Nucleophilic reactivity of copper(ii)–alkylperoxo complexes

Abstract

Copper(ii)-alkylperoxo adducts, [Cu(CHDAP)(OOR)] (CHDAP = N,N'-dicyclohexyl-2,11-diaza[3,3](2,6)pyridinophane; R = C(CH)Ph and Bu), were prepared and characterized using various physicochemical methods. These are the first synthetic Cu(ii)-alkylperoxo complexes that can perform aldehyde deformylation (i.e., nucleophilic reactivity) under the stoichiometric reaction conditions, which was confirmed by kinetic studies.

Nucleophilic reactivity of a copper(II)-hydroperoxo complex

“…3a, inset). 1-16 O 2 H exhibits two isotope sensitive bands at 834 and 501 cm −1 , which shifted to 790 and 482 cm −1 , respectively, in 1-18 O 2 H. The results support the assignments of these features as O-O and Cu-O stretching vibration on the basis of [16][17][18] Δ value of 44 and 19 cm −1 ( 16-18 Δ (calcd) = 48 and 23 cm −1 for diatomic harmonic oscillator), respectively [18][19][20][21][22][23][24] . Upon 2 H-substitution in 1, the characteristic Cu-O and O-O stretching vibrational features exhibited a 2-cm −1 downshift each ( Supplementary Fig.…”

“…A bimolecular mechanism for the nucleophilic oxidative reaction by 1 is suggested by the observed negative entropy and the second-order kinetics. Compared with the reactivity of a previously reported iron(III)-hydroperoxo complex 40 and copper (II)-alkylperoxo adducts 17 , the reactivity of 1 (k 2 = 3.6 × 10 -1 M -1 s -1 at -40°C) is higher than that of the iron(III)-hydroperoxo species (k 2 = 1.3 × 10 -1 M -1 s -1 at -40°C) and those of copper(II)-alkylperoxo complexes (k 2 = 1.2-1.8 × 10 -1 M -1 s -1 at -40°C) in aldehyde deformylation of 2-PPA (Supplementary Table 7). It should be noted that the reactivity of 1 (k 2 = 3.4 M -1 s -1 at -80°C) with CCA is also higher than that of a Cu(II)-superoxo complex, [Cu(βDK)(O 2 )] -(k 2 = 1.4 M -1 s -1 at -80°C), which was a highly reactive oxidant in aldehyde deformylation reported so far (Supplementary Table 8) 41 .…”

“…Notably, to our knowledge no reports of direct reactions of Cu (II)-OOH species with external substrates, i.e., prior to O-O bond cleavage, have yet appeared in the literature, although numerous examples of electrophilic reactivity in Cu(II)-OOH complexes have been shown to occur via O-O bond cleaved intermediates [14][15][16] . By contrast the nucleophilic reaction of Cu(II)-alkylperoxo complexes was reported very recently 17 .…”

Characterization and chemical reactivity of room-temperature-stable MnIII–alkylperoxo complexes

“…4 In biological systems, metal-alkylperoxo adducts are common intermediates in a variety of oxygenase enzymes, where they can be directly involved in substrate oxidation or precede the formation of high-valent metal-oxo species. 9,10 Given the importance of metal-alkylperoxo species in such reactions, there are now many examples of synthetic Fe-, 11,12 Co-, 1,4,5 and Cu-alkylperoxo 3,13,14 adducts, and these complexes are capable of oxidizing substrates such as 1,4-cyclohexadiene, 2-phenylpropionaldehyde, and triphenylphosphine.…”

Copper-Promoted Functionalization of Organic Molecules: from Biologically Relevant Cu/O2 Model Systems to Organometallic Transformations

“…Mononuclear copper(II)-alkylperoxide complexes were generated by addition of alkylhydroperoxides in the presence of triethylamine (Figure 54). 229 These E AP II species were characterized by low-temperature UV–vis, CSI-MS, rRaman, and EPR. It was also found that these complexes reacted with benzoyl chloride and 2-phenylpropionaldehyde to yield the corresponding oxidation products (benzoic acid and acetophenone).…”