Advances in f-element cyanide chemistry

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Lanthanide and Actinide Chemistry

Background:

• Cyanide chemistry is well-explored for d-transition metals but less so for 4f (lanthanide) and 5f (actinide) elements.
• The cyanide ligand (CN-) offers unique bonding properties that can lead to unexpected structural motifs.

Purpose of the Study:

• To provide an overview of the development of cyanide chemistry for 4f and 5f elements.
• To explore the synthesis and structural characterization of novel cyanide complexes of lanthanides and actinides.
• To investigate the factors influencing coordination preferences and the stabilization of high oxidation states.

Main Methods:

• Synthesis of mono- and polycyanide complexes using various lanthanide and actinide precursors.
• Isolation and structural determination of complexes, including linear metallocenes and bent actinocenes.
• Utilized density functional theory (DFT) computations to predict coordination modes and bonding energies.

Main Results:

• Discovery of unprecedented coordination geometries, such as linear metallocenes ([U(Cp*)2(CN)5](3-)) and bent actinocenes ([An(Cot)2(CN)](-)).
• Demonstrated differential reactivity between Thorocene and Uranocene in forming sterically crowded cyanide complexes.
• Observed cyanide linkage isomerism to differentiate Ce(III), U(III), and U(IV) ions.
• Synthesized U(V) and U(VI) complexes, showcasing cyanide's ability to stabilize high oxidation states.

Conclusions:

• Cyanide ligand chemistry in 4f and 5f elements yields unique coordination geometries and complexes.
• Reactivity differences between Thorocene and Uranocene are significant for complex synthesis.
• DFT calculations accurately predict metal-cyanide bonding preferences.
• Cyanide ligands are effective in stabilizing high oxidation states of uranium.