Morpholine-N-carboxylate as a ligand in coordination chemistry – Syntheses and structures of three heteroleptic copper(ii) and zinc complexes.

The first three morpholine- N -carboxylate complexes, with copper(II) and zinc(II) have been prepared and studied by single crystal X-ray diffraction. All three compounds comprise of discrete mono- or dinuclear heteroleptic complex molecules. Three different ways of bonding of morph COO– anions have been observed – as a monodentate, chelating, and as a bridging ligand. In all cases only the carboxyl group of the morpholinecarboxylate anion was found to bind to the metal cation, while the oxygen atom of the morpholine ring participates only in weak C–H‧‧‧O hydrogen bonds. Changes in the geometry of the coordinated morph COO– anion relative to the free ligand (in its morpholinium salt) were observed in all three modes of binding to the metal center. Image 1 • Morpholinecartboxylate has been successfully employed as a ligand. • Its complexes with Cu(II) and Zn(II) have been synthesized and studied. • It always coordinates metal atoms solely with the carboxylate oxygen atoms. • It can coordinate as a monodentate, chelating or a bridging ligand. [ABSTRACT FROM AUTHOR]