New horizons in organo-f-block chemistry

Organo-f-element chemistry has a long history – the first organometallic compounds of the two “footnotes” in the periodic table date back to the 1950s when tris(cyclopentadienyl)lanthanide and uranium complexes were reported, shortly after the discovery of ferrocene. The high sensitivity of these compounds to oxygen, and especially water, made them a real experimental challenge, although nowadays the ready availability of high integrity dry-boxes makes life much easier. It also became apparent that size really does matter with these elements – in the early days, satisfying their large coordination spheres proved difficult and use of the classical organometallic ligands then available often led to hard to characterise, polymeric materials of limited solubility. However, the advent of the pentamethylcyclopentadienyl ligand in the late 1970s revolutionised organo-f-element chemistry and the field has blossomed ever since. Indeed, the development of new bulky ligands has been a major feature in f-element organometallic chemistry and continues unabated. It also rapidly became clear that f-element complexes offer unique types of reactivity not previously seen with transition metals – for example, it was an organolanthanide complex which was responsible for the first homogeneous activation of methane in the early 1980s. This has been a continuing trend, and organo-f-element chemistry has resulted in striking developments in homogeneous catalysis, materials chemistry, organic synthesis, alkane functionalisation and CO oligomerisation, to name but a few. The description of bonding and electronic structures in organo-f-element complexes has also proved a rich area for computational chemists. Whilst largely now resolved, the role of the f-electrons in the bonding of organometallic ligands to f-element centres was the matter of an intense debate for some time, and modern DFT methods continue to provide key insights into current controversial issues such as oxidation state ambiguity in organo-cerium complexes. I have absolutely no doubt that the f-elements will continue to yield spectacular and unique discoveries in a whole range of chemistries and that only the tip of a large iceberg has been discovered thus far.

This themed issue contains contributions from leaders in the area from all over the world, and encompasses a wide range of new developments in organo-f-element chemistry. I am sure that you will find it both informative and thought-provoking.

Professor Geoff Cloke

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