Potential Precursors for Terminal Methylidene Rare-Earth-Metal Complexes Supported by a Superbulky Tris(pyrazolyl)borato Ligand |
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Authors: | Verena M Birkelbach Dr Renita Thim Dr Christoph Stuhl Dr Cäcilia Maichle-Mössmer Prof?Dr Reiner Anwander |
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Institution: | Institut für Anorganische Chemie, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany |
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Abstract: | A series of solvent-free heteroleptic terminal rare-earth-metal alkyl complexes stabilized by a superbulky tris(pyrazolyl)borato ligand with the general formula TptBu,MeLnMeR] have been synthesized and fully characterized. Treatment of the heterobimetallic mixed methyl/tetramethylaluminate compounds TptBu,MeLnMe(AlMe4)] (Ln=Y, Lu) with two equivalents of the mild halogenido transfer reagents SiMe3X (X=Cl, I) gave TptBu,MeLnX2] in high yields. The addition of only one equivalent of SiMe3Cl to TptBu,MeLuMe(AlMe4)] selectively afforded the desired mixed methyl/chloride complex TptBu,MeLuMeCl]. Further reactivity studies of TptBu,MeLuMeCl] with LiR or KR (R=CH2Ph, CH2SiMe3) through salt metathesis led to the monomeric mixed-alkyl derivatives TptBu,MeLuMe(CH2SiMe3)] and TptBu,MeLuMe(CH2Ph)], respectively, in good yields. The SiMe4 elimination protocols were also applicable when using SiMe3X featuring more weakly coordinating moieties (here X=OTf, NTf2). X-ray structure analyses of this diverse set of new TptBu,MeLnMeR/X] compounds were performed to reveal any electronic and steric effects of the varying monoanionic ligands R and X, including exact cone-angle calculations of the tridentate tris(pyrazolyl)borato ligand. Deeper insights into the reactivity of these potential precursors for terminal alkylidene rare-earth-metal complexes were gained through NMR spectroscopic studies. |
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Keywords: | alkyls halides heteroleptic compounds rare-earth metals scorpionates |
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