Lanthanide amidinates and guanidinates in catalysis and materials science: a continuing success story

Abstract

Today the rare-earth elements play a critical role in numerous high-tech applications. This is why various areas of rare-earth chemistry are currently thriving. In organolanthanide chemistry the search for new ligand sets which are able to satisfy the coordination requirements of the large lanthanide cations continues to be a hot topic. Among the most successful approaches in this field is the use of amidinate and guanidinate ligands of the general types [RC(NR')(2)](-) (R = H, alkyl, aryl; R' = alkyl, cycloalkyl, aryl, SiMe(3)) and [R(2)NC(NR')(2)](-) (R = alkyl, SiMe(3); R' = alkyl, cycloalkyl, aryl, SiMe(3)), which can both be regarded as steric cyclopentadienyl equivalents. Mono-, di- and trisubstituted lanthanide amidinate and guanidinate complexes are all readily available. Various rare earth amidinates and guanidinates have turned out to be very efficient homogeneous catalysts e.g. for the polymerization of olefins and dienes, the ring-opening polymerization of cyclic esters or the guanylation of amines. Moreover, certain alkyl-substituted lanthanide tris(amidinates) and tris(guanidinates) were found to be highly volatile and are thus promising precursors for ALD (= atomic layer deposition) and MOCVD (= metal-organic chemical vapor deposition) processes in materials science, e.g. for the production of lanthanide nitride thin layers. This tutorial review covers the continuing success story of lanthanide amidinates and guanidinates which have undergone an astonishing transition from mere laboratory curiosities to efficient homogeneous catalysts as well as ALD and MOCVD precursors within the past 10 years.

Easy access to nucleophilic boron through diborane to magnesium boryl metathesis

“…6b). Although the formation of this new anion is completely analogous to the widely employed reaction of carbodiimides with the M–C bonds of polar σ-organometallics5455, the only precedent for similar M–B insertion is provided by a scandium derivative, which was itself prepared from compound 1 (ref. 18).…”

Chemical Vapor Deposition of Phase‐Pure Uranium Dioxide Thin Films from Uranium(IV) Amidate Precursors

“…[14] However,t he preparation of phase-pure thin films in aCVD process can be challenging,since the precursors must be both sufficiently volatile and decompose cleanly by asingle mechanism to minimize the formation of side products. [14,[16][17][18][19][20][21][22] In contrast to the myriad quantity of CVD precursors that have been described for these metals,o nly as mall handful of uranium oxide CVD precursors have ever been reported. [14,[16][17][18][19][20][21][22] In contrast to the myriad quantity of CVD precursors that have been described for these metals,o nly as mall handful of uranium oxide CVD precursors have ever been reported.…”

Bismuth(III) Complexes Based on Bis(triazol) Ligands: Effect of Fluorine Substitution on the Structure and Catalysis for the Polymerization of Glycolide

“…[12] Recent studies showed that the introduction of different substituents on the ligand backbone can greatly affect the catalytic activity in ROP reactions. [13] Detailed studies of the effect of fluorinated and nonfluorinated ligands on the structures and properties of metal-organic crystalline materials were performed. [14][15][16][17] To further extend this research, two flexible bis(triazol) derivatives were chosen in this work (see Scheme 1), namely nonfluorinated 1,4-bis[ (1,2,4- www.zaac.wiley-vch.de ARTICLE more, comparative catalytic activities of both complexes in the bulk ROP of glycolide are described.…”