title: Contrasting copper-dioxygen chemistry arising from alike tridentate alkyltriamine copper(I) complexes.
abstract: Copper(I)-dioxygen interactions are of great interest due to their role in biological O2-processing as well as their importance in industrial oxidation processes. We describe here the study of systems which lead to new insights concerning the factors which govern Cu(II)-mu-eta2:eta2 (side-on) peroxo versus Cu(III)-bis-mu-oxo species formation. Drastic differences in O2-reactivity of Cu(I) complexes which differ only by a single -CH3 versus -H substituent on the central amine of the tridentate ligands employed are observed. [Cu(MeAN)]B(C6F5)4 (1) (MeAN = N,N,N',N',N'-pentamethyl-dipropylenetriamine) reacts with O2 at -80 degrees C to form almost exclusively the side-on peroxo complex [{CuII(MeAN)}2(O2)]2+ (3) in CH2Cl2, tetrahydrofuran, acetone, and diethyl ether solvents, as characterized by UV-vis and resonance Raman spectroscopies. In sharp contrast, [Cu(AN)]B(C6F5)4 (2) (AN = 3, 3'-iminobis(N,N-dimethyl-propylamine) can support either Cu2O2 structures in a strongly solvent-dependent manner. Extreme behavior is observed in CH2Cl2 solvent, where 1 reacts with O2 giving 3, while 2 forms exclusively the bis-mu-oxo species [{CuIII(AN)}2(O)2]2+ (4Oxo). Stopped-flow kinetics measurements also reveal significant variations in the oxygenation reactions of 1 versus 2, including the observations that 4Oxo forms much faster than does 3; the former decomposes quickly, while the latter is quite stable at 193 K. The solvent-dependence of the bis-mu-oxo versus side-on peroxo preference observed for 2 is opposite to that reported for other known copper(I) complexes; the factors which may be responsible for the unusual behavior of 1/O2 versus 2/O2 (possibly N-H hydrogen bonding in the AN chemistry) are suggested. The factors which affect bis-mu-oxo versus side-on peroxo formation continue to be of interest.
authors.affiliation: Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.forename: Hong-Chang
authors.initials: HC
authors.lastname: Liang
authors.forename: Christiana Xin
authors.initials: CX
authors.lastname: Zhang
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Henson
authors.forename: Roger D
authors.initials: RD
authors.lastname: Sommer
authors.forename: Karen R
authors.initials: KR
authors.lastname: Hatwell
authors.forename: Susan
authors.initials: S
authors.lastname: Kaderli
authors.forename: Andreas D
authors.initials: AD
authors.lastname: Zuberbühler
authors.forename: Arnold L
authors.initials: AL
authors.lastname: Rheingold
authors.forename: Edward I
authors.initials: EI
authors.lastname: Solomon
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Karlin
mesh_terms: D000588:Amines / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D007700:Kinetics; D009942:Organometallic Compounds / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*
chemical_list: D000588:Amines; D009942:Organometallic Compounds; D003300:Copper; D010100:Oxygen