Intramolecular Phosphine_Phosphine Donor_Acceptor Complexes

摘要

The reaction of 5-diphenoxyphosphanyl-6-diisopropylphosphinoacenaphthene 12 with chlorotrimethylsilane unexpect_edly gave a phosphonium-phosphine compound 13, containing the structural motif of four phosphorus atoms connected in a chain. To explain the mechanism of this complex transformation, a proposed intermediate 5-dichlorophosphino_6-diisopropylphosphinoacenaphthene 14 was synthesized by an alternative method. The two (formally) phosphine environments in 14 form an intramolecular donor_acceptor (phosphonium-phosphoranide) complex, stable at room temperature in the solid state and as a solution in certain solvents. A ~31P NMR mechanistic study showed that, ' despite the presence of a rigid acenaphthene backbone, 14 is unstable in the presence of nucleophiles and disproportionates into 13 and other phosphorus containing products. Both 13 and 14 have been crystallographically characterized.