The formation of a bis(μ-oxido)dicopper complex with the ligand 2-(diethylaminoethyl)-6-phenylpyridine (PPN) and its subsequent hydroxylation of the pendant phenyl group (studied earlier by Holland et al., Angew. Chem. Int. Ed.- 1999, 38, 1139-1142) has been reinvestigated to gain a better understanding of such systems in view of the development of new synthetic applications. To this end, we prepared a simple copper imine complex system that also affords selective o-hydroxylation of aromatic aldehydes by using dioxygen as the oxidant: Applying the ligand N'-benzylidene-N,N-diethylethylenediamine (BDED), salicylaldehyde was prepared in good yields and we show that this reaction also occurs through an intermediate bis-μ-oxido copper complex. The underlying reaction mechanism for the PPN-supported complex was studied at the BLYP-D/TZVP level of density functional theory and the results for representative stationary points along reaction paths of the BDED-supported complex reveal a closely related mechanistic scenario. The results demonstrate a new facile synthetic way to introduce OH groups into aromatic aldehydes.

Keywords: Charge transfer / NMR spectroscopy / Density functional calculations / Rhodium / IridiumOur recent results of the chemistry of group 9 Rh and Ir metal complexes bearing the ubiquitous pyridine, diimine (PDI) terdentate nitrogen donor are reviewed. Examples reflecting the special nature of the PDI ligand include a facile C-H activation process and the stabilization of a very rare late transition metal iridium nitrido compound, (PDI)IrϵN, and its direct hydrogenation to the corresponding amido complex according to (PDI)IrϵN + H 2 Ǟ (PDI)Ir-NH 2 . The amount of electron transfer to the PDI ligands in (PDI)Rh,Ir-R,X com-

Joining forces Mechanistic studies based on low‐temperature stopped‐flow kinetics and DFT calculations allow the development of a simple copper complex system for selective hydroxylation of aromatic aldehydes, as reported by F. Tuczek, M. C. Holthausen, S. Schindler et al. in the Full Paper on (Graphics and design by Dr. Sabine Becker).