Five-Membered Cyclic Metal Carbyne: Synthesis of Osmapentalynes by the Reactions of Osmapentalene with Allene, Alkyne, and Alkene

通讯作者地址: Zhu, JThe synthesis of small cyclic metal carbynes is challenging due to the large angle strain associated with the highly distorted nonlinear triple bonds. Herein, we report a general route for the synthesis of five-membered cyclic metal carbyne complexes, osmapentalynes, by the reactions of an osmapentalene derivative with allene, alkyne, and alkene. Experimental observations and theoretical calculations document the aromaticity in the fused five-membered rings of osmapentalynes. The realization of transforming osmapentalene to osmapentalyne through this general route would not only allow further exploration of metallapentalyne chemistry but also show promising applications of this novel aromatic system with broad absorption band and high molar absorption coefficient.973 Program 2012CB821600 NSFC 21332002 21174115 21172184 Program for New Century Excellent Talents in University NCET-13-0511 program for Changjiang Scholars and Innovative Research Team in Universit

One Amino Acid Change of Angiotensin II Diminishes Its Effects on Abdominal Aortic Aneurysm

Angiotensin (Ang) A is formed by the decarboxylation of the N terminal residue of AngII. The present study determined whether this one amino acid change impacted effects of AngII on abdominal aortic aneurysm (AAA) formation in mice. Computational analyses implicated that AngA had comparable binding affinity to both AngII type 1 and 2 receptors as AngII. To compare effects of these two octapeptides in vivo, male low-density lipoprotein receptor (Ldlr) or apolipoprotein E (Apoe) deficient mice were infused with either AngII or AngA (1 μg/kg/min) for 4 weeks. While AngII infusion induced AAA consistently in both mouse strains, the equivalent infusion rate of AngA did not lead to AAA formation. We also determined whether co-infusion of AngA would influence AngII-induced aortic aneurysm formation in male Apoe−/− mice. Co-infusion of the same infusion rate of AngII and AngA did not change AngII-induced AAA formation. Since it was reported that a 10-fold higher concentration of AngA elicited comparable vasoconstrictive responses as AngII, we compared a 10-fold higher rate (10 μg/kg/min) of AngA infusion into male Apoe−/− mice with AngII (1 μg/kg/min). This rate of AngA led to abdominal aortic dilation in three of ten mice, but no aortic rupture, whereas the 10-fold lower rate of AngII infusion led to abdominal aortic dilation or rupture in eight of ten mice. In conclusion, AngA, despite only being one amino acid different from AngII, has diminished effects on aortic aneurysmal formation, implicating that the first amino acid of AngII has important pathophysiological functions

Planar Möbius aromatic pentalenes incorporating 16 and 18 valence electron osmiums

夏海平课题组长期致力于芳香体系的拓展研究。作为金属杂戊搭炔化学又一重要进展，在此研究中，他们发现金属杂戊搭炔的卡拜碳原子宛如“变色龙”，既具有亲核性，又具有亲电性。通过金属杂戊搭炔与亲电试剂反应揭示了其三键迁移的神秘面纱，并成功地捕捉了三键迁移的中间体——金属中心为16电子的金属杂戊搭烯；通过金属杂戊搭炔与亲核试剂反应，得到金属中心为18电子的金属杂戊搭烯。 　　朱军课题组通过理论计算，对金属杂戊搭烯进行深入理论研究。发现金属中心16电子、18电子金属杂戊搭烯均具有芳香性。深入的CMO-NICS计算表明，本质上，金属杂戊搭炔中Mobius芳香性来源于金属杂戊搭烯，正如苯炔的芳香性来源于苯。Mobius芳香性自1958年提出以来，实际合成的例子稀少，且前人已分离并报道的Möbius芳香体系均具有扭曲的拓扑结构。金属杂戊搭烯/炔代表着一类平面型的Möbius芳香性体系。从而颠覆了传统的芳香化学，为构筑其他平面型Möbius芳香体系奠定了基础。 　　该工作的合成和结构表征是在夏海平教授指导下由博士生朱从青（第一作者）、罗明和硕士生朱琴完成，我校温庭斌教授参与了产物结构表征的讨论。理论计算由朱军副教授完成，我校吕鑫教授、美国佐治亚大学P.v.R.Schleyer教授和J.I-C.Wu博士也参与了芳香性的讨论。Aromaticity, a highly stabilizing feature of molecules with delocalized electrons in closed circuits, is generally restricted to ‘Hückel’ systems with 4n+2 mobile electrons. Although the Möbius concept extends the principle of aromaticity to 4n mobile electron species, the rare known examples have complex, twisted topologies whose extension is unlikely. Here we report the realization of osmapentalenes, the first planar Möbius aromatic complexes with 16 and 18 valence electron transition metals. The Möbius aromaticity of these osmapentalenes, documented by X-ray structural, magnetic and theoretical analyses, demonstrates the basis of the aromaticity of the parent osmapentalynes. All these osmapentalenes are formed by both electrophilic and nucleophilic reactions of the in-plane π component of the same carbyne carbon, illustrating ambiphilic carbyne reactivity, which is seldom observed in transition metal chemistry. Our results widen the scope of Möbius aromaticity dramatically and open prospects for the generalization of planar Möbius aromatic chemistry.国家自然科学基金委、科技部和美国科学基金会的资

