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-^tBu₃C₆H₂) to form 1,3-diphospha-2-silaallylic complexes 3a−f. From the latter, the corresponding free allylic anions could be liberated by complexation 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 bonding in the Li complexes was further investigated using ab initio calculations of double-ξ quality. The influence of cation solvation on the 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-triphospha-2-silabutenes-(1) 5a−e and 6a were prepared.