Synthesis, Crystal Structure, and Molecular Structure of Maleate Tris(Benzohydrazide) Cobalt(II) Tetrahydrate [Co(L1)3](Mal) · 4H2O and Maleate Tris(Phenylacethydrazide) Nikel(II) Monohydrate [Ni(L2)3](Mal) · H2O

Coordination compounds [Co(L1)3](Mal) · 4H2O (I) and [Ni(L2)3](Mal) · H2O (II) (L1 is benzohydrazide, L2 is phenylacethydrazide, and H2Mal is maleic acid) have been synthesized and characterized by IR spectroscopy and diffuse reflectance spectroscopy. Crystal structures of I and II have been determined by single-crystal X-ray diffraction. Structural units of crystals I and II are complex cations [Co(L1)3]2+ and [Ni(L2)3]2+, respectively, maleate-ions Mal2–, and crystallized water molecules bound by a branched system of hydrogen bonds. Metal atoms at the complex cations of crystals I and II have octahedral coordination (3O + 3N) formed by three bidentate chelate ligands Ln (n = 1, 2).