STRUCTURE OF [(TMPP)2AG]+2[AG5I7]2- - AN UNUSUAL IONIC ADDUCT OF TRIS(2,4,6-TRIMETHOXYPHENYL)PHOSPHINE (TMPP) WITH SILVER(I) IODIDE

A single-crystal structure determination is reported for [(tMPP)2Ag]2+ [Ag5I7]2-, a product isolated from the reaction of the highly basic, sterically hindered tertiary phosphine ligand tris(2,4,6-trimethoxyphenyl)phosphine (tmpp) with silver(I) iodide. This complex is triclinic, P1BAR, a 22.01(D2), b 19-98(1), c 16.48(1) angstrom, alpha 94-49(6), beta 92.46(7), gamma 116.76(5)-degrees, Z 2; R was 0.11 for 3436 'observed' reflections. The asymmetric unit contains two crystallographically inequivalent [(tMPP)2Ag]+ cations in which the silver atoms are quasi-linearly coordinated to two phosphorus atoms with P-Ag-P angles of 175-9(9) and 179(1)-degrees, and a mean Ag-P distance of 2.38 angstrom. The anion has a novel one-dimensionally polymeric structure which is based on a double-stranded 'ladder' polymer of AgI units to which are bonded one I- and one AgI2- unit for every four AgI units. In the resulting polymer, all silver atoms are four-coordinate, while iodide coordination numbers of two, three and four are observed, with associated Ag-I distances of 2.75-2.86(1), 2.72-2.91(1) and 2.90-3.08(1) angstrom respectively.