MOLECULAR RIBBONS COMPOSED OF CALCIUM ATOMS BRIDGED BY CARBOXYLATE OXYGENS IN THE X-RAY STRUCTURE OF CALCIUM COMPLEX WITH 3-AMINOPYRAZINE-2-CARBOXYLIC ACID

The crystals of monoaquabis(mu-3-amino-2-pyrazinato)calcium(II) are mo noclinic, space group Cc, a = 22.787(5), b = 6.367(1), c = 9.906(2) An gstrom, beta = 110.58(3) deg., Z = 4. Each calcium atom is coordinated by two aminopyrazinate molecules via their heteroring nitrogens (Ca-N = 2.594 Angstrom) and the nearest to them two oxygens of the carboxyl ate groups (Ca-O = 2.385 Angstrom) and by one water molecule with Ca-O = 2.344 Angstrom, making with aminopyrazinate ligands a planar ''step ''. Two other oxygen atoms are chelated to the calcium atom, each cont ributed by the second oxygen atom of the carboxylic group situated in the ''step'' above and below (mean Ca-O = 2.363 Angstrom). The carboxy lic groups are bidentate and bridge the ''steps'' into ribbons propaga ting along the c axis. The ribbons are linked by strong hydrogen bonds of 2.71(1) and 2.74(1) Angstrom operating between the coordinated wat er oxygen and the carboxylic oxygens in the adjacent ribbons.