Abstract
The rate constants of the oxidative addition of the transition-metal iodocyclopentadienyl complexes (η5-C5H4-I)MLn (MLn = Mn(CO)3 (1a), Re(CO)3 (1b), CpFe (1c)) with Pd0(PPh3)4 have been determined in DMF. As expected, the oxidative addition is faster for the electron-acceptor groups Mn(CO)3 and Re(CO)3 than for the electron-donor group FeCp, with the reactivity order 1a > 1b ≫ 1c. Comparison of the rate constants of the oxidative additions affords a new strategy for the evaluation of the electronic properties of transition-metal units ligated to the iodocyclopentadienyl moiety with the following decreasing electron-acceptor properties: Mn(CO)3 > Re(CO)3 ≫ FeCp. The complexes formed in the oxidative addition are characterized as trans-[(η5-C5H4)PdI(PPh3)2]MLn (MLn = Mn(CO)3 (2a), Re(CO)3 (2b), CpFe (2c)) with the decreasing stability order in DMF: 2c ≫ 2b > 2a. The relevance to the efficiency of palladium-catalyzed Stille or Sonogashira reactions from related complexes 1 is discussed.
Published Version
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