Successive modification of polydentate complexes gives access to planar carbon-and nitrogen-based ligands

以碳和氮为键合原子的多齿螯合物是配合物家族中非常重要的一类。具有更高齿数的平面构型NC螯合物实例相对较少，代表性的例子为四齿金属碳卟啉类化合物，这类螯合物以其独特的结构和丰富的物理化学性质引起广泛关注。然而平面五齿、六齿的NC螯合物由于几何构型“拥挤”导致合成难度高，该工作从含三元环内金属卡宾结构的CCCC型碳龙配合物出发，利用经典有机反应（炔烃对金属卡宾的插入反应），成功地实现了CCCCN/NCCCN型平面五齿螯合物的合成。这一研究为高配位型螯合物的合成提供了新思路并为平面五齿螯合物家族添加新成员。特别是，这些高配位型螯合物在可见光和近红外区域均有较好的吸收，表现出良好的光声成像、光热转换及声动力学性能。 该研究工作在张弘教授指导下完成，第一作者为iChEM博士后周小茜。该工作充分体现了多学科协同研究优势：相关化合物的合成、表征及理论计算工作由周小茜博士完成；声动力学性能研究由厦门大学公共卫生学院庞鑫博士及刘刚教授完成；光声成像研究由厦门大学公共卫生学院聂立铭教授完成。iChEM fellow卓庆德博士、博士生卓凯玥、陈志昕参与了部分实验工作。夏海平教授、香港科技大学林振阳教授和南京大学朱从青教授对研究工作给予了大力支持。【Abstract】Polydentate complexes containing combinations of nitrogen and carbon (N and C) ligating atoms are among the most fundamental and ubiquitous molecules in coordination chemistry, yet the formation of such complexes with planar high-coordinate N/C sites remains challenging. Herein, we demonstrate an efficient route to access related complexes with tetradentate CCCN and pentadentate CCCCN and NCCCN cores by successive modification of the coordinating atoms in complexes with a CCCC core. Combined experimental and computational studies reveal that the rich reactivity of metal-carbon bonds and the inherent aromaticity of the metallacyclic skeletons play key roles in these transformations. This strategy addresses the paucity of synthetic approaches to mixed N/C planar pentadentate chelating species and provides valuable insights into the synthesis of carbon-based high-coordinate complexes. Furthermore, the resulting complexes are the examples of organometallic species with combined photoacoustic, photothermal, and sonodynamic properties, which makes them promising for application in related areas.This research was supported by the National Natural Science Foundation of China (Nos. 21572185, 21561162001, and 81571744), the Research Grants Council of Hong Kong (N_HKUST603/15), the Excellent Youth Foundation of Fujian Scientific Committee (2018J06024), and the Fundamental Research Funds for the Central Universities (20720170065).该工作得到国家自然科学基金委、香港研究资助局、福建省自然科学基金、厦门大学校长基金的资助

