| Summary: | The oxidation of transition metals such as manganese and copper by dioxygen (O<sub>2</sub>) is of great interest to chemists and biochemists for fundamental and practical reasons. In this report, the O<sub>2</sub> reactivities of 1:1 and 1:2 mixtures of [(TPP)Mn<sup>II</sup>] (<b>1</b>; TPP: Tetraphenylporphyrin) and [(tmpa)Cu<sup>I</sup>(MeCN)]<sup>+</sup> (<b>2</b>; TMPA: Tris(2-pyridylmethyl)amine) in 2-methyltetrahydrofuran (MeTHF) are described. Variable-temperature (−110 °C to room temperature) absorption spectroscopic measurements support that, at low temperature, oxygenation of the (TPP)Mn/Cu mixtures leads to rapid formation of a cupric superoxo intermediate, [(tmpa)Cu<sup>II</sup>(O<sub>2</sub><sup>•–</sup>)]<sup>+</sup> (<b>3</b>), independent of the presence of the manganese porphyrin complex (<b>1</b>). Complex <b>3</b> subsequently reacts with <b>1</b> to form a heterobinuclear <i>μ</i>-peroxo species, [(tmpa)Cu<sup>II</sup>–(O<sub>2</sub><sup>2–</sup>)–Mn<sup>III</sup>(TPP)]<sup>+</sup> (<b>4</b>; <i>λ</i><sub>max</sub> = 443 nm), which thermally converts to a <i>μ</i>-oxo complex, [(tmpa)Cu<sup>II</sup>–O–Mn<sup>III</sup>(TPP)]<sup>+</sup> (<b>5</b>; <i>λ</i><sub>max</sub> = 434 and 466 nm), confirmed by electrospray ionization mass spectrometry and nuclear magnetic resonance spectroscopy. In the 1:2 (TPP)Mn/Cu mixture, <b>4</b> is subsequently attacked by a second equivalent of <b>3</b>, giving a <i>bis</i>-<i>μ</i>-peroxo species, i.e., [(tmpa)Cu<sup>II</sup>−(O<sub>2</sub><sup>2−</sup>)−Mn<sup>IV</sup>(TPP)−(O<sub>2</sub><sup>2−</sup>)−Cu<sup>II</sup>(tmpa)]<sup>2+</sup> (<b>7</b>; <i>λ</i><sub>max</sub> = 420 nm and δ<sub>pyrrolic</sub> = −44.90 ppm). The final decomposition product of the (TPP)Mn/Cu/O<sub>2</sub> chemistry in MeTHF is [(TPP)Mn<sup>III</sup>(MeTHF)<sub>2</sub>]<sup>+</sup> (<b>6</b>), whose X-ray structure is also presented and compared to literature analogs.
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