Copper dioxygen adducts: formation of bis(mu-oxo)dicopper(III) versus (mu-1,2)Peroxodicopper(II) complexes with small changes in one pyridyl-ligand substituent.
The preference for the formation of a particular Cu 2O 2 isomer coming from (ligand)-Cu (I)/O 2 reactivity can be regulated with the steric demands of a TMPA (tris(2-pyridylmethyl)amine) derived ligand possessing 6-pyridyl substituents on one of the three donor groups of the tripodal tetradentate ligand. When this substituent is an -XHR group (X = N or C) the traditional Cu (I)/O 2 adduct forms a (mu-1,2)peroxodicopper(II) species ( A). However, when the substituent is the slightly bulkier XR 2 moiety {aryl or NR 2 (R not equal H)}, a bis(mu-oxo)dicopper(III) structure ( C) is favored. The reactivity of one of the bis(mu-oxo)dicopper(III) species, [{(6tbp)Cu (III)} 2(O (2-)) 2] (2+) ( 7-O 2 ) (6tbp = (6- (t)Bu-phenyl-2-pyridylmethyl)bis(2-pyridylmethyl)amine), was probed, and for the first time, exogenous toluene or ethylbenzene hydrocarbon oxygenation reactions were observed. Typical monooxygenase chemistry occurred: the benzaldehyde product includes an 18-O atom for toluene/ 7- (1) (8)O 2 reactivity, and a H-atom abstraction by 7-O 2 is apparent from study of its reactions with ArOH substrates, as well as the determination of k H/ k D approximately 7 in the toluene oxygenation (i.e., PhCH 3 vs PhCD 3 substrates). Proposed courses of reaction are presented, including the possible involvement of PhCH 2OO (*) and its subsequent reaction with copper(I) complex, the latter derived from dynamic solution behavior of 7-O 2 . External TMPA ligand exchange for copper in 7-O 2 and O-O bond (re)formation chemistry, along with the ability to protonate 7-O 2 and release of H 2O 2 indicate the presence of an equilibrium between [{(6tbp)Cu (III)} 2(O (2-)) 2] (2+) ( 7-O 2 ) and a (mu-1,2)peroxodicopper(II) form.
Maiti
Debabrata
D
Department of Chemistry, The Johns Hopkins University, Baltimore, MD 21218, USA.
Woertink
Julia S
JS
Narducci Sarjeant
Amy A
AA
Solomon
Edward I
EI
Karlin
Kenneth D
KD
D001555:Benzene Derivatives / Q000737:chemistry; D003300:Copper / Q000737:chemistry*; D008024:Ligands; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D010545:Peroxides / Q000737:chemistry; D010636:Phenols / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013059:Spectrum Analysis, Raman; D014050:Toluene / Q000031:analogs & derivatives
D001555:Benzene Derivatives; D008024:Ligands; D009942:Organometallic Compounds; D010545:Peroxides; D010636:Phenols; D011725:Pyridines; D014050:Toluene; D003300:Copper; C004912:ethylbenzene; D010100:Oxygen