Metallacyclobutadienes: Intramolecular Rearrangement from Kinetic to Thermodynamic Isomers.

Metallacyclobutadienes (MCBDs) are key intermediates of alkyne metathesis reactions. There are in principle two isomerization pathway from kinetic to thermodynamic MCBDs, intermolecular and intramolecular. However, systems that simultaneously isolate two kinds of MCBD isomers have not been achieved, thus restricting the mechanistic studies of the isomerization. Here the reactivity of a metallapentalyne that contains an M≡C bond within the aromatic ring, with alkynes to afford a series of MCBD-fused metallapentalenes is studied. In some cases, both kinetic and thermodynamic products are isolated in the same system, which has never been observed in previous MCBD reactions. Furthermore, the isomerization of MCBD-fused metallapentalenes is investigated both experimentally and theoretically, indicating that it is an intramolecular process involving a metallatetrahedrane (MTd) intermediate. This research provides experimental evidence demonstrating that one MCBD can undergo intramolecular rearrangement to transform into another.

Reasons and promotion strategies of physical activity constraints in obese/overweight children and adolescents.

To explore the reasons for low levels of physical activity in obese/overweight children and adolescents and to propose appropriate strategies to promote their physical activity (PA). This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines by searching and analyzing the literature of studies related to physical activity in obese/overweight children and adolescents published between January 2003 and January 2023 in Web of Science, Scopus, and PubMed databases. A total of 31 relevant studies were included for analysis, of which 16 were quantitative and 15 qualitative. According to these studies, the PA of obese/overweight children and adolescents is mainly constrained by negative factors: Individual, interpersonal, and environmental. Among these factors, low levels of individual motivation and psychological sensitivity and vulnerability, lack of family support, negative social feedback, insufficient protection from government policies, and inadequate support from the built environment are the main reasons that constrain their PA. The promotion of PA in obese/overweight children and adolescents, who are subject to more constraints at all levels, requires a system of security that involves the government, the community, the school, and the family to address the problems they encounter and enhance the sustainability of engagement in PA.

Aromatic chloroosmacyclopentatrienes.

Aromatic metallacycles are of considerable current interest. Reported aromatic metallacycles are mainly those with carbon, nitrogen, oxygen and sulfur. In this work, we report the synthesis and characterization of aromatic chloroosmacyclopentatrienes, which represent the first structurally confirmed metallaaromatic with a chlorine atom in its framework. Single-crystal X-ray diffraction studies show that these planar chloroosmacyclopentatrienes possess a very short Os-ClC distance suggesting M=ClC bond character.

Synthesis and Characterization of a Rhenanaphthalene Isomer.

Exploration of organometallic metallacycles has led to the development of various polycyclic compounds with fascinating structures, which could be used as functional materials. In this work, a new rhenanaphthalene isomer was isolated from the reaction of ReH5 (PMe2 Ph)3 with o-ethynylphenyl alkyne in the presence of excess HCl. Its structure was then identified using the single-crystal X-ray diffraction and NMR spectroscopy. DFT studies suggest that its formation involves two protonation reactions and two migration reactions. This new rhenanaphthalene isomer enriches the family of metallacycles.

Synthesis and Characterization of Cyclopropaosmanaphthalenes Containing a Fused σ-Aromatic Metallacyclopropene Unit.

Metalla-aromatics are important complexes that show unique properties owing to their highly conjugated systems, which show Hückel or Möbius aromaticity. Recently, several metalla-aromatics showing spiro-aromaticity or σ-aromaticity have been reported. Herein, we report the isolation of the first cyclopropametallanaphthalenes, in which the metallacyclopropene ring shows σ-aromaticity and weak hyperconjugative aromaticity. The reaction of OsCl2 (PPh3 )3 with o-ethynylphenyl alkynes in the presence of PPh3 followed by protonation with HCl yielded the first cyclopropametallanaphthalenes. The reaction mechanism and the aromaticity were also investigated by density functional theory studies.

Synthesis and characterization of metallapentalenoxazetes by the [2+2] cycloaddition of metallapentalynes with nitrosoarenes.

Cycloaddition reactions of carbynes in metallacycles with π-bond substrates have been rarely reported. We report the first [2+2] cycloaddition of metallapentalynes with nitrosoarenes to obtain the first metallapentalenoxazetes, and their photophysical and electrochemical properties were studied by UV-Vis spectroscopy and cyclic voltammetry with the help of theoretical calculations.

Synthesis, Characterization and Electronic Structure of Dirhenadehyro[12]annulene Complexes.

Treatment of the SiMe3 -protected dichloro-rhenium carbyne complexes Re{≡CCH=C(R)C≡CSiMe3 }Cl2 (PMe2 Ph)3 (R = CMe3 , 1-adamantyl) with CsF in methanol directly afforded the 12-membered metallacycles {ReCl(PMe2 Ph)3 }2 {≡CCH=C(R)C≡C-}2 . The electronic structure of the metallacycle was investigated by density functional calculations. The UV-vis spectrum of the metallacycle shows a red-shifted band compared to that of the starting dichlorocarbyne complex. Treatment of {ReCl(PMe2 Ph)3 }2 {≡CCH=C(CMe3 )C≡C-}2 with HCl produced the dichloro-rhenium carbyne complex Re{≡CCH=C(CMe3 )C≡CH}Cl2 (PMe2 Ph)3 , which is consistent with the electronic structure of the 12-membered metallacycles.

