PREPARATION OF THE FIRST SILENYL ZINC, R-Zn-(R)Si=CR₂. TRANSMETALLATION VS. ADDITION REACTIONS BETWEEN SILENYL LITHIUM AND SILYL ZINC

The study of the structure, properties and reactivity of doubly-bonded silicon compounds has made tremendous progress, but many challenges remain. Recently we reported the isolation of silenyl lithium 1. Now we report the synthesis of the first silenyl zincs 2a-c.

Reaction of 1 with ZnCl₂ leads to a complex mixture of products and a metallic residue (Scheme, path a). Reaction of 1 with 1 equivalents of RZnCl (R= tBuMe₂Si, tBu₂MeSi, Ethyl) in toluene at 0⁰C gave after stirring for 30 minutes the trasmetallation silenyl zinc products: 2a, 2b and 2c, respectively (path b). Reaction of silenyl lithium 1 with 1 equivalents of (tBu₂MeSi)₂Zn (toluene) at 0⁰C gave after stirring for 30 minutes 2b (path c). In contrast, reaction of 1 with 2 eq of (tBuMe₂Si)₂Zn in toluene yields 3: the first solvent-separated ion pair of a 1,2-zinclithiomethylsilane (path d). We are currently studying the reactions of these novel silenyl zincs 2a-c.