Relocalisation of the π system in benzoquinonediimines induced by metal coordination

We report the synthesis and characterization of the tungsten carbonyl complexes 8 , R = neopentyl; 10 , R = benzyl), which contain a chelating ortho-diimine moiety. Their formation can be explained by a metal coordination-induced relocalisation of the π system of the precursor para -benzoquinonediimine ligand C 6 H 2 (NHR) 2 (=NR) 2 ( 3 , R = neopentyl; 9 , R = benzyl). The UV–visible spectra of complexes 8 and 10 revealed the presence of a strong band at 607 and 620 nm, respectively, which is characteristic of a MLCT transition.