Deprotonation of 1,1′-methylenebis[4-tert-butyl-2-(diphenylphosphino)-benzene] and its analogues: synthesis and crystal structure of {5-But-2-[4-But-2-(Ph2P)C6H3(Ph)CH]C6H3P(Ph)K(OEt2)}2

Abstract

Oxidation of 1,1′-methylenebis[4-tert-butyl-2-(diphenylphosphino) benzene] by H2O2 or S8 in toluene affords two new PCP-type pincer ligands. The methylene group deprotonation in the new ligands as well as in their precursor by n-BuLi or LiCH2SiMe3 failed, while the methylene group in the precursor 1,1′-methylenebis[4-tert-butyl-2-(diphenylphosphino)benzene] was readily metallated by Lochmann–Schlosser superbase to form the unstable potassium complex which in turn was readily transformed into new {5-But-2-[4-But-2-(Ph2P)C6H3(Ph)CH]C6H3P(Ph)K(OEt2)}2 complex due to phenyl group migration.