Bimetallic Homogeneous Hydroformylation

Fernando, Ranelka G.; Gasery, Ciera D.; Moulis, Marshall D.; Stanley, George G.

doi:10.1007/3418_2015_147

Cited by 8 publications

(7 citation statements)

References 43 publications

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“…Noteworthy, binuclear cooperativity has been reported for some Co- and Rh-catalyzed hydroformylation processes; ,,, however, a mechanistic proposal involving binuclear cooperativity in Pd-catalyzed hydroformylation as well as its dependence on the halide anions are unprecedented.…”

Section: Resultsmentioning

confidence: 72%

“…The formation of Pd-hydride species does not require the presence of a Brønsted acid as cocatalyst, in contrast to previous speculations. Noteworthy, binuclear cooperativity has been reported for some Co-and Rh-catalyzed hydroformylation processes; 13,59,72,73 however, a mechanistic proposal involving binuclear cooperativity in Pd-catalyzed hydroformylation as well as its dependence on the halide anions are unprecedented.…”

Section: ■ Results and Discussionmentioning

confidence: 89%

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Binuclear Pd(I)–Pd(I) Catalysis Assisted by Iodide Ligands for Selective Hydroformylation of Alkenes and Alkynes

et al. 2020

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Since its discovery in 1938, hydroformylation has been thoroughly investigated and broadly applied in industry (>10 7 metric ton yearly). However, the ability to precisely control its regioselectivity with well-established Rh-or Co-catalysts has thus far proven elusive, thereby limiting access to many synthetically valuable aldehydes. Pd-catalysts represent an appealing alternative, yet their use remains sparse due to undesired side-processes. Here, we report a highly selective and exceptionally active catalyst system that is driven by a novel activation strategy and features a unique Pd(I)− Pd(I) mechanism, involving an iodide-assisted binuclear step to release the product. This method enables β-selective hydroformylation of a large range of alkenes and alkynes, including sensitive starting materials. Its utility is demonstrated in the synthesis of antiobesity drug Rimonabant and anti-HIV agent PNU-32945. In a broader context, the new mechanistic understanding enables the development of other carbonylation reactions of high importance to chemical industry.

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Section: Resultsmentioning

confidence: 72%

Section: ■ Results and Discussionmentioning

confidence: 89%

Binuclear Pd(I)–Pd(I) Catalysis Assisted by Iodide Ligands for Selective Hydroformylation of Alkenes and Alkynes

et al. 2020

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“…Stanley reported a class of binucleating tetraphosphine ligands that assemble dirhodium complexes active toward alkene hydroformylation . In particular, the rac-40 ligand system, possessing a short methylene tether between the two central phosphine donors, enforces a close proximity between the two metals such that they are poised to form a Rh(II)–Rh(II) bonding interaction.…”

Section: Metal–metal Bonds In Transient Catalytic Intermediatesmentioning

confidence: 99%

Metal–Metal Bonds in Catalysis

2016

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Transition metals can assemble to form multinuclear complexes by engaging in direct metal-to-metal interactions. Metal–metal covalent bonds provide a large perturbation in electronic structure, relative to mononuclear metal ions, and the unique properties of these dinuclear fragments can be harnessed in a broad range of applicationsfor example, as chromophores in photochemical processes, redox centers in molecular electronics, or structural elements in metal–organic materials. There is a growing body of evidence that metal–metal bonds may also be formed under conditions relevant to catalysis and play a key role in transformations that were previously assumed to only involve mononuclear species. These findings have stimulated interest in characterizing multinuclear reaction pathways and developing well-defined multinuclear platforms as catalytic active sites. In this Perspective, we present case studies in this emerging area of catalysis research, emphasizing the impact of metal–metal bonding in either enhancing or depressing the rate and/or selectivity of a catalytic organic transformation.

