Silver–iodocarbon complexes: crystal structures of eight compounds obtained from the reactions of AgPF6 or AgNO3 with CH2I2, I(CH2)3I and simple aryl iodides

Abstract

Eight silver(I)–iodocarbon complexes have been prepared and structurally characterized by single-crystal X-ray diffraction. In [Ag{I(CH₂)₃I}₂]PF₆, [Ag(ICH₂I)₂]PF₆, [Ag(1,2-I₂C₆H₄)₃]PF₆ and [Ag(1,2-BrIC₆H₄)₄]PF₆ the silver ions are four-co-ordinate and bonded to four iodine atoms of four iodocarbon ligands, the co-ordination geometry varying from slightly distorted tetrahedral to trigonal pyramidal. Typical Ag–I bond lengths are in the range 2.8–2.9 Å though the axial Ag–I bond in [Ag(1,2-I₂C₆H₄)₃]PF₆ is significantly elongated to 3.2–3.3 Å. The diiodocarbons function as bridging ligands in [Ag{I(CH₂)₃I}₂]PF₆ and [Ag(ICH₂I)₂]PF₆. The structure of the former consists of a chain polymer built from Ag[I(CH₂)₃I]₂Ag rings whilst the latter consists of (AgICH₂I)_n chains cross-linked by Ag(ICH₂I)₂Ag rings. The compound [Ag(1,2-I₂C₆H₄)₃]PF₆ is a tetrameric cyclic structure in which one-third of the 1,2-I₂C₆H₄ ligands bridge two silvers via the two iodine atoms, the others functioning as monodentate to a silver atom via one of the iodine atoms. The compound [Ag₂(O₂PF₂)₂(p-IC₆H₄Me)] contains a complex sheet Ag(O₂PF₂)_n structure in which an iodotoluene bridges two silvers via an iodo and an η²-arene linkage. Each difluorophosphate links four silvers via two µ-oxygen bridges. The compound [Ag(O₂PF₂)(1,4-I₂C₆H₄)] contains [Ag(O₂PF₂)]_n chains in which the difluorophosphate forms a three-atom O,O′ bridge. These chains are cross-linked via bridging 1,4-I₂C₆H₄ ligands which co-ordinate to silver via the iodine atoms. The compound [Ag(NO₃)(CH₂I₂)] is a sheet array derived from fused Ag₄(µ-NO₃)₂(µ-ICH₂I)₂ 16-atom rings with each silver bonded to two oxygen and two iodine atoms in a distorted-tetrahedral array. The compound [Ag(NO₃)(1,2-I₂C₆H₄)] is composed of spiral chains of [Ag(µ-NO₃)]_n in which the nitrate uses only one oxygen atom to bridge two silvers. Each silver is bonded to two iodine and two oxygen atoms. The ‘AgI₂O₂’ bond angles range from 82 to 134°. The 1,2-I₂C₆H₄ ligands bridge alternate first and third silvers along the chain and stack on either side of the [Ag(NO₃)]_n chain to produce two complementary spiral arrays.