Biphenol-based tetradentate N2O2 donor scaffold binuclear Zn(II) and trinuclear Cu(II) Complexes: Synthesis, Structure, Characterizations, and catalytic cyanosilylation of aldehydes at room temperature

Abstract

In this work, two dinuclear Zn(II) complexes [Zn(H2L1)]2(complex 1), [Zn(H2L2)]2(complex 2), and a trinuclear Cu(II) complex [Cu(H2L2)]3 (complex 3) (H2L1 = 3,3′-bis-[(2,6-dimethyl-phenylimino)-methyl]-[1,1′]-biphenyl-2,2′-diol, H2L2 = 2,6-diethyl phenylimino)-ethyl]-[1,1′]-biphenyl-2,2′- diol) are reported. The complexes 1, 2 &3 have been produced and isolated for the first time in a well-defined and air-stable form by reacting biphenol-based tetradentate N2O2-type (H2L1 and H2L2) ligands with the respective metal acetate salts. The synthesised compounds were characterized by UV–Vis spectroscopy, elemental analysis, mass spectrometry and Fourier-transform infrared spectroscopy (FT-IR). Single crystal X-ray diffraction (SCXRD) study revealed distorted tetrahedral geometry surrounding the core Zn2+ cations (1–2) that were bridging the teradentate N2O2 ligands. In complex-3, the Cu(II) center is four-coordinated via tetradentate N2O2 donor ligand, forming slightly distorted square planar geometry with an angular C2-symmetric core and exhibits weak antiferromagnetic (AF) interactions. Hirshfeld surface analysis and fingerprint plots were used to investigate the intermolecular interactions in the crystalline state. Strong H…H and H… C/C…H intermolecular interactions were seen on the Hirshfeld surface when it was mapped over dnorm, shape index, and curvature. These interactions were found to be the main contributors to crystal packing. Excellent catalytic activity was demonstrated for the dinuclear zinc(II) complexes [Zn(H2L1)]2 (1)and [Zn(H2L2)]2 (2) in the cyanosilylation reaction of various aryl aldehydes into value-added cyanohydrins at room temperature and under solvent free conditions.