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 morphCOO(-) 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 center dot center dot center dot O hydrogen bonds. Changes in the geometry of the coordinated morphCOO(-) anion relative to the free ligand (in its morpholinium salt) were observed in all three modes of binding to the metal center. (c) 2019 Elsevier B.V. All rights reserved.