Actinide metal alkoxides

Two additional problems in understanding heterogeneous catalytic CO reduction concern the means by which MrO bonds are cleaved to produce alcohols and the fate of the metal oxides once formed. In regard to the former issue, most metal alkoxides (including those of actinides) readily undergo protolysis to form alcohols (97) (eq.(31)). The source of the protons could be... 

Alkoxide and aryloxide ligands are excellent ligands for the actinides. As a result, these ligands have been studied extensively in the coordination chemistry and reactivity of tri-, tetra-, penta-, and hexavalent actinides. The alkoxides and aryloxides can be synthesized by a variety of routes the two most popular routes include direct reaction of actinide halides with alkali metal salts of the alkoxide or aryloxide of interest and protonolysis of actinide amides by alcohols. 

It is important to note that efforts to synthesize metal alkoxides and aryloxides (particularly lanthanide and actinide complexes) have sometimes produced unexpected products, incorporating halide or oxide ligands, for example. As a result, some early literature may contain incorrect formulations. ... 

Various cyclopentadienyl-ligated early metal and actinide alkoxides were prepared by reactions of the alcohols with the metal hydride precursors to eliminate hydrogen gas,266,275,277,278 g j.jy metal alkoxides, as well as their high-valent late-metal analogs, can also be formed by attack of an alkyl group at an oxo ligand, where the alkyl could be added as a carbocation, a radical, or a carbanion (Equation 4.59). ... 

The scope of organic synthesis, essentially, is the synthesis of new molecules from existing molecules. The addition reactions could be realized as a very important category in which two or more different molecules reacted with each other to form a new compound. Transesterification and cyclization reactions also have been used for the synthesis of new compounds, sometimes. There are excessively other reactions in this area but we only consider some of them which could be catalyzed or co-catalyzed with metal alkoxides. There are also many routs for the classification of these reactions but the focus of this chapter is on metal alkoxides so we use particular types of metal for this purpose and divide metals to four categories of s-block (alkali and alkaline earth), p-block, d-block (transition), and f-block (actinides and lanthanides) metals. 

The actinides and lanthanides or f-block metal alkoxides are the last group. According to the report of Nawaratna and co-workers, yttrium isopro-poxide has been catalyzed transesterification reaction of fatty acids (reaction 7.13) [78]. Hatano et al. have used this strategy in the presence of lanthanum alkoxides for transestrification of carboxylic esters and preparation of new esters [79]. 

Metal alkoxides (of early transition, lanthanide, actinide, and main group metals, except silicon) react with a variety of primary, secondary, and tertiary alcohols (R OH) to set up an equilibrium rapidly of the type shown in Eq. (2.193) ... 

Metallotropic rearrangement, in mercury tri-azenide complexes, 30 41 Metals, see also Heterobimetallics specific element Transition metal complex alkoxides, 15 159-297 of actinides, 15 290-293 of alkali metals, 15 260-263 of alkaline earths, 15 264-266 of aluminium, 15 266-272 of beryllium, 15 264-266 double type, 15 293-294 of gallium, 15 266-272 of lanthanides, 15 290-293 of magnesium, 15 264-266 properties of, 15 260 of transition metals, 15 272-290 trialkylsilyloxides, 15 295-297 of zinc, 15 264-266... 

Alcohols. Alcohols are among the most common solvate ligands in actinide chemistry (Table 13) historically the hydrated chloride complexes were reacted with alcohol in benzene, and the water of hydration removed by azeotropic distillation of the benzene. More recent examples result from the crystallization of anhydrous halides from alcoholic solvent. Similarly, solvates of alkoxide complexes result from rnetathesis or solvolysis reations in alcohol. The molecular structures of the halides AnCl4(Pr OH)4 (An = Th, U) have been reported,the coordination geometry about the metal is a distorted dodecahedron. 

Extensive work on the reactions of alkoxides of different metal(loid)s (e.g., B, Al, Ga, Si, Ge, Sn, Sb, Se, Te, Ti, Zr, Nb, Ta, lanthanides, and actinides) with a variety of glycols was carried out by Mehrotra and coworkers (6), but. the results were not included since they were summarized (6) in 1978. For the last 15 years much research was carried out in this area. The following account deals mainly with their results. 

What type of compounds will be covered in this overview. Strictly, only compounds which have at least one metal-carbon bond (with the exception of metal carbides) are called organometaiiic. However, this definition was not adopted in this chapter because many families of compounds that are relevant in organometaiiic chemistry would not be included (e.g., alkoxides). By metal we mean any element from groups 1 (except hydrogen), 2, 3 (including lanthanides and actinides), 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 (except boron), 14 (except carbon and silicon), and 15 (antimony and bismuth only). Most of the available thermochemical data for all these species are freely available in a single on-line database the NIST Chemistry WebBook Unless stated otherwise, all the data included in this chapter were quoted from that reference. 

---