Rare-earth metals, organometallic compounds

The rare earths are very reactive metals as expected from their position in the periodic table. They combine readily with nearly all of the other elements to form a wide variety of materials in both solid and solution states. In addition, the synthesis of rare earth-containing organometallic compounds has received considerable attention in the past 2 decades. The preparation and properties of these materials are briefly described here. 

Organometallic compounds of the rare earth metals have been a curiosity till only a few decades ago. That changed in the last 20 years of the twentieth century after the availability of modem preparative and analytical techniques and with the discovery of the high potential of those compounds,... 

Ge, S.Z., Meetsma, A., and Hessen, B. (2008) Neutral and cationic rare earth metal alkyl and benzyl compounds with the l,4,6-trimethyl-6-pyrrolidin-l-yl-l,4-diazepane Ugand and their performance in the catalytic hydroamination cyclization of aminoalkenes. Organometallics, 27, 5339. 

In summary, the present volume of Structure and Bonding shows the substantial activity carried out in recent years in the held of synthesis of inorganic and organometallic rare-earth metal compounds and their use as catalysts for a number of different transformations. The future holds great promise for the rapid growth of this held of chemistry and for new spectacular results. 

The chemistry of organometallic group 4 metal compounds is well developed, thanks to their importance in polyolefin synthesis. Hence, their application in catalytic asymmetric hydroamination reactions is highly desirable. Group 4 metal complexes are commonly less sensitive and easier to prepare than rare earth metal complexes. Most important of all, many potential precatalysts or catalyst precursors are com mercially available. 

The known organometallic compounds with bonds between the rare earth metals and oxygen are shown in table 35. 

The rare-earth-transition-metal organometallic compounds are tabulated in table... 

The first indications of the existence of organometallic compounds of the lanthanoides was furnished in the observation that methyl radicals do react with lanthanum metal (l). The publication of the successful syntheses of Sc(C2Hs)3 and Y(C2H5)3 (2), the first supposed alkyl derivatives of the rare earth metals, however, proved to be wrong (3). Also, all attempts to prepare the first phenyl derivatives of lanthanum, carried out by Gilman and coworkers in connection with the separation of... 

Dianions present in the same derivative frequently appear as important synthetic intermediates and often show synergistic effects inside the same molecule and toward useful transformations of substrates. This volume deals with dianionic compounds which contain carbon anions with various metals (such as Li, Mg, Ca, Ba, Al, Fe, Zn, Cu, rare earth metals, etc.). Synthesis and structures of dianionic compounds containing two identical or different metals are briefly introduced. Their synthetic applications based on their synergistic effects are focused especially on making organic compounds and organometallic compounds via novel improved processes. 

Synthetic routes include anionic, cationic, zwitterionic, and coordination polymerization. A wide range of organometallic compounds has been proven as effective initiators/catalysts for ROP of lactones Lewis acids (e.g., A1C13, BF3, and ZnCl2) [150], alkali metal compounds [160], organozinc compounds [161], tin compounds of which stannous octoate [also referred to as stannous-2-ethylhexanoate or tin(II) octoate] is the most well known [162-164], organo-acid rare earth compounds such as lanthanide complexes [165-168], and aluminum alkoxides [169]. Stannous-2-ethylhexanoate is one of the most extensively used initiators for the coordination polymerization of biomaterials, thanks to the ease of polymerization and because it has been approved by the FDA [170]. 

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