Article ID Journal Published Year Pages File Type
1323591 Journal of Organometallic Chemistry 2011 11 Pages PDF
Abstract

Studies from authors’ group (at the University of Tennessee) on alkylidene complexes and α-H migration in alkyl alkylidyne complexes, leading to unusual tautomerization equilibria between bis-alkylidenes and alkyl alkylidynes, are reviewed. Preparation of silyl alkylidene complexes (Me3ECH2)2Ta(CHEMe3)(SiR3) [R3 = (SiMe3)3, E = C, 3a, Si, 3b; R3 = ButPh2, E = C, 4a, Si, 4b] and the pathway in the formation of 3b are discussed first. Pathways in the formation of archetypical Schrock-type alkyl alkylidenes (Me3ECH2)3TaCHEMe3 (E = C, 5a; Si, 5b), including the work using Ta(CD2CMe3)5 (21-d10) to confirm that it is the precursor to (Me3CCD2)3TaCDCMe3 (5a-d7), are then considered. Tautomerization of silyl alkylidyne (Me3CCH2)2W(CCMe3)(SiButPh2) (6a) with bis-alkylidene (Me3CCH2)W(CHCMe3)2(SiButPh2) (6b) as well as (Me3SiCH2)3W(CSiMe3)(PR3) [R3 = Me3, 7a; Me2Ph, 8a; Me2(CH2)2PMe2 (DMPE-P), 9a] with (Me3SiCH2)2W(CHSiMe3)2(PR3) (R3 = Me3, 7b; Me2Ph, 8b; DMPE-P, 9b) [P refers to a dangling P atom in Me2P(CH2)2PMe2] is covered next. Finally the conversion of the tungsten phosphine tautomerization mixtures to alkyl alkylidene alkylidyne (Me3SiCH2)W(CHSiMe3)(CSiMe3)(PR3)2 [(PR3)2 = (PMe3)2, 10; (PMe2Ph)2, 11; DMPE, 12], including its pathway, is presented.

Graphical abstractPathways in the formation of archetypical Schrock-type alkyl alkylidenes (Me3ECH2)3TaCHEMe3 (E = C; Si) and silyl alkylidene complexes (Me3ECH2)2Ta(CHEMe3)(SiR3) are discussed. Tautomerization of alkyl alkylidynes with bis-alkylidenes, including (Me3CCH2)2W(CCMe3)(SiButPh2)⇌(Me3CCH2)W(CHCMe3)2(SiButPh2) as well as (Me3SiCH2)3W(CSiMe3)(PR3)⇌(Me3SiCH2)2W(CHSiMe3)2(PR3), is covered next. Finally the conversion of the tautomerization mixtures to alkyl alkylidene alkylidyne (Me3SiCH2)W(CHSiMe3)(CSiMe3)(PR3)2 including its pathway, is presented.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Review of transition metal alkylidene complexes. ► Preparation of alkylidene complexes including silyl alkylidenes. ► Pathway in the formation of archetypical alkylidene (Me3CCH2)3TaCHCMe3. ► α-H migration in alkyl alkylidynes and unusual tautomerization to bis-alkylidenes. ► Pathway in the formation of tungsten alkyl alkylidene alkylidyne complexes.

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Physical Sciences and Engineering Chemistry Inorganic Chemistry
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