Electronic Communication in Binuclear Osmium- and Iridium-Polyhydrides

Cancela, Lara; Esteruelas, Miguel A.; Galbán, Javier; Oliván, Montserrat; Oñate, Enrique; Vélez, Andrea; Vidal, Juan C.

doi:10.1021/acs.inorgchem.0c03680

Cited by 10 publications

(7 citation statements)

References 79 publications

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“…In spite of it being argued as the reason for the degradation of some hydrogenation catalysts 28 and of being known for the rupture of P–C bonds of some quaternary phosphonium salts under catalytic conditions, 29 the hydrogenolysis of P–C bonds is a slightly common reaction. It should be furthermore mentioned that, although complex 1 has shown a notable ability to activate σ-bonds, 30 including C–C, 31 C–N, 32 and C–O 33 among others, it had never participated in the rupture of a C–P bond.…”

Section: Resultsmentioning

confidence: 99%

Alternative Conceptual Approach to the Design of Bifunctional Catalysts: An Osmium Germylene System for the Dehydrogenation of Formic Acid

et al. 2021

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The reaction of the hexahydride OsH 6 (P i Pr 3 ) 2 with a P,Ge,P-germylene-diphosphine affords an osmium tetrahydride derivative bearing a Ge,P-chelate, which arises from the hydrogenolysis of a P–C(sp 3 ) bond. This Os(IV)–Ge(II) compound is a pioneering example of a bifunctional catalyst based on the coordination of a σ-donor acid, which is active in the dehydrogenation of formic acid to H 2 and CO 2 . The kinetics of the dehydrogenation, the characterization of the resting state of the catalysis, and DFT calculations point out that the hydrogen formation (the fast stage) exclusively occurs on the coordination sphere of the basic metal center, whereas both the metal center and the σ-donor Lewis acid cooperatively participate in the CO 2 release (the rate-determining step). During the process, the formate group pivots around the germanium to approach its hydrogen atom to the osmium center, which allows its transfer to the metal and the CO 2 release.

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Section: Resultsmentioning

confidence: 99%

Alternative Conceptual Approach to the Design of Bifunctional Catalysts: An Osmium Germylene System for the Dehydrogenation of Formic Acid

et al. 2021

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“…In contrast to 11 and 12, complex 13 is formed by two different osmium(IV) fragments bridged by an asymmetric pentadentate ligand, which acts as a monoanionic C,N-chelate with the trihydride OsH 3 (P i Pr 3 ) 2 unit and as a dianionic C,N,Cpincer with the dihydride OsH 2 (P i Pr 3 ) 2 moiety. [28] The HOMO of the binuclear derivatives 11-13 spreads out over the osmium-bridge-osmium system (Figure 1) with comparable participation of the three fragments, whereas the LUMO is mainly centered on the bridging heterocycle. The cyclic voltammograms of 11-13 exhibit three quasi-reversible oxidation peaks ([Os 2 ]/[Os 2 ] + , [Os 2 ] + /[Os 2 ] 2 + , and [Os 2 ] 2 + / [Os 2 ] 3 + ).…”

Section: Osmium(iv) Emittersmentioning

confidence: 99%

“…This poor efficiency has been ascribed to the low values of the radiative rate constants. [28] Complex 1 also activates the NÀ H bond of 2-(1H-pyrazol-3yl)pyridine. The activation leads to 14, bearing the N,N'pyrazolate-pyridyl chromophore.…”

Section: Osmium(iv) Emittersmentioning

confidence: 99%

Recent Advances in Synthesis of Molecular Heteroleptic Osmium and Iridium Phosphorescent Emitters

2021

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The application of new procedures of organometallic synthesis based on alternative starting complexes has given rise to a significant enhancement in the preparation of osmium(IV), osmium(II), and iridium(III) emitters, since 2012. The choice of the precursors should be done taking into account its ligands, since they may cooperate in the emitter synthesis. Three different functions are clearly pointed out in the revised procedures: the ligands of the starting compounds can direct the selectivity of competitive ruptures of σ-bonds of the chromophores, without having direct participation in the activation; on the contrary, they can directly participate in the generation of a ligand, being a part of the new coordinated group; and the ligands can also act as internal base in σ-bond heterolytic activation reactions. In addition, the ability of the polyhydrides OsH 6 (P i Pr 3 ) 2 and IrH 5 (P i Pr 3 ) 2 to activate CÀ H bonds is pointed out as one of the determining factors of the success in many cases.

