+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

Autocatalytic O2 cleavage by an OCO3 trianionic pincer Cr(III) complex: isolation and characterization of the autocatalytic intermediate [Cr(IV)]2(μ-O) dimer

Autocatalytic O2 cleavage by an OCO3 trianionic pincer Cr(III) complex: isolation and characterization of the autocatalytic intermediate [Cr(IV)]2(μ-O) dimer

Journal of the American Chemical Society 133(34): 13661-13673

Synthetic and kinetic experiments designed to probe the mechanism of O(2) activation by the trianionic pincer chromium(III) complex [(t)BuOCO]Cr(III)(THF)(3) (1) (where (t)BuOCO = [2,6-((t)BuC(6)H(3)O)(2)C(6)H(3)](3-), THF = tetrahydrofuran) are described. Whereas analogous porphyrin and corrole oxidation catalysts can become inactive toward O(2) activation upon dimerization (forming a μ-oxo species) or product inhibition, complex 1 becomes more active toward O(2) activation when dimerized. The product from O(2) activation, [(t)BuOCO]Cr(V)(O)(THF) (2), catalyzes the oxidation of 1 via formation of the μ-O dimer {[(t)BuOCO]Cr(IV)(THF)}(2)(μ-O) (3). Complex 3 exists in equilibrium with 1 and 2 and thus could not be isolated in pure form. However, single crystals of 3 and 1 co-deposit, and the molecular stucture of 3 was determined using single-crystal X-ray crystallography methods. Variable (9.5, 35, and 240 GHz) frequency electron paramagnetic resonance spectroscopy supports the assignment of complex 3 as a Cr(IV)-O-Cr(IV) dimer, with a high (S = 2) spin ground state, based on detailed computer simulations. Complex 3 is the first conclusively assigned example of a complex containing a Cr(IV) dimer; its spin Hamiltonian parameters are g(iso) = 1.976, D = 2400 G, and E = 750 G. The reaction of 1 with O(2) was monitored by UV-visible spectrophotometry, and the kinetic orders of the reagents were determined. The reaction does not exhibit first-order behavior with respect to the concentrations of complex 1 and O(2). Altering the THF concentration reveals an inverse order behavior in THF. A proposed autocatalytic mechanism, with 3 as the key intermediate, was employed in numerical simulations of concentration versus time decay plots, and the individual rate constants were calculated. The simulations agree well with the experimental observations. The acceleration is not unique to 2; for example, the presence of OPPh(3) accelerates O(2) activation by forming the five-coordinate complex trans-[(t)BuOCO]Cr(III)(OPPh(3))(2) (4).

Please choose payment method:

(PDF emailed within 0-6 h: $19.90)

Accession: 051721725

Download citation: RISBibTeXText

PMID: 21780813

DOI: 10.1021/ja2050474

Related references

An OCO3- trianionic pincer tungsten(VI) alkylidyne: rational design of a highly active alkyne polymerization catalyst. Journal of the American Chemical Society 134(10): 4509-4512, 2012

Synthesis, characterization, and reactivity of a d2, Mo(IV) complex supported by a new OCO-trianionic pincer ligand. Journal of the American Chemical Society 130(4): 1116-1117, 2008

The influence of reversible trianionic pincer OCO(3-)μ-oxo Cr(IV) dimer formation ([Cr(IV)]2(μ-O)) and donor ligands in oxygen-atom-transfer (OAT). Dalton Transactions 41(8): 2237-2246, 2011

Carbon dioxide cleavage across a tungsten-alkylidyne bearing a trianionic pincer-type ligand. Dalton Transactions 45(40): 15783-15785, 2016

A new ONO(3-) trianionic pincer ligand with intermediate flexibility and its tungsten alkylidene and alkylidyne complexes. Dalton Transactions 44(42): 18475-18486, 2016

Characterization of poliovirus 2A proteinase by mutational analysis: residues required for autocatalytic activity are essential for induction of cleavage of eukaryotic initiation factor 4F polypeptide p220. Journal of Virology 65(8): 4226-4231, 1991

Autocatalytic processing of the streptococcal cysteine protease zymogen. Processing mechanism and characterization of the autoproteolytic cleavage sites. European Journal of Biochemistry 263(1): 145-151, 1999

Characterization of a self-splicing mini-intein and its conversion into autocatalytic N- and C-terminal cleavage elements: Facile production of protein building blocks for protein ligation. Gene (Amsterdam) 231(1-2): 1-13, April 29, 1999

Autocatalytic creation of closed dimer and extended helix metallosupramolecular architectures. Chemistry 15(39): 10021-4, 2009

Autocatalytic cleavage of Clostridium difficile toxin B. Nature London 446(7134): 415-419, 2007

Autocatalytic cleavage of Clostridium difficile toxin. Nature (London) 446(7134): 415-419, 2007

Cleavage of SPATEs and Bordetella autotransporters: A novel autocatalytic mechanism. 2007

Noble metals role in autocatalytic phosphate coatings on TAV alloys. I.Ag functionalization of autocatalytic phosphate deposition on TAV alloys. Surface and Coatings Technology 282: 171-179, 2015

Cleavage of a bacterial autotransporter by an evolutionarily convergent autocatalytic mechanism. EMBO (European Molecular Biology Organization) Journal 26(7): 1942-1952, 2007

Autocatalytic cleavage site and use thereof in a protein expression vector. Official Gazette of the United States Patent & Trademark Office Patents 1223(3), Jun 15, 1999