Reversible dioxygen binding on asymmetric dinuclear rhodium centresElectronic supplementary information (ESI) available: Synthesis and spectral data, crystal data, selected bond lengths and angles, ORTEP diagrams for 1b and 2c, and DFT calculations data. CCDC 928791 (1a), 928792 (1b), 928793 (2c) and 928794 (2d). For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c3cc41815d

Electron-deficient dinuclear rhodium complexes [Rh 2 Cl 2 (-dpmppp)(RNC)] ( 1 ), with the linear tetraphosphine ligand dpmppp, showed reversible binding of molecular oxygen to form asymmetric dirhodium 2 -peroxo complexes [Rh 2 Cl 2 (O 2 )(-dpmppp)(RNC)] ( 2 ) stabilized by a RhRh dative bond. Electron-deficient dirhodium( i ) complexes showed reversible binding of dioxygen to form asymmetric 2 -peroxo Rh I Rh III complexes stabilized by a RhRh dative bond.