Structural, Spectroscopic, and Theoretical Characterization of Bis(-oxo)dicopper Complexes, Novel Intermediates in Copper-Mediated Dio
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- 作者：Samiran Mahapatra ; Jason A. Halfen ; Elizabeth C. Wilkinson ; Gaofeng Pan ; Xuedong Wang ; Victor G. Young Jr. ; Christopher J. Cramer ; Lawrence Que ; Jr. ; and William B. Tolman
- 刊名：Journal of the American Chemical Society
- 出版年：1996
- 出版时间：November 20, 1996
- 年：1996
- 卷：118
- 期：46
- 页码：11555 - 11574
- 全文大小：770K
- 年卷期：v.118,no.46(November 20, 1996)
- ISSN：1520-5126
文摘
A description of the structure and bonding of novelbis(
-oxo)dicopper complexes and theirbis(-hydroxo)dicopper decomposition products was derived from combined X-raycrystallographic, spectroscopic, and ab initiotheoretical studies. The compounds[(LCu)2(-O)2]X2 weregenerated from the reaction of solutions of [LCu(CH3CN)]X with O2 at -80 
C (L =1,4,7-tribenzyl-1,4,7-triazacyclononane,LBn3;1,4,7-triisopropyl-1,4,7-triazacyclononane, LiPr3; or1-benzyl-4,7-diisopropyl-1,4,7-triazacyclononane,LiPr2Bn; X = varietyof anions). Thegeometry of the[Cu2(-O)2]2+ core wasdefined by X-ray crystallography for[(d21-LBn3Cu)2(-O)2](SbF6)2and byEXAFS spectroscopy for the complexes capped byLBn3 andLiPr3; notable dimensions includeshort Cu-O (~1.80Å) and Cu···Cu (~2.80 Å) distances like those reportedfor analogous M2(-O)2 (M = Fe or Mn)rhombs. The coregeometry is contracted compared to those of thebis(-hydroxo)dicopper(II) compounds that result fromdecompositionof the bis(-oxo) complexes upon warming. X-ray structuresof the decomposition products[(LBn3Cu)(LBn2HCu)(-OH)2](O3SCF3)2·2CH3CO,[(LiPr2HCu)2(-OH)2](BPh4)2·2THF,and[(LiPr2BnCu)2(-OH)2](O3SCF3)2showed thatthey arise from N-dealkylation of the original capping macrocycles.Manometric, electrospray mass spectrometric,and UV-vis, EPR, NMR, and resonance Raman spectroscopic data for thebis(-oxo)dicopper complexes in solutionrevealed important topological and electronic structural features ofthe intact [Cu2(-O)2]2+core. The bis(-oxo)dicopper unit is diamagnetic, undergoes a rapid fluxional processinvolving interchange of equatorial and axial N-donorligand environments, and exhibits a diagnostic ~600cm-1 18O-sensitive feature inRaman spectra. Ab initiocalculations on a model system,{[(NH3)3Cu]2(-O)2}2+,predicted a closed-shell singlet ground-state structurethatagrees well with the bis(-oxo)dicopper geometry determinedby experiment and helps to rationalize many of itsphysicochemical properties. On the basis of an analysis of thetheoretical and experimental results (including abond valence sum analysis), a formal oxidation level assignment for thecore is suggested to be[CuIII2(-O2-)2]2+,although a more complete molecular orbital description indicates thatthe oxygen and copper fragment orbitals aresignificantly mixed (i.e., there is a high degree ofcovalency).
-oxo)dicopper complexes and theirbis(-hydroxo)dicopper decomposition products was derived from combined X-raycrystallographic, spectroscopic, and ab initiotheoretical studies. The compounds[(LCu)2(-O)2]X2 weregenerated from the reaction of solutions of [LCu(CH3CN)]X with O2 at -80 C (L =1,4,7-tribenzyl-1,4,7-triazacyclononane,LBn3;1,4,7-triisopropyl-1,4,7-triazacyclononane, LiPr3; or1-benzyl-4,7-diisopropyl-1,4,7-triazacyclononane,LiPr2Bn; X = varietyof anions). Thegeometry of the[Cu2(-O)2]2+ core wasdefined by X-ray crystallography for[(d21-LBn3Cu)2(-O)2](SbF6)2and byEXAFS spectroscopy for the complexes capped byLBn3 andLiPr3; notable dimensions includeshort Cu-O (~1.80Å) and Cu···Cu (~2.80 Å) distances like those reportedfor analogous M2(-O)2 (M = Fe or Mn)rhombs. The coregeometry is contracted compared to those of thebis(-hydroxo)dicopper(II) compounds that result fromdecompositionof the bis(-oxo) complexes upon warming. X-ray structuresof the decomposition products[(LBn3Cu)(LBn2HCu)(-OH)2](O3SCF3)2·2CH3CO,[(LiPr2HCu)2(-OH)2](BPh4)2·2THF,and[(LiPr2BnCu)2(-OH)2](O3SCF3)2showed thatthey arise from N-dealkylation of the original capping macrocycles.Manometric, electrospray mass spectrometric,and UV-vis, EPR, NMR, and resonance Raman spectroscopic data for thebis(-oxo)dicopper complexes in solutionrevealed important topological and electronic structural features ofthe intact [Cu2(-O)2]2+core. The bis(-oxo)dicopper unit is diamagnetic, undergoes a rapid fluxional processinvolving interchange of equatorial and axial N-donorligand environments, and exhibits a diagnostic ~600cm-1 18O-sensitive feature inRaman spectra. Ab initiocalculations on a model system,{[(NH3)3Cu]2(-O)2}2+,predicted a closed-shell singlet ground-state structurethatagrees well with the bis(-oxo)dicopper geometry determinedby experiment and helps to rationalize many of itsphysicochemical properties. On the basis of an analysis of thetheoretical and experimental results (including abond valence sum analysis), a formal oxidation level assignment for thecore is suggested to be[CuIII2(-O2-)2]2+,although a more complete molecular orbital description indicates thatthe oxygen and copper fragment orbitals aresignificantly mixed (i.e., there is a high degree ofcovalency).