Organometallic compounds of the actinides

A77. C. Keller, The Chemistry of the Transuranium Elements. Verlag Chemie, Weinheim, 1971. Chapter 8, Organometallic compounds of the actinides, pp. 187-193 (36). Not as comprehensive as reference 4.39. 

The first weU-characterized organometallic compounds of the lanthanides or actinides were the tricyclopentadienides of various lanthanide ions S3mthesized by Birmingham and Wilkinson in 1954 (97—98). Anhydrous metal chlorides were reacted with sodium cyclopentadienide in tetrahydrofuran as follows ... 

Among the natural and artificial radioactive elements (Tc, Pm, Po, Fr, Ra, Ac, and actinides), coordination and organometallic compounds of only technetium and the actinide series (An) are well represented at the present time. The interest in their metal complexes has been motivated by the extended use of Tc, available in kilogram amounts, for medical and technical purposes, meanwhile actinides are important on their own for the nuclear industry. A lot of original papers, reviews, and chapters of some books are dedicated to Tc and An complexes [263-281], In the present section, dedicated to the coordination and organometallic chemistry of the actinides and Tc, we intend to present the synthetic techniques for these compounds according to their ligand nature. 

Organometallic Compounds of the Lanthanides, Actinides, and Early Transition Metals. (Edit. Cardin, D.J.). Chapman Hall London, 1985. 

The past decade has witnessed a dramatic expansion in what we know about the organometallic compounds of the 5f elements. It is now evident that the actinides have a very rich, intricate, and instructive organo-metallic chemistry, and that we have much to learn about the basic principles governing structure, bonding, and reactivity. Nowhere is this situation more obvious than in the area of metal hydrocarbyls (i.e., alkyls, aryls, alkenyls, etc.) and hydrides, and the growth in this area since our last ASI review in 1978 [ll has been phenomenal. 

The first organometallic compound of an actinide to be synthesized was the red-brown UCP3CI prepared by Reynolds and Wilkinson (eq. 1) (3), a more convenient and higher yield synthesis utilizes the air stable TlCp (eq. 2) (4). Recently highly reactive... 

The organic hgands of the actinide and lanthanide organometallics will be used here as an arbitrary basis of classification. The emphasis will be on the structure and bonding of these compounds rather than their S5uithetic chemistry. Several earher reviews exist which cover the chemical aspects of the organoactinides and -lanthanides [1—7). 

The T -bonding of the CO and RNC insertion products is characteristic of these actinide compounds, but has some parallels in the organometallic chemistry of the d-block elements. There are similar insertions into An—NR2 bonds to give products with rf ligands, namely,... 

Although the elements of the lanthanide and actinide series have long been known to exhibit a quite extensive organometallic chemistry, it is only within the last decade that typical sandwich species have been prepared and studied. These systems however, although resembling the familiar metallocene and bis-arene compounds of the d-block elements, are not strictly their analogues since in both f-orbital series the known sandwich complexes are derived only from the cyclooctatetraenyl dianion. 

Compounds of the stoichiometry MCp 2X2 provide an opportunity to compare actinides with block elements. Several such species have been studied both by gas phase PE experiments as well as by theoretical approaches. Thus, the first comparative study of the PE spectra of a series of transition metal and actinide organometallic compounds with exacdy the same ligand array was carried out on MCp 2X2 (M = Zr, Th, U, and X = CH3 and Cl) complexes. Comparable bonding was found along the series with smaller differences than encountered in the parent series involving transition elements. The major differences between Zr and the actinides are due to the involvement of yin the bonding. 

The actinide elements begin with actinium. Actinium serves as a starting point for the other actinide series elements, which span 14 spaces across the periodic table from actinium to lawrencium. Actinides are more reactive than lanthanides. They form covalent compounds and organometallic complexes. Most of the actinide elements were discovered during development of the nuclear bomb. The set of actinides is represented by the symbol An. 

Organometallic compounds of highly electropositive metals such as the heavier alkali and alkaline earths (and possibly lanthanides and actinides) are generally ionic. Exceptions to this occur in the case of some Li, Be and Mg derivatives in which the bonding may be covalent rather than ionic [60,61]. 

E)espite substantial recent advances in the organometallic chemistry of other actinide elements, progress with curium has been slow. This lack of progress apparently is due to the nuclear properties of the element rather tlm to an inherent chemical instability of the organometallic compounds. For more detailed discussion of this topic, especially comparison with organometallics containing other actinide metals, the reader is directed to Chapters 22 and 23 of this volume. 

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