Metallapentalenofuran: Shifting Metallafuran Rings Promoted by Substituent Effects.

Bulky substituents play important roles in controlling the reaction pathways or producing selected products. This work reports that the shift of metallafuran rings in a metallapentalenofuran complex can be promoted by the substituent effect via a reversible C-H bond reductive elimination and oxidative addition. The starting osmapentalyne, a so-called 7-carbon carbolong complex, was produced by the oxidation of a metallapentalenofuran with FeCl3 . It was then allowed to react with nucleophiles, followed by a C-H activation, to give the aforementioned metallapentalenofuran complex. This work enriches the family of carbolong complexes and reveals a new strategy to promote, but not prevent reactions by the bulky substituents.

Synthesis and Characterization of Photothermal Osmium Carbolong Complexes.

Metallacycles with chelating polydentate conjugated-carbon chain ligands are called carbolong complexes, which are expected to have interesting properties. In this work, the preparation of 12-carbon carbolong complexes in which all of the coordinated atoms in the equatorial plane are carbon atoms was studied. With the help of the well-established mechanism, a new approach to prepare coplanar carbolong complexes bearing different organic functional groups was developed by adding different terminal alkynes in sequence. In the presence of HBF4 , these coplanar carbolong complexes were converted to η3 -allyl osmapentalene derivatives, which can be produced directly from the reaction of cyclopropaosmapentalene 1 with terminal alkynes in the presence of AgBF4 under anhydrous conditions. This study offers a new route for the preparation of functional osmium carbolong complexes with excellent photothermal properties, which can be used to prepare photothermal materials.

Cylindrical NIR-Responsive Metallopolymer Containing Möbius Metalla-aromatics.

Metalla-aromatic complexes are very stable and excellent light-absorbing compounds, owing to their highly conjugated frameworks. The metallopolymers containing metalla-aromatic substructures consist of a new type of functional polymer, because they exhibit characteristics of both metalla-aromatic and polymeric units. Herein, we reported a corn-like cylindrical metallopolymer, prepared from the controlled polymerization of N-isopropylacrylamide (NIPAM) by a polyrotaxane-based macroinitiator, followed by postpolymerization modification with a photothermal metalla-aromatic complex. The corn-like shape of this metallopolymer was confirmed by transmission electron microscopy (TEM). Combining the photothermal effect of the metalla-aromatic unit and the thermosensitive property of PNIPAM, the corn-like metallopolymer exhibits a NIR-responsive behavior and represents a new smart material.

Metallapentalenofurans and Lactone-Fused Metallapentalynes.

Metalla-aromatics are attractive species because they exhibit the properties of both organometallics and aromatics. Reported metal-bridged polycyclic aromatic complexes, as well as Möbius aromatic species, are still rare. Herein, we present the construction of two new metal-bridged polycyclic aromatic frameworks, α-metallapentalenofurans and lactone-fused metallapentalynes, by the reactions of osmapentalyne with terminal aryl alkynes in the presence of H2 O or HBF4 /H2 O, respectively. DFT calculations show that the α-metallapentalenofurans possess rare planar Craig-type Möbius aromaticity derived from the 11-center-12-electron dπ -pπ π-conjugation. This study offers a new route for the construction of polycyclic metalla-aromatics as well as planar Möbius aromatic species.

Synthesis and Characterization of Dirhenadehydro[12]annulenes.

The 12-membered-ring metallacycles [mer-Re{≡CCH=C(R)C≡C-}Cl(PMe2 Ph)3 )]2 (R=CMe3 , 1-adamantyl), which are organometallic analogues of antiaromatic octadehydro[12]annulene, are prepared by heating the methyl carbyne complexes mer-Re{≡CCH=C(R)C≡CH}(CH3 )Cl(PMe2 Ph)3 . An intermolecular σ-bond metathesis between the Re-CH3 bond and the acetylenic C-H bond is proposed for their formation.

Synthesis and characterization of rhenabenzyne complexes.

Reactions of [ReH(5)(PMe(2)Ph)(3)] with alkynols HC≡CC(OH)(R)C≡CSiMe(3) (R=tBu, iPr, 1-adamantyl) in the presence of HCl give the vinylcarbyne complexes [Re{≡CCH=C(R)C≡CSiMe(3)}Cl(2)(PMe(2)Ph)(3)], which react with tBuMgCl to give [Re{≡CCH=C(R)C≡CSiMe(3)}HCl(PMe(2)Ph)(3)]. Treatment of [Re{≡CCH=C(R)C≡CSiMe(3)}HCl(PMe(2)Ph)(3)] with nBu(4)NF gives [Re{≡CCH=C(R)C≡CH}HCl(PMe(2)Ph)(3)], which first isomerizes to the bicyclic complexes [Re{CH=CH-C(R)=CCH=}Cl(PMe(2)Ph)(3)], and then to the rhenabenzynes [Re{≡CCH=C(R)CH=CH}Cl(PMe(2)Ph)(3)]. The NMR spectroscopic and structural data as well as the aromatic stabilization energy (ASE) and nucleus-independent chemical-shift (NICS) values suggest that these rhenabenzynes have aromatic character.