Annulation of Metallabenzenes: From Osmabenzene to Osmabenzothiazole to Osmabenzoxazole

Wang, Tongdao; Li, Shunhua; Zhang, Hong; Lin, Ran; Han, Feifei; Lin, Yumei; Wen, Ting Bin; Xia, Haiping

doi:10.1002/anie.200902738

Cited by 66 publications

(46 citation statements)

References 57 publications

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“…On the other hand, the good stability of our osmacycles in air, water, and heat may enable their potential applications as materials. We have investigated, for the first time, the optical, 25 electrochemical, 15,30 and magnetic 36 properties of these intriguing metalla-aromatics. Some of these properties are promising for use in materials science.…”

Section: Discussionmentioning

confidence: 99%

“…We reported the first S N Ar reaction of metallabenzene under ambient conditions. 25 Osmabenzene 5 reacted with MeONa/MeOH to generate osmabenzothiazole 16 (Scheme 6). The proposed mechanism revealed that the addition reaction of 5 with MeONa gave intermediate C, which then underwent intramolecular nucleophilic attack to afford intermediate D.…”

Section: Osmabenzenementioning

confidence: 99%

“…Heating 16 in wet chloroform gave osmabenzothiazolone 52 (Scheme 19), 25 as a result of the hydrolysis of the methoxy group on the thiazole ring. When osmabenzothiazole 16 was treated with silver nitrate and then NaOH, another fused metallaaromatic compound, osmabenzoxazole sulfonate 53, was obtained (Scheme 19).…”

Section: Osmabenzothiazolone and Osmabenzoxazolementioning

confidence: 99%

“…When osmabenzothiazole 16 was treated with silver nitrate and then NaOH, another fused metallaaromatic compound, osmabenzoxazole sulfonate 53, was obtained (Scheme 19). 25 The formation of 53 involved the oxidation and ring-opening of the thiazole moiety. The subsequent coordination of the ester carbonyl oxygen atom to the osmium center formed the new oxazole ring.…”

Section: Osmabenzothiazolone and Osmabenzoxazolementioning

confidence: 99%

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The Chemistry of Aromatic Osmacycles

et al. 2013

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A romatic compounds, such as benzene and its derivatives, porphyrins, fullerenes, carbon nanotubes, and graphene, have numerous applications in biomedicine, materials science, energy science, and environmental science. Metalla-aromatics are analogues of conventional organic aromatic molecules in which one of the (hydro)carbon segments is formally replaced by an isolobal transition-metal fragment. Researchers have studied these transition-metalcontaining aromatic molecules for the past three decades, particularly the synthesis and reactivity of metallabenzenes. Another focus has been the preparation and characterization of other metalla-aromatics such as metallafurans, metallapyridines, metallabenzynes, and more. Despite significant advances, remaining challenges in this field include the limited number of convenient and versatile synthetic methods to construct stable and fully characterized metalla-aromatics, and the relative shortage of new topologies.To address these challenges, we have developed new methods for preparing metalla-aromatics, especially those possessing new topologies. Our synthetic efforts have led to a large family of closely related metalla-aromatics known as aromatic osmacycles. This Account summarizes the synthesis and reactivity of these compounds, with a focus on features that are different from those of compounds developed by other groups. These osmacycles can be synthesized from simple precursors under mild conditions. Using these efficient methods, we have synthesized aromatic osmacycles such as osmabenzene, osmabenzyne, isoosmabenzene, osmafuran, and osmanaphthalene. Furthermore, these methods have also created a series of new topologies, such as osmabenzothiazole and osmapyridyne. Our studies of the reactivity of these osma-aromatics revealed unprecedented reaction patterns, and we demonstrated the interconversion of several osmacycles.Like other metalla-aromatics, osma-aromatics have spectroscopic features of aromaticity, such as ring planarity and the characteristic bond lengths between a single and double bond, but the osma-aromatics we have prepared also exhibit good stability towards air, water, and heat. Indeed, some seemingly unstable species proved stable, and their stability made it possible to study their optical, electrochemical, and magnetic properties. The stability of these compouds results from their aromaticity and the phosphonium substituents on the aromatic plane: most of our osma-aromatics carry at least one phosphonium group. The phosphonium group offers stability via both electronic and steric mechanisms. The phosphonium acts as an electron reservoir, allowing the circulation of electron pairs along metallacycles and lowering the electron density of the aromatic rings. Meanwhile, the bulky phosphonium groups surrounding the aromatic metallacycle prevent most reactions that could decompose the skeleton.

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