Bimetallic Reactivity. One-Site Addition Two-Metal Oxidation Reaction of Dioxygen with a Bimetallic Dicobalt(II) Complex Bearing Five- and Six-Coordinate Sites

Abstract

The di-Co(2+) complex, [Co(2+)(mu-OH)(oxapyme)Co(2+)(H(2)O)](+), contains an unsymmetrical binucleating ligand (oxapyme) which provides five- and six-coordinate metal sites when a hydroxide bridge is introduced. This complex absorbs 1 equiv of O(2) irreversibly in solution, producing an unstable di-Co(3+) oxygenated product. The oxygenated product has been studied at low temperatures, where its electronic absorption and (1)H NMR spectra were recorded. It is probable that the oxygenation reaction involves a one-site addition two-metal oxidation reaction to produce an end-on-bonded peroxide ligand at the available coordination site, giving the complex [Co(3+)(mu-OH)(oxapyme)Co(3+)(mu(1)-O(2))](+). Addition of 1 equiv of HClO(4) to this oxygenation product gives a stable peroxide complex, [Co(3+)(mu,eta(1):eta(2)-O(2))(oxapyme)Co(3+)](2+), where one of the oxygen atoms bridges the two metals and is sideways bonded to one of the metals. The formation of this stable complex involves expulsion of the OH(-) bridge. Addition of NO(2)(-) to the sideways-bonded peroxide complex leads to the formation of another stable complex, [Co(3+)(mu,eta(1):eta(1)-O(2))(oxapyme)Co(3+)(NO(2))](+), where the peroxide forms a classic di-end-on bridge to the two metals. Both of these complexes have been fully characterized. Addition of acid to this second stable dioxygen complex leads to the release of HNO(2) and the formation of the mu,eta(1):eta(2) sideways-bonded peroxide complex.

Tagging (Arene)ruthenium(II) Anticancer Complexes with Fluorescent Labels

“…In those complexes, however, the fragment is part of a larger dinucleating ligand framework. [33][34][35][36][37][38] …”

Well‐Defined Heterometallic and Unsymmetric M2O2 Complexes Arising from Binding and Activation of O2

“…For comparative purposes, symmetric systems have also been included (Figure 2a, e). [29,30] As shown in Figure 2, in both strategies the lack of symmetry can arise from the nature of the metal ion (M ϶ MЈ, Figure 2c), [31] the first coordination sphere of the metal ions (L ϶ LЈ, Figures 2b, f), [32,33] or both (LM ϶ LЈMЈ, Figures 2d, g). [27,34] …”

“…Furthermore, when 46 The design of the ligand oxapyme, which contains two different coordination sites, was used by Bosnich and coworkers to synthesize unsymmetric dinuclear Co II complex 50 ( Figure 11). [33] One of the cobalt ions is bound to four N atoms of the dinucleating ligand, and the other is bound to five. A bridging hydroxide moiety connects the two metal ions, and a water molecule fulfils the coordination sphere of the N 4 Figure 11.…”

Transition Metal Peroxides. Synthesis and Role in Oxidation Reactions*Dedicated, on the occasion of his 80th birthday, to our ‘vitae ac studiorum magister in secunda et in adversa fortuna’ Emeritus Professor Giorgio Modena, Padova University, who showed us the way toward Chemistry.

“…The two metals have an octahedral arrangement and the bond lengths for the peroxidic moiety are all in the expected range. This di-iridium complex also reacts with CO giving rise to the formation of a new complex, 25, whose structure was solved, showing the (µ-η 1 :η 1 -O 2 ) group intact together with a (µ-CO) ligand 53 76 . Both species were characterized in the solid state and interesting aspects of transformation of dioxygen ligand in bimetallic species were therefore explored.…”