Osmium–carbon multiple bonds: Reduction and C–C coupling reactions

Bolaño, Tamara; Esteruelas, Miguel A.; Oñate, Enrique

doi:10.1016/j.jorganchem.2011.04.029

Cited by 41 publications

(23 citation statements)

References 105 publications

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“…However, osmium is more reducing than ruthenium and, preferring saturated species, stabilizes the saturated oxidized form. 42 [ with the strongly reducing character of osmium and its marked preference to form saturated species, complex 81 undergoes a C α -to-Os migration of the phenoxy group to give the alkylidyne complex OsHCl(OPh){≡CMe}(P i Pr 3 ) 2 (83). In contrast to the latter, compound 82 eliminates ROH to afford OsHCl(=C=CH 2 )(P i Pr 3 ) 2 (84), which is one of the few five-coordinate hydride-vinylidenes known.…”

Section: C-c Bond Activationmentioning

confidence: 99%

Sigma-bond activation reactions induced by unsaturated Os(IV)-hydride complexes

Esteruelas

Oliván

Oñate

2020

Advances in Organometallic Chemistry

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Section: C-c Bond Activationmentioning

confidence: 99%

Sigma-bond activation reactions induced by unsaturated Os(IV)-hydride complexes

Esteruelas

Oliván

Oñate

2020

Advances in Organometallic Chemistry

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“…For instance, the sequential replacement of the chloride ligands of OsHCl 2 (≡CCH=CPh 2 )(P i Pr 3 ) 2 by acetonitrile molecules produces a sequential decrease of the activation energy of the hydride migration from the metal center to the alkylidyne carbon atom, as a consequence of the gradual decrease of the electron richness of the metal center. 11 A carbonyl group increases further the stability of the alkylidene form. 12 …”

Section: Introductionmentioning

confidence: 99%

“…DFT calculations suggest that five-coordinate osmium alkylidene and six-coordinate osmium hydride alkylidyne have similar energies. 11 Therefore, at first glance, the alkylidene form might be accessible, provided there is a viable synthetic approach and relatively high activation energy for the interconversion. Herein we demonstrate that introducing an amide group in the alkyllic chain of the substituent of a terminal alkyne allows control of the regioselectivity of its reaction with OsH 2 Cl 2 (P i Pr 3 ) 2 and generates the otherwise elusive five-coordinate alkylidene osmium derivatives instead of standard hydride alkylidyne complexes.…”

Section: Introductionmentioning

confidence: 99%

Amide-Directed Formation of Five-Coordinate Osmium Alkylidenes from Alkynes

et al. 2015

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The amide-directed synthesis of five-coordinate osmium alkylidene derivatives from alkynes is reported. These types of complexes, which have been elusive until now because of the tendency of osmium to give hydride alkylidyne species, are prepared by reaction of the dihydride OsH2Cl2(PiPr3)2 (1) with terminal alkynes containing a distal amide group. Complex 1 reacts with N-phenylhex-5-ynamide and N-phenylhepta-6-ynamide to give OsCl2{=C(CH3)(CH2)nNH(CO)Ph}(PiPr3)2 (n = 3 (2), 4 (3)). The relative position of carbonyl and NH groups in the organic substrates has no influence on the reaction. Thus, treatment of 1 with N-(pent-4-yn-1-yl)benzamide leads to OsCl2{=C(CH3)(CH2)3NHC(O)Ph}(PiPr3)2 (4). The new compounds are intermediate species in the cleavage of the C–C triple bond of the alkynes. Under mild conditions, they undergo the rupture of the Cα–CH3 bond of the alkylidene, which comes from the alkyne triple bond, to afford six-coordinate hydride–alkylidyne derivatives. In dichloromethane, complex 2 gives a 10:7 mixture of OsHCl2{≡C(CH2)3C(O)NHPh}(PiPr3)2 (5) and OsHCl2{≡CCH(CH3)(CH2)2C(O)NHPh}(PiPr3)2 (6). The first complex contains a linear separation between the alkylidyne Cα atom and the amide group, whereas the spacer is branched in the second complex. In contrast to the case for 2, complex 4 selectively affords OsHCl2{≡C(CH2)3NHC(O)Ph}(PiPr3)2 (7). In spite of their instability, these compounds give the alkylidene–allene metathesis, being a useful entry to five-coordinate vinylidene complexes, including the dicarbon-disubstituted OsCl2(=C=CMe2)(PiPr3)2 (8) and the monosubstituted OsCl2(=C=CHCy)(PiPr3)2 (9).

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“…Carbyne complexes, i.e., transition metal complexes with metal-carbon triple bonds, can be described as analogs of alkynes, whereas a transition metal replaces one of the sp carbons. They have attracted considerable attention because of their remarkable features and their significance as catalysts or reagents for various types of organic transformations [5][6][7][8][9][10][11]. Part of the reactivities of carbynes paralleled that of their organic parents, such as nucleophilic reactions, electrophilic reactions, photochemistry, oxidation and reduction, reactions with chalcogenides, reactions with unsaturated organic substrates (cycloadditions) and substitution on the α carbon (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

Recent Advances in the Reactions of Cyclic Carbynes

Qian¹,

Ding²,

Du³

et al. 2020

Molecules

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The acyclic organic alkynes and carbyne bonds exhibit linear shapes. Metallabenzynes and metallapentalynes are six- or five-membered metallacycles containing carbynes, whose carbine-carbon bond angles are less than 180°. Such distortion results in considerable ring strain, resulting in the unprecedented reactivity compared with acyclic carbynes. Meanwhile, the aromaticity of these metallacycles would stabilize the ring system. The fascinating combination of ring strain and aromaticity would lead to interesting reactivities. This mini review summarized recent findings on the reactivity of the metal–carbon triple bonds and the aromatic ring system. In the case of metallabenzynes, aromaticity would prevail over ring strain. The reactions are similar to those of organic aromatics, especially in electrophilic reactions. Meanwhile, fragmentation of metallacarbynes might be observed via migratory insertion if the aromaticity of metallacarbynes is strongly affected. In the case of metallapentalynes, the extremely small bond angle would result in high reactivity of the carbyne moiety, which would undergo typical reactions for organic alkynes, including interaction with coinage metal complexes, electrophilic reactions, nucleophilic reactions and cycloaddition reactions, whereas the strong aromaticity ensured the integrity of the bicyclic framework of metallapentalynes throughout all reported reaction conditions.

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Osmium–carbon multiple bonds: Reduction and C–C coupling reactions

Cited by 41 publications

References 105 publications

Sigma-bond activation reactions induced by unsaturated Os(IV)-hydride complexes

Sigma-bond activation reactions induced by unsaturated Os(IV)-hydride complexes

Amide-Directed Formation of Five-Coordinate Osmium Alkylidenes from Alkynes

Recent Advances in the Reactions of Cyclic Carbynes

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