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“… 22 Among the compounds of this class, the osmium-hexahydride OsH 6 (P i Pr 3 ) 2 23 ( 1 ) occupies a prominent position due to its versatility for promoting C–H bond activation reactions. 24 We are not strangers to the interest in the polyhydride chemistry nor to the aromatic C–H bond activations of substrates asymmetrically 1,3-disubstituted. Thus, in the search for understanding the factors that govern the challenging selectivity of these reactions, we have investigated the behavior of the [BF 4 ] − and [BPh 4 ] − salts of cations 1-(3-(isoquinolin-1-yl)phenyl)-3-methylimidazolium and 1-(3-(isoquinolin-1-yl)phenyl)-3-methylbenzimidazolium ( Chart 2 ) toward 1 .…”

Section: Introductionmentioning

confidence: 99%

“…Such a prospect is the consequence of the proven ability of these compounds to activate σ-bonds, which allows them to connect with fields such as organic synthesis, the preparation of new types of phosphorescent emitters for OLED devices, , and hydrogen storage and transport . Among the compounds of this class, the osmium-hexahydride OsH 6 (P i Pr 3 ) 2 ( 1 ) occupies a prominent position due to its versatility for promoting C–H bond activation reactions . We are not strangers to the interest in the polyhydride chemistry nor to the aromatic C–H bond activations of substrates asymmetrically 1,3-disubstituted.…”

Section: Introductionmentioning

confidence: 99%

Azolium Control of the Osmium-Promoted Aromatic C–H Bond Activation in 1,3-Disubstituted Substrates

et al. 2021

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The hexahydride complex OsH 6 (P i Pr 3 ) 2 promotes the C–H bond activation of the 1,3-disubstituted phenyl group of the [BF 4 ] − and [BPh 4 ] − salts of the cations 1-(3-(isoquinolin-1-yl)phenyl)-3-methylimidazolium and 1-(3-(isoquinolin-1-yl)phenyl)-3-methylbenzimidazolium. The reactions selectively afford neutral and cationic trihydride-osmium(IV) derivatives bearing κ 2 - C,N - or κ 2 - C,C -chelating ligands, a cationic dihydride-osmium(IV) complex stabilized by a κ 3 - C,C,N -pincer group, and a bimetallic hexahydride formed by two trihydride-osmium(IV) fragments. The metal centers of the hexahydride are separated by a bridging ligand, composed of κ 2 - C,N - and κ 2 - C,C -chelating moieties, which allows electronic communication between the metal centers. The wide variety of obtained compounds and the high selectivity observed in their formation is a consequence of the main role of the azolium group during the activation and of the existence of significant differences in behavior between the azolium groups. The azolium role is governed by the anion of the salt, whereas the azolium behavior depends upon its imidazolium or benzimidazolium nature. While [BF 4 ] − inhibits the azolium reactions, [BPh 4 ] − favors the azolium participation in the activation process. In contrast to benzimidazolylidene, the imidazolylidene resulting from the deprotonation of the imidazolium substituent coordinates in an abnormal fashion to direct the phenyl C–H bond activation to the 2-position. The hydride ligands of the cationic dihydride-osmium(IV) pincer complex display intense quantum mechanical exchange coupling. Furthermore, this salt is a red phosphorescent emitter upon photoexcitation and displays a noticeable catalytic activity for the dehydrogenation of 1-phenylethanol to acetophenone and of 1,2-phenylenedimethanol to 1-isobenzofuranone. The bimetallic hexahydride shows catalytic synergism between the metals, in the dehydrogenation of 1,2,3,4-tetrahydroisoquinoline and alcohols.

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Electronic Communication in Binuclear Osmium- and Iridium-Polyhydrides

Cited by 10 publications

References 79 publications

Alternative Conceptual Approach to the Design of Bifunctional Catalysts: An Osmium Germylene System for the Dehydrogenation of Formic Acid

Alternative Conceptual Approach to the Design of Bifunctional Catalysts: An Osmium Germylene System for the Dehydrogenation of Formic Acid

Recent Advances in Synthesis of Molecular Heteroleptic Osmium and Iridium Phosphorescent Emitters

Azolium Control of the Osmium-Promoted Aromatic C–H Bond Activation in 1,3-Disubstituted Substrates

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