| Autor: |
R. Humphrey, Elizabeth, L. V. Mann, Karen, R. Reeves, Zöe, Behrendt, Andreas, C. Jeffery, John, P. Maher, John, A. McCleverty, Jon, D. Ward, Michael |
| Zdroj: |
New Journal of Chemistry; February 21, 1999, Vol. 23 Issue: 4 p417-424, 8p |
| Abstrakt: |
The mononuclear copper(II) complexes of the following potentially hexadentate podand ligands have been prepared and crystallographically characterised: tris[3-{2-(methylsulfanyl)phenyl}pyrazol-1-yl]hydroborate [L1]-, phenyltris[3-(2-pyridyl)pyrazol-1-yl]methane (L2), and tris[3-{(6-methyl)-pyrid-2-yl}pyrazol-1-yl]hydroborate [L3]-. Of these, [L1]- [a potentially N3S3 donor with three pyrazolyl and three thioether groups, based on a tris(pyrazolyl)borate core] and L2 [a potentially N6 donor with three pyrazolyl and three pyridyl groups, based on a tris(pyrazolyl)methane core] have been prepared for the first time. In [Cu(L1)][PF6] the Cu(II) centre is in a five-coordinate N3S2 coordination environment which is approximately square pyramidal; the pendant thioether group has a weak, long-range interaction with the sixth coordination site of Cu(II). [Cu(L1)][PF6] undergoes a reversible Cu(I)–Cu(II) redox conversion. In [Cu(L2)(MeOH)][PF6]2 the ligand is four-coordinate via two bidentate pyridyl/pyrazolyl arms, with the third arm pendant; an axial methanol ligand completes the square-pyramidal coordination. In [Cu(L3)(H2O)][PF6], which is five coordinate and approximately trigonal bipyramidal, [L3]- acts as an N4 donor via all three pyrazolyl groups but only one pyridyl group; the two pendant pyridyl groups are involved in O–H···N hydrogen-bonding interactions with the coordinated water molecule. This ‘second-sphere’ stabilisation of a coordinated ligand is strongly reminiscent of the cooperative interactions by which substrates are bound to the active sites of metalloproteins. The EPR spectra of this complex are solvent-dependent, showing a change from a dz2 ground state in non-donor solvents to a dx2-y2 ground state in donor solvents. |
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Supplemental Index |
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