Acetate Bridged Trinuclear Zn, Ca and Mg Metal Complexes with 2- and 4-Substituted Pyridines

Abstract

The structures of the complexes [Zn₂(C₅H₆N₂)₂(C₂H₃O₂)₆Ca], compound 1; [Zn(C₇H₁₀N₂)₂Cl₂] compound 2; and [Zn₂(C₅H₆N₂)₂(C₂H₃O₂)₆Mg] compound 3 were established by spectral and X-ray diffraction studies. These complexes form part of the project of design and synthesis of new alkaline-earth metal complexes with multiple applications in the fields of catalysis, material science and biochemistry. Compound 1 crystallizes in the monoclinic space group P2₁/c with unit cell parameters a = 11.6918(11), b = 8.2850(8), c = 15.3472(15) Å, β = 96.4140(10)°, Z = 2. Compound 2 crystallizes in the orthorhombic space group Pccn with unit cell parameters a = 13.6485(13), b = 14.2962(14), c = 18.2459(18) Å, Z = 8. Compound 3 crystallizes in the monoclinic space group P2₁/c with unit cell parameters a = 7.5531(8), b = 22.905(3), c = 8.7137(9) Å, Z = 2. All three structures (1–3) were solved by direct methods and refined to R = 0.0257, 0.0346 and 0.0244, respectively. For compound 1 crystallizes with the Ca²⁺ ion coincident with crystallographic centre of symmetry forming a dimer. The Ca²⁺ ion is six-fold coordinated by three acetate ligands. The Ca polyhedron may be described as a distorted tricapped trigonal prism. The Zn²⁺ ion is four-fold coordinated by three O atoms from three acetate groups (atoms O₂, O₄ and O₅) and an N atom from the 2-aminopyridine moiety. The Zn polyhedral may be described as a distorted tetrahedral coordination. Compound 2 crystallizes as a crystallographic C₂-symmetric complex, in which each Zn²⁺ ion is bound to two 4-dimethylaminopyridine units, and two Cl⁻¹ ions. The tetracoordinated Zn atoms adopt a distorted tetrahedral geometry. Compound 3 crystallizes with the Mg²⁺ ion coincident with crystallographic centre of symmetry forming a dimer. The Mg²⁺ ion is octahedrally coordinated by six O atoms from three acetate groups. The Zn²⁺ ions are in a tetrahedral geometry. In the crystal structures 1 and 3, the molecules are stabilized by N–H······O; C–H······O interactions. However in the crystal structure 2, the molecules are stabilized by C–H·····Cl interactions.

Graphical Abstract

The crystal structures of three new acetate bridged trinuclear metal complexes with 2- and 4-substituted aminopyridines and their conformation were obtained by X-ray diffraction techniques from suitable single crystals. These complexes form part of the project for design and synthesis of new alkaline-earth metal complexes with multiple applications in the fields of catalysis, material science and biochemistry.