Ligand-assisted reduction of Co(II) to Co(I) and subsequent coordination of dinitrogen

Abstract

Reaction of the bis-aminopyridine dianion {[2,6-[2,6-(i-Pr)2PhN-C=(CH2)]2(C5H3N)]Li(THF)}{Li(THF)4} with CoCl2(THF)1.5 under Ar afforded the dinuclear complex {[2,6-(i-Pr)2PhN-C=(CH2)](C5H3N)[2,6-(i-Pr)2PhN=C(CH2)]}2[Co(µ-Cl)Li(THF)3]2·4(THF) (1) in which the ligand is coupled to a second identical unit at a terminal methylene carbon. In turn, the C—C bond formation caused reduction of the Co(II) center to the monovalent state. The same reaction performed under a nitrogen atmosphere afforded the double dinitrogen complex {[2,6-(i-Pr)2PhN-C=(CH2)](C5H3N)[2,6-(i-Pr)2PhN=C(CH2)]}2[Co(N2)]2·2(toluene) (2). Key words: low-valent Co, diiminopyridinato, dinitrogen fixation.