Synthesis and characterization of oxorhenium(v) diamido pyridine complexes that catalyze oxygen atom transfer reactionsElectronic supplementary information (ESI) available: CIF files for 1, 2, and 8 and full crystallographic details. CCDC reference numbers 831035-831037. For ESI and crystallographic data in CIF or other electronic format, see DOI: 10.1039/c1dt11143d

The detailed syntheses of complexes 1-4 , Re(O)(X)(DAP) (X = Me, 1 ; Cl, 2 ; I, 3 ; OTf (triflate), 4 ) incorporating the diamido pyridine (DAP) ancillary ligand (2,6-bis((mesitylamino)methyl)pyridine) are described and shown to be effective catalysts for oxygen atom transfer (OAT) reactions of PyO to PPh 3 . The catalytic activities are as follows: 4 3 > 2 > 1 . The observed electronic trend is consistent with the turnover limiting reduction of the proposed Re( vii ) dioxo intermediate, Re(O) 2 (X)(DAP), during the catalytic cycle. The catalytic activity of complexes 1-3 was compared to previously published diamido amine (DAAm) oxorhenium complexes of the type Re(O)(X)(DAAm) (X = Me, 5 ; Cl, 6 ; I, 7 and DAAm = N , N -bis(2-arylaminoethyl)methylamine) which exhibit hydrolytic degradation during the catalytic reaction. Complexes 1-3 displayed higher turnover frequencies compared to 5-7 . This higher catalytic activity was attributed to the more rigid DAP ligand backbone, which makes the complexes less susceptible to decomposition. However, another decomposition pathway was proposed for this catalytic system due to the observation of Re(O) 3 ((MesNCH 2 )(MesNCH)NC 5 H 3 ) 8 in which one arm of the DAP ligand is oxidized. Complexes 1-4 which incorporate DAP ligands were shown to be effective catalysts for OAT reactions. These complexes show increased activity compared to their DAAm counterparts 5-7 because of the more rigid ligand.