Seven novel adducts of ethylenediamine (en), N, N'-dimethylethylenediamine (dmen) and N, N-dimethylethylenediamine (ndmen) with saccharinate, orotate and salicylate as counter-ions were synthesized and characterized with physico-chemical methods (IR and UV/vis spectroscopy, magnetic susceptibility and thermoanalytical measurements) and X-ray diffraction. Reaction of dmen with tetraaquabis(saccharinato-N)copper(II) dihydrate yielded diaquabis(dmen)copper(II) saccharinate, whereas with the corresponding nickel derivative it afforded bis(dmen)bis(saccharinato-O)nickel(II). In the copper complex the coordinated water and the primary nitrogen end of the donor ligand interact with the saccharinate anion [O1w... O3 = 2.833(2), N1... N2 = 2.992(2) Angstrom]. Adjacent molecules are linked by two more hydrogen bonds into a layer structure. In the nickel compound, the dmen ligand also chelates the metal atom, which is bonded to the carbonyl oxygen of the anionic group. The negatively-charged nitrogen atom of the anion is intramolecularly linked to the dmen [N1... N2 = 2.968(2) Angstrom]; hydrogen bonds link the molecules into layers. Under mildly basic conditions, the reaction of orotic acid with cobalt(II) afforded tetraaqua(2,6-dioxo-1,2,6-trihydropyrimidine-4-carboxylato-N,O)cobalt(II) hydrate. The complex was oxidatively reacted with en to give a mixed-ligand cobalt(III) adduct which includes both mono- and bisdeprotonated orotate ions. The metal atom in tetraaqua(2,6-dioxo-1,2,6-trihydropyriniidine-4-carboxylato-N,O)cobalt(II) hydrate is chelated by the orotato dianion through the carboxyl oxygen and 3-pyrimidyl nitrogen atoms, and its octahedral geometry is completed by four water molecules. The 1-pyrimidyl nitrogen atom engages in hydrogen bonding with the lattice water molecule. The cobalt atom is similarly chelated by the orotato dianion in bis(en)(2,6-dioxo-1,2,6-trihydropyrimidine-4-carboxylato-NO)cobalt(III) 2,6-dioxo-1,2,3,6-tetrahydropyridimidine-4-carboxylate pentahydrate. The copper atom in the five-coordinate aqua(en)orotatocopper(II) monohydrate is chelated by the en ligand, the deprotonated N1 pyrimidine atom and the orotate carboxylate oxygen; the water molecule completes the square-pyramidal coordination. The nickel and copper atoms in bis(en)bis(salicylato-O)nickel(II) and bis(ndmen)bis(salicylato-O)copper(II) monomeric octahedral complexes are coordinated by the salicylato monoanion through the carboxylate oxygen in a monodentate fashion and by the en and ndmen molecules through the two amine nitrogen atoms in a bidentatechelating manner. In the copper complex, the carboxylate oxygen atom engages in hydrogen bonding with the lattice water molecule. (C) 2003 Elsevier B.V. All rights reserved.