PREPARATION AND CHARACTERIZATION OF SOME METAL(II) COMPLEXES OF ISOCINCHOMERONIC ACID AND X-RAY CRYSTAL-STRUCTURE OF CIS-DIAQUABIS(HYDROGEN ISOCINCHOMERONATO)MANGANESE(II)

The reactions between Mn(II), Co(II), Ni(II), and Zn(II) ions with isocinchomeronic acid (H-2-isocin) afforded complexes of the general formula M(H-isocin)2 . 2H2O, whereas Fe(II) gives both red and deep red-brown products of the same formula. Various physical measurements suggest that the complexes of M = Co, Ni, Zn, and Fe (brown) are octahedrally coordinated by two aqua ligands and two trans-N,O-bidentate H-isocin- anions with dimeric hydrogen bonding. Those for M = Mn and Fe (red) are the corresponding cis isomers. The structure of the manganese complex as determined by X-ray crystallography exhibits C2 molecular symmetry with Mn-N = 2.279(2), Mn-O(H-isocin)- = 2.196(2), and Mn-O(aqua) = 2.137(2) angstrom. Each aqua ligand forms two donor 0-H ... 0 hydrogen bonds with carboxy groups of different molecules in adjacent chains.