COORDINATION CHEMISTRY OF ALKALI AND ALKALINE-EARTH CATIONS - X-RAY STRUCTURAL-ANALYSIS OF CALCIUM(PICRATE)2(2,2'-BIPYRIDYL)2

Ca(Pic)2 (Pic = 2, 4, 6-trinitrophenolate) and 2, 2’-bipyridyl (BIPY) react fast to produce Ca(Pic)2(BIPY)2 irrespectiv e of whether the reaction medium is protic (alcoholic) or aprotic (acetone). Crystals of the title compound C32H20N10O14Ca, Mr = 808.7, are orthorhombic, space group Pbca, a = 24.154(5), b = 16.128(5), c = 18.068(6)Å, V = 7038.5 Å3, Z = 8, = 1.528, Dm= 1.532 gcm~ 3(flotation), for MoKα, = 2.53 cm-1. X-ray data were collected at room temperature. R refined to 0.68 for 1263 observed reflections. The calcium ion is 8-coordinate, four N atoms of the two BIPY molecules and four O atoms of the two Pic anions constituting a distorted square antiprism. In the coordination polyhedron, the Ca-O distances (2.292 and 2.357 Å) to phenoxide oxygens are shorter than the Ca-O nitro interactions (2.574 and 2.502 Å) and Ca-N (2.492-2.578 Å). The four binding groups are not symmetrically distributed around the cation. The nitro groups are severely rotated out of the plane of the ring. In both BIPY molecules the rings are twisted. © 1990, Taylor & Francis Group, LLC. All rights reserved.