Synthesis, Structural Characterization of a New Ni(II) Complex and Its Catalytic Activity for Oxidation of Benzyl Alcohol

In ethanol-water (v:v = 1:1), a new Ni(II) complex, [Ni(L)2(H2O)2] (1) (HL = 6-phenylpyridine-2-carboxylic acid) was synthesized using 6-phenylpyridine-2-carboxylic acid, NaOH and Ni(CH3COO)2.4H2O. The structure of complex 1 has been determined by elemental analysis and single crystal X-ray diffraction. The single crystal analysis shows that complex 1 contains one Ni(II) ion, two L ligands and  two coordinated water molecules. In 1, the Ni(II) ion is six-coordinated to two O atoms and two N atoms from L ligands and two O atoms from coordinated water molecules, respectively, which form a distorted octahedral coordination geometry. The whole unit of complex 1 is interconnected to each other through intermolecular N−H•••O hydrogen bonds involving oxygen atom of coordinated water molecule and the oxygen atoms of  L ligand to form 1D molecular architecture. The catalytic activity of complex 1 for oxidation of benzyl alcohol with O2 was investigated. The complex 1 shows good catalytic performance for the oxidation of benzyl alcohol, the benzyl alcohol conversion, benzaldehyde selectivity, and benzaldehyde yield were 49.1%, 92.0%, and 45.2%, respectively, at 90 °C under 0.7 Mpa O2 for 2 h. Moreover, complex 1 could be recovered easily by centrifugation and used repetitively for at least four times. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Syntheses, structures and magnetic properties of two CoII/NiII isostructural coordination polymers based on an asymmetric semirigid tricarboxylate ligand

Two new isostructural complexes, namely, poly[aqua[μ₃-2-(4-carboxyphenoxy)terephthalato-κ³O¹:O⁴:O^4'](1,10-phenanthroline-κ²N,N')cobalt(II)], [Co(C₁₅H₈O₇)(C₁₂H₈N₂)(H₂O)]_n or [Co(μ₃-Hcpota)(phen)(H₂O)]_n, I, and poly[aqua[μ₃-2-(4-carboxyphenoxy)terephthalato-κ³O¹:O⁴:O^4'](1,10-phenanthroline-κ²N,N')nickel(II)], [Ni(C₁₅H₈O₇)(C₁₂H₈N₂)(H₂O)]_n or [Ni(μ₃-Hcpota)(phen)(H₂O)]_n, II, have been synthesized by solvothermal reactions. Complexes I and II were fully characterized by IR spectroscopy, elemental analyses, thermogravimetric analyses, and powder and single-crystal X-ray diffraction. They both present two-dimensional structures based on [M₂(μ-COO)₂]²⁺ (M = Co^II or Ni^II) dinuclear metal units with a fes topology and a vertex symbol (4·8²). Interestingly, the positions of the two dimeric metal motifs and the two partially deprotonated Hcpota^2- ligands reproduce regular flying butterfly arrangements flipped upside down and sharing wings in the ab plane. Magnetic studies indicate antiferromagnetic interactions (J = -5.21 cm^-1 for I and -11.53 cm^-1 for II) in the dimeric units, with Co...Co and Ni...Ni distances of 4.397 (1) and 4.358 (1) Å, respectively, that are related to double syn-anti carboxylate bridges.

Synthesis, crystal structure and magnetic properties of a one-dimensional Mn2+ complex constructed from (+)-dibenzoyltartaric acid and 2,2'-bipyridine

The self-assembly reaction of (+)-dibenzoyltartaric acid (D-H₂DBTA) with 2,2'-bipyridine (bpy) and Mn(CH₃CO₂)₂·4H₂O yielded a new coordination polymer, namely, catena-poly[[[diaqua(2,2'-bipyridine-κ²N,N')manganese(II)]-μ-2,3-bis(benzoyloxy)butanedioato-κ²O²:O³] dihydrate], {[Mn(C₁₈H₁₂O₈)(C₁₀H₈N₂)(H₂O)₂]·2H₂O}_n or {[Mn(DBTA)(bpy)(H₂O)₂]·2H₂O}_n, (I). Complex (I) has been characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TGA) and single-crystal and powder X-ray diffraction. It crystallizes in the orthorhombic space group P2₁2₁2₁. In the complex, the Mn²⁺ cation displays a distorted octahedral {MnO₄N₂} geometry, formed from two carboxylate O atoms of two DBTA^2- ligands, two cis-oriented N atoms from one chelating 2,2'-bipyridine ligand and two trans-oriented O atoms from coordinated water molecules. The polymer displays a 1D chain with an Mn...Mn distance of 9.428 (1) Å. Due to the presence of flexible polycarboxylate and rigid bipyridyl ligands in the molecular structure, a high thermal stability of the complex is attained. The magnetic properties of (I) were analyzed based on the mononuclear Mn²⁺ model due to the long intramolecular Mn...Mn distance. The zero field splitting (ZFS) contribution in the high-spin Mn²⁺ cation is almost negligible and there are weak antiferromagnetic couplings between 1D chains [zJ' = -0.062 (5) cm^-1], corresponding to an intermolecular Mn...Mn distance of 7.860 (2) Å.