Normal‐to‐Abnormal NHC Rearrangement of AlIII,GaIII, and InIII Trialkyl Complexes: Scope,Mechanism, Reactivity Studies,and H2 Activation

The present contribution reports experimental and theoretical mechanistic investigations on a normal‐to‐abnormal (C2‐to‐C4‐bonded) NHC rearrangement processes occurring with bulky group 13 metal NHC adducts, including the scope of such a reactivity for Al compounds. The sterically congested adducts (nItBu)MMe₃ (nItBu=1,3‐di‐tert‐butylimidazol‐2‐ylidene; M=Al, Ga, In; 1 a – c ) readily rearrange to quantitatively afford the corresponding C4‐bonded complexes (aItBu)MMe₃ ( 4 a – c ), a reaction that may be promoted by THF. Thorough experimental data and DFT calculations were performed on the nNHC‐to‐aNHC process converting the Al‐nNHC ( 1 a ) to its aNHC analogue 4 a . A nItBu/aItBu isomerization is proposed to account for the formation of the thermodynamic product 4 a through reaction of transient aItBu with THF–AlMe₃. The reaction of benzophenone with (nItBu)AlMe₃ afforded the zwitterionic species (aItBu)(CPh₂‐O‐AlMe₃) ( 6 ), reflecting the unusual reactivity that such bulky adducts may display. Interestingly, the nItBu/Al(iBu)₃ Lewis pair behaves like a frustrated Lewis pair (FLP) since it readily reacts with H₂ under mild conditions. This may open the way to future reactivity developments involving commonly used trialkylaluminum precursors.     

Expanded ring N-heterocyclic carbene complexes of zero valent platinum dvtms (divinyltetramethyldisiloxane): Highly efficient hydrosilylation catalysts

The synthesis and characterisation of a series of new 6- and 7-membered NHC (N-heterocyclic carbene) complexes 7-12 of zero valent platinum dvtms (divinyltetramethyldisiloxane), [Pt(NHC)(dvtms)] are reported. A number of the complexes were investigated as catalyst precursors in the hydrosilylation of a range of unsaturated substrates, including alkynes, alkenes and a ketone with triethylsilane and bis(trimethylsiloxy)methylsilane (MD’M), at low catalyst loading (0.005 mol %); in general, the activity, and the selectivity for 1-functionalised product was found to be high.     

四种N-杂环卡宾钯配合物的电喷雾质谱研究

利用电喷雾质谱技术研究了四种N-杂环钯卡宾配合物,优化出较适宜检测的电喷雾质谱条件极性较高的溶剂(如乙腈),较低的离子源温度,样品浓度以1.0×10-4mol/L左右为宜,使用较低锥孔电压(5~35V).在此实验条件下,在全扫描电喷雾正离子谱中都会出现[M-I CH3CN] 及[M-I] 的质谱峰.通过源内碰撞诱导电离(CID)技术进一步分析样品在溶液中的性质.实验说明ESI不仅可作为一种分析工具,也可作为获得更多信息的一种方法,来研究有机金属基团在溶液中的性质.     

An Imidazolylidene-Based Mesoionic Carbene–Mn(I) Complex and Its Catalytic Potential in N-Heteroarene Hydrogenation

Herein we report the first mesoionic carbene (MIC)-Mn(I) complex Mn-bim-MIC^imz derived from imidazolylidene motif. Structurally the octahedral Mn(I) complex Mn-bim-MIC^imz was assembled with an anionic benzimidazolato-anchored imidazolylidene MIC-based bidentate ligand ( bim-MIC^imz ) and four CO ligands, as supported by detailed characterization using NMR and FTIR spectroscopy, mass spectrometry, and single crystal X-ray diffraction study. We reckoned that the bim-MIC^imz ligand would provide a robust and stable bonding with the Mn(I) centre, and also enhance electron density at the Mn(I) centre through its stronger σ-donating/weaker π-accepting property. These structural and electronic attributes triggered to exploit Mn-bim-MIC^imz in catalytic hydrogenation of N-heteroarenes, where efficient hydride (Mn−H) delivery is a key step.     

The Influence of C(sp3)H–Selenium Interactions on the 77Se NMR Quantification of the π-Accepting Properties of Carbenes

Selenium NMR has become a standard tool for scaling the π-accepting character of carbenes. Herein, we highlight that non-classical hydrogen bonding (NCHB), likely resulting from hyperconjugation, can play a significant role in the carbene–selenium ⁷⁷Se NMR chemical shift, thus triggering a non-linear behavior of the Se-Scale.