Nature of the Arsonium-Ylide Ph 3 As=CH 2 and a Uranium(IV) Arsonium-Carbene Complex.

Autor: Seed JA; Department of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK., Sharpe HR; Department of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK., Futcher HJ; Department of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK., Wooles AJ; Department of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK., Liddle ST; Department of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
Jazyk: angličtina
Zdroj: Angewandte Chemie (International ed. in English) [Angew Chem Int Ed Engl] 2020 Sep 07; Vol. 59 (37), pp. 15870-15874. Date of Electronic Publication: 2020 Jun 30.
DOI: 10.1002/anie.202004983
Abstrakt: Treatment of [Ph 3 EMe][I] with [Na{N(SiMe 3 ) 2 }] affords the ylides [Ph 3 E=CH 2 ] (E=As, 1As; P, 1P). For 1As this overcomes prior difficulties in the synthesis of this classical arsonium-ylide that have historically impeded its wider study. The structure of 1As has now been determined, 45 years after it was first convincingly isolated, and compared to 1P, confirming the long-proposed hypothesis of increasing pyramidalisation of the ylide-carbon, highlighting the increasing dominance of E + -C - dipolar resonance form (sp 3 -C) over the E=C ene π-bonded form (sp 2 -C), as group 15 is descended. The uranium(IV)-cyclometallate complex [U{N(CH 2 CH 2 NSiPr i 3 ) 2 (CH 2 CH 2 SiPr i 2 CH(Me)CH 2 )}] reacts with 1As and 1P by α-proton abstraction to give [U(Tren TIPS )(CHEPh 3 )] (Tren TIPS =N(CH 2 CH 2 NSiPr i 3 ) 3 ; E=As, 2As; P, 2P), where 2As is an unprecedented structurally characterised arsonium-carbene complex. The short U-C distances and obtuse U-C-E angles suggest significant U=C double bond character. A shorter U-C distance is found for 2As than 2P, consistent with increased uranium- and reduced pnictonium-stabilisation of the carbene as group 15 is descended, which is supported by quantum chemical calculations.
(© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)
Databáze: MEDLINE
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