Oxygen Transfer from Trimethylamine N-Oxide to Cu^I Complexes Supported by Pentanitrogen Ligands

[N,N-bis(1-methyl-2-benzimidazolyl)methyl-N-(bis-2-pyridylmethyl)amine] (L¹) and [N,N-bis(2-quinolylmethyl)-N-bis(2-pyridyl)methylamine] (L²) were employed to prepare Cu^II and Cu^I complexes for spectroscopic and structural characterization. [L¹Cu^II(H₂O)](NO₃)₂ and [L²Cu^II(NO₃)]NO₃ have Jahn–Teller distorted octahedral geometries and give rise to isotropic EPR spectra in frozen solution. [L¹Cu^I(CH₃CN)]OTf and [L²Cu^I(CH₃CN)]OTf have distorted trigonal bipyramidal and tetrahedral solid-state structures, respectively. The N-donors display labile behavior in solution, based on variable-temperature ¹H NMR studies. Addition of trimethylamine N-oxide (Me₃NO) to solutions of [L¹Cu^I(CH₃CN)]OTf and [L²Cu^I(CH₃CN)]OTf resulted in diamagnetic species tentatively assigned as the corresponding adducts upon replacement of coordinated acetonitrile, based on ¹H NMR spectroscopy. Heating [L¹Cu^I(CH₃CN)]OTf to 50–60 °C in the presence of Me₃NO resulted in its cupric analogue [L¹Cu^II(CH₃CN)]²⁺, as well as a small amount of 2-dipyridylketone, along with other oxidation by-products. In the case of [L²Cu^I(CH₃CN)]OTf, the reaction with Me₃NO resulted in the cupric complex bis(2-quinolinecarboxamidato)copper(II), along with 2-dipyridylketone as oxidation products.