A new, extremely bulky, and electron-rich N-phosphinomethyl-functionalized N-heterocyclic carbene ligand, 5a (tBuNHCPtBu), and a somewhat less bulky congener, 5b (MesNHCPtBu), forming five-membered chelate rings with metal centers, have been synthesized in four steps starting from the easily accessible di-tert-butyl(hydroxymethyl)phosphine oxide (1). 5a was isolated and fully characterized by spectroscopic
一种新的,非常笨重且富含电子的N-膦甲基甲基官能化的N-杂环卡宾配体5a(t Bu NHCP t Bu)和体积较小的同类物5b(Mes NHCP t Bu),形成五元螯合物从容易获得的二叔丁基(羟甲基)氧化膦(1)开始,已通过四个步骤合成了具有金属中心的环。分离并通过包括紫外光电子能谱和X射线衍射的能谱方法充分表征了5a。的反应5a中,以[Ru(COD)氯2 ] n在氢气压力下或与[Ru(p- Cymene)Cl 2 ] 2导致形成不饱和双核络合物[Ru(t Bu NHCP t Bu)(μ-Cl)(Cl)] 2(6) ,它用作使用取代的苯基重氮甲烷(p -XC 6 H 4(CH)N 2; X = H(a),Br(b),CF 3(c)的一系列钌卡宾配合物(7a - f)的前体),NO 2,(d),CH 3(e))和三甲基甲硅烷基重氮甲烷(f)。用膦或吡啶配体处理6导致形成单核加合物[Ru(t
Cooperative duplex formation by synthetic H-bonding oligomers
作者:Alexander E. Stross、Giulia Iadevaia、Christopher A. Hunter
DOI:10.1039/c5sc03414k
日期:——
Flexible phenol-phosphine oxide oligomers show promise as a new class of synthetic information molecule.
灵活的酚-膦氧寡聚物被认为是一种新型合成信息分子的有前途的类别。
Mix and match backbones for the formation of H-bonded duplexes
作者:Giulia Iadevaia、Alexander E. Stross、Anja Neumann、Christopher A. Hunter
DOI:10.1039/c5sc04467g
日期:——
The formation of well-defined supramolecular assemblies involves competition between intermolecular and intramolecular interactions, which is quantified by effective molarity. Formation of a duplex between two oligomers equipped with recognition sites displayed along a non-interacting backbone requires that once one intermolecular interaction has been formed, all subsequent interactions take place
Experimental and Theoretical Study of Ni
<sup>II</sup>
‐ and Pd
<sup>II</sup>
‐Promoted Double Geminal C(sp
<sup>3</sup>
)−H Bond Activation Providing Facile Access to NHC Pincer Complexes: Isolated Intermediates and Mechanism
A gem of a reaction: The first examples of stepwise (Pd) or direct (Ni) metal-promoted double geminal activation of C −H bonds leading to imidazole-type N-heterocyclic carbene metal pincer complexes under mild conditions are presented.
反应的瑰宝:逐步(Pd)或直接(Ni)金属促进的 C 双孪生活化的第一个例子 提出了在温和条件下产生咪唑型N-杂环卡宾金属钳配合物的-H键。
Relationship between Chemical Structure and Supramolecular Effective Molarity for Formation of Intramolecular H-Bonds
作者:Hongmei Sun、Christopher A. Hunter、Cristina Navarro、Simon Turega
DOI:10.1021/ja406235d
日期:2013.9.4
Effective molarity (EM) is a key parameter that determines the efficiency of a range of supramolecular phenomena from the folding of macromolecules to multivalent ligand binding. Coordination complexes formed between zinc porphyrins equipped H-bond donor sites and pyridine ligands equipped with H-bond acceptor sites have allowed systematic quantification of EM values for the formation of intramolecular H-bonds in 240 different systems. The results provide insights into the relationship of EM to supramolecular architecture, H-bond strength, and solvent. Previous studies on ligands equipped with phosphonate diester and ether H-bond acceptors were inconclusive, but the experiments described here on ligands equipped with phosphine oxide, amide, and ester H-bond acceptors resolve these ambiguities. Chemical double-mutant cycles were used to dissect the thermodynamic contributions of individual H-bond interactions to the overall stabilities of the complexes and hence determine the values of EM, which fall in the range 1-1000 mM. Solvent has little effect on EM, and the values measured in toluene and 1,1,2,2-tetrachloroethane are similar. For H-bond acceptors that have similar geometries but different H-bond strengths (amide and ester), the values of EM are very similar. For H-bond acceptors that have different geometries but similar H-bond strengths (amide and phosphonate diester), there is, little correlation between the values of EM. These results imply that supramolecular EMs are independent of solvent and intrinsic H-bond strength but depend on supramolecular architecture and geometric complementarity.