Synthetic and Structural Study of the Coordination Chemistry of a <i>peri</i>-Backbone-Supported Phosphino-Phosphonium Salt

Abstract

Coordination chemistry of an acenaphthene <i>peri</i>-backbone-supported phosphino-phosphonium chloride (<b>1</b>) was investigated, revealing three distinct modes of reactivity. The reaction of <b>1</b> with Mo­(CO)₄(nor) gives the Mo(0) complex [(<b>1</b>)­Mo­(CO)₄Cl] (<b>2</b>), in which the ligand <b>1</b> exhibits monodentate coordination through the phosphine donor and the P–P bond is retained. PtCl₂(cod) reacts with the chloride and triflate salts of <b>1</b> to form a mononuclear complex [(<b>1</b>Cl)­PtCl₂] (<b>3</b>) and a binuclear complex [((<b>1</b>Cl)­PtCl)₂]­[2TfO] (<b>4</b>), respectively. In both of these complexes, the platinum center adds across the P–P bond, and subsequent chloride transfer to the phosphenium center results in phosphine-chlorophosphine bidentate coordination. [((<b>1</b>)­PdCl)₂] (<b>5</b>) was isolated from the reaction of <b>1</b> and Pd₂(dba)₃ (dba = dibenzylideneacetone). Oxidative addition to palladium(0) results in a heteroleptic phosphine bridging phosphide coordination to the Pd­(II) center. In addition, reaction of <b>1</b> with BH₃·SMe₂ leads to the bis­(borane) adduct of the corresponding mixed tertiary/secondary phosphine (<b>6</b>), with BH₃ acting as both a reducing agent and a Lewis acid. The new compounds were fully characterized, including X-ray diffraction. The ligand properties of <b>1</b> and related bonding issues are discussed with help of DFT computations