Structures of bis(salicylaldoximato)- and bis(5-chlorosalicylaldoximato)nitrosylcobalt, examples of nitrosyls containing a bent Co-N-O group

Abstract

The crystal and molecular structures of [Co(NO)(salox)2] and [Co(NO)(5-Clsalox)2], where saloxH is salicylaldoxime and 5-ClsaloxH is its 5-chloro derivative, have been determined. The unsubstituted nitrosyl crystallizes in the orthorhombic system,a=11.557,b=15.333,c=8.245 A,Z=4, space groupPna21. The structure was determined by theDIRDIF difference structure factors method, using MoKα diffractometer data, and refined by full-matrix least squares toR=0.055 for 685 observed reflexions. The 5-chloro analogue crystallizes in the monoclinic system,a=8.553,b=12.510,c=15.702 A, β=102.84°,Z=4, space groupP21/c. This structure was determined by the heavy-atom method, using MoKα diffractometer data, and refined by full-matrix least squares toR=0.043 for 2107 observed reflections. In both compounds, the molecule excluding the nitrosyl group is approximately planar. The cobalt atom is 5-coordinate in an essentially square pyramidal arrangement with the basal plane defined bytrans bidentate oximato ligands between which are strong hydrogen bonds. The nitrosyl group occupies the apical position, and the Co-N-O angles and the N-O bond lengths are 116(2)° and 1.48(3) A ([Co(NO)(salox)2]), and 123.4(3)° and 1.070(5) A ([Co(NO)(5-Clsalox)2]). The more acute angle and unusually long N-O bond of [Co(NO)(salox)2] may be due to disorder and/or an interaction between the NO oxygen atom and one of the oxime groups.