1781 Å 3 , and Z ) 2. The Ge 3 core consisted of an equilateral triangle with a Ge-Ge distance of 2.460(1) Å, the shortest so far measured in cyclotrigermanes. The second product was tentatively identified by its NMR spectra as a cyclotetragermane, ((Me 3 Si) 3 GeGeCl) 4 , and this was confirmed by elemental analyses and an X-ray structure determination on the yellow crystals formed from pentane. The product was found to crystallize as a complex with two molecules of Ge(SiMe 3 ) 4 in the F2 3 (cubic) space group with a ) 22.7731(3) Å, V ) 11 810.5 Å 3 , and Z ) 8. The Ge 4 core consisted of a nonplanar four-membered ring (fold angle ) 18.7°) disordered over three positions related by 3-fold symmetry. In the assumed ordered structure, ring Ge-Ge distances averaged 2.503 Å. When the reaction was repeated with GeCl 2 ‚dioxane and 2 equiv of Li(THF) 3 Si(SiMe 3 ) 3 , the known disilagermirane, (Me 3 Si) 2 Ge(Si(SiMe 3 ) 2 ) 2 , was isolated (66% yield) along with a small yield of the known cyclotetragermane, ((Me 3 Si) 3 SiGeCl) 4 . Reaction of GeI 2 with Li(THF) 2.5 Ge(SiMe 3 ) 3 gave only traces of the cyclotrigermane.

New Si-Ge and Si-Ge-Sn compounds bearing the bulky groups -E(SiMe3>3 (E = Si, Ge) were obtained by treatment of MCU (M = Ge, Sn) with either (THF)3LiSi(SiMe3)3 or (THF)2.5LiGe(SiMe3)3. The cyclic tetragermane [(Me3-SOsSiGeCl^-CeHe crystallizes in the monoclinic space group C2/c with a = 21.835(7) Á, b = 26.342(9) A, c = 14.464(4) Á, ß = 103.45°, V = 8092 Á3, and Z = 4. The Ge4 ring was nonplanar with an average torsion angle of 17.2°. The tetragermane [(Me3Si)3GeGeCl2]2 was characterized by elemental analyses and NMR spectra, which were consistent with a linear tetragermane backbone for the molecule. Dichlorobis(tris(trimethylsilyl)germyl)tin(IV), ((Me3Si)3Ge)2SnCl2, crystallizes in the monoclinic space group C2/c with a = 16.106(4) A,b = 10.034(2) Á, c = 47.375(11) Á, ß = 90.02°, V = 7656 Á3, and Z = 8. The coordination geometry around tin is extremely distorted with Ge-Sn-Ge = 142.1°and Cl-Sn-Cl = 98.8°. The three compounds were stable in air except (( ß3-Si)3Ge)2SnCl2 was mildly hygroscopic. Reactions of the compounds with Li, L1AIH4, and (THF)2.5LiGe(SiMe3)3 were carried out, but no new products were identified. Treatment of LaCU with 3 equiv of (THF)3LiSi(SiMe3)3 afforded (THF)La(Si(SiMe3)3)2Cl as a very hygroscopic white solid. All attempts to substitute more than two -Si(SiMe3)3 groups on a central atom were unsuccessful.

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