Ferrocene-Functionalized Dithiocarbamate Zinc(II) Complexes as Efficient Bifunctional Catalysts for the One-Pot Synthesis of Chromene and Imidazopyrimidine Derivatives via Knoevenagel Condensation Reaction

• Published in: Inorganic chemistry Vol. 60; no. 9; pp. 6446 - 6462
• Main Authors: Anamika, Yadav, Chote Lal, Drew, Michael G. B, Kumar, Kamlesh, Singh, Nanhai
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 03.05.2021
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.1c00162

Four new mononuclear/coordination polymeric (CP) zinc­(II) complexes (1–4) of ferrocenyl/pyridyl-functionalized dithiocarbamate ligands, N-ferrocenylmethyl-N-butyl dithiocarbamate (L1), N-ferrocenylmethyl-N-ethylmorpholine dithiocarbamate (L2), N-ferrocenylmethyl-N-2-(diethylamino)­ethylamine dithiocarbamate (L3), and N-4-methoxybenzyl-N-3-methylpyridyl dithiocarbamate (L4), have been synthesized and characterized by elemental analyses, IR, UV–vis, and 1H and 13C­{1H} NMR spectroscopic techniques. The solid-state structures of complexes 1, 3, and 4 have been determined by single-crystal X-ray crystallography as well as powder X-ray diffraction. Single-crystal X-ray crystallography revealed a monomeric structure for complex 1 but 1D polymeric structures for complexes 3 and 4. In all complexes, dithiocarbamate ligands are bonded to the Zn­(II) metal ion in a S^S chelating mode, and in the CPs, N atoms on the 2-(diethylamino)­ethylamine and 3-pyridyl functionalities in the ligands on the neighboring molecules are also bonded to metal centers, leading to the formation of either a discrete tetrahedral molecule in 1 or 1D CP structures in 3 and 4. The Zn­(II) metal centers in the polymeric structures exhibited either square-pyramidal or octahedral geometries. The supramolecular structures in these complexes are sustained via C–H···π (ZnCS2, chelate; 3 and 4), C–H···π, and H···H interactions. The catalytic performances of complexes have also been assessed in the Knoevenagel condensation and one-pot multicomponent reactions. Catalysis results showed that the CP 3 acts as a heterogeneous bifunctional catalyst with excellent transformation efficiency at low catalyst loading.