The synthesis, characterization and structures of the chromium(III) dinitrito complexes: trans-[Cr(L)(ONO)(2)](+) (L=1,4,8,11-tetraazacyclotetradecane or 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane)

Described are the syntheses plus the spectroscopic and structural character izations of the chromium(III) complexes trans-[Cr(cyclam)(ONO)(2)](BF4) (1) (cyclam = 1,4, 8,11-tetraazacyclotetradecane) and [Cr(tetA)(ONO)(2)](NO3). H2O (2) (tetA = 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecan e). The optical absorption spectra of these are dominated by a spin allowed ligand field band at 476 and 480, respectively, and by a nitrite ligand lo calized n-->pi* band at 336 and 344 nm, respectively. The crystalline phase s of both materials consist of Cr(III) complex ions situated at unit cell e dge and face centers that correspond to the crystallographic inversion cent ers. For 1 the charge balancing BF4- anions are orientationally disordered and are positioned in the cavities formed by the complexes. For 2, the nitr ate anion and water molecule forms pairs through the O-H...O type hydrogen bond and each pair has two statistical orientations. (C) 2000 Elsevier Scie nce S.A. All rights reserved.