Tris compounds actinide

Pentamethylcyclopentadienyl complexes CpjAnX, 4, 207 Cp AnX2 and Cp AnX, 4, 206 Cp MX compounds, 4, 62 with iridium amidinates, 7, 366 mono(Cp ) actinide(IV) compounds, 4, 207 with Ni-C cr-bonded ligands, 8, 108-109 with rhodium, 7, 152 with ruthenium, 6, 632 tris(Cp ) actinide(IV) compounds, 4, 219 with zirconium amidinates, 12, 730 l, 2, 3, 4, 5 -Pentamethyl-l-formylruthenocene, preparation, 6, 643... 

Figure 3. The lattice parameter for the family of rock-salt structure actinide-antimonide compounds is shown where the line is for the corresponding lanthanide compounds. The metallic radii for the light actinide elements are plotted. The smooth line simply connects Ac to the heavy actinides. In both cases the smooth line represents the ideal tri-valent behavior.

Recently there has been a renewed interest in the extraction of actinides with various neutral bifunctional organophosphorus extractants (1-9). An excellent review on this subject has been published recently by Schulz and Navratil (9). Interest in neutral bifunctional organophosphorus extractants stems largely from the fact that these compounds have the ability to extract tri-... 

Bradley, D.C., Ghotra, J.S., and Hart, F.A. (1973) Low co-ordination numbers in lanthanide and actinide compounds. Part I. The preparation and characterization of tris bis(trimethylsilyl)-amido lanthanides. Journal cf of the Chemical Society, Dalton Transactions, 1021. 

We took advantage of the property of different solvents to extract selectively the tetravalent actinide and lanthanide elements. Some of them are sufficiently stable in the presence of oxidizing agents. Among the organonitrogen and organophosphorus compounds we used were tri-laurylmethylammonium (TLMA) salts and tributyl phosphate (TBP) in carbon tetrachloride. 

A second reason for the wealth of chemical investigations of the early actinide elements is the relative diversity of their chemistry. While the chemistry of the later actinides is most often restricted to that of the tri- and tetravalent oxidation states, compounds of the early actinides can be isolated in all oxidation states from +3 to +7. The accessibility of a range of oxidation states is the impetus for signficant chemical interest in the early actinides, but also vastly complicates investigation of these elements under some circumstances, such as aqueous redox behavior. In the case of plutonium, ions in four different oxidation states (+3, +4, +5, and - -6) can exist simultaneously in comparable concentrations in the same solution. 

BRM(P04)3. CaAmPu(P04)3 has been synthesized recently and the monazite structure type has been attributed to it [81]. It is the only known compound among the BRM(P04)3 phosphates where tri- and tetravalent actinides are present together. Obviously, the Am and Pu" cations occupy cation sites with CN = 9 (monoclinic, space group P2 ln). The phosphate CaAmPu(P04)3 has an intermediate composition in the CaxAm3 2xPux(P04)3 series with x = 1. The first member of the row is AmP04 (x = 0) and the last one is Cai sPui 5(P04)3. CaPu(P04)2 (x = 1.5) has a monazite-type stmcture as well. 

At the same time, the structural chemistry of tri- and tetravalent actinide orthophosphates is not well-known. A small number of theoretically possible compounds have been discussed [14]. The collection of information on actinide compounds may take a long period of time, on account of the experimental difficulties of work with actinides that require special conditions and equipment. Consequently, single crystal data are available for a few compounds only in most cases, the analysis was based on powder diffraction data and analogy to other structures. 

Table 1. Stractural modifications of known tri- and tetravalent actinide phosphates (and other compounds with XO4 = Si04, VO4, ASO4)...

Nai+x[Zr2-xRx(P04)3] with Xmax < 1, where R is a rare earth cation (Fig. 10) [97-102], One can suppose that a similar situation can be observed for actinide(III) compounds (or solid solutions). However, none of them has been reported to the present time. An overview on known structures of actinide and similar lanthanide phosphates described above demonstrates a wide variety of coordinations for tri- and tetravalent actinides. The ThOn, UOn, and some LnOn polyhedra with n changing from 10 to 6 are shown in Fig. 12. 

Structural chemistry of tri- and tetravalent actinide orthophosphates (and their analogues) is an important part of scientific field dealing with the influence of f-electronic shell and electronic structure of tri- and tetravalent elements upon structure formation and properties of their solid compounds. 

The question of how much steric crowding is possible in tris( 75-pentamethylcyclopentadienyl)actinide complexes has been addressed by the synthesis of the hitherto unknown compounds Cp 3UCl and Cp 3UF. Reaction of Cp 3U with 1 equiv. of PhCl gives Cp 3UC1 as the primary product (Scheme 63). Upon addition of another equivalent of PhCl this... 

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