[(ClImDipp)PP(Dipp)][GaCl4]: a polarized, cationic diphosphene†
The reaction of the neutral diphosphanide [(ClImDipp)P–P(Cl)(Dipp)] (6) (ClImDipp = 4,5-dichloro-1,3-bis(Dipp)-imidazol-2-yl; Dipp = 2,6-di-iso-propylphenyl) with methyl triflate (MeOTf) leads to the formation of cationic diphosphane [(ClImDipp)(Me)P–P(Cl)(Dipp)]+ (8+) in a stereoselective methylation. In contrast, reacting 6 with the Lewis acid GaCl3 yields cationic diphosphene [(ClImDipp)PP(Dipp)]+ (7+), which is explained by a low P–Cl bond dissociation energy. The significantly polarized PP double bond in 7+ allows for its utilization as an acceptor for nucleophiles – the reaction with Cl− regenerates diphosphanide 6 and the reaction with PMe3 gives cation [(ClImDipp)P–P(PMe3)(Dipp)] (9+). In depth DFT investigation provides detailed insights into the bonding situation of the reported compounds.