Actinides organoactinide complexes

Tebakis(cyclopentadienyl) actinide complexes, ( 5115)4An, were among the earliest organoactinide complexes synthesized and can be prepared by metathesis see Metathesis) of the anhydrous tetrachlorides (AnCLi) with potassium cyclopentadieitide (KCp) in refluxing benzene (equation 1, for An = Th, U, and Np). Another member of this series, Cp4Pa,... 

The application of theoretical electronic structure methods to organoactinide complexes has long been hampered by some well-known challenges. Before we detail the computational methodology used in the present studies, we will briefiy summarize some of the particular challenges inherent in the theoretical study of actinide complexes ... 

Because of the aforementioned challenges that theoretical actinide chemistry has posed, applications of traditional correlated ab initio methods are very expensive for organoactinide complexes and are thus limited to either small molecules or small basis sets and/or small active configuration spaces. During the past two... 

The first actinide organometallic complex, red-brown (C5H5)3UC1, was prepared and characterized by Reynolds and Wilkinson in 1956 or shortly after the discovery of ferrocene see Ferrocene, (C5H5)2pe. However, it was not until the preparation and structural characterization of bis(cyclooctatetraenyl)uranium, (C8H8)2U ( uranocene , see Uranocene) in 1968 and the isolation and characterization of uranium alkyls see Alkyl Complexes) in 1973 that the field developed momentum. The purpose of this chapter is to provide an overview of organoactinide chemistry that reflects historical as well as recent developments and achievements in the field it is not meant to be an exhaustive review of the primary literature. More detailed discussion, background material, and extensive references to the literature can be found in several excellent reviews. 

We have shown in this review that neutral and cationic organoactinide complexes have been extensively studied, in the last decade, as catalysts for several organic transformations [9-12, 111]. Polymerization of alkenes[112,113], oligomerization of terminal alkynes [55, 114], hydrosilylation of terminal alkynes [41], and 1,1-insertion of isonitriles into terminal alkynes [28] comprise some other studied processes not presented here. However, due to the high oxophilicity of the actinide complexes (as mentioned above), substrates containing oxygen have been excluded because of the expected and predictable oxygen—actinide interaction. 

In this review we have shown the unique properties of the actinide complexes and some of the many novel features such as multielectron oxidation-reduction, catalytic activities towards various organic conversions etc The catalytic chemistry of the organoactinide complexes is new, demanding, and... 

Finally, actinide complexes such as [MCp 2R2] (M = Th or U, R = alkyl or H) are very active catalysts for the hydrogenation and polymerization of olefins. The complexes [U(allyl)3X] (X = Cl, Br, I) are excellent initiators for the stereospecific polymerization of butadiene, which produces rubbers that have remarkable mechanical properties. Some other complexes are active for the heterogeneous CO reduction and alkene metathesis. The field of catalysis using organoactinide complexes should considerably expand in the near future. 

The organoactinide surface complexes exhibited catalytic activities comparable to Pt supported on sihca [at 100% propylene conversion at —63°C, >0.47s (U) and >0.40 s (Th)], despite there being only a few active sites (circa 4% for Th, as determined by CO poisoning experiments and NMR spectroscopy) [92]. Cationic organoactinide surface complexes [Cp An(CH3 ) ] were proposed as catalytic sites. This hypothesis could be corroborated by the use of alkoxo/hydrido instead of alkyl/hydrido surface ligands, which led to a marked decrease of the catalytic activity, owing to the oxophilic nature of the early actinides [203, 204]. Thermal activation of the immobihzed complexes, support effects, different metal/ligand environments and different olefins were also studied. The initial rate of propylene conversion was increased two-fold when the activation temperature of the surface complexes under H2 was raised from 0 to 150°C (for Th 0.58 0.92 s" ). 

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