trans-Bis(dimethyl sulfoxide-κO)bis­(3-oxo-3,4-dihydroquinoxaline-2-carboxyl­ato-κ²N¹,O²)copper(II)

The title compound, [Cu(C₉H₅N₂O₃)₂(C₂H₆OS)₂], consists of octa­hedrally coordinated Cu^II ions, with the 3-oxo-3,4-dihydroquinoxaline-2-carboxyl­ate ligands acting in a bidentate manner [Cu—O = 1.9116 (14) Å and Cu—N = 2.1191 (16) Å] and a dimethyl sulfoxide (DMSO) mol­ecule coordinated axially via the O atom [Cu—O = 2.336 (5) and 2.418 (7) Å for the major and minor disorder components, respectively]. The whole DMSO mol­ecule exhibits positional disorder [0.62 (1):0.38 (1)]. The octa­hedron around the Cu^II atom, which lies on an inversion centre, is elongated in the axial direction, exhibiting a Jahn–Teller effect. The ligand exhibits tautomerization by H-atom transfer from the hydroxyl group at position 3 to the N atom at position 4 of the quinoxaline ring of the ligand. The complex mol­ecules are linked through an inter­molecular N—H...O hydrogen bond [N...O = 2.838 (2) Å] formed between the quinoxaline NH group and a carboxyl­ate O atom, and by a weak inter­molecular C—H...O hydrogen bond [3.392 (11) Å] formed between a carboxyl­ate O atom and a methyl C atom of the DMSO ligand. There is a weak intra­molecular C—H...O hydrogen bond [3.065 (3) Å] formed between a benzene CH group and a carboxyl­ate O atom.

A one-dimensional Cd^II coordination polymer: catena-poly[cadmium(II)-bis­(μ-6-methyl­picolinato)]

In the title compound, [Cd(C₇H₆NO₂)₂]_n, the Cd^II ion has a distorted octa­hedral geometry. The 6-methyl­pyridine-2-carboxyl­ate anions are perpendicular to one another and act as bidentate and bridging ligands. Two carboxyl­ate O atoms bridge the Cd^II ions, forming centrosymmetric dinuclear units. These units are further connected via carboxyl­ate O atoms into a one-dimensional polymeric chain which extends in the [100] direction.

A new coordination mode of 6-methyl­nicotinic acid in trans-tetra­aquabis­(6-methyl­pyridine-3-carboxyl­ato-κO)cobalt(II) tetra­hydrate

The title compound, [Co(C₇H₆NO₂)₂(H₂O)₄]·4H₂O, contains a Co^II ion lying on a crystallographic inversion centre. The Co^II ion is octa­hedrally coordinated by two 6-methyl­pyridine-3-carboxyl­ate ligands in axial positions [Co—O = 2.0621 (9) Å] and by four water mol­ecules in the equatorial plane [Co—O = 2.1169 (9) and 2.1223 (11) Å]. There are also four uncoordinated water mol­ecules. The 6-methyl­pyridine-3-carboxyl­ate ligands are bound to the Co^II ion in a monodentate manner through a carboxyl­ate O atom. There is one strong intra­molecular O—H...O hydrogen bond, and six strong inter­molecular hydrogen bonds of type O—H...O and one of type O—H...N in the packing, resulting in a complex three-dimensional supra­molecular structure.