Solid state and solution structural studies of silver(I) cyclic complexes bearing the (Bzim)Ph2P ligand

Cyclic silver(I) compounds having a [μ-(Bzim)Ph2PAg]22+ unit ((Bzim)Ph2P=1-benzyl-2-imidazolyldiphenylphosphine) and NO3− (I), BF4− (II), and B[3,5-(CF3)2C6H3]4− (III) as counterions were characterized in the solid state by X-ray crystal structure determinations (I, II), and in solution by 1H-, 13C-, 19F- and 31P-NMR spectroscopies. The crystal structure of complex [μ-(Bzim)Ph2PAg(NO3)]n (n=2, 4) (I) (triclinic, space group P1̄ (no. 2), a=15.118(5), b=17.755(3), c=14.123(4) Å, α=90.23(2), β=111.67(2), γ=85.92(2)°, Z=2) shows two conformers A and B in the unit cell. The conformer A consists of a tetranuclear species formed by two [μ-(Bzim)Ph2PAg]22+ moieties, related by a center of symmetry, bonded together by two bridging nitrate anions. The nitrate anions are coordinated to the silver atoms in an unusual fashion. The conformer B is a dinuclear species where the silver atoms present in the eight-membered ring complete their tetracoordination with two chelate nitrate anions. The crystal structure of complex {[μ-(Bzim)Ph2PAg(BF4)]2}∞ (II) (monoclinic, space group P21/c (no. 14), a=11.563(3), b=8.353(4), c=26.188(7) Å, β=95.88(2)°, Z=2) consists of infinite chains of the dinuclear cyclic silver moieties held together by BF4− bridging anions. The low temperature experimental and simulated 31P-NMR spectra of complexes I–III show complex apparent doublets of multiplets due to the resonance of the spin systems of the three isotopomers of the silver atoms present in the cyclic units. The interionic solution structure of complex II was investigated by 19F{1H}-HOESY NMR spectroscopy. In methylene chloride solution the BF4− anion is not more coordinated to the silver(I) atoms as in the solid state, and it is localized in between the phenyl and benzyl groups of the ligand.