A Series of Rare‐Earth Mesoionic Carbene Complexes

John A. Seed, Lisa Vondung, Franky Barton, Ashley J. Wooles, Erli Lu, Matthew Gregson, Stephen Liddle, Ralph Adams

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We report the synthesis and characterisation of a series of rare-earth mesoionic carbene complexes, [RE{N(SiMe 3 ) 2 } 3 {CN(Me)C(Me)N(Me)CH}] ( 3RE , RE = Sc, Ce, Pr, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), greatly expanding the limited library of f-block mesoionic carbene complexes. These complexes were prepared by treatment of the parent RE-triamides with an N-heterocyclic olefin (NHO), where an NHO backbone proton undergoes a formal 1,4-proton migration to the NHO-methylene group. For all RE(III) metals, as expected, quantum chemical calculations suggest only a σ - component to the metal-carbene bonding, in contrast to a previously reported uranium(III) congener where the 5f 3 metal engages in a weak π -back-bond to the MIC. All complexes were characterized by static variable-temperature magnetic measurements, and dynamic magnetic measurements reveal that 3Dy and 3Er are field-induced single-molecule magnets (SMMs), with U eff energy barriers of 35 and 128 K, respectively. Complex 3Dy is, as expected, a poorly performing SMM, but conversely 3Er performs unexpectedly well.
Original languageEnglish
JournalChemistry – A European Journal
Early online date26 Apr 2022
Publication statusPublished - 26 Apr 2022


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