Tuning the reactivity of metals held in a rigid ligand environment

Abstract

Research on the chemistry of monoanionic aryl ligands having ortho- or bis-orthodimethylaminomethyl substituents, i.eC 6 H 4 (CH 2 NMe 2)-2, A, C 10 H 6 NMe 2 -8, B and C 6 H 3 (CH 2 NMe 2) 2 -2,6, C, that form organometallic compounds with a direct M-C ar yl σ-bond, will be discussed. Through coordination of the N-donor site(s) of the ortho CH2NMe2 arm(s) five-membered M-C-C-C-N chelate ring formation occurs. In particular, the rigid bis-ortho chelation of the terdentate ligand C provides the complexed metal centre with a set of unusual properties. Firstly, this ligand restricts the number of coordination sites that are available for incoming reagents and other ligands. This is a situation that can frustrate the normal course of, for example, an oxidative reaction at the bound d 8 metal centre and lead to “trapped intermediates” with a considerable stability. Secondly, the hard C and N donor atoms make these ligands extremely electron-rich and consequently they afford complexed (d 8) metal centres with an enhanced nucleophilicity. Together, these features provide their complexes with unexpected and novel properties; e.g. n 1 -coordination of I2 to Pt 11, stable Ni III -carbon bonds, and intramolecular rearrangements involving C-H bond activation. Here, the first experiments aimed at modelling the available space for incoming reagents by a variation of the alkyl substituents at the nitrogen donor atoms will be described. © 1989 IUPAC