Reduction of 2,2′-dinitrobiphenyl with hydrazine hydrate catalyzed by Pd/C: Cobalt(II), zinc(II) and mercury(II) complexes with benzo[c]cinnoline and N2,N2′-bis(3-phenylallylidene)biphenyl-2,2′-diamine

The catalytic reduction of 2,2′-dinitrobiphenyl with different molar ratios of hydrazine hydrate resulted in two different compounds; benzo[c]cinnoline (L1) and 2,2′-diaminobiphenyl. N2,N2′-bis(3-phenylallylidene)biphenyl-2,2′-diamine (L2) has been synthesized by the condensation of 2,2′-diaminobiphenyl with cinnamaldehyde. Complexes of the type ML12X2 and ML2X2 (M = Co(II), Zn(II); X = Cl, Br or I and Hg(L2)Cl2) have been synthesized and characterized by CHN analysis, IR, 1H NMR and UV–Vis spectroscopy. The crystal structures of Co(L1)2Cl2, Zn(L1)2Br2 and Hg(L2)Cl2 were determined using single crystal X-ray diffraction. In these three complexes, the coordination polyhedron about the central metal ion is best described as a distorted tetrahedron. The Co(L1)2Cl2, and Zn(L1)2Br2 complexes exhibit supramolecular structures resulting from π–π stacking of the benzo[c]cinnoline ligands. The diimine ligand, L2, in the Hg(L2)Cl2 complex coordinates to Hg(II) through the two nitrogens of the two phenyl rings to form a seven-membered metallocycle. Furthermore, the ligand prefers a trans–trans arrangement in the Hg(L2)Cl2 complex.

Graphical abstractCatalytic reduction of 2,2′-dinitrobiphenyl with different molar ratios of hydrazine hydrate resulted in two different compounds: benzo[c]cinnoline and 2,2′-diaminobiphenyl. N2,N2′-bis(3-phenylallylidene)biphenyl-2,2′-diamine (L2) has been synthesized by the condensation of 2,2′-diaminobiphenyl with cinnamaldehyde. Cobalt(II), zinc(II) and mercury(II) complexes of the type MLnX2 with these ligands have been synthesized.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Reduction of 2,2′-dinitrobiphenyl with hydrazine hydrate catalyzed by Pd/C. ► Benzo[c]cinnoline and 2,2′-diaminobiphenyl. ► N2,N2′-bis(3-phenylallylidene)biphenyl-2,2′-diamine. ► Cobalt(II), zinc(II) and mercury(II) complexes of the type MLnX2.