Bimetallic Lithium–Cobalt(II) Complexes Based on β ‐Diketiminate Ligands: Syntheses, Structures, and Utilization as Catalysts for the Construction of Trisubstituted Benzenes

A series of cobalt–lithium bimetallic complexes and a monometallic cobalt complex of formulas [(L 1 )CoCl 2 Li(Et 2 O) 2 ] ( 1 ), [(L 2 )CoCl 2 Li(Et 2 O)(THF)] ( 2 ), [(L 3 )CoCl 2 Li(THF) 2 ] ( 3 ), [(L 4 )CoCl 2 Li(THF) 2 ] ( 4 ), and [(L 5 )CoCl] ( 5 ) (HL 1 = 2,4,6‐tricyclopentyl‐N‐4‐((2‐methoxyphenyl)imino)pent‐2‐en‐2‐yl)‐aniline; HL 2 = N‐(4‐((4‐chlorophenyl)imino)pent‐2‐en‐2‐yl)‐2,4,6‐tricyclopentyl‐aniline; HL 3 = N‐(4‐((2,4,6‐trimethyl)imino)pent‐2‐en‐2‐yl)‐2,4,6‐tricyclopentylaniline; HL 4 = N‐(4‐((2,6‐dimethyl phenyl)imino)pent‐2‐en‐2‐yl)‐2,6‐diisopropylaniline; and HL 5 = N‐(4‐((pyridin‐2‐ylmethyl)imino)pent‐2‐en‐2‐yl)‐2,6‐diisopropyl‐aniline) were synthesized and characterized. The targets of this work were to study the influences of changes in the substituents of the ligand backbones on the structures and catalytic properties of the cobalt–lithium bimetallic complexes. Their catalytic performances were evaluated in the [2 + 2 + 2] cyclotrimerization of terminal alkynes. All complexes exhibited catalytic activity, with bimetallic complex 1 exhibiting superior efficiency compared to the monometallic complex 5 and other bimetallic analogs. Under the optimized conditions, the catalytic reactions proceeded under mild room‐temperature conditions, displaying broad substrate compatibility and affording the corresponding aromatic products in good to excellent isolated yields. This work demonstrates the potential of bimetallic cobalt(II)‐lithium complexes as practical and efficient catalysts for aromatic ring construction via alkyne cyclotrimerization.