Highly Reactive NiII‐Bound Nitrile–Oxime Coupling Intermediates Stabilized by Substituting Conventional Nitriles with a Dialkylcyanamide

Abstract

AbstractNickel(II)‐mediated coupling between the cyanamide Me2NCN and the ketoximes Me(R)C=NOH (R = Me, Ph) gives chelates of the general formula [NiClx(H2O)y{HN=C(NMe2)(ON=C(R)Me)}2]n+ ([1]+: R = Me; x = 1, y = 0; salts with both Cl– and [NiCl4]2– were isolated; [2]2+: R = Me; x = 0, y = 2; salt with Cl– was isolated; [3]+: R = Ph; x = 1, y = 1; salt with Cl– was isolated) and the iminium salts [H2N=C(NMe2)ON=C(R)Me]+ ([4]+: R = Me; salt with [NiCl4]2– was isolated; [5]+: R = Ph; salt with Cl– was isolated). This reaction demonstrates the difference in the reactivity between conventional nitriles and dialkylcyanamides: whereas nitriles RCN (R = Alk, Ar) react with NiII/ketoxime systems to afford (1,3,5‐triazapentadiene)NiII species, formed by postulated nitrile–oxime coupling intermediates, cyanamides under the same conditions give either stable cyanamide–oxime coupling products or the Busch‐type complex [Ni{HN=C(Me)CH2C(Me2)NH2}2]Cl2 ([6]Cl2). The reason for the different stability of the coupling products was interpreted theoretically on the basis of quantum chemical calculations (M06‐L/6‐31G* level of theory). The NMe2 moiety in the chelate ligands leads to an increase in electron‐density delocalization and also stabilizes the systems in terms of electrostatic factors.