Spectroscopic and structural studies on 1:1 adducts of silver(I) salts with tricyclohexylarsine

Adducts of a number of silver(I) salts, AgX, with tricyclohexylarsine, of 1 : 1 AgX:As(C6H11)(3) stoichiometry have been synthesized for X = Cl, Br, I, NO3, NCO or CN and subjected to room temperature single crystal X-ray determinations and studies of their low frequency vibrational spectra. The chloride is binuclear [{(C6H11)(3)As}Ag(mu-Cl)(2)Ag{As(C6H11)(3)}], isomorphous with its previously recorded P(C6H11)(3) X = Cl, Br counterparts, the silver environment being quasi-planar, trigonal AsAg(mu-C1)(2); the nitrate is isomorphous, with a central planar Ag(mu-O)(2)Ag array, a pair of oxygen atoms, one from each of a pair of symmetry-related nitrate groups, bridging the two silver atoms. The present bromide, unlike its P(C6H11)(3) counterpart, is not a dimer, but, like the iodide, a 'cubane' tetramer; the iodide is isomorphous with its P(C6H11)(3) analogue, a crystallographic 2 axis passing through a pair of opposed faces of the tetramer, but the bromide is of a new type, rhombohedral space group R (3) over bar. Remarkably, the cyanate is also of the cubane form, the first recorded (other than an organometallic) incorporating a first-row atom, obtained unsolvated and bis(pyridine) solvated. The cyanide is a linear polymer... {(C6H11)(3)As}(2)AgNCAgCN{As(C6H11)(3)}(2)AgNC... ('alpha' phase, from 2-methylpyridine); a second 'beta' phase was obtained from 2,4,6-trimethylpyridine, of similar form, while from pyridine, a solvate of 3:4:2 AgCN:As(C6H11)(3):py stoichiometry [{Ag[As(C6H11)(3)](2)(py)}(2)(CN)][Ag(CN)(2)] was obtained. The structure of the E = Px = CN unsolvated 1 : 1 analogue was also determined, also being a linear polymeric array like its E = As counterpart. The far-IR spectra of the halide complexes exhibit bands due to v(AgX) vibrational modes at 229, 148 cm(-1) (X = Cl), 167, 151, 125, 109 cm(-1) (X = Br) and at ill, 86 cm(-1) (X = I). These spectra were interpreted in terms of idealised C-2h Ag2Cl2 and TdAg4X4 structures of the silver halide cores.