A NEW SILVER(I) CARBOXYLATE CHELATE TYPE - A 6-MEMBERED RING IN THE N-OXIDE-PICOLINATE

A new silver(I) carboxylate derivative was prepared from AgNO3 and N-o xide-2-pyridinecarboxylic acid (HL). The complex Ag(5)L(4) (NO3) cryst allizes 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 reflection s to R = 0.033. The crystal is a three-dimensional polymeric network w ith three different coordination sites. Two silver atoms of the asymme tric unit are included in a (Ag-O-C-O)(2) eight-membered ring, with tw o types of coordination : (a) a very distorded octahedral arrangement for the Ag1 atom linked to a second Ag2 atom (Ag1...Ag2 = 2.9094(3) An gstrom), 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 e xhibits a very distorded octahedral environment with two carboxylic ox ygen 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 si lver(I) carboxylate showing a six-membered chelate ring. Ag1 is includ ed in a such chelate ring involving the N-oxide group and the carboxyl ic function of a same ligand while Ag3 is simultaneously included in t wo ones. The main features of the silver(I) carboxylates exhibiting th e (Ag-O-C-O)(2) eight-membered ring are reviewed and compared.