363625-74-5Relevant articles and documents
Resonance Raman investigation of equatorial ligand donor effects on the CU2O22+ core in end-on and side-on μ-peroxo-dicopper(II) and bis-μ-oxo-dicopper(III) complexes
Henson, Mark J.,Vance, Michael A.,Zhang, Christiana Xin,Hong-Chang, Liang,Karlin, Kenneth D.,Solomon, Edward I.
, p. 5186 - 5192 (2003)
The effect of endogenous donor strength on CU2O2 bonds was studied by electronically perturbing [{(R-TMPA)CuII}2(O2)]2+ and [{(R-MePY2)Cu}2(O2)]2+ (R = H, MeO, Me2N), which form the end-on μ-1,2 bound peroxide and an equilibrium mixture of side-on peroxo- dicopper(II) and bis-μ-oxo-dicopper(III) isomers, respectively. For [{(R-TMPA)CUII}2(O2)]2+, vo-o shifts from 827 to 822 to 812 cm-1 and VCu-O(sym) shifts from 561 to 557 to 551 cm-1, respectively, as R- varies from H to MeO to Me2N. Thus, increasing the N-donor strength to the copper decreases peroxide π*σ donation to the copper, weakening the Cu-O and O-O bonds. A decrease in vCu-O of the bis-μ-oxo- dicopper(III) complex was also observed with increasing N-donor strength for the R-MePY2 ligand system. However, no change was observed for vO-O of the side-on peroxo. This is attributed to a reduced charge donation from the peroxide π*σ orbital with increased N-donor strength, which increases the negative charge on the peroxide and adversely affects the back-bonding from the Cu to the peroxide σ*orbital. However, an increase in the bis-μ-oxo-dicopper(III) isomer relative to side-on peroxo-dicopper(II) species is observed for R-MePY2 with R = H 2N. This effect is attributed to the thermodynamic stabilization of the bis-μ-oxo-dicopper(III) isomer relative to the side-on peroxo-dicopper(II) isomer by strong donor ligands. Thus, the side-on peroxo-dicopper(II)/bis-μ-oxo-dicopper(III) equilibrium can be controlled by electronic as well as steric effects.
