Catecholato complexes of cobalt and nickel with 1,4-disubstituted-1,4-diazabutadiens-1,3 and 1,2-bis(diphenylphosphino)ethane

Divalent cobalt and nickel form four-coordinate complexes with sterically hindered 3,6-di- tert -butylcatecholato dianion (3,6-DBCat) and neutral bidentate 1,4-disubstituted-1,4-diazabutadiens-1,3 (DAB). Structural study of (1,4-di- tert -butyl-1,4-diazabutadiene-1,3)(3,6-di-tert-butyl-catecolato)nickel and (1,4-bis-(2,6-di-iso-propylphenyl)-2,3-dimethyl-1,4-diazabutadiene-1,3)(3,6-di-tert-butyl-catecolato)cobalt indicates square-planar environment of metals. Chemical one-electron oxidation of nickel complexes proceeds through catecholate ligand and leads to o -semiquinonato adducts. EPR spectral parameters indicate preservation of square-planar configuration after oxidation. Complexes (DAB)M(Cat) (M = Ni, Co) undergo neutral ligand substitution reactions. Graphical Abstract A number of four-coordinated square-planar mono-catecholato complexes of cobalt and nickel of general formula (L)M(3,6-DBCat) were synthesized and characterized (L= N,N’-disubstituted 1,4-diazabutadienes-1,3 (DAB), dipyridine, bis(diphenylphosphino)ethane; M=Co, Ni; 3,6-DBCat =3,6-di-tert-butyl-catecholato dianion).