Podand ligands

Reeves, Z. R. Mann, K. L. V. Jeffery, J. C. McCleverty, J. A. Ward, M. D. Barigelletti, F. Armaroli, N. Lanthanide complexes of a new sterically hindered potentially hexadentate podand ligand based on a tris(pyrazolyl)borate core crystal structures, solution structures and luminescence properties. J. Chem. Soc., Dalton Trans. 1999, 349-355. 

Clearly, while porphyrin complexes are obvious candidates for modelling these kinds of biomimetic oxidations, a range of non-heme iron complexes based on macrocyclic and podand ligand have also proved to be successful structural and functional mimics.19 To take one example, Figure 12.13 shows the X-ray structure of the iron (IV) tetramethylcyclam (tmc) oxo complex [Felv(tmc)(0)(MeCN)]2+... 

The potassium salt of the podand ligand tris[3-(2-pyridyl)-pyrazol-l-yl]borate O Tp) reacts with thorium tetra(nitrate) to generate the complex (P Tp)Th(N03)3. The crystal structure of the complex reveals that the metal center is 12-coordinate, binding to the six nitrogen atoms of the podand ligand, and to two of the oxygen atoms of each nitrate. The molecule has three-fold symmetry, and the nitrates are located between the bidentate arms of the podand. 

Groups 3 and 4. 45Sc NMR spectroscopy was used to follow the formation of complexes between ScCl3 and podand ligands (inorganic esters of polyoxyethylene glycols).1116... 

The new podand ligand hydrotris[3-(6-methyl)pyridin-2-ylpyrazol-l-yl]borate, (Tp2< 6Me py), has been reported by McCleverty and Ward.171 It possesses a methyl group attached to the C6 positions of the pyridyl rings, which interferes when the ligand is coordinated in a fully hexadentate manner. In fact, [M(Tp216Melpy)(N03)2(H20)] (M = Eu, Tb or Gd) (Fig. 1.21) showed partial dissociation of the podand occurring to relieve potential steric problems either one or two of the pyridyl groups are not coordinated, such that Tp2(6Me,py... 

The bpy unit was used as a chromophore in the podands 48-51. Figure 12 schematically shows the podand ligands of the Eu3+ complexes examined. Some photophysical data and the number of coordinated solvent molecules of these complexes are gathered in Table 3. 

Among the most enduringly popular podand ligands are tripodal species based on tris(aminoethyl)amine (tren, 21). 

Hirao et. al. developed an efficient system for the catalytic epoxidation reaction of olefins -methyl-styrene, stilbene) with molecular oxygen by the utilization of FeCl2 and the Wheterocyclic podand ligand, The reaction... 

An efficient catalytic system for oxygenation of phenols to p- or o-quinones with molecular oxygen was achieved by utilization of a catalyst consisting of Co(OAc)2 and the multidentate N-heterocyclic podand ligand, A,A -bis-2-(2-pyridyl)ethyl)-2,6-pyridinedicarboxamide, 2-BPEPA (Figure... 

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