Seed John A, Sharpe Helen R, Futcher Harry J, Wooles Ashley J, Liddle Stephen T
Department of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
Angew Chem Int Ed Engl. 2020 Sep 7;59(37):15870-15874. doi: 10.1002/anie.202004983. Epub 2020 Jun 30.
Treatment of [Ph EMe][I] with [Na{N(SiMe ) }] affords the ylides [Ph E=CH ] (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 -C) over the E=C ene π-bonded form (sp -C), as group 15 is descended. The uranium(IV)-cyclometallate complex [U{N(CH CH NSiPr ) (CH CH SiPr CH(Me)CH )}] reacts with 1As and 1P by α-proton abstraction to give [U(Tren )(CHEPh )] (Tren =N(CH CH NSiPr ) ; 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.
用[Na{N(SiMe₃)₂}]处理[Ph₃EMe][I]可得到叶立德[Ph₃E=CH₂]（E = As，1As；P，1P）。对于1As，这克服了以往合成这种经典砷叶立德时遇到的困难，这些困难在历史上阻碍了对其更广泛的研究。1As的结构现已确定，在其首次被确凿分离45年后，并与1P进行了比较，证实了长期以来提出的关于叶立德 - 碳的锥化增加的假设，突出了随着第15族元素族数降低，E - C偶极共振形式（sp³ - C）相对于E = C烯π键合形式（sp² - C）的主导地位日益增强。铀（IV） - 环金属化配合物[U{N(CH₂CH₂NSiPr₂)₂(CH₂CH₂SiPr₂CH(Me)CH₂)}]通过α - 质子提取与1As和1P反应，生成[U(Tren)(CHEPh₂)]（Tren = N(CH₂CH₂NSiPr₂)₂；E = As，2As；P，2P），其中2As是一种前所未有的具有结构表征的砷卡宾配合物。较短的U - C距离和钝角的U - C - E角表明存在显著的U = C双键特征。发现2As的U - C距离比2P短，这与随着第15族元素族数降低卡宾的铀稳定化增加和鎓稳定化降低一致，量子化学计算支持了这一点。
