Phosphinopnictonium Cations: High Yield and General Preparative Procedures for New Interpnictogen Frameworks Exploiting As→P and Sb→P Coordinate Bonds

摘要

Reactions of R_3Pn (Pn = As or Sb; R = Me, Et or Ph) with R'_2PCI or R'PCl_2 (R' = Me, Et, Ph, Cy, ~iPr), in the presence of a halide abstracting agent (Me_3SiOSO_2CF_3, GaCl_3, or AlCl_3), give salts with cations containing Pn-P bonds. The bond formation is envisaged to proceed by activation of the P-Cl bond and coordination of the pnictine to the resulting phosphorus cation (R'_2P~+ or R'P~(2+), respectively). Salts of the first phosphinoarsonium cations, [R_3As-PR'_2]~+, and the first 2-phosphino-1,3-diarsonium dications, [R_3AsP(R')AsR_3]~(2+), have been isolated and comprehensively characterized. In contrast, reactions involving Ph_3Sb give 2,3-diphosphino-1,4-distibonium dications, [R_3SbP(R')P(R')SbR_3]~(2+), resulting from a single P-Cl activation (abstraction) at each of two phosphorus centers and reductive P-P coupling effected by Ph_3Sb. The analogous 2,3-diphosphino-1,4-diarsonium dication [R_3AsP(R')P(R')AsR_3]~(2+) can be accessed from the 2,3-diphosphino-1,4-distibonium cation by a ligand exchange reaction, which also provides the phosphorus derivative 2,3-diphosphino-1,4-diphosphonium [R_3PP(R')P(R')PR_3]~(2+). The versatile synthetic methodologies toward the new P-As and P-Sb frameworks demonstrate the potential for diversification and systematic expansion of interpnictogen compounds.