Synthesis, characterization and catalytic activities of Zn(II) and Cd(II) complexes supported by unsymmetrical aryl thiourea ligands

We report a series of Zn(II) and Cd(II) metal complexes [L-2(1)(ZnCl2)] (1), [L-2(1)(ZnBr2)] (2), [L-2(1)(CdCl2)] (3), [L-2(1)(CdI2)] (4), [L-2(2)(ZnCl2)] (5), [L-2(2)(ZnBr2)] (6), [L-2(2)(ZnI2)] (7), [L-2(2)(CdCl2)] (8), [L-2(3)(CdCl2)] (9) and [L-2(4)(ZnBr2)] (10), synthesized using various unsymmetrical aryl thiourea ligands: 1-(2,6-diisopropylphenyl)-3-phenylthiourea (L-1), 1-mesityl-3-phenylthiourea (L-2), 1-(2-fluorophenyl)-3-phenylthiourea (L-3) and symmetrical 1,3-bis(2-fluorophenyl)thiourea (L-4). The ligands and metal complexes were characterized by H-1, C-13{H-1} NMR, FT-IR analysis. Solid-state structures of the zinc and cadmium metal complexes (1-8) were established using the single-crystal diffraction analysis technique. Furthermore, the catalytic activities of the Zn(II) complexes towards hydroboration of aldehydes and ketones (-C=O) as substrates were studied. Excellent yields of the corresponding boronate esters were achieved.