The mutual influence of the imine substituents of terephthal-bis-imines concerning their reactivity towards Fe-2(CO)(9)

The reaction of terephthal-bis-imines with Fe-2(CO)(9) proceeds via a C-H a ctivation reaction in the ortho position with respect to one of the imine f unctions. The corresponding hydrogen atom is shifted towards the former imi ne carbon atom producing a methylene group instead. The dinuclear iron comp lexes formed by this reaction sequence and showing no coordination of the s econd imine group were isolated from reactions of bis-imines with both phen yl and cyclohexyl substituents at the imine nitrogen atoms. In addition, we observed three different reaction pathways of the second imine substituent of the starting material which is obviously thus influenced by the fact th at the first one is coordinating an Fe-2(CO)(6) moiety. If the organic subs tituent at the imine nitrogen atoms is a phenyl group the formation of a tr inuclear complex is achieved in which an additional Fe(CO)(3) group is coor dinating the CN double bond and one of the carbon-carbon bonds of the centr al phenyl ring in an eta (4)-fashion. The same reaction leads to the isolat ion of a tetranuclear iron-carbonyl compound in which both imine substituen ts were transformed via the pathway described above, each building up dinuc lear subunits. In contrast to this the reaction of a bis-imine with cyclohe xyl groups at the imine nitrogen and thus an enhanced nucleophilicity leads to the formation of a tetranuclear complex in which only one imine group r eacts under C-H activation with subsequent hydrogen migration towards the f ormer imine carbon atom. The second imine substituent also shows a C-H acti vation reaction in the ortho position with respect to the imine group but t he corresponding hydrogen atom is transferred to one of the aromatic carbon atom of the central phenyl ring of the ligand. The C=N double bond remains unreacted and only coordinates the second Fe,(CO), moiety via the nitrogen lone pair. (C) 2000 Elsevier Science S.A. All rights reserved.