Syntheses, structures and vibrational spectroscopy of some 1:1 and 1:2 adducts of silver(I) oxyanion salts with 2,2′-bis(pyridine) chelates

Abstract

Syntheses and room-temperature single-crystal X-ray structure determinations are recorded for a number of adducts of 1:1 stoichiometry of silver(I) oxyanion salts (perchlorate, nitrate, trifluoroacetate (‘tfa’) (increasing basicity)) with 2,2′-bis(pyridine) ligands (2,2′-bipyridyl, ‘bpy’; 2,2′-biquinolyl, ‘bq’; 2,2′-dipyridylketone, ‘dpk’; 2,9-dimethylphenanthroline, ‘dmp’). The adducts take two forms: (a) neutral mononuclear molecules, in which the 2,2′-bis(pyridine) ligand behaves as a chelate, with the silver coordination number dependent on the denticity of the anion; these are Agtfa:bpy (1:1) and AgClO 4:bq (1:1) (and various (ionic) acetonitrile or pyridine solvates AgClO 4:bq/dmp:MeCN/py (1:1:1), in which the solvent molecules are coordinated); and (b) one-dimensional polymers. The latter are diverse: in AgClO 4:bpy, dpk (1:1), the anion is discrete, the polymer made up of an array of two-coordinate silver atoms linked by bpy ligands twisted about their central connecting element. In AgNO 3:bpy, bq (1:1), the bpy ligands are chelating with the oxyanions bridging, cf. previously reported AgNO 3:dpk (1:1), in which the nitrate chelates the metal, with the dpk bridging, chelating N,O to one silver, while the other nitrogen bridges to the next. With Agtfa, a novel binuclear adduct has been isolated in conjunction with the hydrated ligand, Agtfa:dpk:(dpk · H 2O) (1:1:2). The far-IR spectra of several of these complexes show bands that can be assigned to the ν(AgN) modes, the positions of these bands correlating well with the relative Ag–N bond lengths. Syntheses and single-crystal X-ray structural characterizations are also reported for various adducts of silver(I) perchlorate, nitrate and trifluoromethanesulfonate with bpy, bq, ‘phen’ (= 1,10-phenanthroline), and ‘dmp’, of stoichiometry AgX:L (1:2). In each case the complex is ionic [AgL 2]X; the silver atom is four-coordinate, but diverse and remarkable variations in stereochemistries associated with changes in the interligand N–Ag–N angles, presumably influenced by the different packing arrangements, are observed.