457883-62-4Relevant academic research and scientific papers
An Example of O2 Binding in a Cobalt(II) Corrole System and High-Valent Cobalt-Cyano and Cobalt-Alkynyl Complexes
Ramdhanie, Bobby,Telser, Joshua,Caneschi, Andrea,Zakharov, Lev N.,Rheingold, Arnold L.,Goldberg, David P.
, p. 2515 - 2525 (2004)
The novel cobalt corrolazine (Cz) complexes (TBP)8CzCoCN (1) and (TBP)8CzCo(CCSiPh3) (2) have been synthesized and examined in light of the recent intense interest regarding the role of corrole ligands in stabilizing high oxidation states. In the case of 2, the molecular structure has been determined by X-ray crystallography, revealing a short Co-C distance of 1.831(4) A and an intermolecular π-stacking interaction between Cz ring planes, and this structure has been analyzed in regards to the electronic configuration. By a combination of spectroscopic techniques it has been shown that 1 is best described as a cobalt(III)-π-cation-radical complex, whereas 2 is likely best represented as the resonance hybrid (Cz)CoIV(CCSiPh3)?(Cz+.)Co III(CCSiPh3). The reduced cobalt(II) complex, [(TBP) 8CzCoII(py)]-, has been generated in situ and shown to bind dioxygen at low temperature to give [(TBP)8CzCo III(py)(O2)]-. For the reduced complex [(TBP)8CzCoII(py)]-, the EPR spectrum in frozen solution is indicative of a low-spin cobalt(II) complex with a d z2 ground state. Exposure of [(TBP)8CzCo III(py)]- to O2 leads to the reversible formation of the cobalt(III)-superoxo complex [(TBP)8CzCo III(py)(O2)]-, which has been characterized by EPR spectroscopy. VT-EPR measurements show that the dioxygen adduct is stable up to T ≈ 240 K. This work is the first observation, to our knowledge, of O2 binding to a cobalt(II) corrole.
Synthesis, structures, and properties of a series of four-, five-, and six-coordinate cobalt(III) triazacorrole complexes: The first examples of transition metal corrolazines
Ramdhanie, Bobby,Zakharov, Lev N.,Rheingold, Arnold L.,Goldberg, David P.
, p. 4105 - 4107 (2008/10/08)
The syntheses of the first transition metal corrolazine complexes, in which the meso carbon atoms of a corrole framework have been replaced by N atoms, are reported. Metalation of the corrolazine [(TBP)8CzH3] (TBP = 4-tert-butylphenyl) (1) with Co-(acac)2 gives [(TBP)8CzCOIII] (2) in good yield. Addition of PPh3 to 2 in pyridine results in the formation of [(TBP)8CzCoIII(PPh3)] (3), which was characterized by X-ray crystallography. Likewise, addition of an excess of pyridine to 2 in CH2Cl2 followed by slow diffusion of MeOH gives [(TBP)8CzCOIII(py)2] (4) as a crystalline solid, which was also characterized by X-ray crystallography. The crystal structures of 3 and 4 reveal that the corrolazine cavity is significantly smaller (～0.1 A) than their regular corrole analogues. Characterization of 2-4 by UV-vis spectroscopy reveals some interesting features in the absorption spectra of these compounds, including a dramatic red-shift of the Soret band. In addition, binding of pyridine to 2 was evaluated quantitatively by UV-vis titration, revealing a formation constant of β2 = 9.0 × 107 M-2, which is larger than any of the regular CoIII corrole analogues.
