Metallacycles, actinide

At variance with the d1 V or Nb complexes described above, the uranium complexes owe their paramagnetism to 5/-electrons. Although these / orbitals, and particularly the 5/in the actinides when compared with the 4/in the lanthanides, interact with the dithiolene orbitals to lead to strong distortions of the US2C2 metallacycles (see Fig. 5) [35, 36, 47, 48], the SOMOs themselves are essentially... 

Some actinide alkoxide complexes can exist in equilibrium, for example, the homoleptic complex Th2(OCH-/-Pr2)8, obtained from a metallacyclic precursor after treatment with HOCH-/-Pr2 (5.50) ... 

Scheme 2 Some reactions of the actinide (IV) metallacycles of the type [(Me3Si)2N]2An SiMc2...

Metallacycles of lantanides, actinides, and early transition elements, structure, reactivity, role in catalysis 90MI44. 

Actinide(IV) alkoxide complexes have been reported which are coordinated by a variety of other bulky ligand sets. Uranium(IV) amido compounds are reagents for the preparation of homoleptic uranium(IV) alkoxides as well as mixed alkoxide/amido species. A variety of mixed aryloxide-diethylamide derivatives have been pr ared including (U(NEt2)(0-2,6-Bu 2C6H3)3 and U(NEtp(0-2,6-R7CftH3)3. R = Pr . Bu ). The previously described metallacycle... 

The hydroamination of olefins has been shown to occur by the sequence of oxidative addition, migratory insertion, and reductive elimination in only one case. Because amines are nucleophilic, pathways are available for the additions of amines to olefins and alkynes that are unavailable for the additions of HCN, silanes, and boranes. For example, hydroaminations catalyzed by late transition metals are thought to occur in many cases by nucleophilic attack on coordinated alkenes and alkynes or by nucleophilic attack on ir-allyl, iT-benzyl, or TT-arene complexes. Hydroaminations catalyzed by lanthanide and actinide complexes occur by insertion of an olefin into a metal-amide bond. Finally, hydroamination catalyzed by dP group 4 metals have been shown to occur through imido complexes. In this case, a [2+2] cycloaddition forms the C-N bond, and protonolysis of the resulting metallacycle releases the organic product. 

---