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.