CCCCC pentadentate chelates with planar Möbius aromaticity and unique properties

本课题充分发挥了厦门大学多学科协同研究优势，通讯作者为夏海平教授（合成、表征）、刘刚教授（生物医学应用）和吕鑫教授（理论计算）。合成实验和结构表征由朱从青（第一作者，目前在麻省理工学院、2005年诺贝尔化学奖得主Richard Schrock教授课题组从事博士后研究）完成；生物医学应用由杨彩霞（共同第一作者）、林凎、杨宇惠、王晓勇合作完成；理论计算由朱军、王永恒、朱从青完成。美国NIH的陈小元教授参与了生物医学应用的讨论。该研究工作得到国家自然科学基金委、科技部项目的支持。The coordinating atoms in polydentate chelates are primarily heteroatoms. We present the first examples of pentadentate chelates with all binding atoms of the chelating agent being carbon atoms, denoted as CCCCC chelates. Having up to five metal-carbon bonds in the equatorial plane has not been previously observed in transition metal chemistry. Density functional theory calculations showed that the planar metallacycle has extended Craig-Möbius aromaticity arising from 12-center–12-electron dπ-pπ π-conjugation. These planar chelates have broad absorption in the ultraviolet-visible–near-infrared region and, thus, notable photothermal performance upon irradiation by an 808-nm laser, indicating that these chelates have potential applications in photothermal therapy. The combination of facile synthesis, high stability, and broad absorption of these complexes could make the polydentate carbon chain a novel building block in coordination chemistry.the National Basic Research Program of China (nos. 2012CB821600 and 2014CB744503) , the National Science Foundation of China (nos. 21332002, 81422023, 51273165, 21490573, and 21573179)

Stabilization of anti-aromatic and strained five-membered rings with a transition metal

1981年诺贝尔化学奖获得者、美国康奈尔大学RoaldHoffmann教授评价该项工作说：'The　paper is an excellent one--it's　quite a mazing that the parent Os　system,molecule 1,chooses to give the osmapentalyne'。德国化学家Uwe Rosenthal教授等在同期《自然—化学》杂志的《News and Views》栏目以《Breaking the rules》为题撰文评述了这一研究成果。全文地址：http://www.nature.com/nchem/journal/vaop/ncurrent/pdf/nchem.1702.pdfAnti-aromatic compounds, as well as small cyclic alkynes or carbynes, are particularly challenging synthetic goals. The combination of their destabilizing features hinders attempts to prepare molecules such as pentalyne, an 8π-electron anti-aromatic bicycle with extremely high ring strain. Here we describe the facile synthesis of osmapentalyne derivatives that are thermally viable, despite containing the smallest angles observed so far at a carbyne carbon. The compounds are characterized using X-ray crystallography, and their computed energies and magnetic properties reveal aromatic character. Hence, the incorporation of the osmium centre not only reduces the ring strain of the parent pentalyne, but also converts its Hückel anti-aromaticity into Craig-type Möbius aromaticity in the metallapentalynes. The concept of aromaticity is thus extended to five-membered rings containing a metal–carbon triple bond. Moreover, these metal–aromatic compounds exhibit unusual optical effects such as near-infrared photoluminescence with particularly large Stokes shifts, long lifetimes and aggregation enhancement

Heterometallic Clusters with Uranium-Metal Bonds Supported by Double-Layer Nitrogen-Phosphorus Ligands

