Rare earth metal complexes bonding

Grignard reagents add with difficulty to imines derived from enolizable carbonyl compounds. The activation of the C=N bond can be achieved either by attachment of an electron-with drawing group or A-coordination with a Lewis acid . The use of a catalytic amount of the soluble rare-earth metal complex LnCl3 2LiCl allows the addition of... 

Zhang, W.X., Nishiura, M., and Hou, Z.M. (2007) Catalytic addition of amine N-H bonds to carbodumides by half-sandwich rare-earth metal complexes efficient synthesis of substituted guanidines through amine protonolysis of rare-earth metal guanidinates. Chemistry-A European Journal, 13, 4037. 

Catalytic applications of organo-rare-earth metal complexes reported prior to 2002 are summarized in two excellent reviews [19,20] and, therefore, will not be discussed unless being relevant for understanding of key reaction details. A recent comprehensive review on theoretical analyses of organo-rare-earth metal-mediated catalytic reactions is available [17], Although o-bond metathesis plays a pivotal role in many rare-earth metal-catalyzed polymerizations, the discussion of these processes is beyond the scope of this review and the interested reader may consult one of the pertaining reviews [21-24],... 

The ability of organo-rare-earth metal complexes to undergo alkene or alkyne insertion provides the possibility to perform polyene cyclizations, producing metal-alkyl species which can then undergo o-bond metathesis with an appropriate reagent to produce a cyclic compound. Thus, termination via protonolysis (6) results in cycloalkane derivatives however, termination via silylation is more desirable as a functionalized cyclic framework is formed (Fig. 9). 

Pioneering work of Watson described the scrambling of CH4 into soluble rare-earth metal complexes Cp 2LnCH3 (Ln = Lu, Y) (59) [212], The lutetocene system was also shown to activate C-H bonds of arenes and alkyl silanes [6,213],... 

This book contains four chapters in which part of the recent development of the use of molecular rare-earth metal compounds in catalysis is covered. To keep the book within the given page limit, not all aspects could be reviewed in detail. For example, the use of molecular rare-earth metal complexes as Lewis acidic catalysts is not discussed in this book. The first two chapters review different catalytic conversions, namely the catalytic o-bond metathesis (Chapter by Reznichenko and Hultzsch) and the polymerization of 1,3-conjugated dienes (Chapter by Zhang et al.). Within these chapters, different catalytic systems and applications are discussed. The final two chapters are more concentrated on recent developments of... 

Recendy, Diaconescu and coworkers reported the bimetaUic cleavage of aromatic C—H bonds by rare-earth metal complexes supported by a l,l -ferrocenediamide When reacting... 

As demonstrated in this review, photoinduced electron transfer reactions are accelerated by appropriate third components acting as catalysts when the products of electron transfer form complexes with the catalysts. Such catalysis on electron transfer processes is particularly important to control the redox reactions in which the photoinduced electron transfer processes are involved as the rate-determining steps followed by facile follow-up steps involving cleavage and formation of chemical bonds. Once the thermodynamic properties of the complexation of adds and metal ions are obtained, we can predict the kinetic formulation on the catalytic activity. We have recently found that various metal ions, in particular rare-earth metal ions, act as very effident catalysts in electron transfer reactions of carbonyl compounds [216]. When one thinks about only two-electron reduction of a substrate (A), the reduction and protonation give 9 spedes at different oxidation and protonation states, as shown in Scheme 29. Each species can... 

X-ray structure analysis revealed a 7-coordinate rare-earth metal center with two asymmetrically / -coordinating tetramethylaluminate ligands, an asymmetrically / -coordinating siloxide ligand and one methyl group of a trimethylaluminum donor molecule (Fig. 28). Such heteroleptic complexes can be regarded as molecular models of covalently bonded alkylated silica surface species. Moreover, isoprene was polymerized in the presence of 1-3 equivalents of diethylaluminum chloride, with highest activities observed for (Cl) (Ln) ratios of 2 1 (Table 12) (Fischbach et al., 2006, personal communication) [150]. 

The complexes (RE)Thi2 (RE = Eu, Yb T = Pd, Au) also form transition metal (T)-centered trigonal prisms by the rare earth metal and indium atoms. The transition metal and indium atoms form a 3D [Tln2] polyanion in which the large rare earth metal atoms occnpy one-dimensional pentagonal tubes. The strongest bonding interactions are found for the In In and Pd-ln contacts the En Pd and En In interactions are mnch weaker. 

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