LITHIUM ZINCATES WITH HETEROLEPTIC TRIORG ANYLZINCATE ANION

Bis(trimethylsilylmethyl)-, bis[bis(trimethylsilyl)methyl]- as well as ,4,4,6,6-hexamethyl-2,4,6-trisila-cyclo-hexyl)zinc react with methyl lithium or phenyl Lithium in the presence of the tridentate 1,3,5-trim ethyl-1,3,5-triazinane (TMTA) to yield zincates of the type LiZnR(2)R' .2TMTA. The compounds are colorless and insoluble in aliphatic or arom atic hydrocarbons. These zincates exist in solution as well as in the crystalline state as separated ions, as confirmed for 6,6-hexamethyl-2 ,3,6-trisila-cyclo-hexyl)-zincate. 2TMTA by X-ray diffraction (P1; a = 1139,5(3); b = 1482,4(4); c = 1528,6(5) pm; alpha = 95,33(2); beta = 100,13(2); gamma = 106,91(2)degrees; Z = 2). The lithium cation is six -coordinated by two TMTA ligands in a distorted anti-prismatic complex . The zinc atom displays a trigonal planar coordination with Zn-C bond lengths of 207 pm to the 2,2,4,4,6,6-hexamethyl-2,4,6-trisila-cyclo-h exyl ligands and of 202 pm to the methyl group. One trisila-cyclo-hexy l substituent exists in the chair, the other one in the twist conforma tion. The reaction of lithium bis(trimethylsilyl)amide with bis(trimet hylsilylmethyl)zinc yields the benzene soluble silyl)amino-bis(trimeth ylsilylmethyl)zincate.TMTA. The molecular structure was confirmed by X -ray diffraction (P2(1)2(1)2(1); a = 1024,8(3); b = 1775,4(7), c = 191 8,2(8) pm; Z = 4). The bridging bis(trimethylsilyl)amino ligand displa ys long Zn-N and Li-N distances of 213 and 208 pm, respectively, due t o the steric inter-ligand repulsion. During the reaction of lithium bi s(trimethylsilyl)amide with bis[bis(trimethylsilyl)methyl]zinc no zinc ate formations observed. The decomposition products lithium bis(trimet hylsilyl)-methanide and the heteroleptic trimethylsilyl)amino-bis(trim ethylsilyl)methylzinc were detected.