"Nindigo": synthesis, coordination chemistry, and properties of indigo diimines as a new class of functional bridging ligandsElectronic supplementary information (ESI) available: Synthesis and characterization of 3a-3d, 4a, and 4b. CCDC 772711 and 772712. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c0cc01736a

Reactions of indigo with anilines provide a simple route to indigo N , N ′-diaryldiimines ("Nindigo"), a new binucleating ligand with two β-diketiminate-type metal binding sites. Bis-palladium complexes have interesting ligand-centred properties such as redox activity and intense near infrared absorption. Reactions of indigo with anilines give the corresponding N , N′ -diaryldiimines ("Nindigo"), a new bridging ligand system. Bis-Pd complexes show ligand-based redox-activity and near-infrared absorption.