Santosh Y. Shetgaonkar

A calcium(II) coordination polymer showing two different bridging 2-carbamoyl-4-nitrobenzoate coordination modes

Aqueous reaction of CaCO3 with 2-carbamoyl-4-nitrobenzoic acid (2-ca-4nbaH) results in the formation of a 1-D coordination polymer [Ca(H2O)2(2-ca-4nba)2] (1), which crystallizes in the centrosymmetric triclinic space group P 1. The structure consists of a central Ca(II), two coordinated waters, a symmetrical bridging (µ2-η 1 : η 1) 2-ca-4nba, and a tridentate bridging (µ2-η 2 : η 1) 2-ca-4nba. The calcium in 1 is coordinated by two water molecules and five oxygens of four symmetry-related 2-ca-4nba, resulting in a distorted pentagonal bipyramidal {CaO7} polyhedron. Pairs of {Ca(H2O)2} units are linked into a 1-D coordination polymer extending along the a-axis with the aid of pairs of bridging 2-ca-4nba ligands. In the infinite chain, alternating pairs of Ca(II) ions exhibit Ca ··· Ca separations of 4.124 and 4.855 Å.

Synthesis and characterization of calcium(II) coordination polymers based on phenylacetic acid

The syntheses, crystal structures, and thermal properties of the coordination polymers [Ca(H2O)2(L1)2] · H2O (1) (L1 = 4-methoxyphenylacetate) and [Ca(H2O)2(L2)2] · 2H2O (2) (L2 = 2-chlorophenylacetate) are described. 1 and 2 can be dehydrated to the anhydrous [Ca(L1)2] (1a) or [Ca(L2)2] (2a), respectively. Compounds 1 and 2 crystallize in the non-centrosymmetric monoclinic space group P21 and the structures consist of a central Ca(II), two terminal waters, and two crystallographically unique L1 (or L2) anions, one of which functions as a chelating bidentate ligand. The second independent L1 (or L2) is tetradentate, coordinated in a μ3-bridging mode leading to the formation of a 1-D coordination polymer. In the infinite chain extending along the b-axis, each Ca(II) is eight-coordinate and bonded to two terminal waters and six oxygens from four different L1 or L2 ligands.