Bridges in Polynuclear Complexes. II. An X-Ray Investigation of the Coordination of Silver Ion to the μ-Peroxo Bridge of a Dinuclear Cobalt(III) Complex

Abstract

Abstract The crystal structure of [(en)2Co(NH2)(O2)Co(en)2](NO3)3·15/8(AgNO3)·H2O has been determined from X-ray diffraction data collected by the counter method. The crystal is monoclinic with the space group C2/c and with a=8.710(3), b=16.413(5), c=20.024(8)Å, β=90.30(4)°, and Z=4. The structure was refined by the block-diagonal least-squares method to R=0.107 for 2157 independent reflections. It has been elucidated that the Ag atom is bound to each of the two peroxo oxygen atoms with the Ag–O bond length of 2.27(1) Å. Each Ag atom is also surrounded by two more oxygen atoms belonging to the nitrate anions and these Ag–O bond lengths are 2.45(2) and 2.50(2) Å. The central five-membered ring has a symmetric envelope conformation, with the peroxo O atom deviating from the Co, N, Co plane, by 0.38 Å. The crystals contain an equal amounts of the enantiomeric forms (δδΛδδδ) and (λλΔλΔλλ). The formation constant of Ag+ and [(en)2Co(NH2)(O2)Co(en)2]3+ in aqueous solution was found to be less than 0.5.