The tetradentate ligands RN4 (RN4 = N,N′-di-alkyl-2,11-diaza[3,3](2,6)pyridinophane, R = Me or iPr) were found to stabilize cationic (RN4)PdMe2 and (RN4)PdMeCl complexes in both PdIII and PdIV oxidation states. This allows for the first time a direct structural and reactivity comparison of the two Pd oxidation states in an identical ligand environment. The PdIII complexes exhibit a distorted octahedral geometry, as expected for a d7 metal center, and display unselective C–C and C–Cl bond formation reactivity. By contrast, the PdIV complexes have a pseudo-octahedral geometry and undergo selective non-radical C–C or C–Cl bond formation that is controlled by the ability of the complex to access a five-coordinate intermediate.
Dalton Transactions
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