Lanthanides and actinides: Annual survey of their organometallic chemistry covering the year 2013

• The first carbene complex of Ce(IV), Ce(BIPMTMS)(ODipp)2, has been reported.
• Two new terminal imido complexes of scandium have been synthesized.
• The first stable complexes of Tb2+, Pr2+, Gd2+, and Lu2+ have been isolated.
• The europium(II) metallocene Eu(CpBIG)2 shows bright orange photoluminescence.
• YCN@C82 represents the first endohedral metallofullerenes entrapping a metal cyanide.
• The chemistry of unusual organolanthanide hydride clusters has been largely expanded.
• The first U(II) compound, [K(2.2.2-cryptand)][(C5H4SiMe3)3U], has been isolated.

This review summarizes the progress in organo-f-element chemistry during the year 2013. The year 2013 witnessed a significant increase of contributions in the fields of organolanthanide and organoactinide chemistry over 2012 (ca. 16% more). An unbroken trend for many years which continued into 2013 was the investigation of highly reactive lanthanide alkyl complexes supported by non-cyclopentadienyl ligands (e.g., amidinates, aminopyridinates, β-diketiminates, etc.). Many of these complexes found useful applications in homogeneous catalysis. Three classes of compounds stand out for having become increasingly important in 2013: carbene complexes of lanthanides and uranium, organolanthanide hydrido clusters, and heterometallic organolanthanide compounds. Notable among the 2013 highlights in the field of organolanthanide chemistry is the successful synthesis of the first carbene complex of tetravalent cerium, Ce(BIPMTMS)(ODipp)2 (BIPMTMS = [C(PPh2NSiMe3)2]2−, Dipp = 2,6-diisopropylphenyl). Two new scandium terminal imido complexes have also been reported. Without doubt a major highlight was the isolation of first examples of crystallographically characterizable complexes of Tb2+, Pr2+, Gd2+, and Lu2+. This finding demonstrates that Ln2+ ions are now accessible in soluble molecules for all of the lanthanides except radioactive promethium. Also quite remarkable is the europium(II) metallocene Eu(CpBIG)2 (CpBIG = (4-nBuC6H4)5-cyclopentadienyl) which exhibits bright orange photoluminescence at room temperature. The class of lanthanide hydride clusters has been largely expanded in 2013, including a series of heterometallic species such as the first heterotrimetallic (Lu/Re/W) and several hexanuclear heterobimetallic Y4/M2- and Y5/M-polyhydride (M = Mo, W) cluster complexes. The same is true for various heterometallic organolanthanide compounds, including, e.g., the unusual new 3d/4f polyphosphide complexes (Cp*Fe)2P10[Sm(η5-C5Me4R)2]2 (R = Me, nPr) and several novel complexes comprising direct bond between lanthanides and main group elements and transition metals. The chemistry of endohedral lanthanide fullerenes continued to attract significant interest in 2013. For example, it was discovered that the Lewis acid CuCl2 is a suitable reagent for the isolation of a broad array of endohedral fullerenes containing metal, metal carbide, metal nitride, and metal oxide clusters, as well as for the separation of their structural isomers. YCN@C82 was shown to be the first endohedral metallofullerenes entrapping a metal cyanide. Several new catalytic applications of organolanthanide compounds have also been uncovered, such as the Ln-catalyzed carbostannylation of olefins and terminal alkynes. Ca. 20% of all publications covered in this review were in the area of organoactinide chemistry. Significant progress has been made in the synthesis and characterization of actinide alkyl complexes, e.g., the preparation of first genuine uranyl(VI) alkyl complex, [Li(DME)1.5]2[UO2(CH2SiMe3)4]. A rich chemistry has been developed around new uranium carbene complexes containing, e.g., the BIPMDipp ligand (BIPMDipp = [C(PPh2NDipp)2]2−; Dipp = C6H3iPr2-2,6). Truly remarkable was the identification of the +2 oxidation state for uranium in a crystalline molecular complex, [K(2.2.2-cryptand)][(C5H4SiMe3)3U], which was made by flash reduction of Cp′3U (Cp′ = C5H4SiMe3) in a column of potassium graphite in the presence of 2.2.2-cryptand. A reinvestigation of the chemistry of (COT)2Th with neutral Lewis bases provided access to novel bent sandwich complexes (COT)2Th(L).