Metal‐Promoted Nucleophilic Addition and Cyclization of Diamines with Dicyanonitrosomethanide, [C(CN)2(NO)]−

Abstract

The metal-promoted nucleophilic addition of diaminoalkanes to dicyanonitrosomethanide, C(CN)2(NO)- (dcnm), and subsequent cyclization has been utilized in the synthesis of novel anionic species. The addition and cyclization of 1,2-diaminoethane (en) to both nitrile groups of dcnm forms the anion diimidazolinylnitrosomethanide (dinm), isolated in the dinuclear complex [{Cu(dinm)(en)}2en][ClO4]2 (1). The same reaction solution yields [Cu(cinm)(ainm)] (cinm=cyanoimidazolinylnitrosomethanide, ainm=(((2-aminoethyl)amino)iminomethyl)imidazolinylnitrosomethanide) (2), which contains intermediates of the dinm species, supporting a stepwise mechanism of addition of the diamine followed by cyclization. 1,3-Diaminopropane (pn) added and cyclized on only one nitrile group to form a 1,4,5,6-tetrahydropyrimidine ring. This resulted in the formation of the cyanonitroso-1,4,5,6-tetrahydropyrimidinylmethanide ligand (cnpm) in complexes with the general formula [M(cnpm)2(pn)] (M=Cu (3a), Ni (3b), Zn (3c)). These reactions are contrasted to the addition of ethanolamine in the pyridine (py) complex [Ni(chnm)2(py)2].(py) (4) (chnm=cyano((2-hydroxyethyl)amino)iminomethylnitrosomethanide) with no cyclization, demonstrating the higher reactivity of amines compared with alcohols. The formation of the complexes [M(cmnm)2(mame)] (M=Co (5a), Ni (5b), cmnm=cyano(imino(methoxy)methyl)nitrosomethanide, mame=1-dimethylamino-2-methylaminoethane) indicate mame may be too sterically hindered to add to dcnm under similar reaction conditions.