Facile C-N coupling of coordinated ammonia and labile carbonyl or acetonitrile promoted by a thiolate-bridged dicobalt reaction scaffold

At low temperature, interaction of the thiolate-bridged dicobalt carbonyl complex [Cp*Co(I)(mu-SEt)(2)(CO)CoCp*][I] (Cp* = eta(5)-C5Me5) (1) with NH3 resulted in the C-N coupling of the coordinated CO and amido group that originate from ammonia activation to afford a dicobalt formylamino complex [Cp*Co(mu-SEt)(2)(mu-eta(1):eta(1)-O-CNH2)CoCp*][I] (2). Interestingly, at relatively high temperatures, the labile CO ligand was replaced by NH3 to give a thiolate-bridged dicobalt ammonia complex [Cp*Co(I)(mu-SEt)(2)(NH3)CoCp*][I] (3). Subsequently, in the presence of the dehalogenation reagent AgPF6, the Co2S2 scaffold can simultaneously activate NH3 and MeCN to produce the complex [Cp*Co(MeCN)(mu-SEt)(2)(NH3)CoCp*][PF6](2)(4). Furthermore, in the presence of NaOEt, the facile occurrence of the intramolecular cyclization led to the formation of acetamidino-bridged dicobalt complex [Cp*Co(mu-SEt)(2)(mu-eta(1):eta(1)-NH(CCH3)NH)CoCp*][PF6] (5), which may proceed through the nucleophilic attack of amido from NH(3)to coordinated MeCN followed by the hydrogen atom transfer process. In the presence of MeCN, treatment of 5 with HBF4 released the corresponding [MeC(NH2)NH2]BF4; meanwhile, the [Co2S2] core structural scaffold remained. In this Co2S2 reaction system, the cooperative activation effect between the two cobalt centers plays an important role for NH3 activation and functionalization.