Actinide complexes ureas

A large number of urea and substituted urea complexes with actinide(IV) compounds are known in these the ligands are bonded to the metal via the carbonyl oxygen atom, and these complexes are therefore described in the section dealing with carboxylic add amide complexes (p. 1164). 

Table 38 Complexes of Actinide(IV) Compounds with Ureas, L = R R2NCONR3R4...

Ureas. Urea adducts (and those of the closely related A-alkylated derivatives) may be prepared from nonaqueous solvents alternatively, preparation in aqueous alcoholic solution leads to the formation of hydrates. In contrast to the carbamides discussed above, there is relatively little variability in the coordination number of reported urea adducts of tetravalent actinides. Most complexes are either six- or seven-coordinate higher coordination numbers are observed for the larger thorium ion (Table 15). 

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