C-H activation of a MeN grouping in one of the CH2NMe2 ortho substituents of a NCN 'pincer' ligand in tungsten chemistry: X-ray structure of [WCl2(NPh)(C6H3 {CH2NMeCH2}-2-{CH2NMe2}-6)]

Reaction of the aryl and alkyl metal derivatives, [Li(C6H3(CH2NMe2)(2)-2,6) ](2) (1), in situ prepared 'Zn(C6H3(CH2NMe2)(2)-2,6)(2), (2), [Li(CH2{C6H(C H2NMe2)(2)-2,6-Me-2-3,5})] (3) and [Zn(CH2{C6H(CH2NMe2)(2)-2,6-Me-2-3,5})(2 )] (4), respectively, with either WOCl4 or [W(NPh)Cl-4(Et2O)] in Et2O yield ed insoluble products. According to elemental analysis and mass balance the adducts that were formed contained all of the starting compounds, includin g the respective Li and Zn salts eventually formed. However, when the arylz inc reagent 2 was reacted with [W(NPh)Cl-4(Et2O)] in CH2Cl2, [WCl2(NPh)(C6H 3{CH2N(Me)CH2}-2-{CH2NMe2}-6)] (6) was formed, which was isolated in high y ield. The single-crystal X-ray determination of 6 showed a NCN ligand that is eta(3)-mer-N,C,N-bonded to the tungsten(VI) center via the (aryl)C-ipso carbon and the two ortho-N-donor atoms. As one of the NCH3 groups has under gone C-H activation, thus forming an azatungstacyclopropane ring, the NCN-p incer ligand is overall bonded to the tungsten centre as a tetradentate, et a(4)-N,C,N,C coordinating dianionic ligand. The corresponding tungsten(VI) alkylidene complex [W(CH2SiMe3)(NPh)(C6H3 {=CHN(Me)CH2}-2-(CH2NMe2)-6)] (7) was generated by reaction of 6 with two equivalents of LiCH2SiMe3. (C) 199 9 Elsevier Science S.A. All rights reserved.