Structure of [(tmpp)₂Ag]⁺₂[Ag₅I₇]^2-; an Unusual Ionic Adduct of Tris(2,4,6-trimethoxyphenyl)phosphine (tmpp) With Silver(I) Iodide

Abstract

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-trimethoxypheny1) phosphine ( tmpp ) with silver(I) iodide. This complex is triclinic, P1, a 22.01(2), b 19.98(1), c 16.48(1) Å , α 94.49(6), β 92.46(7), γ 116.76(5)',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)°, and a mean Ag-P distance of 2.38 Å . 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) Å respectively.