Treatment of [Ph₃EMe][I] with [Na{N(SiMe₃)₂}] affords the ylides [Ph₃E=CH₂] (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 (sp³‐C) over the E=C ene π‐bonded form (sp²‐C), as group 15 is descended. The uranium(IV)–cyclometallate complex [U{N(CH₂CH₂NSiPrⁱ₃)₂(CH₂CH₂SiPrⁱ₂CH(Me)CH₂)}] reacts with 1As and 1P by α‐proton abstraction to give [U(Tren^TIPS)(CHEPh₃)] (Tren^TIPS=N(CH₂CH₂NSiPrⁱ₃)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.

中文翻译：

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son-叶立德Ph3 As = CH2和铀（IV）son-碳络合物的性质。

用[Na {N（SiMe ₃）₂ }]处理[Ph ₃ EMe] [I]，得到叶立德[Ph ₃ E = CH ₂ ]（E = As，1As； P，1P）。对于1A来说，这克服了以前合成经典砷化钇的困难，这在历史上一直阻碍其广泛的研究。的结构1AS现已确定45年后它首先被令人信服地分离，并与1P，证实长提出增加叶立德-碳pyramidalisation，突出E的增加支配地位的假说⁺ -C ^-偶极共振表格（sp ³C）在E = C烯π键形式（sp ² -C）上，第15组下降。铀（IV）-环金属盐络合物[U {N（CH ₂ CH ₂ NSiPr ⁱ ₃）₂（CH ₂ CH ₂ SiPr ⁱ ₂ CH（Me）CH ₂）}]通过α-质子抽象与1As和1P反应生成给出[U（Tren ^TIPS）（CHEPh ₃）]（Tren ^TIPS = N（CH ₂ CH ₂ NSiPr ⁱ ₃）₃ ; E = As，2As ; P，2P），其中2As是前所未有的具有结构特征的characterized-卡宾络合物。短的UC距离和钝的UC角表明了显着的U = C双键特征。较短的ù-C距离被发现2AS大于2P，与作为组15被下降卡宾，其通过量子化学计算支持的增加铀和减少pnictonium稳定化是一致的。