Sulfonium cations as versatile strongly π-acidic ligands

Li, Ruiping; Barel, Nitsan; Subramaniyan, Vasudevan; Cohen, Orit; Tibika, Francoise; Tulchinsky, Yuri

doi:10.1039/d2sc00588c

Cited by 7 publications

(9 citation statements)

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“…2 Surprisingly, their coordination chemistry remained ignored for the last few decades, despite being isolobal and isoelectronic to the tertiary phosphines, which are perhaps the most common ligands in homogeneous catalysis. Indeed, prior to our recent work, 3 the only known sulfonium complexes were reported in the 1980's. These were coordinatively saturated 18e -complexes of the d 6 metals (Mn(I), Mo(0), W(0), and Ru (II)), 4 where the sulfonium ligands could be easily displaced.…”

Section: Introductionmentioning

confidence: 90%

“…However, we have shown that embedding sulfonium cations within a pincer framework might provide a sufficient protection from complex decomposition. With the aliphatic and aromatic sulfonium pincer ligands, P Et SP and P Ph SP, respectively (Chart 1), we were able to report preparation of the first sulfonium complexes of Rh(I) and Pt(II) 3 two d 8 metal centers widely used in homogeneous catalysis, 5 thus reviving the remarkable chemistry of sulfonium cations as one of the few positively charged ancillary ligands. 6 The presence of a metal-sulfur bond in these complexes was unequivocally confirmed by multinuclear NMR in solution and XRD in the solid state.…”

Section: Introductionmentioning

confidence: 99%

“…XRD quality single crystals were obtained by a slow evaporation of complex [3]BPh4 from its CH3NO2 solution at rt. 1 H NMR (400 MHz, CD3NO2): δ 7.85 (m, 4 H, ArH), 7.75 (m,4 H,ArH),12 H,ArH), 3.96-3.83(m, 2 H, SCH2CH2), 3.44 (q, 2 H, JH-H = 7.4 Hz, CH2), 6 H,PCH2CH2 and SCH2CH2) HRMS for 3[PF6] was not acquired, as the mass would be identical to that found for 3 [Cl].…”

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confidence: 99%

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Sulfonium-Pincer Ligands Flexibility in Pt(II) Complexes

Barel

Subramaniyan

et al. 2022

Preprint

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The coordination chemistry of sulfonium cations, dormant since the early eighties, was recently revived when we reported the synthesis and characterization of the first Rh(I) and Pt(II) pincer sulfonium complexes. With the Pt(II) complexes, we had noticed the hemilability of our sulfonium pincer ligands, further explored here. This hemilability led to mononuclear bidentate complexes with both the aromatic and aliphatic sulfonium ligands. With the latter, due to its flexibility, dimeric structures of two different kinds were also allowed. The more rigid aromatic backbone adopted only a mononuclear bidentate mode, leading to a dynamic equilibrium between two asymmetric geometries. Computational study of this process predicted a local energy minimum for a pincer sulfonium-PtCl complex. However, the activation energy of its formation, as a possible intermediate, was found to be too high and indeed was not observed experimentally. Nevertheless, such PtCl complex was prepared and characterized by XRD. Although its S-Pt bond was significantly shorter than in its PtMe analog, the former was easily dissociated in coordinating solvents. It seems that lowering the dz2 orbital in this complex by strong π-back donation, renders the Pt(II) nucleus more susceptible to nucleophilic attacks. This comprehensive study should lay the ground for future applications of pincer sulfonium-Pt(II) complexes in π-acid catalysis.

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Section: Introductionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

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Sulfonium-Pincer Ligands Flexibility in Pt(II) Complexes

Barel

Subramaniyan

et al. 2022

Preprint

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“…A similar example are sulfonium ions, which can be regarded as isoelectronic and thus cationic analogues of tertiary phosphines. [24][25][26][27][28] The bonding situation in many cationic ligands is usually represented by several resonance structures that indicate a delocalisation of the positive charge to neighbouring and stabilising atoms.…”

Section: Introductionmentioning

confidence: 99%

Cationic ligands between σ-donation and hydrogen-bridge-bond-stabilisation of ancillary ligands in coinage metal complexes with protonated carbodiphosphoranes

2022

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“…Scheme 107: Sulfonium salts and their applications [219] Unlike phosphines, however, sulfonium salts are not used as spectator ligands, with a few exceptions. [220] Due to their increased reactivity, as a result of the cationic charge, they are rather used as stoichiometric reagents in synthesis (Scheme 107). [219] For example, sulfonium salts can be used as starting materials for S-ylides 335 due to their α-CH-acidity.…”

Section: Sulfonium Salts and Their Synthetic Applicationsmentioning

confidence: 99%

Tuning the donor properties of bipyridyl-substituted phosphines by metal ion encapsulation & Photocatalytic synthesis of 6H-benzo[c]chromenes from S-aryl sulfonium salts

Karreman¹

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Lewis acid catalysis vs. Brønsted acid catalysisWith the corresponding costs for ligands and noble metals, the question arises why one cannot simply use proton catalysis instead (Brønsted acid catalysis). A proton is after all isolobal to the LAu + and Hg 2+ fragments. An evident difference is the contrasting hardness according to the Pearson concept. [6] Protons are hard Lewis acids, while mentioned metal fragments are soft Lewis acids. This difference leads to the fact that protons often need harsh reaction conditions and are less selective. The softer metal fragments, however, have higher affinity to soft substrates and therefore require less harsh conditions and react in higher selectivity. Besides this evident difference, the use of metal fragments also allows the possibility of stabilizing carbene-like intermediates and to unlock their reactivity. In the case of gold(I), this topic is highly controversial, and resonances of gold carbenes or gold-stabilized carbocations are discussed (→"carbenoid" [6] or "carbene" [11] , Scheme 2). [11,12] Scheme 2: Gold carbene [11] Scheme 14:Chalk-Harrod mechanism [36] The latter mechanism is composed of oxidative addition (I) followed by ligand association (II), insertion (III) and reductive elimination (IV). As a side reaction, mainly β-hydride elimination is present. Because of its ability to activate inert bonds, platinum(II) is also used in the activation of methane, which represents a classic example of CꟷH activation (Shilov system). [37] Methanol and chloromethane can Scheme 20: Oxidation of phosphines to phosphine selenides [55] Since the J-coupling constant contains information about the electronic environment, bonding situation and hybridization of 31 P (I = ½) and 77 Se (I = ½) via the Fermi contact interaction, it is also strongly influenced by the polarization of the PꟷSe bond. If electron pushing substituents are chosen on the phosphorus, the coupling constant 1 JPSe decreases, while electron withdrawing substituents result in high coupling constants. In other words, the coupling constant decreases as the basicity of the corresponding unoxidized phosphine increases (Scheme 21).

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Sulfonium cations as versatile strongly π-acidic ligands

Abstract: More than a century old, sulfonium cations are still intriguing species in the landscape of organic chemistry. On one hand they have found broad applications in organic synthesis and material...

Cited by 7 publications

References 124 publications

Sulfonium-Pincer Ligands Flexibility in Pt(II) Complexes

Sulfonium-Pincer Ligands Flexibility in Pt(II) Complexes

Cationic ligands between σ-donation and hydrogen-bridge-bond-stabilisation of ancillary ligands in coinage metal complexes with protonated carbodiphosphoranes

Tuning the donor properties of bipyridyl-substituted phosphines by metal ion encapsulation & Photocatalytic synthesis of 6H-benzo[c]chromenes from S-aryl sulfonium salts

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