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
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
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DOI：
10.1021/ja0276366
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发表时间：
2003-04-30
影响因子：
15
通讯作者：
Solomon, EI
中科院分区：
文献类型：
--
作者：
Henson, MJ;Vance, MA;Solomon, EI
通过电子微扰[{(R-TMPA)Cu-II}(2)(O-2)](2+)和[{(R-MePY2)Cu}(2)(O-2)](2+)(R=H，MeO，Me2N)(R=H，MeO，Me2N)，研究了内源施主强度对Cu2O2键的影响.对于[{(R-TMPA)Cu-II}(2)(O-2)](2+)，当R-从H到MeO再到Me2N时，v(o-o)从827到822移动到812 cm(-1)，v(Cu-O(Sym))从561到557移动到551 cm(-1)。因此，增加铜的N-给体强度会减少给铜的过氧化氢pi*(Sigma)，削弱了铜-O和O-O键。对于R-MePY2配体体系，随着N-给体强度的增加，双钼氧二铜(III)络合物的v(Cu-O)值也随之降低。而侧基过氧基的v(O-O)变化不大。这归因于过氧化氢pi*(Sigma)轨道的电荷给予减少，N-给体强度增加，这增加了过氧化氢上的负电荷，并不利地影响了从铜到过氧化氢sigma*轨道的回键。然而，对于R=H<；MeO<；Me2N的R-MePY2，观察到双钼氧二铜(III)异构体相对于侧面过氧二铜(II)物种的增加。这一效应归因于强给体配体对双钼氧二铜(III)异构体相对于侧向过氧二铜(II)异构体的热力学稳定作用。因此，过氧二铜(II)/双钼氧二铜(III)的侧向平衡可以由电子效应和空间效应控制。
The effect of endogenous donor strength on Cu2O2 bonds was studied by electronically perturbing [{(R-TMPA)Cu-II}(2)(O-2)](2+) and [{(R-MePY2)Cu}(2)(O-2)](2+) (R = H, MeO, Me2N), which form the end-on mu-1,2 bound peroxide and an equilibrium mixture of side-on peroxo-dicopper(II) and bis-mu-oxo-dicopper(III) isomers, respectively. For [{(R-TMPA)Cu-II}(2)(O-2)](2+), v(o-o) shifts from 827 to 822 to 812 cm(-1) and v(Cu-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 pi*(sigma), donation to the copper, weakening the Cu-O and O-O bonds. A decrease in v(Cu-O) of the bis-mu-oxo-dicopper(III) complex was also observed with increasing N-donor strength for the R-MePY2 ligand system. However, no change was observed for v(O-O) of the side-on peroxo. This is attributed to a reduced charge donation from the peroxide pi*(sigma), 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 sigma* orbital. However, an increase in the bis-mu-oxo-dicopper(III) isomer relative to side-on peroxo-dicopper(II) species is observed for R-MePY2 with R = H < MeO < Me2N. This effect is attributed to the thermodynamic stabilization of the bis-mu-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-mu-oxo-dicopper(III) equilibrium can be controlled by electronic as well as steric effects.