Lanthanide III Complexes

The bis(phthalocyaninato) lanthanide (III) complexes have generated a great deal of interest because they are found to show electrochromic and semiconducting properties [87, 203]. They have been characterized by a range of spectroscopic methods, but much research interest has been directed towards understanding the f-electronic structures and their magnetic properties. In order to understand... 

Synthesis of Heteroleptic Lanthanide(III) Complexes Containing Porphyrin-Based Ligands 235... 

In the presence of a catalytic amount of chiral lanthanide triflate 63, the reaction of 3-acyl-l,3-oxazolidin-2-ones with cyclopentadiene produces Diels-Alder adducts in high yields and high ee. The chiral lanthanide triflate 63 can be prepared from ytterbium triflate, (R)-( I )-binaphthol, and a tertiary amine. Both enantiomers of the cycloaddition product can be prepared via this chiral lanthanide (III) complex-catalyzed reaction using the same chiral source [(R)-(+)-binaphthol] and an appropriately selected achiral ligand. This achiral ligand serves as an additive to stabilize the catalyst in the sense of preventing the catalyst from aging. Asymmetric catalytic aza Diels-Alder reactions can also be carried out successfully under these conditions (Scheme 5-21).19... 

It was not until quite recently that the presence of octahedral lanthanide(III) complexes with CN = 6 has been demonstrated. In 1966 Ryan and Jergensen were able to prepare the anionichexahalide complexes of the lanthanides, [MXe] " in non-aqueous (nitriles) solvents [33, 34). Complexes of the type [(C6H5)3PH]3 [MXe] and [C5H5NH]3 [MXe], where M =Pr, Nd, Sm, Eu, Dy, Er, Yb and X- = Cl, Br were obtained as solids. The electronic (/- -/) transitions in these and in hexaiodide, [Mle] -, complexes are extremely weak, except for the magnetic dipole allowed transitions [35). Both electronic and electron transfer spectra (4f- 5d) indicated the presence of octahedral MX species. 

Klink, S. I. Hebbik, G. A. Grave, L. Peters, F. G. A. Van Veggel, F. C. J. M. Reinhoudt, D. N. Hofstraat, J. W. Near-infrared and visible luminescence from terphenyl-based lanthanide(III) complexes bearing amido and sulfonamido pendant arms. Bur. J. Org. Chem. 2000,1923-1931. 

Casellato, U. Tamburini, S. Tomasin, P. Vigato, P. A. Botta, M. Lanthanide(III) complexes with a podand Schiff base containing an N403 coordination site. Inorg. Chim. Acta 1996, 247,143-145. 

Kobayashi reported an asymmetric Diels-Alder reaction catalyzed by a chiral lanthanide(III) complex 24, prepared from ytterbium or scandium triflate [ Yb(OTf)3 or Sc(OTf)3], (Zf)-BINOL and tertiary amine (ex. 1,2,6-trimethylpiperidine) [30], A highly enantioselective and endose-lective Diels-Alder reaction of 3-(2-butenoyl)-l,3-oxazolidin-2-one (23) with cyclopentadiene (Scheme 9.13) takes place in the presence of 24. When chiral Sc catalyst 24a was used, asymmetric amplification was observed with regard to the enantiopurity of (/ )-BINOL and that of the endoadduct [31 ]. On the other hand, in the case of chiral Yb catalyst 24b, NLE was affected by additives, that is, when 3-acetyl-l,3-oxazolidin-2-one was added, almost no deviation was observed from linearity, whereas a negative NLE was observed with the addition of 3-pheny-lacetylacetone. 

Wietzke, R., Mazzanti, M., Latour, J.M., Pecaut, J., Cordier, P.Y., Madic, C. 1998. Lanthanide(III) complexes of tripodal N-donor ligands Structural models for the species involved in solvent extraction of actinides(III). Inorganic Chemistry 37(26) 6690-6697. 

Guillaumont, D. 2004. Quantum chemistry study of actinide(III) and lanthanide(III) complexes with tridentate nitrogen ligands. Journal of Physical Chemistry 108(33) 6893-6900. 

Pyrrole ligands can form both Ln-N or-bonds and tjs-n-Ln bonds. complexes with sterically less crowded pyrrole ligands [195]. The introduction of sterically demanding groups in a-position as in 2,5-di-fert-butylpyrrole led to a shielding of the nitrogen and subsequent -coordination to the lanthanide center [196]. Additionally, rj1-coordination to a sodium atom is observed in the obtained ate complex. 

Fused heterocyclic dianionic ligands are also accessible to lanthanide(III) complexes which has been shown for quinoxaline and phenazine [204] (Table 16). The existence and availability of the alkali metal precursors allows the usual metathesis reaction. 

The crystallographic ionic radii of the rare-earth elements in oxidation states +2 (CN = 6), +3 (CN = 6), and +4 (CN = 6) are presented in Table 18.1.3. The data provide a set of conventional size parameters for the calculation of hydration energies. It should be noted that in most lanthanide(III) complexes the Ln3+ center is surrounded by eight or more ligands, and that in aqueous solution the primary coordination sphere has eight and nine aqua ligands for light and heavy Ln3+ ions, respectively. The crystal radii of Ln3+ ions with CN = 8 are listed in Table 18.1.1. 

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