Binuclear cobalt() complexes: synthesis, structure, characterizations and catalytic applications in acceptor-less dehydrogenation (AD) of primary alcohols into aldehydes

In this study, three novel binuclear, distinctly defined, air-stable cobalt( ii ) complexes, denoted by the formulas [Co(H 2 L 1 )] 2 ( 1 ), [Co(H 2 L 2 )] 2 ( 2 ) and [Co(H 2 L 3 )] 2 ( 3 ), are reported. Binuclear cobalt( ii ) complexes ( 1-3 ) namely bis -[3,3′- bis [(2,6-dimethyl-phenylimino)-methyl]-[1,1′]-biphenyl-2,2′-dioxo cobalt( ii )] ( 1 ), bis -[3,3′- bis [(2,6-di- i -sopropylphenyl)imino)methyl)-[1,1′-biphenyl]-2,2′-dioxodicobalt( ii )] ( 2 ) and bis -[3,3′- bis [(2,6-diethyl-phenylimino)-ethyl]-[1,1′]-biphenyl-2,2′-dioxo cobalt( ii )] ( 3 ) were synthesised and isolated for the first time. Several techniques, including mass spectrometry, UV-visible spectra, FT-IR spectra, elemental analysis, and single-crystal X-ray diffraction, were used to ascertain the structural properties of the binuclear cobalt( ii ) complexes. All these binuclear cobalt( ii ) [Co(H 2 L 1 )] 2 , [Co(H 2 L 2 )] 2 and [Co(H 2 L 3 )] 2 complexes ( 1-3 ) demonstrated excellent catalytic activity for the acceptor-less dehydrogenation (AD) reaction of primary alcohols to create the corresponding aldehydes and molecular hydrogen (H 2 ). Multiple alcohols, including those that are electron-rich/electron-poor primary alcohols, have been successfully converted into the corresponding aldehydes using catalytic acceptor-less dehydrogenation (CAD), which only produces molecular hydrogen as a byproduct. The new binuclear ( ii ) complexes ( 1-3 ) with high catalytic activity for acceptor-less dehydrogenation (AD) of diverse primary alcohols into value-added aldehydes under mild conditions.