International audienceCONSPECTUS: Heterometallic clusters with M-M bonds have significantly interested chemists because of their attractive structures and synergistic effects in small-molecule activation and catalysis. However, reports of the isolation of heterometallic clusters with uranium-transition metal (U-TM) bonds remain very limited. In this Account, we describe our research in the construction of heterometallic molecular clusters with multiple U-TM single or multiple bonds supported by novel double-layer N-P ligands. Multimetallic synergistic catalysis and small-molecule activation with these species are also summarized. First, according to the hard-soft acid-base theory, we employed a three-armed N-P ligand, which can be used to construct heterometallic clusters with four or six U-Ni bonds. This strategy was also effective in the construction of complexes with direct rare earth metal-TM bonding. The similar two-armed N-P ligands also are effective platforms for the synthesis of heterometallic complexes with U-Ni, U-Pd, and U-Pt bonds. Second, a set of heterometallic clusters featuring U Rh, U Co, and U Fe triple bonds were constructed under routine experimental conditions. X-ray diffraction analysis of these clusters exhibits the shortest U-TM bond distance (1.9693(4) angstrom for the U Fe triple bond) in these complexes. Theoretical studies reveal that the nature of the triple bond is one covalent sigma bond and two TM -> U dative pi bonds. A large Wiberg bond index (WBI) of 2.93 and a significant degree of covalency for the U TM triple bonds were also found in these complexes. Third, these uranium complexes supported by the double-layer N-P ligands exhibit great potential in small-molecule activation. For instance, N-2 cleavage without an external reducing agent was achieved by a U(III)-P(III) synergistic six-electron reduction. The synergism between U(III) and P(III) enables the activation of other small molecules, such as O-2, P-4, and As-(nano)(0), and highlights the importance of the P atom in the double-layer N-P ligand for the activation of small molecules. A heterometallic cluster with U-Rh bonds can break the strong N N triple bond in N-2 in the presence of potassium graphite, suggesting a synergistic effect between U and Rh. This multimetallic synergistic effect was also observed in catalytic processes. A heterometallic cluster with U Co triple bonds shows excellent selectivity and activity in the hydroboration of a series of alkynes under mild conditions. These results lead to effective methods for the construction of heterometallic molecular clusters with U-TM single or multiple bonds and could promote the application of heterometallic clusters with U-TM bonds in catalysis and the activation of small molecules

Facile Dinitrogen and Dioxygen Cleavage by a Uranium(III) Complex: Cooperativity Between the Non-Innocent Ligand and the Uranium Center

International audienceActivation of dinitrogen (N-2, 78 %) and dioxygen (O-2, 21 %) has fascinated chemists and biochemists for decades. The industrial conversion of N-2 into ammonia requires extremely high temperatures and pressures. Herein we report the first example of N-2 and O-2 cleavage by a uranium complex, [N((CH2CH2NPPr2)-Pr-i)(3)U](2)(TMEDA), under ambient conditions without an external reducing agent. The N-2 triple bond breaking implies a U-III-P-III six-electron reduction. The hydrolysis of the N-2 reduction product allows the formation of ammonia or nitrogen-containing organic compounds. The interaction between U-III and P-III in this molecule allows an eight-electron reduction of two O-2 molecules. This study establishes that the combination of uranium and a low-valent nonmetal is a promising strategy to achieve a full N-2 and O-2 cleavage under ambient conditions, which may aid the design of new systems for small molecules activation

Dinitrogen cleavage and hydrogenation to ammonia with a uranium complex

International audienceThe Haber–Bosch process produces ammonia (NH3) from dinitrogen (N2) and dihydrogen (H2), but requires high temperature and pressure. Before iron-based catalysts were exploited in the current industrial Haber–Bosch process, uranium-based materials served as effective catalysts for production of NH3 from N2. Although some molecular uranium complexes are known to be capable of combining with N2, further hydrogenation with H2 forming NH3 has not been reported to date. Here, we describe the first example of N2 cleavage and hydrogenation with H2 to NH3 with a molecular uranium complex. The N2 cleavage product contains three uranium centers that are bridged by three imido μ2-NH ligands and one nitrido μ3-N ligand. Labeling experiments with 15N demonstrate that the nitrido ligand in the product originates from N2. Reaction of the N2-cleaved complex with H2 or H+ forms NH3 under mild conditions. A synthetic cycle has been established by the reaction of the N2-cleaved complex with trimethylsilyl chloride. The isolation of this trinuclear imido-nitrido product implies that a multi-metallic uranium assembly plays an important role in the activation of N2