Syntheses, Characterization, and Dioxygen Reactivities of Cu(I) Complexes with <i>cis</i>,<i>cis</i>-1,3,5-Triaminocyclohexane Derivatives:  A Cu(III)<sub>2</sub>O<sub>2</sub> Intermediate Exhibiting Higher C−H Activation

Six Cu(I) complexes with <i>cis</i>,<i>cis</i>-1,3,5-triaminocyclohexane derivatives (R<sub>3</sub>CY, R = Et, iBu, and Bn), [Cu(MeCN)(Et<sub>3</sub>CY)]SbF<sub>6</sub> (<b>1</b>), [Cu(MeCN)(iBu<sub>3</sub>CY)]SbF<sub>6</sub> (<b>2</b>), [Cu(MeCN)(Bn<sub>3</sub>CY)]SbF<sub>6</sub> (<b>3</b>), [Cu(CO)(Et<sub>3</sub>CY)]SbF<sub>6</sub> (<b>4</b>), [Cu(CO)(iBu<sub>3</sub>CY)]SbF<sub>6</sub> (<b>5</b>), and [Cu(CO)(Bn<sub>3</sub>CY)]SbF<sub>6</sub> (<b>6</b>), were prepared to probe the ability of copper complexes to effectively catalyze oxygenation reactions. The complexes were characterized by elemental analysis, electrochemical and X-ray structure analyses, electronic absorption spectroscopy, IR spectroscopy, <sup>1</sup>H NMR spectroscopy, and ESI mass spectrometry. The crystal structures of <b>1</b><b>−</b><b>3</b> and <b>6</b> and the CO stretching vibrations (ν<sub>CO</sub>) of <b>4</b><b>−</b><b>6</b> demonstrate that the ability of R<sub>3</sub>CY to donate electron density to the Cu(I) atom is stronger than that of the previously reported ligands, 1,4,7-triazacyclononane (R<sub>3</sub>TACN) and 1,4,7-triazacyclodecane (R<sub>3</sub>TACD). Reactions of complexes <b>1</b><b>−</b><b>3</b> with dioxygen in THF or CH<sub>2</sub>Cl<sub>2</sub> at −105 to −80 °C yield bis(μ-oxo)dicopper(III) complexes <b>7</b><b>−</b><b>9</b> as intermediates as confirmed by electronic absorption spectroscopy and resonance Raman spectroscopy. The Cu−O stretching vibrations, ν(Cu−O) for <b>7</b> (<sup>16</sup>O<sub>2</sub>:  553, 581 cm<sup>-1</sup>and <sup>18</sup>O<sub>2</sub>:  547 cm<sup>-1</sup>) and <b>8</b> (<sup>16</sup>O<sub>2</sub>:  571 cm<sup>-1</sup> and <sup>18</sup>O<sub>2</sub>:  544 cm<sup>-1</sup>), are observed in a lower energy region than previously reported for bis(μ-oxo) complexes. The decomposition rates of complexes <b>7</b><b>−</b><b>9</b> in THF at −90 °C are 2.78 × 10<sup>-4</sup> for <b>7</b>, 8.04 × 10<sup>-4</sup> for <b>8</b>, and 3.80 × 10<sup>-4</sup> s<sup>-1</sup> for <b>9</b>. The decomposition rates of <b>7</b> and <b>8</b> in CH<sub>2</sub>Cl<sub>2</sub> were 5.62 × 10<sup>-4</sup> and 1.62 × 10<sup>-3</sup> s<sup>-1</sup>, respectively, and the thermal stabilities of <b>7</b><b>−</b><b>9</b> in CH<sub>2</sub>Cl<sub>2</sub> are lower than the values measured for the complexes in THF. The decomposition reactions obeyed first-order kinetics, and the H/D isotope experiments for <b>8</b> and <b>9</b> indicate that the N-dealkylation reaction is the rate-determining step in the decomposition processes. On the other hand, the decomposition reaction of <b>7</b> in THF results in the oxidation of THF (acting as an exogenous substrate) to give 2-hydroxy tetrahydrofuran and γ-butyrolactone as oxidation products. Detailed investigation of the N-dealkylation reaction for <b>8</b> by kinetic experiments using N−H/D at −90 °C showed a kinetic isotope effect of 1.25, indicating that a weak electrostatic interaction between the N−H hydrogen and μ-oxo oxygen contributes to the major effect on the rate-determining step of N-dealkylation. X-ray crystal structures of the bis(μ-hydroxo)dicopper(II) complexes, [Cu<sub>2</sub>(OH)<sub>2</sub>(Et<sub>3</sub>CY)<sub>2</sub>](CF<sub>3</sub>SO<sub>3</sub>)<sub>2</sub> (<b>10</b>), [Cu<sub>2</sub>(OH)<sub>2</sub>(iBu<sub>3</sub>CY)<sub>2</sub>](CF<sub>3</sub>SO<sub>3</sub>)<sub>2</sub> (<b>11</b>), and [Cu<sub>2</sub>(OH)<sub>2</sub>(Bn<sub>3</sub>CY)<sub>2</sub>](ClO<sub>4</sub>)<sub>2</sub> (<b>12</b>), which have independently been prepared as the final products of bis(μ-oxo)dicopper(III) intermediates, suggest that an effective interaction between N−H and μ-oxo in the Cu(III)<sub>2</sub>(μ-O)<sub>2</sub> core may enhance the oxidation ability of the metal−oxo species.