Preparation and crystal structures of the silver(I) carboxylates [Ag2{C6H4(CO2)2}(NH3)2], [NH4][Ag5{C6H3(CO2)3}2(NH3)2(H2O)2]·H2O and [NH4][Ag{C4H2N2(CO2)2}]

Abstract

Two silver ammine complexes with the polyprotic aromatic acids benzene-1,2-diacarboxylic acid (phthalic acid) and benzene-1,3,5-tricarboxylic acid (trimesic acid) have been prepared and their structures determined using single-crystal X-ray diffraction and infrared spectroscopy. Complex 1, [Ag₂{C₆H₄(CO₂)₂}(NH₃)₂], is a hydrogen-bonded polymer based on a simple diamminephthalatodisilver(I) species, with an ammonia molecule and a single phthalate carboxylate oxygen bonded to separate silver atoms, giving essentially linear co-ordination [Ag–N 2.116(3), Ag–O 2.134(2)Å, O–Ag–N 175.3(1)°]. All three ammine hydrogens are involved in intermolecular hydrogen-bonding interactions, giving a chain polymer. Complex 2, [NH₄][Ag₅{C₆H₃(CO₂)₃}₂(NH₃)₂(H₂O)₂]·H₂O, is a two-dimensional sheet polymer based on a pseudo-centrosymmetric S-type trimer unit, linked by the carboxylate groups of two independent trimesate residues [Ag ⋯ Ag 2.928(1), 2.946(1)Å]. The two ammonia molecules are also bonded linearly to two independent silvers [Ag–N 2.141 (6), 2.159(7)Å; N–Ag–O 166.1(2), 170.2(2)°]. The terminal silvers provide bonding links to adjacent trimesate carboxyl oxygens between the layers while the third trimesate carboxyl group forms conventional centrosymmetric bis[(carboxylato-O,O′)silver(I)] dimers [Ag ⋯ Ag 2.847(1), 2.856(4)Å], with water molecules in the axial sites for the dimer. A third compound 3, ammonium silver(I) pyrazine-2,3-dicarboxylate [NH₄][Ag{C₄H₂N₂(CO₂)₂}], has also been prepared using a procedure similar to that for 1 and 2. However, unlike them, it has no bonded ammines but has a distorted trigonal-planar co-ordination involving two carboxylate oxygens [Ag–O 2.333(6), 2.376(5)Å] and one heteronitrogen [Ag–N 2.249(6)Å], from three separate ligand molecules, giving a polymer structure.