Metal-induced cyclization of functionalized alkynes represents one of the most general approaches to prepare organic heterocycles. AlthoughR u II centers are well-established to promote alkyne to vinylidener earrangements and many Ru II -mediated alkyne cyclizations have been rationalized to be the resultso fp ost-vinylidene transformations, recent discoveries indicate that Ru II centers can serve as electrophiles and induce alkyne cyclizationsw ithoutv inylidene intermediacy. In this Minireview,a no verview of the Ru II -induced cyclization of heteroatom-functionalized alkynes in the last decadei sp rovided, with an emphasis on the discoveries and validations of the unconventional "non-vinylidene-involving" pathways. Recent Progress of Ruthenium-Induced Cyclization of AlkynesResearcho nt he activation of heteroatom-functionalizeda lkynes by Ru II complexes for oxygen-and nitrogen-containing heterocycles of different ring sizes (5-to 8-membered) continues unabated. Most reported Ru complexes ares upported by Cp (Cp = cyclopentadienyl) or structurally analogous h 5 -ligands, amine-or mixed amine/phosphine-basedc helates. In general, the catalyst loadings are almost lower than 10 mol %a nd can be as low as 0.5 mol %. Although the cyclizations are mostly demonstrated with terminala lkynes, there are increasing number of successful reports on cyclizing internal alkynes.T he use of proton shuttles( internal or external bases which facilitate protont ransfer) has been found to be critical in many of these catalytic reactions. Noteworthy,s everal recent studies clearly indicatet hat the "vinylidene-involving" and "non-vinylidene-involving" pathwaysd epicted in Scheme 1are competing mechanisms. In this section, Ru-catalyzedc yclization of heteroatom-functionalized alkynes in the last decade is discussed in chronological order,e xcept in the cases of certain serial or outlying works. Catalytic Ru II -mediated cyclizations of N/O-functionalized alkynesthrough "vinylidene-involving" pathwaysThe successful isolations of Fe-, Ru-, and Os-oxacarbene complexesf rom the reactions between homopropargylic/bis-ho-Scheme1.(a) Established mechanisms for the formation of Ru-vinylidene species. (b) Electrophilic cyclizationso fheteroatom-functionalized alkynes induced by Ru.[a] Dr.Scheme8.Ru-catalyzed cycloisomerizations of alkynols into 5-, 6-and 7membered oxacycles developed by Jia and co-workers. [13,14] Scheme7.Ru-catalyzed cyclizationso fa niline-and phenol-tethered alkynes into indoles and benzofurans, respectively developed by Grotjahn and coworkers. [11,12] Scheme9.Ru-catalyzed cycloisomerizations of hydroxyl-and amine-substituteda lkynes into isochromenes, indolesa nd isoquinolinones developedby Blacquiereand co-workers. [15][16][17] Scheme10. Ru-catalyzed cycloisomerizations of alcohol-tethered alkynes developedb yWen and co-workers. [18] Chem.E ur.Scheme20. Isolation of, and proposed formation mechanism for 4a.The synthesis of 4b is also depictedf or reference [31].Scheme21. Isolation of, and proposed formation mechanism for...

Ruthenafuran and osmafuran monocationic complexes [Ru([14]aneS4)(C ∧ O)] + or [M(bpy) 2 (C ∧ O)] + (C ∧ O = anionic bidentate chelate [C(OR)CHC(Ph)O] − ; [14]aneS4 = 1,4,8,11-tetrathiacyclotetradecane; M = Ru, Os; bpy = 2,2′-bipyridine) have been prepared from reactions between phenylynone HCC(CO)Ph and [Ru ([14]aneS4)Cl 2 ] or [M-(bpy) 2 Cl 2 ] in alcoholic solvents ROH. The formation of metal− vinylidene intermediate, followed by nucleophilic attack by RO − , and carbonyl group coordination to the metal center are believed to be the key steps in the formation of these metallafurans. The nature of the anionic C ∧ O ligand was investigated by electrochemical, spectroscopic, and theoretical means. ■ INTRODUCTIONActivation of alkynes for functional and novel organic products by transition-metal complexes is one of the most important topics in organometallic chemistry. 1 It is well documented that alkynes generally interact with d6-transition-metal centers through the formation of reactive yet sometimes isolable metal−vinylidene intermediates, which can further transform into other carbon-rich organometallic species including metal− acetylide, −acyl, −allenylidene, −alkoxycarbene, and −carbyne complexes, depending on the functionality of the alkynes and the reactants available in the reaction mixture. 2, 3 Our group has been scrutinizing the reactivity between a variety of organic substrates and structurally well-defined d6-transition-metal complexes, and the spectroscopic properties of the derived organometallic complexes. 4 As an extension of this research direction, we now present the reactivity of a specific type of alkyne, phenyl-ynone HCC(CO)Ph, toward [Ru([14]aneS4)Cl 2 ] and [M(bpy) 2 Cl 2 ] (M = Ru and Os; [14]aneS4 = 1,4,8,11-tetrathiacyclotetradecane; bpy = 2,2′-bipyridine) in alcoholic solvents ROH. Our results reveal that the resultant products are metallafuran monocationic complexes [Ru([14]aneS4)(C ∧ O)] + and [M(bpy) 2 (C ∧ O)] + , where C ∧ O represents an anionic bidentate [C(−OR)CHC(−Ph) O] − chelate. It is worth mentioning that metallafuran and other members of metallacycles have received extensive attention in the field of organometallic and theoretical chemistry, 5,6 and the reactivity reported in this work may represent a general synthetic approach for different metallafurans. Moreover, the electronic properties of the ruthenafurans and osmafuran have been probed by electrochemical, spectroscopic, and theoretical studies. ■ RESULTS AND DISCUSSION Synthesis and Characterizations. Ruthenafuran and osmafuran monocationic complexes 1−3 have been prepared in high yield (50−80%) from reactions between phenyl-ynone HCC(CO)Ph and metal precursors [Ru([14]aneS4)Cl 2 ] or [M(bpy) 2 Cl 2 ] (M = Ru, Os) in alcoholic solvents (Scheme 1).These metallafuran complexes are air stable in both solution and solid forms. The alkoxy group attached to the C α is determined by the alcoholic solvent used (cf. synthesis of 1 and 1′). The carbenoid character for the M−C bonds is indicated by the low-field 13 C NMR ...

