Tetraphosphinitoresorcinarene Complexes:  Cationic Silver(I) and Copper(I) Halide Complexes as Mercurate(II) Anion Receptors

The reactions of mercury(II) halides with the tetraphosphinitoresorcinarene complexes [P₄M₅X₅], where M = Cu or Ag, X = Cl, Br, or I, and P₄ = (PhCH₂CH₂CHC₆H₂)₄(O₂CR)₄(OPPh₂)₄ with R = C₆H₁₁, 4-C₆H₄Me, C₄H₃S, OCH₂CCH, or OCH₂Ph, have been studied. The reactions of the complexes with HgX₂ when M = Ag and X = Cl or Br occur with elimination of silver(I) halide and formation of [P₄Ag₂X(HgX₃)], but when M = Ag and X = I, the complexes [P₄Ag₄I₅(HgI)] are formed. When M = Cu and X = I, the products were the remarkable capsule complexes [(P₄Cu₂I)₂(Hg₂X₆)]. When M = Ag and X = I, the reaction with both CuI and HgI₂ gave the complexes [P₄Cu₂I(Hg₂I₅)]. Many of these complexes are structurally characterized as containing mercurate anions weakly bonded to cationic tetraphosphinitoresorcinarene complexes of copper(I) or silver(I) in an unusual form of host−guest interaction. In contrast, the complex [P₄Ag₄I₅(HgI)] is considered to be derived from an anionic silver cluster with an iodomercury(II) cation. Fluxionality of the complexes in solution is interpreted in terms of easy, reversible making and breaking of secondary bonds between the copper(I) or silver(I) cations and the mercurate anions.