Osmium(III) Complexes with POP Pincer Ligands: Preparation from Commercially Available OsCl<sub>3</sub>·3H<sub>2</sub>O and Their X-ray Structures

Asensio, Gregorio; Cuenca, Ana B.; Esteruelas, Miguel A.; Medio‐Simón, Mercedes; Oliván, Montserrat; Valencia, Marta

doi:10.1021/ic101498h

Cited by 46 publications

(39 citation statements)

References 56 publications

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“…As a consequence, they can be adapted to the requirements of the catalytic intermediates, playing relevant roles in catalysis . 9,9‐Dimethyl‐4,5‐bis(diisopropylphosphino)xanthene (xant(P i Pr 2 ) 2 ) is a ligand of this class that has demonstrated to have a higher capacity than other POP‐diphosphines to act as pincer . It even gets to stabilize the mer ‐trisboryl derivative Ir(Bcat) 3 {κ 3 ‐P,O,P‐[xant(P i Pr 2 ) 2 ]}, which challenges the concept of trans ‐influence .…”

Section: Introductionmentioning

confidence: 99%

Direct C−H Borylation of Arenes Catalyzed by Saturated Hydride‐Boryl‐Iridium‐POP Complexes: Kinetic Analysis of the Elemental Steps

Esteruelas

Martínez

Oliván

et al. 2020

Chemistry A European J

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The saturated trihydride IrH 3 {k 3-P,O,P-[xant(PiPr 2) 2 ]} (1;x ant(PiPr 2) 2 = 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene)a ctivates the BÀHb ond of two molecules of pinacolborane (HBpin) to give H 2 ,t he hydride-boryl derivatives IrH 2 (Bpin){k 3-P,O,P-[xant(PiPr 2) 2 ]} (2)a nd IrH(Bpin) 2 {k 3-P,O,P-[xant(PiPr 2) 2 ]} (3)i nasequential manner.Complex 3 activates aC ÀHb ond of two molecules of benzene to form PhBpin and regenerates 2 and 1,a lso in as equentialm anner.T hus, complexes 1, 2,a nd 3 define two cycles for the catalytic direct CÀHb orylation of arenes with HBpin,w hich have di-hydride 2 as ac ommon intermediate. CÀHb ond activation of the arenes is the rate-determining step of both cycles, as the CÀHo xidative addition to 3 is faster than to 2.T he results from ak inetic study of the reactions of 1 and 2 with HBpin support ac ooperative function of the hydride ligands in the BÀHb ond activation.T he addition of the boron atom of the borane to ah ydride facilitates the coordinationo ft he BÀHb ond through the formation of k 1-a nd k 2-dihydrideborate intermediates. Scheme1.Proposed catalytic cycle for the borylation of arenes catalyzed by Ir(Bpin) 3 L 2 .

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Section: Introductionmentioning

confidence: 99%

Direct C−H Borylation of Arenes Catalyzed by Saturated Hydride‐Boryl‐Iridium‐POP Complexes: Kinetic Analysis of the Elemental Steps

Esteruelas

Martínez

Oliván

et al. 2020

Chemistry A European J

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“…The sterically-encumbered ligand 4,6-bis(di-tert-butylphosphino)dibenzo [b,d]furan (POP) was prepared via a modification of literature procedures for the isopropyl congener developed by Asensio et al 31 Dilithiation of dibenzofuran with secbutyllithium/TMEDA followed by addition of t Bu2PCl yielded dbf-tBu POP in 92% yield. NMR spectroscopy reveals that the phosphine environments in POP are rendered inequivalent due to relatively slow rotation of the t Bu2P moiety at room temperature but is sufficiently rapid that metalation occurs without complication.…”

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Rh Methylidenes from Redox Cascade Activation of Chloroalkanes

Morrow¹,

Gipper²,

Christman³

et al. 2019

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<div><div><div><p>Oxidative addition of carbon-halogen bonds at transition metals typically follow either a two-electron pathway (concerted M-R/M-X formation) or a radical chain pathway (stepwise M-R/M-X formation). When the reactive metal species is generated slowly, however, both mechanisms can compete to yield unexpected reactivity paths. The present report highlights the synthesis of rhodium methylidenes from chloroalkanes (e.g. CH2Cl2 and CHCl3) at POP-pincer frameworks (e.g. POP = 4,6-bis(di-tert- butylphosphino)dibenzo[b,d]furan) via a cascade of halide abstraction and electron transfer steps. Experimental and computational studies are reported that support the proposed mechanism, including characterization of important reaction intermediates. The overall transformation represents a route towards reactive metal alkylidenes using milder and less-reactive carbenoid precursors than what is presently used.</p></div></div></div>

