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Highly Reactive Ni II ‐Bound Nitrile–Oxime Coupling Intermediates Stabilized by Substituting Conventional Nitriles with a Dialkylcyanamide
Author(s) -
Andrusenko Elena V.,
Kabin Evgeniy V.,
Novikov Alexander S.,
Bokach Nadezhda A.,
Starova Galina L.,
Zolotarev Andrey A.,
Kukushkin Vadim Yu.
Publication year - 2015
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201500693
Subject(s) - chemistry , cyanamide , oxime , nitrile , moiety , salt (chemistry) , medicinal chemistry , reactivity (psychology) , protonation , iminium , chelation , nickel , stereochemistry , inorganic chemistry , organic chemistry , ion , medicine , alternative medicine , pathology
Nickel(II)‐mediated coupling between the cyanamide Me 2 NCN and the ketoximes Me(R)C=NOH (R = Me, Ph) gives chelates of the general formula [NiCl x (H 2 O) y {H N =C(NMe 2 )(O N =C(R)Me)} 2 ] n + ([ 1 ] + : R = Me; x = 1, y = 0; salts with both Cl – and [NiCl 4 ] 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 [H 2 N=C(NMe 2 )ON=C(R)Me] + ([ 4 ] + : R = Me; salt with [NiCl 4 ] 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 Ni II /ketoxime systems to afford (1,3,5‐triazapentadiene)Ni II 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)CH 2 C(Me 2 )NH 2 } 2 ]Cl 2 ([ 6 ]Cl 2 ). 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 NMe 2 moiety in the chelate ligands leads to an increase in electron‐density delocalization and also stabilizes the systems in terms of electrostatic factors.