Cationic Phosphorus Compounds Based on a Bis(1-piperidinyl)-Substituted Carbodiphosphorane: Syntheses, Structures, and Csp3–H Activation,Organometallics

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Cationic Phosphorus Compounds Based on a Bis(1-piperidinyl)-Substituted Carbodiphosphorane: Syntheses, Structures, and Csp3–H Activation
Organometallics ( IF 2.5 ) Pub Date : 2020-08-26 , DOI: 10.1021/acs.organomet.0c00412
Alexander Kroll ₁ , Henning Steinert ₁ , Mike Jörges ₁ , Tim Steinke ₁ , Bert Mallick ₁ , Viktoria H. Gessner ₁

Affiliation

The use of the bis(1-piperidinyl)-substituted carbodiphosphorane (Ph₂(Pip)P)₂C (1) as an NCN ligand for the stabilization of phosphorus cations was studied. A simple ligand for halide exchange allowed the synthesis and isolation of a series of phosphorus monocations of the type [1-PR₂]⁺ (with R = Cl, Br, I, CyCl, Ph). These cations exhibit characteristic NMR and structural properties which nicely correlate with the charge at the central phosphorus atom and the interaction between the ligand and the PR₂ moiety. Halide abstraction from the monocations does not result in isolable dicationic compounds but in an unexpected intramolecular C_sp³–H activation in the piperidinyl group. DFT studies show that the selective activation of the CH₂ group next to the nitrogen atom instead of a CH group at the phenyl substituents proceeds via an iminium intermediate formed by hydride transfer from the carbon atom to the cationic phosphorus center. This observation clearly demonstrates the pronounced π acidity of the dicationic phosphorus species in comparison to compounds with a further π-donor substituent.

中文翻译：

基于双（1-哌啶基）取代的碳二膦烷的阳离子磷化合物：合成，结构和C _{sp ^{3 –}} H活化。

研究了使用双（1-哌啶基）-取代的碳二磷烷（Ph ₂（Pip）P）₂ C（1）作为NCN配体来稳定磷阳离子。一个简单的卤化物交换配体允许合成和分离一系列[ 1 -PR ₂ ] ⁺类型的磷单阳离子（R = Cl，Br，I，CyCl，Ph）。这些阳离子具有特征性的NMR和结构性质，与中心磷原子上的电荷以及配体与PR ₂部分之间的相互作用密切相关。从单阳离子中提取卤化物不会导致可分离的二价化合物，但会导致意外的分子内C _sp哌啶基中的_³ -H活化。DFT研究表明，取代基上氮原子旁边的CH₂基团而不是苯基取代基上的CH基团的选择性活化是通过氢化物从碳原子转移到阳离子磷中心形成的亚胺中间体进行的。该观察结果清楚地表明，与具有其他π-供体取代基的化合物相比，二价磷物质具有明显的π酸度。

更新日期：2020-08-26

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