共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
3.
Stefan Gruber Andreas Pfaltz 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(7):1927-1931
Previously elusive iridium dihydride alkene complexes have been identified and characterized by NMR spectroscopy in solution. Reactivity studies demonstrated that these complexes are catalytically competent intermediates. Additional H2 is required to convert the catalyst‐bound alkene into the hydrogenation product, supporting an IrIII/IrV cycle via an [IrIII(H)2(alkene)(H2)(L)]+ intermediate, as originally proposed based on DFT calculations. NMR analyses indicate a reaction pathway proceeding through rapidly equilibrating isomeric dihydride alkene intermediates with a subsequent slow enantioselectivity‐determining step. As in the classical example of asymmetric hydrogenation with rhodium diphosphine catalysts, it is a minor, less stable intermediate that is converted into the major product enantiomer. 相似文献
4.
Jiao‐Jiao Li Zong‐Jie Guan Zhen Lei Feng Hu Quan‐Ming Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(4):1095-1099
Two homoleptic alkynyl‐protected gold clusters with compositions of Na[Au25(C≡CAr)18] and (Ph4P)[Au25(C≡CAr)18] (Na? 1 and Ph4P? 1 , Ar=3,5‐bis(trifluoromethyl)phenyl) were synthesized via a direct reduction method. 1 is a magic cluster analogous to [Au25(SR)18]? in terms of electron counts and metal‐to‐ligand ratio. Single‐crystal structure analysis reveals that 1 has an identical Au13 kernel to [Au25(SR)18]?, but adopts a distinctly different arrangement of the six peripheral dimer staple motifs. The steric hindrance of alkynyl ligands is responsible for the D3 arrangement of Au25. The introduction of alkynyl also significantly changes the optical absorption features of the nanocluster as supported by DFT calculations. This magic cluster confirms that there is a similar but quite different parallel alkynyl‐protected metal cluster universe in comparison to the thiolated one. 相似文献
5.
Patricia J. Nance Niklas B. Thompson Paul H. Oyala Jonas C. Peters 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(19):6286-6290
Species with 2‐center, 3‐electron (2c/3e?) σ bonds are of interest owing to their fascinating electronic structures and potential for interesting reactivity patterns. Report here is the synthesis and characterization of a pair of zerovalent (d9) trigonal pyramidal Rh and Ir complexes that feature 2c/3e? σ bonds to the Si atom of a tripodal tris(phosphine)silatrane ligand. X‐ray diffraction, continuous wave and pulse electron paramagnetic resonance, density‐functional theory calculations, and reactivity studies have been used to characterize these electronically distinctive compounds. The data available highlight a 2c/3e? bonding framework with a σ*‐SOMO of metal 4‐ or 5dz2 parentage that is partially stabilized by significant mixing with Si (3pz) and metal (5‐ or 6pz) orbitals. Metal‐ligand covalency thus buffers the expected destabilization of transition‐metal (TM)‐silyl σ*‐orbitals by d–p mixing, affording well‐characterized examples of TM–main group, and hence polar, 2c/3e? σ “half‐bonds”. 相似文献
6.
Stefan Seidel Konrad Seppelt 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2000,112(21):4072-4074
7.
8.
9.
10.
Peng‐Fei Cui Yang Gao Shu‐Ting Guo Yue‐Jian Lin Zhen‐Hua Li Guo‐Xin Jin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(24):8213-8217
In this work, a pincer‐type complex [Cp*Ir‐(SNPh)(SNHPh)(C2B10H9)] ( 2 ) was synthesized and its reactivity studied in detail. Interestingly, molecular hydrogen can induce the transformation between the metalloradical [Cp*Ir‐(SNPh)2(C2B10H9)] ( 5 .) and 2 . A mixed‐valence complex, [(Cp*Ir)2‐(SNPh)2(C2B10H8)] ( 7 .+), was also synthesized by one‐electron oxidation. Studies show that 7 .+ is fully delocalized, possessing a four‐centered‐one‐electron (S‐Ir‐Ir‐S) bonding interaction. DFT calculations were also in good agreement with the experimental results. 相似文献
11.
12.
13.
14.
15.
16.
17.
Kenichi Kato Atsuhiro Osuka 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(25):8634-8638
meta‐ and para‐Phenylenediamine‐fused nickel(II) porphyrin dimers were synthesized by SNAr reaction of meso,β,β‐trichloro nickel(II) porphyrin with meta‐ and para‐phenylenediamines and subsequent Pd‐catalyzed intramolecular C?H arylation. Their tetrachlorinated dication diradicals are very stable, allowing SQUID magnetometry and revealing clear open‐shell characters for both meta and para isomers with ferro‐ and anti‐ferromagnetic interactions, respectively. The nitrogen analogue of Thiele's hydrocarbon usually displays predominant closed‐shell nature but its hidden diradical characters increase either in a twisted conformation or upon insertion of an additional phenylene spacer. The observed distinct diradical nature of the para‐congener indicates that diradical properties can be enhanced also by efficient spin delocalization. 相似文献
18.
Matthew R. Gyton Baptiste Leforestier Adrian B. Chaplin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(43):15439-15442
The synthesis of two well‐defined rhodium(I) complexes of nitrous oxide (N2O) is reported. These normally elusive adducts are stable in the solid state and persist in solution at ambient temperature, enabling comprehensive structural interrogation by 15N NMR and IR spectroscopy, and single‐crystal X‐ray diffraction. These methods evidence coordination of N2O through the terminal nitrogen atom in a linear fashion and are supplemented by a computational energy decomposition analysis, which provides further insights into the nature of the Rh–N2O interaction. 相似文献
19.