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“…Cooperative effects between the adjacent d 8 metal centers of dinuclear complexes have been reported to facilitate the formation of stabilizing metal–metal bonds in the intermediates of catalytic reactions, involving oxidative addition–reductive elimination processes, which allows pathways and products unavailable from mononuclear complexes . Pd 2 (III,III) or Rh 2 (II,II) species are some examples of low-energy transition states for C–H functionalization , or alkene hydroformylation reactions, respectively. In the chemistry of dinuclear platinum(II) complexes it is well-known that [Pt 2 (POP) 4 ] 4– (POP = pyrophosphito) exhibits a rich luminescence and photochemistry associated with the presence of Pt···Pt interactions, resulting in short intermetallic separation (2.925 Å).…”

Section: Introductionmentioning

confidence: 99%

Metal–Metal Cooperation in the Oxidation of a Flapping Platinum Butterfly by Haloforms: Experimental and Theoretical Evidence

et al. 2020

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The model 1-DFT for the butterfly complex [{Pt(C ∧ C*)(μ-pz)} 2 ] (1; HC ∧ C* = 1-(4-(ethoxycarbonyl)phenyl)-3-methyl-1H-imidazol-2-ylidene) shows two minima in the potential energy surface of the ground state in acetone solution: the butterfly-wing-spreading molecules 1-s, (d Pt−Pt ≈ 3.20 Å) and the wing-folding molecules 1-f (d Pt−Pt ≤ 3.00 Å). Both minima are very close in energy (ΔG°= 1.7 kcal/mol) and are connected through a transition state, which lies only 1.9 kcal/mol above 1-s and 0.2 kcal/mol above 1-f. These very low barriers support a fast interconversion process, resembling a butterfly f lapping, and the presence of both conformers in acetone solution. However, the 1-f ratio is so low that it is undetectable in the excitation and emission spectra of 1 in 2-MeTHF of diluted solutions (10 −5 M) at 77 K, while it is seen in more concentrated solutions (10 −3 M). In acetone solution, 1 undergoes a [2c, 2e] oxidation by CHX 3 (X = Cl, Br) in the sunlight to render the Pt 2 (III,III) compounds [{Pt(C ∧ C*)(μ-pz)X)} 2 ] (X = Cl (2-Cl), Br (2-Br)). In concentrated solutions, 1 can react with CHCl 3 under blue light to give 2-Cl and with CHBr 3 in the dark, the latter rendering the compound [BrPt(C ∧ C*)(μ-pz) 2 Pt(C ∧ C*)CHBr 2 ] (3-Br) or mixtures of 2-Br and 3-Br if the reaction is performed under an argon atmosphere or in the air, respectively. Mechanistic studies showed that in concentrated solutions the oxidation processes follow a radical mechanism being the MMLCT-based species 1-f, those which trigger the reaction of 1 with CHBr 3 and CHCl 3 . In the ground state (S 0f ), it promotes the thermal oxidation of 1 by CHBr 3 and in the first singlet excited state (S 1f ) the blue-light-driven photooxidation of 1 by CHCl 3 . Complexes, 2-Cl, 2-Br, and 3-Br were selectively obtained and fully characterized, showing Pt−Pt distances (ca. 2.6 Å) shorter than that of the starting complex, 1. They are, together with the analogous [{Pt(C ∧ C*)(μ-pz)I)} 2 ] and [IPt(C ∧ C*)(μpz) 2 Pt(C ∧ C*)CHI 2 ], the only dinuclear metal−metal-bonded Pt III (μ-pz) 2 Pt III compounds reported to date.

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Bimetallic Homogeneous Hydroformylation

Cited by 8 publications

References 43 publications

Binuclear Pd(I)–Pd(I) Catalysis Assisted by Iodide Ligands for Selective Hydroformylation of Alkenes and Alkynes

Binuclear Pd(I)–Pd(I) Catalysis Assisted by Iodide Ligands for Selective Hydroformylation of Alkenes and Alkynes

Metal–Metal Bonds in Catalysis

Metal–Metal Cooperation in the Oxidation of a Flapping Platinum Butterfly by Haloforms: Experimental and Theoretical Evidence

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