A new silver(I) carboxylate chelate type: A six-membered ring in the N-oxide-picolinate

A new silver(I) carboxylate derivative was prepared from AgNO3 and N-oxide-2-pyridinecarboxylic acid (HL). The complex Ag(5)L(4) (NO3) crystallizes in the space group P2/c with a = 15.565(2), b = 7.133(1), c = 13.533(2) Angstrom, beta = 109.93(1) degrees, V = 1412.5(4) Angstrom(3) and Z = 2. The structure was refined for 3143 independent reflections to R = 0.033. The crystal is a three-dimensional polymeric network with three different coordination sites. Two silver atoms of the asymmetric unit are included in a (Ag-O-C-O)(2) eight-membered ring, with two types of coordination : (a) a very distorded octahedral arrangement for the Ag1 atom linked to a second Ag2 atom (Ag1...Ag2 = 2.9094(3) Angstrom), to three carboxylic oxygen atoms (Ag1-O = 2.288(3), 2.307(3) and 2.631(3) Angstrom) and to two N-oxide oxygen atoms (Ag1-O = 2.437(3) and 2.546(3) Angstrom); (b) a pseudo square planar arrangement for the Ag2 atom linked to Ag1, to two carboxylic oxygen atoms (Ag2-O = 2.209(2) and 2.218(2) Angstrom) and to one N-oxide oxygen atom (Ag2-O = 2.507(2) Angstrom). The third silver atom lays on a twofold axis and exhibits a very distorded octahedral environment with two carboxylic oxygen atoms (Ag3-O = 2.451(3) Angstrom) and four N-oxide oxygen atoms (Ag3-O = 2.569(3) and 2.603(2) Angstrom). This compound is the first silver(I) carboxylate showing a six-membered chelate ring. Ag1 is included in a such chelate ring involving the N-oxide group and the carboxylic function of a same ligand while Ag3 is simultaneously included in two ones. The main features of the silver(I) carboxylates exhibiting the (Ag-O-C-O)(2) eight-membered ring are reviewed and compared.