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The two families of Ru -chromene and -chromone complexes isolated in this work represent the first examples of metalated chromene and chromone complexes synthesized through transition-metal-mediated cyclization of phenol-tethered ynone. These unprecedented metalated heterocyclic compounds exhibit remarkable features, such as pH-switchable metal-carbon bonding interactions, photo-triggerable release of organic chromone upon visible-light irradiation, and superior antioxidative property to their organic analogue (1,4-benzopyrone). These findings not only offer mechanistic insights into metal-induced activation of functionalized alkynes, but also add a new dimension to rational design of antioxidants and photo-responsive drug delivery systems.

Indolizine zwitterion coordinated metal species have been commonly proposed as intermediates in the mechanisms of metal-catalyzed cycloisomerization of propargylic pyridines for indolizines. Yet, it is only recently that the first metal–indolizine complexes have been isolated by our group. Considering from the perspective of molecular materials, the π-interaction between the dπ(M) and the π-system of the indolizine skeleton in the electronic ground or excited states may allow charge delocalization and offer functionalities for optoelectronic applications. We herein report the synthesis and spectroscopic and theoretical investigations on two classes of Ru–indolizine zwitterion complexes. The synthetic strategy employed, i.e., cycloisomerization of propargylic pyridines, represents a general preparation method for stable metal–indolizine complexes. Indolizine zwitterions in this work have been found to exhibit strong trans effect. Spectroscopic studies on these complexes reveals the tunability of the π*(indolizine) level and its impact on the luminophores nearby. Overall, indolizine zwitterion represents a new class of organometallic ligand with high potential in the design of functional molecular electronic/photonic elements.

Chemical bonds, including covalent and ionic bonds, endow semiconductors with stable electronic configurations but also impose constraints on their synthesis and lattice-mismatched heteroepitaxy. Here, the unique multi-scale van der Waals (vdWs) interactions are explored in one-dimensional tellurium (Te) systems to overcome these restrictions, enabled by the vdWs bonds between Te atomic chains and the spontaneous misfit relaxation at quasi-vdWs interfaces. Wafer-scale Te vdWs nanomeshes composed of self-welding Te nanowires are laterally vapor grown on arbitrary surfaces at a low temperature of 100 °C, bringing greater integration freedoms for enhanced device functionality and broad applicability. The prepared Te vdWs nanomeshes can be patterned at the microscale and exhibit high field-effect hole mobility of 145 cm2/Vs, ultrafast photoresponse below 3 μs in paper-based infrared photodetectors, as well as controllable electronic structure in mixed-dimensional heterojunctions. All these device metrics of Te vdWs nanomesh electronics are promising to meet emerging technological demands.

Metallafuran complexes with a fused five‐membered phosphonium ring were synthesized from reactions between terminal ynones HC≡C(C=O)R and cis‐[Ru/Os(dppm)2Cl2] (dppm=1,1‐bis(diphenylphosphino)methane). A metal–vinylidene‐involving pathway was found to be an energetically feasible formation mechanism for these complexes. These phosphonium‐containing metallafurans, like many phosphonium‐functionalized drugs, have the ability to induce mitochondrial dysfunction. They also exhibit stronger cytotoxicity against several human cancer cell lines in comparison with their metal precursors and the classic anticancer drug cisplatin. Overall, this work provides structural and mechanistic insights for the rational design of functional metallacycles via activation of alkynes by RuII and OsII centers.

Two types of unexpected quinolizinium complexes were obtained from the reactions between pyridine-functionalized propargylic alcohol HCCC(OH)(Ph)(CH₂(2-py)) (L1) and cis-[M(L^L)₂Cl₂] (M = Ru, Os; L^L = dppm, bpy).