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“…dibenzofuran-and xanthene-based). 31,32 Generation of strong transition metal electrophiles typically requires protonation or abstraction of X-type ligands in weakly-polar non-donating solvents. Maintaining solubility sometimes requires the use of chlorinated solvents for cation generation, and although oxidative addition of such solvents is known, [33][34][35] it has been shown to be somewhat mitigated by the use of bulky substituents on phosphorus.…”

mentioning

confidence: 99%

Rh Methylidenes from Redox Cascade Activation of Chloroalkanes

Morrow¹,

Gipper²,

Christman³

et al. 2019

Preprint

View full text Add to dashboard Cite

Oxidative addition of carbon-halogen bonds at transition metals typically follow either a two-electron pathway (concerted M-R/M-X formation) or a radical chain pathway (stepwise M-R/M-X formation). When the reactive metal species is generated slowly, however, both mechanisms can compete to yield unexpected reactivity paths. The present report highlights the synthesis of rhodium methylidenes from chloroalkanes (e.g. CH2Cl2 and CHCl3) at POP-pincer frameworks (e.g. POP = 4,6-bis(di-tertbutylphosphino)dibenzo [b,d]furan) via a cascade of halide abstraction and electron transfer steps. Experimental and computational studies are reported that support the proposed mechanism, including characterization of important reaction intermediates. The overall transformation represents a route towards reactive metal alkylidenes using milder and less-reactive carbenoid precursors than what is presently used.Transition metal alkylidene complexes are profoundly important entities, owing to their use in a variety of chemical transformations including olefin metathesis, 1-5 cyclopropanation, 6 and C-H insertions. 7-10 Although a large number of transition metal complexes bearing metal-carbon double bonds have been reported, mononuclear complexes of the simplest carbene (i.e. terminal methylidenes, LnM=CH2) are considerably rarer due to their high reactivity. Due to their importance as fundamental models of catalytic intermediates, metal alkylidenes have been the subject of intense synthetic effort and computational study. Over the past half-century, these studies have yielded dividends in the form of new alkylidene synthons for catalytic transformations.Several synthetic methods are available for the preparation of reactive transition metal alkylidenes, such as the use of phosphonium or sulfonium ylides, 11,12 but diazo derivatives are among the most common in carbenoid catalysis. [13][14][15][16][17] Although many such reagents are kinetically stabilized by the addition of electron-donating groups, 18 these species are notoriously toxic, reactive, and poorly-stabilized derivatives can explode unexpectedly. Polyhalogenated precursors have proven to be sources of carbene fragments in stoichiometric reactions involving polarized M-CR2-X intermediates, most notably in the Simmons-Smith reaction. [19][20][21] Recently Baker and Ozerov have independently shown that a mixture of CsF and Me3SiCF3 (i.e. the Ruppert-Prakash reagent) 22,23 provides a straightforward route to difluoromethylidene transition metal complexes of Co, Rh, Ni, Such species are also accessible from 'standard' haloalkanes, as Goldman has reported the isolation of (PNP)IrCF2 from initial C-H activation of HCF3. 28 To date, however, the use of halogenated alkanes for the synthesis of nonhalogenated terminal metal carbenes has not been demonstrated.One of the research areas of our group has focused on the generation of transition metal electrophiles for heterolytic C-H activation chemistry, 29,30 most recently exploring late-metal pincer systems. In an effort to minimize...

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Osmium(III) Complexes with POP Pincer Ligands: Preparation from Commercially Available OsCl₃·3H₂O and Their X-ray Structures

Cited by 46 publications

References 56 publications

Direct C−H Borylation of Arenes Catalyzed by Saturated Hydride‐Boryl‐Iridium‐POP Complexes: Kinetic Analysis of the Elemental Steps

Direct C−H Borylation of Arenes Catalyzed by Saturated Hydride‐Boryl‐Iridium‐POP Complexes: Kinetic Analysis of the Elemental Steps

Rh Methylidenes from Redox Cascade Activation of Chloroalkanes

Rh Methylidenes from Redox Cascade Activation of Chloroalkanes

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Osmium(III) Complexes with POP Pincer Ligands: Preparation from Commercially Available OsCl3·3H2O and Their X-ray Structures

Cited by 46 publications

References 56 publications

Direct C−H Borylation of Arenes Catalyzed by Saturated Hydride‐Boryl‐Iridium‐POP Complexes: Kinetic Analysis of the Elemental Steps

Direct C−H Borylation of Arenes Catalyzed by Saturated Hydride‐Boryl‐Iridium‐POP Complexes: Kinetic Analysis of the Elemental Steps

Rh Methylidenes from Redox Cascade Activation of Chloroalkanes

Rh Methylidenes from Redox Cascade Activation of Chloroalkanes

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Osmium(III) Complexes with POP Pincer Ligands: Preparation from Commercially Available OsCl₃·3H₂O and Their X-ray Structures