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)

Abstract Described are the syntheses plus the spectroscopic and structural characterizations of the chromium(III) complexes trans -[Cr(cyclam)(ONO) 2 ](BF 4 ) ( 1 ) (cyclam=1,4,8,11-tetraazacyclotetradecane) and [Cr(tetA)(ONO) 2 ](NO 3 )·H 2 O ( 2 ) (tetA=5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane). 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 localized n →π* band at 336 and 344 nm, respectively. The crystalline phases of both materials consist of Cr(III) complex ions situated at unit cell edge and face centers that correspond to the crystallographic inversion centers. For 1 the charge balancing BF 4  − anions are orientationally disordered and are positioned in the cavities formed by the complexes. For 2 , the nitrate anion and water molecule forms pairs through the OH⋯O type hydrogen bond and each pair has two statistical orientations.