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

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Reactions of R(3)Pn (Pn = As or Sb; R = Me, Et or Ph) with R'(2)PCl or R'PCl(2) (R' = Me, Et, Ph, Cy, (i)Pr), in the presence of a halide abstracting agent (Me(3)SiOSO(2)CF(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'(2)P(+) or R'P(2+), respectively). Salts of the first phosphinoarsonium cations, [R(3)As-PR'(2)](+), and the first 2-phosphino-1,3-diarsonium dications, [R(3)AsP(R')AsR(3)](2+), have been isolated and comprehensively characterized. In contrast, reactions involving Ph(3)Sb give 2,3-diphosphino-1,4-distibonium dications, [R(3)SbP(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(3)Sb. The analogous 2,3-diphosphino-1,4-diarsonium dication [R(3)AsP(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(3)PP(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.