Lanthanide II Complexes

Some bis(phthalocyaninato)lanthanide (II) complexes (68) have been examined by both electrospray and MALDI, using Ira/u-retanoic acid as matrix. The resolution of the MALDI-TOF experiment was not good enough to unambiguously identify whether the ions observed were the molecular ion, M+ or [MH]+, but the complexes survived the MALDI process. 

It was also reported that living s-caprolactone polymerization can be carried with bis(acryloxy-) lanthanide (II) complexes based on samarium [110]. Thus, (ArO)2Sm(THF)4, (where ArO = 2,6-di-ferf-butyl-4-methyl-phenoxy) yielded 98% conversion in toluene at 60°C in 1 h. The central ions and ligands appear to have an effect on the activity of the catalyst [110]. 

SOMO and LUMO orbitals are corresponding to an / and tt, respectively, pointing out again the validity of this approach. Hence, by using this very simple method someone can define very quickly if the SET step corresponds to an endoergic or to exothermic. In the first case, the use of computationally heavy methods as multi-reference one is essential, as it influences the whole reaction process as much as the subsequent bimetallic reactivity. For the second case, where the SET step is just favorable (coordination induced SET and exothermic SET) so that it is the subsequent bimetallic reactivity that is crucial there is no need for extra theoretical investigation. Einally, this method, which is simple to handle, appears to be powerful to predict the reduction ability of lanthanide(II) complexes allowing someone to proceed safely on the reactivity computational studies. 

Secondary amines can be added to certain nonactivated alkenes if palladium(II) complexes are used as catalysts The complexation lowers the electron density of the double bond, facilitating nucleophilic attack. Markovnikov orientation is observed and the addition is anti An intramolecular addition to an alkyne unit in the presence of a palladium compound, generated a tetrahydropyridine, and a related addition to an allene is known.Amines add to allenes in the presence of a catalytic amount of CuBr " or palladium compounds.Molybdenum complexes have also been used in the addition of aniline to alkenes. Reduction of nitro compounds in the presence of rhodium catalysts, in the presence of alkenes, CO and H2, leads to an amine unit adding to the alkene moiety. An intramolecular addition of an amine unit to an alkene to form a pyrrolidine was reported using a lanthanide reagent. 

In addition to the systems just mentioned, recent kinetic and mechanistic studies have included those involving copper(II) (409,410) and zinc(II) (411) species, various binuclear metal(II) complexes of first row transition elements (412-414), especially iron (407), cobalt (415), copper (305,416), and zinc (417,418), yttrium (419,420) and lanthanide (421,422) species, and thorium(IV) (423). 

Recently, rare-earth metal complexes have attracted considerable attention as initiators for the preparation of PLA via ROP of lactides, and promising results were reported in most cases [94—100]. Group 3 members (e.g. scandium, yttrium) and lanthanides such as lutetium, ytterbium, and samarium have been frequently used to develop catalysts for the ROP of lactide. The principal objectives of applying rare-earth complexes as initiators for the preparation of PLAs were to investigate (1) how the spectator ligands would affect the polymerization dynamics (i.e., reaction kinetics, polymer composition, etc.), and (2) the relative catalytic efficiency of lanthanide(II) and (III) towards ROPs. 

Homoleptic germylenes, preparation and properties, 3, 773 Homoleptic lanthanide(II) alkyl compounds, properties, 4, 4 Homoleptic manganese aryl complexes, preparation, 5, 816 Homoleptic manganese isonitrilates, preparation, 5, 773—774 Homoleptic molybdenum complexes, preparation and characteristics, 5, 514... 

The cadmium(II) complex corresponding to 9 (M = Cd n = 2) was the first texaphyrin made [6], This aromatic expanded porphyrin was found to differ substantially from various porphyrin complexes and it was noted that its spectral and photophysical properties were such that it might prove useful as a PDT agent. However, it was also appreciated that the poor aqueous solubility and inherent toxicity of this particular metal complex would likely preclude its use in vivo [29-31], Nonetheless, the coordination chemistry of texaphyrins such as 9 was soon generalized to allow for the coordination of late first row transition metal (Mn(II), Co(II), Ni(II), Zn (II), Fe(III)) and trivalent lanthanide cations [26], This, in turn, opened up several possibilities for rational drag development. For instance, the Mn(II) texaphyrin complex was found to act as a peroxynitrite decomposition catalyst [32] and is being studied currently for possible use in treating amyotrophic lateral sclerosis. This work, which is outside the scope of this review, has recently been summarized by Crow [33],... 

It is the 4-coordinate square-planar geometry that makes Pt(II) complexes very different from those of most of the other metal ions familiar to the inorganic photochemist, including Cr(III), Ru(II), Os(II), Rh(III), Ir(III) (almost always 6-coordinate octahedral), copper(I) (4-coordinate tetrahedral), and lanthanides (8 or 9 coordinate). The square planar conformation is responsible for many of the key features that characterize the absorption, luminescence and other excited state properties of platinum(II) complexes. 

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