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-phenanthroline) and [Cu(bipy)(2)(ONO)](HSO4) (2; bipy = 2,2'-bipyridine) have been determined. The latter is isostructural with [Cu(bipy)(2)(ONO)](BF4) (4); The coordination geometry of the Jahn-Teller distorted [Cu(diimine)(2)(ONO)](+) cation in 2 is best described as square pyramidal (monodentate O-bonded nitrite). That in 1, which is similar to that in [Cu(phen)(2)(ONO)](BF4) (3), is distorted towards the cis-distorted octahedral (bidentate chelating O-bonded nitrite) coordination geometry adopted 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 in the analogous acetates and formates. They suggest that modification of coordination mode principally involves rotation of the nitrite (acetate, formate) moiety about its nitrogen (carboxylate carbon) atom. (C) 1997 Elsevier Science Ltd.