Syntheses, crystal structures and coordination compounds of some 2-hetarylcyanoximes

Abstract

2-hetarylcyanoximes which have the general formula HO–NC(CN)–R, where R is a heterocyclic group such as 2-pyridyl, 2-quinolyl, 2-benzthiazolyl etc., have been found to be good multidentate ligands for coordination chemistry. They form intensely colored complexes with iron(II) and bis-compounds with copper(I), which are used in analytical chemistry. Stability constants for anionic Fe 2+ tris-cyanoximates were determined. The detailed syntheses and crystal structures of 2-pyridilcyanoxime (HPCO), 2-quinolylcyanoxime (HQCO) and 2-thiazolylcyanoxime (HTLCO) are reported. Molecules of HPCO in the crystal state adopt a non-planar cis– anti conformation. HQCO crystallizes as a monohydrate and this cyanoxime has a trans– anti non-planar conformation in the solid state. Molecules of HTLCO showed a trans– syn planar conformation in the solid state. Crystal structures of other known cyanoxime ligands are reviewed, as well as syntheses and the coordination modes for 2-hetarylcyanoximes in various complexes with s-, p- and d-metals.