BIS(DIIMINE)NITRITOCOPPER(II) CATIONS - CRYSTAL AND MOLECULAR-STRUCTURES OF [CU(PHEN)(2)(ONO)]BF4-CENTER-DOT-H2O AND [CU(BIPY)(2)(ONO)]HSO4(PHEN EQUALS 1,10-PHENANTHROLINE, BIPY EQUALS 2,2'-BIPYRIDINE)

The crystal and molecular structures of the bis(diimine)nitritocopper( II) complexes [Cu(phen)(2)(ONO)](BF4). H2O (1; phen = 1,10-phenanthrol ine) and [Cu(bipy)(2)(ONO)](HSO4) (2; bipy = 2,2'-bipyridine) have bee n determined. The latter is isostructural with [Cu(bipy)(2)(ONO)](BF4) (4); The coordination geometry of the Jahn-Teller distorted [Cu(diimi ne)(2)(ONO)](+) cation in 2 is best described as square pyramidal (mon odentate O-bonded nitrite). That in 1, which is similar to that in [Cu (phen)(2)(ONO)](BF4) (3), is distorted towards the cis-distorted octah edral (bidentate chelating O-bonded nitrite) coordination geometry ado pted by [Cu(bipy)(2)(ONO)](NO3) (5). As the nitrite coordination mode changes from monodentate towards bidentate chelating, distinct trends in structural parameters are discernible. Identical trends are found i n the analogous acetates and formates. They suggest that modification of coordination mode principally involves rotation of the nitrite (ace tate, formate) moiety about its nitrogen (carboxylate carbon) atom. (C ) 1997 Elsevier Science Ltd.