Cu(II), Ni(II) and Fe(III) complexes with 2 ',2 '''-(2,6-pyridindiyldiethylidene)-dioxamohydrazide in a monoanionic form. The crystal structure of aqua-2 ',2 '''-(2,6-pyridindiyldiethylidene)-dioxamohydrazidecopper(II) perchlorate

Starting from Cu(II) and Ni(II) perchlorate and Fe(III) chloride in the pre sence of 2,6-diacetylpyridine (dap) and semioxamazide (sox), the [Cu(Hdapso x)H2O]ClO4 (I), [Ni(Hdapsox)(MeOH)(2)]ClO4 (II) and [Fe(Hdapsox)Cl-2]. 1/2H (2)O (III) complexes with a singly deprotonated ligand Hdapsox(-) of the ac yl hydrazone class (with H(2)dapsox = 2',2'''-(2,6-pyridindiyldiethylidene) dioxamohydrazide) have been obtained and characterized for the first time b y a template synthesis. The previously assumed [1] square-pyramidal structu re of the Cu(II) complex with an asymmetrical coordination of Hdapsox(-) ha s been confirmed by a single-crystal X-ray analysis. In II Hdapsox(-) is oc tahedrally coordinated around a Ni(II) ion, while III is found to be a pent agonal-bipyramidal complex with a symmetrically bonded Hdapsox(-). Causes o f a ligand deprotonation occurring in a very acid medium (pH = 0) and of a different coordination pattern in the case of Cu(II), NI(II) and Fe(III) ar e interpreted by a d(n) configuration and an effective nuclear charge of th e central metal ion (crystal field effects). (C) 1998 Elsevier Science Ltd. All rights reserved.