Jiangxi Chen

Synthesis and Characterization of a Rhenabenzyne Complex

There has been much interest in the chemistry of transitionmetal-containing metallaaromatic compounds. In particular metallabenzenes, which are organometallic compounds derived by the formal replacement of a C H group in benzene with an isolobal transition metal fragment, have attracted considerable attention. Previous studies have led to the isolation and characterization of an impressive number of stable metallabenzenes, especially those of osmium, iridium, platinum, ruthenium, 11] and rhenium. Metallabenzynes, which are organometallic compounds derived from formal replacement of a carbon atom or a C H group in benzyne with an isolobal transition metal fragment, are closely related to metallabenzenes. At first sight, one might expect that metallabenzynes may be too unstable to be isolated, because organic compounds with a C C bond in the six-membered ring, for example, benzyne and cyclohexyne, are thermally highly unstable because of ring strain. Nevertheless, in recent years, several stable osmabenzynes have been isolated and their interesting chemical properties have been demonstrated. For example, osmabenzynes, such as metallabenzenes and aromatic compounds, can undergo electrophilic substitution reactions. Compared with the chemistry of metallabenzenes, that of metallabenzynes is much less developed. For instance, while stable metallabenzenes with several metals are known, to date, isolated metallabenzynes are limited to those containing an osmium center. The synthesis and characterization of metallabenzynes with metals other than osmium remain important goals in the development of the chemistry of these compounds. Herein, we report the preparation and structural characterization of the first stable rhenabenzyne complex. The rhenabenzyne complex was synthesized by the synthetic route outlined in Scheme 1. Reaction of [ReH5(PMe2Ph)3] (1) with alkynol 2 in the presence of HCl produced the dichlorocarbyne complex 3. Treatment of 3 with tert-butylmagnesium chloride produced the hydridochlorocarbyne complex 4, likely through the intermediate [Re( C-CH=C(tBu)C CSiMe3)Cl(tBu)(PMe2Ph)3], which underwent b-H elimination. Experimentally, the side product CH2=CMe2 has indeed been detected by in situ H NMR spectroscopy. Complex 4 was isolated as a blue solid in 63% yield, and could be stored under nitrogen at room temperature for a week without appreciable decomposition. The Me3Si group in 4 could be easily removed by treatment of 4 with nBu4NF to give carbyne complex 5. The new carbyne complexes 3–5 can be readily identified by NMR spectroscopy. For example, the H NMR spectrum of 5 shows the Re–H signal at 1.85 ppm as a doublet of triplets with P–H coupling constants of 50.0 and 28.0 Hz, the Re CCH signal at 4.42 ppm, and the C CH signal at 3.22 ppm; the C{H} NMR spectrum of 5 shows the Re C signal at 254.1 ppm and the C CH signals at 88.4 and 83.8 ppm. In the solid state, complex 5 can be stored under nitrogen for at least three days without any decomposition, however, it is thermally unstable in solution. When a solution of 5 in benzene was stored at room temperature for three days, complex 5 completely rearranged to form complex 6. The rearrangement reaction was complete within 4 h when a solution of 5 in benzene/hexane was heated at 50 8C. Complex Scheme 1. Preparation of rhenabicyclo[3.1.0]hexatriene 6 and rhenabenzyne 7.

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.

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.

Amphipathic metal-containing macromolecules with photothermal properties

Metal-containing macromolecules with extraordinary properties have attracted a great deal of interest owing to their potential application in the development of functional materials. Here, we report the synthesis of novel amphipathic metal-containing macromolecules by the click reaction of methoxypolyethylene glycol azides with a unique metalla-aromatic complex containing a terminal alkynyl group. The resultant amphipathic macromolecules self-assembled into micellar nanoparticles with diameters of ca. 145 nm in water, which exhibited high stability, water-dispersibility, biocompatibility, and excellent photothermal behavior under 808 nm laser irradiation. Our study opens promising avenues for providing metal-containing macromolecules as photothermal materials.

Photothermal Möbius aromatic metallapentalenofuran and its NIR-responsive copolymer

Mobius aromatics are very interesting and rare complexes owing to their brand-new chemistry and interesting properties. In this work, metallapentalenofurans with thiophene groups were easily prepared from the reaction of metallapentalyne, terminal arylalkynes, and water in air. The metallapentalenofuran containing a terthiophene moiety showed a good photothermal effect and was the first photothermal Mobius aromatic complex induced by J-aggregates. This photothermal metallapentalenofuran was chemically modified to carry an olefinic group and then was co-polymerized with oligo-(ethylene glycol)methacrylate to afford a thermoresponsive copolymer, whose phase transition behavior can be triggered by near-infrared radiation at 808 nm. This near-infrared-responsive metal-containing copolymer represents a new stimuli-responsive macromolecule.

Effects of substituents on the formation of rhenium carbyne and η2-vinyl complexes from the reactions of ReH5(PMe2Ph)3 with terminal alkynes

The reactions of the rhenium polyhydride complex ReH5(PMe2Ph)3 with HCCAr (Ar = p-C6H4CF3, o-C6H4CF3, o-C6H4Me and o-C6H4Br) have been carried out. Treatment of ReH5(PMe2Ph)3 with HCC(p-C6H4CF3) in the presence of two equiv. of HCl produces a mixture of the carbyne complex Re(CCH2(p-C6H4CF3))Cl2(PMe2Ph)3 and the η2-vinyl complex Re(η2-CH2C(p-C6H4CF3))Cl2(PMe2Ph)3. Treatment of ReH5(PMe2Ph)3 with HCCAr (Ar = o-C6H4CF3, o-C6H4Me, o-C6H4Br) in the presence of two equiv. of HCl produces only the carbyne complexes Re(CCH2Ar)Cl2(PMe2Ph)3. The mechanism of the reactions of ReH5(PMe2Ph)3 with HCCR has also been studied with the aid of DFT calculations, which suggests that the reactions are kinetically controlled and the pathways leading to the carbyne and η2-vinyl complexes are influenced by the steric and electronic effects of the substituents of the alkynes.

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.

Correction: Photothermal Möbius aromatic metallapentalenofuran and its NIR-responsive copolymer

Correction for ‘Photothermal Mobius aromatic metallapentalenofuran and its NIR-responsive copolymer’ by Zhengyu Lu et al., Polym. Chem., 2018, 9, 2092–2100.

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.