Lanthanides and actinides: Annual survey of their organometallic chemistry covering the year 2015

• The +2 oxidation state is now available for all lanthanide elements.
• New lanthanide phosphido and phosphinidene complexes have been prepared.
• Novel actinide metallacyclocumulenes and metallacyclopentadienes have been reported
• Homoleptic uranium(IV) tetrabenzyl complexes have been prepared.
• The first bis(imido) thorium complex, K[Th(NDipp))(NR2)3], has been reported.

This review summarizes the progress in organo-f-element chemistry during the year 2015. The year 2015 witnessed a slight increase of contributions in the fields of organolanthanide and organoactinide chemistry over 2014 (ca. 10% more). A continuing trend for many years which continued into 2015 was the investigation of highly reactive lanthanide alkyl complexes supported by non-cyclopentadienyl ligands (e.g. amidinates, β-diketiminates etc.). Many of these complexes found useful applications in homogeneous catalysis. Trinuclear rare-earth metal methylidene (CH22−) complexes are an emerging class of compounds that serve as methylidene transfer agents for the methylenation of carbonyl compounds. The range of rare-earth metal alkyl complexes bearing different types of carbene ligands have also been further expanded. Several new lanthanide phosphido and phosphinidene complexes have been stabilized by specially designed N,N′-chelating ligands. The range of fully characterized lanthanide(II) compounds of the type [K(2.2.2-cryptand)][Cp′3Ln] (Cp′ = C5H4SiMe3) has again been significantly expanded so that the +2 ions are now available for yttrium and all the lanthanides (except promethium, which was not studied due to its high radioactivity). The first well-defined lutetacyclopentadienes have been synthesized and their reactivity has been studied. The synthesis, structure, and reactivity of the extremely reactive yttrium metallocene ethyl complex Cp*2Y(CH2CH3), including activation of methane, have been reported. Significant progress has also been made in the field of endohedral metallofullerenes. Notably, encapsulation of a large La2C2 cluster inside D5(450)C100 induced a 5% axial compression of the cage, as compared with the structure of La2@D5(450)C100. The number of well-characterized heterometallic organolanthanide complexes has also witnessed a remarkable growth. An impressive number of interesting contributions have been published in the field of organolanthanide catalysis, with an emphasis on Ln-catalyzed olefin and diene polymerization. Approximately 20% of the papers published in 2015 were in the area of organoactinide chemistry. Notable results include the synthesis and characterization of homoleptic uranium(IV) tetrabenzyl complexes and a simple mono(imido) thorium complex and the first bis(imido) thorium complex, K[Th(NDipp))(NR2)3] and K2[Th(NDipp)2)(NR2)2] (Dipp = 2,6-diisopropylphenyl, R = SiMe3). The reactivity of the unusual base-free imido complex [η5-1,2,4-(Me3C)3C5H2]2ThN(p-tolyl) has also been studied. A highly remarkable achievement in 2015 was the synthesis of crystalline molecular complexes of the [{C5H3(SiMe3)2}3Th]− anion containing thorium in the formal +2 oxidation state. Various unusual transformations have been achieved using the Cp*2Th platform. For example, a unique thorium phosphinidene complex obtained from the reaction of Cp*2Th(CH3)2 with H2P(2,4,6-iPr3C6H2) has been prepared and structurally characterized. Other remarkable results include the preparation of novel actinide metallacyclocumulenes and metallacyclopentadienes. The synthesis of [3]thoro- and [3]uranocenophanes, the first structurally authenticated ansa-bridged actinocenes, has also been reported. Finally, significant progress has been made in the field of organoactinide catalysis.