Alkalimetallamid‐stabilisierte Titancarben‐Komplexe

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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Potential Precursors for Terminal Methylidene Rare‐Earth‐Metal Complexes Supported by a Superbulky Tris(pyrazolyl)borato Ligand

Birkelbach

Thim

Stuhl

et al. 2019

Chemistry A European J

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Nickel‐Catalyzed Anionic Cross‐Coupling Reaction of Lithium Sulfonimidoyl Alkylidene Carbenoids With Organolithiums

Erdelmeier

Won

Park

et al. 2020

Chemistry A European J

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The mechanistic platform for a novel nickel0‐catalyzed anionic cross‐coupling reaction (ACCR) of lithium sulfonimidoyl alkylidene carbenoids (metalloalkenyl sulfoximines) with organometallic reagents is reported herein, affording substituted alkenylmetals and lithium sulfinamides. The Ni0‐catalyzed ACCR of three different types of metalloalkenyl sulfoximines, including acyclic, axially chiral and exocyclic derivatives, with sp2 organolithiums and sp2 and sp3 Grignard reagents has been studied. The ACCR of metalloalkenyl sulfoximines with PhLi in the presence of the Ni0‐catalyst and precatalyst Ni(PPh3)2Cl2 afforded alkenyllithiums, under inversion of configuration at the C atom and complete retention at the S atom. In a combination of experimental and DFT studies, we propose a catalytic cycle of the Ni0‐catalyzed ACCR of lithioalkenyl sulfoximines. Computational studies reveal two distinctive pathways of the ACCR, depending on whether a phosphine or 1,5‐cyclooctadiene (COD) is the ligand of the Ni atom. They rectify the underlying importance of forming the key Ni0‐vinylidene intermediate through an indispensable electron‐rich Ni0‐center coordinated by phosphine ligands. Fundamentally, we present a mechanistic study in controlling the diastereoselectivity of the alkenyllithium formation via the key lithium sulfinamide coordinated Ni0‐vinylidene complex, which consequently avoids an unselective formation of an alkylidene carbene Ni‐complex and ultimately racemic alkenyllithium.

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Cyclic Bis‐alkylidene Complexes of Titanium and Zirconium: Synthesis, Characterization, and Reaction

Zhang

Zhong

et al. 2020

Chemistry A European J

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Alkalimetallamid‐stabilisierte Titancarben‐Komplexe

Cited by 3 publications

References 52 publications

Potential Precursors for Terminal Methylidene Rare‐Earth‐Metal Complexes Supported by a Superbulky Tris(pyrazolyl)borato Ligand

Potential Precursors for Terminal Methylidene Rare‐Earth‐Metal Complexes Supported by a Superbulky Tris(pyrazolyl)borato Ligand

Nickel‐Catalyzed Anionic Cross‐Coupling Reaction of Lithium Sulfonimidoyl Alkylidene Carbenoids With Organolithiums

Cyclic Bis‐alkylidene Complexes of Titanium and Zirconium: Synthesis, Characterization, and Reaction

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