1,3-DIPHOSPHA-2-SILAALLYLIC LITHIUM COMPLEXES AND ANIONS - SYNTHESIS,CRYSTAL-STRUCTURES, REACTIVITY, AND BONDING PROPERTIES

Trichlorosilanes RSiCl3 (R = t-Bu, Mes, Cp, Is, OAr) reacted with a 4 -fold excess of lithium phosphanide ArPHLi (Ar = 2,4,6-tBu(3)C(6)H(2)) to form 1,3-diphospha-2-silaallylic complexes 3a-f. From the latter, the corresponding free allylic anions could be liberated by complexati on of the lithium cation with [15]-crown-[5], as could be established on the basis of NMR spectra and X-ray structures. In addition, the bon ding in the Li complexes was further investigated using ab initio calc ulations of double-xi quality. The influence of cation solvation on th e complex geometry was explored as well. The chemical reactivity of 1, 3-diphospha-2-silaallylic anions with electrophiles (E = H+, ClPR'R'') was investigated. 1,3-Diphospha-2-silapropenes 4a-d and 1,3,4-triphos pha-2-silabutenes-(1) 5a-e and 6a were prepared.