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 [CpCo(i)(μ-SEt)(CO)CoCp][I] (Cp* = η-CMe) (1) with NH resulted in the C-N coupling of the coordinated CO and amido group that originate from ammonia activation to afford a dicobalt formylamino complex [CpCo(μ-SEt)(μ-η:η-O[double bond, length as m-dash]CNH)CoCp][I] (2). Interestingly, at relatively high temperatures, the labile CO ligand was replaced by NH to give a thiolate-bridged dicobalt ammonia complex [CpCo(i)(μ-SEt)(NH)CoCp][I] (3). Subsequently, in the presence of the dehalogenation reagent AgPF, the CoS scaffold can simultaneously activate NH and MeCN to produce the complex [CpCo(MeCN)(μ-SEt)(NH)CoCp][PF] (4). Furthermore, in the presence of NaOEt, the facile occurrence of the intramolecular cyclization led to the formation of acetamidino-bridged dicobalt complex [CpCo(μ-SEt)(μ-η:η-NH(CCH)NH)CoCp][PF] (5), which may proceed through the nucleophilic attack of amido from NH to coordinated MeCN followed by the hydrogen atom transfer process. In the presence of MeCN, treatment of 5 with HBF released the corresponding [MeC(NH)NH]BF; meanwhile, the [CoS] core structural scaffold remained. In this CoS reaction system, the cooperative activation effect between the two cobalt centers plays an important role for NH activation and functionalization.