2,2,4,4-TETRAMETHYL-2,4-DISILA-CYCLO-BUTY LZINC CHLORIDE-CENTER-DOT-TMEDA AND RELATED-COMPOUNDS

The reaction of (tmeda)lithium 2,2,4,4-tetramethyl-2,4-disila-cyclo-bu tanide with anhydrous zinc(II) chloride in pentane in the molar ratio of 2:1 does not yield the expected dialkylzinc derivative but the mono substitution product 2,2,4,4-Tetramethyl-2,4-disila-cyclo-butylzinc ch loride . tmeda 1. This derivative crystallizes in the orthorhombic spa ce group Pnma with a = 1235.0(1); b = 1696.8(2); c = 1148.0(1) pm and Z = 4. The Zn-C bond lengths lie with 198,4 pm in the characteristic r egion for compounds containing a tetrahedrally coordinated zinc atom. The thermolysis of 1 leads under elimination of ZnCl2 to the formation of is(2,2,4,4-tetramethyl-2,4-disila-cyclo-butyl)zinc . tmeda 2. (tme da)LiCH(SiMe(3))(2) reacts analogously with one equivalent of ZnCl2 to Bis(trimethylsilyl)methylzinc chloride . tmeda 3. Lithium methanide o r Lithium butanide add to a Si-C bond of 1,1,3,3-tetsamethyl-1,3-disil a-cyclo-butane, and these acyclic lithium alkanides 4 (a: R = Me, b: R = n-Bu) yield with zinc(II) chloride the destillable dialkyl zinc com pounds Bis(2,2,4,4-tetramethyl-2,4-disila-pentyl)-5a and Bis(2,2,4,4-t etramethyl-2,4-disila-octyl)zinc 5b.