Osmapyridine and Osmapyridinium from a Formal [4+2] Cycloaddition Reaction

Herein, we describe a novel, green, and efficient synthesis of a series of different substituted osmanaphthalynes (including -H, -Br, -I, -CH and -CF ) and the first examples of the preparation of α-osmaanthracyne and α-osmaphenanthryne by means of a visible light-induced intramolecular cyclization reaction of their corresponding osmium hydrido alkenylcarbyne complexes. This visible-light-driven method provides an efficient and straightforward approach to afford the desired fused metal heterocyclic complexes constructed with an Os atom as the metal center in high yield under mild conditions.

Section: Methodssupporting

confidence: 87%

A Visible‐Light‐Induced Strategy To Construct Osmanaphthalynes, Osmaanthracyne, and Osmaphenanthryne

Zhang

Lü

et al. 2018

“…The X‐ray structure (Figure ) clearly shows that complex 2 a contains an essentially planar six‐membered metallapyridinium unit. The structural features associated with the metallacycle of 2 a are similar to those of our previously reported osmapyridinium . The mean deviation from the least‐squares plane through Os1, N1, and C1–C4 is 0.0584 Å, and the sum of the angles of the six‐membered ring is 718.2°, which is very close to the ideal value of 720°.…”

Section: Resultssupporting

confidence: 83%

Synthesis of Cyclic Vinylidene Complexes and Azavinylidene Complexes by Formal [4+2] Cyclization Reactions

Chen

Huang

Lü

et al. 2016

Self Cite

Reactions of the hydrido-butenylcarbyne complex [OsHCl2(≡CC(PPh3)=CHEt)(PPh3)2]BF4 (1) with nitriles RC≡N (R=2-cyclopropyl-2-oxopropyl, 3-amino-2-oxobutyl) lead to six-membered cyclic vinylidene complexes 3 and azavinylidene complexes 4, that is, iso-osmapyridiniums. Treatment of 1 with excess 2-formylbenzonitrile at reflux temperature in CHCl3 in the presence of air produces a fused osmapyridinium 8, which is first oxidized to the tricyclic iso-osmapyridinium derivative 7, then to iso-osmapyridinium 9, which contains a fused naphthalenone fragment. The conversion of iso-osmapyridinium 9 (with a vinylidene segment) to the iso-osmapyridinium compounds 10 and 11 (with azavinylidene segments) was achieved in the presence of a hydrogen halide, such as HCl or HI. The molecular structures of the complexes synthesized were confirmed by X-ray studies. Moreover, the aromatic stabilization energy and nucleus-independent chemical-shift values of the osmapyridiniums and the strain in the iso-osmapyridinium rings were investigated by DFT calculations.

“…The significantly downfield 1 H and 13 C NMR chemical shifts of C α ‐H (typically ranging between 12.6–23.1 ppm for Os, 13.7–18.1 ppm for Ru, and 10.4–14.7 ppm for Ir) and C α (typically ranging between 143.1–262.0 ppm for Os, 244.8–294.1 ppm for Ru, and 176.9–302.1 ppm for Ir) of metallabenzenes indicate the carbene character of the corresponding M−C bonds. However, the 1 H NMR signal of osmapyridinium (C α −H: 48.0 ppm) is unusually downfield compared to typical metallaaromatic systems, which is attributed to its paramagnetism …”

Section: Structural Features Of the M−c Bonds Within Six‐membered Metmentioning

confidence: 99%

“…In some cases, the metal–carbon bonds of metallaaromatics possess carbene character, which are suitable to undergo insertion reaction with unsaturated molecules. In 2009, we reported an osmapydinium complex 33 , which was prepared by a formal [4+2] cycloaddition reaction of metalladiene complex with nitrile . As shown in Scheme , the Os−C bond of 33 reacted with propargyl alcohols PhCH(OH)C≡CH or EtCH(OH)C≡CH, producing the corresponding insertion products 34 a or 34 b in high yield …”

Section: Reactions With Unsaturated Compoundsmentioning

confidence: 99%

Reactions of Metal–Carbon Bonds within Six‐Membered Metallaaromatic Rings

Zhou

Zhang

2018

Metallaaromatics represent a distinct and attractive class of heterocycles, which have greatly expanded the library of known aromatics. They have garnered extensive research interest on account of their unique properties, organometallic reactivity, and aromaticity. The metal-carbon bonds have been regarded as the most active reaction sites of metallaaromatics and a variety of related reactions have been demonstrated in the literature. This Minireview summarized recent findings on the reactivity of the metal-carbon bonds, mainly relevant to the representative metallaaromatics with six-membered ring scaffolds. A series of reactions occurred on the metal-carbon bonds, including the nucleophilic addition reactions, nucleophilic aromatic substitution reactions, electrophilic addition reactions, reactions with unsaturated compounds, and migratory insertion reactions, have been classified. These reactions demonstrate that the metal-carbon bonds of metallaaromatics can undergo typical reactions for both aromatic species and metal carbene/carbyne complexes. Meanwhile, the reactivity trends of the metal-carbon bonds are strongly affected by the metal centers and the effect of the corresponding substituents of metallacycles.