Synthesis and Structure of Zwitterionic Silylborates and Silylzincates with Pendant Polydonor Arms

The synthesis and structure of well-defined zinc- and potassium-containing heterobimetallic zwitterions that have pendant polydonor arms is reported. The zwitterionic complexes [Me2ZnSi­(SiMe2OCH2CH2OMe)3Li] (Li-2), [Cl2ZnSi­(SiMe2OCH2CH2OMe)3K] (K-3), and [I2ZnSi­(SiMe2OCH2CH2OMe)3K] (K-4) were prepared from reactions of [Si­(SiMe2OCH2CH2OMe)3M] (M = Li, K) (M-1) with ZnCl2, ZnI2, and ZnMe2, respectively. Reaction of K-1 with B­(C6F5)3 gave the potassium silyl borate [(C6F5)3BSi­(SiMe2OCH2CH2OMe)3K] (K-5) in 90% yield. Treatment of 2 equiv of K-1 with ZnCl2 afforded the nonzwitterionic zinc silanide Zn­(Si­(SiMe2OCH2CH2OMe)3)2 (6), as a liquid, which upon treatment with 1 equiv of ZnMe2 and 4 equiv of B­(C6F5)3 could be converted into the zwitterionic zinc silyl borate [(C6F5)3BSi­(SiMe2OCH2CH2OMe)3Zn]­[MeB­(C6F5)3] (7). The structures of the zwitterionic complexes K-4, K-5, and 7 were determined by X-ray crystallography.