Organoactinide chemistry

Most common organoactinide complexes involve π-bonding with ligands such as cyclopentadienyl, but there are a few exceptions with σ-bonding, namely in thorium and uranium chemistry as these are the most easily handleable elements of this group.

Attempts to synthesize uranium alkyls were first made during the Manhattan project by Henry Gilman, inspired by the volatility of main group organometallics.

Mixed phosphine containing complexes of thorium and uranium tetramethyls have also been made, using dmpe as the organophosphorus ligand stabilising the structure (amides can also assume this role).

[9] All these derivatives are much more soluble in organic solvents such as benzene, in which they form green solutions that are more air sensitive than the crystalline solids.

The reaction is easily noticeable by the THF solution changing to a dark red colour, characteristic of Pu(IV).

[10] The neptunium equivalent with the trisubstituted COT’’’ has also been reported[11] and the complexes of both the tri- and di- substituted ligands with thorium and uranium are well known.

[13] The synthesis of the AnCp3 usually follows the reaction scheme shown above[4][14] with a few more added steps that are sometimes needed to synthesize the trichlorides from the commercially supplied oxides.

Kovàcs and coworkers were able to analyse the plutonium and uranium complexes, finding that all three structures were similar, with an asymmetrical distribution of cylopentadienide ligands and a higher covalent character to the carbon-actinide bond than in organolanthanide compounds.

[16] Tetravalent thorium, uranium and neptunium easily form MCp4 compounds by a metathesis reaction from potassium cyclopentadienide using benzene as a solvent.