Neutral mononuclear, dinuclear, tetranuclear d7/d10 metal complexes containing bis-pyrazole/pyridine ligands supported by 2,6-bis(3-pyrazolyl)pyridine: synthesis, structure, spectra, and catalytic activity.

A series of novel bis-pyrazole/pyridine complexes, [Zn2(HL1)2(μ2-SO4)]2·EtOH·H2O (1), [Co2(HL1)2(μ2-SO4)]2·2DMF·6H2O (2), [Zn4(HL1)4(μ4-SO4)][OH]2 (3), [Zn2(HL2)2(μ2-SO4)]·2H2O (4), [Zn(H2L2)(H2O)2](SO4)·0.87H2O (5) (H2L1 = 2,6-di-(5-phenyl-1H-pyrazol-3-yl)pyridine, H2L2 = 2,6-di-(5-methyl-1H-pyrazol-3-yl)pyridine), were synthesized hydrothermally from the self-assembly of Zn(II) or Co(II) with different types of bipyrazolyl/pyridine derivative ligands. All the complexes were characterized by elemental analysis, IR and UV–vis spectroscopy, powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction. Structural analyses revealed that metal atoms (Zn and Co) in complexes 1–5 are five-coordination modes, forming slightly distorted trigonal bipyramidal geometries. In complexes 1–3, H2L1 ligand connected the two metal centers via the tetradentate fashion, and the same form of connection was found in complex 4 with H2L2 ligand. While in complex 5, H2L2 only connected with one metal center via the trid...