Antimony as a Donor Atom in Silver Coordination Chemistry: Synthesis, IR Spectra and Structure of the Silver(I) Cyanoximate Complexes with Triphenylstibine and Triphenylphosphine Model Compounds

Abstract

Silver(I) cyanoximate complexes Ag{ONC(CN)-R} (R = COPh, {L1}; COC(CH3)3, {L2}; benzothiazol-2-yl, {L3}) with triphenylphosphine and -stibine of compositions Ag(PPh3)n{L} (n = 2, 4) and Ag(SbPh3)n{L} (n = 3 for {L1} and {L2}, n = 2 for {L3}) were synthesized by the reaction of the components in acetonitrile solution and characterized by elemental analyses and IR spectroscopy. The crystal structures of Ag(SbPh3)3{L} (L = {L1} (1), {L2} (2), Ag(SbPh3)2{L3} ∙ CH3CN (3) and Ag(PPh3)2{L1} ∙ CH3CN (4), have been determined by X-ray diffraction. For all the compounds examined the coordination environment of the silver atom has the geometry of a distorted terahedron ([AgP2NO] (4); [AgSb3N] (1), (2); [AgSb2N2] (3)). The bis adducts Ag(EPh3)n{L} adopt molecular structures, in which the organic anions are coordinated in bidentate chelate fashion via the nitroso nitrogen atom and the oxygen (nitrogen for {L3}) atom of the substituent R. In the tris-stibino complexes (Ag-Sb 2.670(4) - 2.7748(8) Å; Sb-Ag-Sb 108.87(4) - 115.00(2)°) the cyanoximates are unidentate ligands and coordinated via the nitroso nitrogen atoms (Ag-N ca. 2.35(1) Å). The different behaviour of N ,O and N,N chelating cyanoximes under the same conditions suggests, that the Sb donor triphenylstibine is able to substitute the oxygen atoms in the silver(I) coordination sphere, but not the nitrogen ones. This causes the formation of 1:3 adducts of Ag{L} with SbPh3 for N ,O donors {L1} and {L2}, and only 1:2 for N,N donor anionic {L3}.