Substrate oxidation by copper-dioxygen adducts: mechanistic considerations.
A series of copper-dioxygen adducts [{Cu(II)(MePY2)(R)}(2)(O(2))](B(C(6)F(5))(4))(2) (1(R)()), systematically varying in their electronic properties via ligand pyridyl donor substituents (R = H, MeO, and Me(2)N), oxidize a variety of substrates with varying C-H or O-H bond dissociation enthalpies. Detailed mechanistic studies have been carried out, including investigation of 1(R)() thermodynamic redox properties, 1(R)() tetrahydrofuran (THF) and N,N'-dimethylaniline (DMA) oxidation kinetics (including analyses of substrate dicopper binding equilibria), and application of mechanistic probes (N-cyclopropyl-N-methylaniline (CMA) and (p-methoxyphenyl)-2,2-dimethylpropanol (MDP)), which can distinguish if proton-coupled electron-transfer (PCET) processes proceed through concerted electron-transfer proton-transfer (ETPT) or consecutive electron-transfer proton-transfer (ET/PT) pathways. The results are consistent with those of previous complementary studies; at low thermodynamic driving force for substrate oxidation, an ET/PT is operable, but once ET (i.e., substrate one-electron oxidation) becomes prohibitively uphill, the ETPT pathway occurs. Possible differences in coordination structures about 1(Me)()()2(N)()/1(MeO)() compared to those of 1(H)() are also used to rationalize some of the observations.
Shearer
Jason
J
Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA.
Zhang
Christiana Xin
CX
Zakharov
Lev N
LN
Rheingold
Arnold L
AL
Karlin
Kenneth D
KD
D000814:Aniline Compounds / Q000737:chemistry; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D005663:Furans / Q000737:chemistry; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry; D013816:Thermodynamics
D000814:Aniline Compounds; D005663:Furans; D009942:Organometallic Compounds; D011725:Pyridines; C018674:tetrahydrofuran; C015157:N,N-dimethylaniline; D003300:Copper; D010100:Oxygen