Abstract: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 … Show more
“…For example, titanocene vinylimido complexes reacted readily with unsaturated organic substrates (ketones, nitriles, and imines) to form titana‐2,5‐dihydropyrimidines . In our previous work, we showed that osmapyridinium and iso‐osmapyridinium were obtained by reactions between osmium hydrido alkenylcarbynes and nitriles. In the present case, heterocumulene was used as the precursor in the formal [4+2] cyclization to access the metal‐bridged osmacycles that contain main‐group heteroatoms.…”
Treatmento fo smacyclopentadiene derivatives 1 with phenyl or isopropyl isothiocyanate gave the fused five and six-membered osmacycles 2-5 by aformal [4+ +2] cyclization. The facile protonation of the newly generated exocyclic imine in complexes 2-5 afforded conjugation-extended osmacycle derivatives 6-9.C ompounds 2-9 each contain two main-group heteroatoms (N and S) in the fused six-membered ring located at the ortho (for S) and para (for N) positions relative to the osmiumc entre;t hese speciesc an be re-garded as rare osma-1,3-thiazine derivatives and represent the first fused metallathiazine derivatives. In contrast to the non-planar organic 6H-1,3-thiazine, nearly coplanar metallathiazines 8 and 9 can be achievedb yt uning the groups on the two nitrogen atoms. These unique metal-bridged osma-1,3-thiazine derivatives exhibit remarkable stabilities, broad spectrala bsorptions spanning the visible spectra, andc onsiderable photothermal properties, which suggests their potential applications in materialscience.Scheme1.The skeleton structures of metallapentalene (I), aza-metallapentalene (II) and metallathiazinederivatives (III).[a] J.
“…For example, titanocene vinylimido complexes reacted readily with unsaturated organic substrates (ketones, nitriles, and imines) to form titana‐2,5‐dihydropyrimidines . In our previous work, we showed that osmapyridinium and iso‐osmapyridinium were obtained by reactions between osmium hydrido alkenylcarbynes and nitriles. In the present case, heterocumulene was used as the precursor in the formal [4+2] cyclization to access the metal‐bridged osmacycles that contain main‐group heteroatoms.…”
Treatmento fo smacyclopentadiene derivatives 1 with phenyl or isopropyl isothiocyanate gave the fused five and six-membered osmacycles 2-5 by aformal [4+ +2] cyclization. The facile protonation of the newly generated exocyclic imine in complexes 2-5 afforded conjugation-extended osmacycle derivatives 6-9.C ompounds 2-9 each contain two main-group heteroatoms (N and S) in the fused six-membered ring located at the ortho (for S) and para (for N) positions relative to the osmiumc entre;t hese speciesc an be re-garded as rare osma-1,3-thiazine derivatives and represent the first fused metallathiazine derivatives. In contrast to the non-planar organic 6H-1,3-thiazine, nearly coplanar metallathiazines 8 and 9 can be achievedb yt uning the groups on the two nitrogen atoms. These unique metal-bridged osma-1,3-thiazine derivatives exhibit remarkable stabilities, broad spectrala bsorptions spanning the visible spectra, andc onsiderable photothermal properties, which suggests their potential applications in materialscience.Scheme1.The skeleton structures of metallapentalene (I), aza-metallapentalene (II) and metallathiazinederivatives (III).[a] J.
“…As ulfur can be abstracted on treatment with CuCl to furnish the unusualm etallapyridyne species 50.T he aromaticity of the metallapyridine and metallapyridyner ings was also established by ASE and NICS value calculations. [184] Some related aromatic speciesh ave also been prepared including iso-osmapyridiniums, [185] as well as metallapyrimidines and metallapyrimidiniums, [186][187][188] in whicht wo Na toms are includedi nt he six-membered metallacycles.…”
Section: Metallabenzynesmentioning
confidence: 99%
“…Some related aromatic species have also been prepared including iso‐osmapyridiniums, as well as metallapyrimidines and metallapyrimidiniums, in which two N atoms are included in the six‐membered metallacycles.…”
Metallaaromatics can be broadly defined as aromatic compounds in which one of the ring atoms is a transition metal. The metallabenzenes are one important class of these compounds that has undergone extensive study recently. Closely related species such as fused-ring metallabenzenes, heterometallabenzenes, π-coordinated metallabenzenes and metallabenzynes have also attracted considerable attention. Although many metallaaromatics can be considered as metalla-analogues of classic organic aromatic compounds, this is not always the case. Recent seminal studies have shown that metallapentalenes and metallapentalynes, which are metalla-analogues of the anti-aromatic compounds pentalene and pentalyne, are in fact aromatic and highly stable. Very unusual spiro-metallaaromatic compounds have also recently been isolated. In this concepts article, key features of all these intriguing metallaaromatic compounds are discussed with reference to the structural, spectroscopic, reactivity and theoretical studies that have been undertaken. These compounds continue to generate much interest, not only because of the contributions they make to fundamental chemical understanding, but also because of the promise of possible practical applications.
“…Boger and co‐workers reported the inverse electron demand Diels‐Alder reactions of 1,2,4,5‐tetrazines with dienophiles [64] . In 2009, Xia and co‐workers synthesized osmapyridine and osmapyridinium complexes via a [4+2] cycloaddition reaction between 1‐metalla‐1,3‐dienes and nitriles (Scheme 1b) [65–67] . However, the application of Diels‐Alder reaction to transition‐metal involved dinitrogen activation has never been reported.…”
As the strongest triple bond in nature, the N≡N triple bond activation has always been a challenging project in chemistry. On the other hand, since the award of the Nobel Prize in Chemistry in 1950, the Diels‐Alder reaction has served as a powerful and widely applied tool in the synthesis of natural products and new materials. However, the application of the Diels‐Alder reaction to dinitrogen activation remains less developed. Here we first demonstrate that a transition‐metal‐involved [4+2] Diels‐Alder cycloaddition reaction could be used to activate dinitrogen without an additional reductant by density functional theory calculations. Further study reveals that such a dinitrogen activation by 1‐metalla‐1,3‐dienes screened out from a series of transition metal complexes (38 species) according to the effects of metal center, ligand, and substituents can become favorable both thermodynamically (with an exergonicity of 28.2 kcal mol−1) and kinetically (with an activation energy as low as 13.8 kcal mol−1). Our findings highlight an important application of the Diels‐Alder reaction in dinitrogen activation, inviting experimental chemists’ verification.
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