Aliphatic C-H bond activation initiated by a (mu-eta2:eta2-peroxo)dicopper(II) complex in comparison with cumylperoxyl radical.
A (mu-eta(2):eta(2)-peroxo)dicopper(II) complex, [Cu(2)(H-L)(O(2))](2+) (1-O(2)), supported by the dinucleating ligand 1,3-bis[bis(6-methyl-2-pyridylmethyl)aminomethyl]benzene (H-L) is capable of initiating C-H bond activation of a variety of external aliphatic substrates (SH(n)): 10-methyl-9,10-dihydroacridine (AcrH(2)), 1,4-cyclohexadiene (1,4-CHD), 9,10-dihydroanthracene (9,10-DHA), fluorene, tetralin, toluene, and tetrahydrofuran (THF), which have C-H bond dissociation energies (BDEs) ranging from approximately 75 kcal mol(-1) for 1,4-CHD to approximately 92 kcal mol(-1) for THF. Oxidation of SH(n) afforded a variety of oxidation products, such as dehydrogenation products (SH((n-2))), hydroxylated and further-oxidized products (SH((n-1))OH and SH((n-2))=O), dimers formed by coupling between substrates (H((n-1))S-SH((n-1))) and between substrate and H-L (H-L-SH((n-1))). Kinetic studies of the oxidation of the substrates initiated by 1-O(2) in acetone at -70 degrees C revealed that there is a linear correlation between the logarithms of the rate constants for oxidation of the C-H bonds of the substrates and their BDEs, except for THF. The combination of this correlation and the relatively large deuterium kinetic isotope effects (KIEs), k(2)(H)/k(2)(D) (13 for 9,10-DHA, approximately > 29 for toluene, and approximately 34 for THF at -70 degrees C and approximately 9 for AcrH(2) at -94 degrees C) indicates that H-atom transfer (HAT) from SH(n) (SD(n)) is the rate-determining step. Kinetic studies of the oxidation of SH(n) by cumylperoxyl radical showed a correlation similar to that observed for 1-O(2), indicating that the reactivity of 1-O(2) is similar to that of cumylperoxyl radical. Thus, 1-O(2) is capable of initiating a wide range of oxidation reactions, including oxidation of aliphatic C-H bonds having BDEs from approximately 75 to approximately 92 kcal mol(-1), hydroxylation of the m-xylyl linker of H-L, and epoxidation of styrene (Matsumoto, T.; et al. J. Am. Chem. Soc. 2006, 128, 3874).
Matsumoto
Takahiro
T
Department of Chemistry, Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
Ohkubo
Kei
K
Honda
Kaoru
K
Yazawa
Akiko
A
Furutachi
Hideki
H
Fujinami
Shuhei
S
Fukuzumi
Shunichi
S
Suzuki
Masatatsu
M
D000166:Acridines / Q000737:chemistry; D000873:Anthracenes / Q000737:chemistry; D001555:Benzene Derivatives / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D053138:Cyclohexenes / Q000737:chemistry; D005449:Fluorenes / Q000737:chemistry; D005663:Furans / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D013764:Tetrahydronaphthalenes / Q000737:chemistry; D014050:Toluene / Q000737:chemistry
D000166:Acridines; D000873:Anthracenes; D001555:Benzene Derivatives; D053138:Cyclohexenes; D005449:Fluorenes; D005663:Furans; D013764:Tetrahydronaphthalenes; C048401:1,4-cyclohexadiene; D014050:Toluene; C018674:tetrahydrofuran; C041509:fluorene; D003300:Copper; C095210:tetralin; C007164:cumene hydroperoxide; D010100:Oxygen