S-Demethylation catalysed by the Formation of Metal Complexes

Lindoy, Leonard F.; Livingstone, Stanley E.; Lockyer, T. N.

doi:10.1038/211519a0

Cited by 15 publications

(4 citation statements)

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“…Intensity measurements on the decrease in the NMR methyl resonance at 3.02 for PdCl2(o-Ph2PC6H4SMe) with time have been used to obtain the rate law. The reaction is first order in PdCl2(o-Ph2C6H4SMe), and the rate of the reaction (eq 3) is dependent PdCl2(o-Ph2PC6H4SMe) + PhCH2NH2 -PdCl2(o-Ph2PC6H4S)-+ PhCH2NH2Me+ (3) on benzylamine concentration. Two sets of data have been collected under different experimental conditions.…”

Section: Crystal Structure Datamentioning

confidence: 99%

“…In 1966 it was suggested that the dealkylation reaction of high-temperature reflux conditions in DMF solvent could be relevant to methylation by S-adenosylmethionine. 3 This particular example is not unique, and a number of other similar examples have been reported whereby a complexed methyl thioether ligand can be converted to a complexed thiolate by refluxing in solvents such as DMF.4 Mechanistic considerations lead one to infer that these transition-metal-induced demethylation reactions can be compared to carbonium ion type electrophilic reactivities and that metal coordination to the thioether can lead to two cooperative effects. First, complexation of the methyl thioether group to the transition-metal ion as a a donor can lead to a reduction of electron density at sulfur and hence carbon; second, the conversion of a weakly bound thioether group to a strongly complexed thiolate moiety will result in a thermodynamic preference for the formation of a (thiolato) metal complex as a leaving group.…”

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confidence: 91%

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A Menschutkin type amine alkylation involving methyl transfer to benzylamine from palladium(II) chelate complexes of o-(diphenylphosphino)thioanisole

Benefiel¹,

Roundhill²,

Fultz³

et al. 1984

Inorg. Chem.

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Section: Crystal Structure Datamentioning

confidence: 99%

mentioning

confidence: 91%

A Menschutkin type amine alkylation involving methyl transfer to benzylamine from palladium(II) chelate complexes of o-(diphenylphosphino)thioanisole

Benefiel¹,

Roundhill²,

Fultz³

et al. 1984

Inorg. Chem.

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“…It is known that metal ions will cleave tert ‐butyl sulfides 18. Therefore, a Pd‐mediated S–C bond cleavage reaction as first described by Lindoy et al was considered 19. Indeed, when 3 was allowed to stir in the presence of one equiv.…”

Section: Resultsmentioning

confidence: 99%

Palladium‐mediated Cleavage of S–C Bonds: Preparation and Characterization of Palladium(II) Complexes of 2, 6‐Diformyl‐4‐tert‐butylthiophenol Dioxime

Gruschinski

Handke

Kersting

2012

Zeitschrift anorg allge chemie

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“…The dealkylation of thioethers in hybrid ligands to form bridging thiolate dimers of this type was first published as a Nature communication in 1966. 181 In this note, Lindoy et al reported that when dimethylformamide solutions of the chelated complexes [PdBr 2 (N,S )] (N,S = 8-(methylthio)quinoline) and [PdX 2 (As,S )] (X = Cl or Br, As,S = dimethyl{2-(methylthio)phenyl}arsine), amongst others, were heated, the sulfur donor atoms demethylated, forming the corresponding thiolate-bridged palladium dimers. A number of palladium halide dimers containing chelating phosphinethiolate ligands have since been synthesised via dealkylation of phosphine-thioethers, either through an amine-assisted method, 182 with heating 183 or spontaneously, 112 and many others have been synthesised from the corresponding phosphine-thiol ligands.…”

Section: [Pdcl 2 L 2 ]mentioning

confidence: 99%

Hybrid P,E Ligands: Synthesis, Coordination Chemistry and Catalysis

Allan¹

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<p>This thesis provides an account of research into a family of novel hybrid P,E ligands containing an o-xylene backbone. A methodology for the synthesis of these ligands has been developed, and their coordination behaviour with platinum(II) and platinum(0) precursors has been explored, with particular focus on a phosphinethioether (P,S) ligand of this type. The coordination modes of this P,S ligand with palladium precursors have also been investigated, and the utility of the ligand in a palladium and copper co-catalysed Sonogashira carbon-carbon bond-forming reaction has been evaluated. A range of hybrid P,E ligands of the type o-C₆H₄(CH₂PBut₂)(CH₂E) (E = PR₂, SR, S(O)But, NR₂, SiPh₂H) have been synthesised in two or three steps from the novel substrate, o-C₆H₄(CH₂PBut₂(BH₃)}(CH₂Cl). The initial step involved treatment of the substrate with the appropriate nucleophilic reagent, or preparation of a Grignard reagent from o-C₆H₄{CH₂PBut₂(BH₃)}(CH₂Cl) and reaction with the appropriate electrophile. In most cases, this versatile strategy produced air-stable crystalline ligand precursors. Phosphine deprotection was achieved via one of three methods, dependent upon the properties of the second functional group. The reactivity of three of these ligands — o-C₆H₄{CH₂PBut₂)(CH₂SBut) (14a), o-C₆H₄{CH₂PBut₂){CH₂S(O)But} (16) and o-C₆H₄(CH₂PBut₂)(CH₂NMe₂) (18a) — with Pt(II) and Pt(0) precursor complexes has been investigated. Chelated [PtCl₂(P,E)] complexes were synthesised with P,S ligand 14a and P,N ligand 18a, but attempts to produce the equivalent species with P,S=O ligand 16 were unsuccessful. The X-ray crystal structure of [PtCl₂(P,S)] complex 21 displayed an unexpectedly small ligand bite angle of 86.1°. A series of platinum(II) hydride complexes of the types [PtHL(P,S)₂] and [PtHL(P,S)₂]CH(SO₂CF₃)₂ (L = Cl¯, H¯, NCMe, −CH₂SBut , CO, pta) have been synthesised, where ligand 14a binds in a monodentate fashion through the phosphorus donor atom. This work has demonstrated the hemilability of ligand 14a, via the facile and reversible conversion between [PtH(κ¹P-14a)(κ²P,S-14a)]CH(SO₂CF₃)₂ (26) and [PtH(NCMe)(κ¹P-14a)₂]CH(SO₂CF₃)₂ (28). The X-ray crystal structure of [PtH₂(P,S)₂] complex 25 was used to calculate a cone angle of 180° for the phosphine moiety in ligand 14a. Reaction of P,S ligand 14a and P,S=O ligand 16 with [Pt(alkene)₃] complexes (alkene = ethene, norbornene) gave the chelated [Pt(alkene)(P,E)] complexes 32–35; however, under similar conditions a [Pt(norbornene)(P,N)] complex did not form. A large ligand bite angle of 106.6° was observed in the X-ray crystal structure of [Pt(norbornene)(P,S)] complex 34. Reaction of two equivalents of each of the P,E ligands with [Pt(norbornene)₃] gave the corresponding 14-electron linear complexes [Pt(P,E)₂] (36–38) with the ligands coordinated through the phosphorus donor atoms only. The reactivity of [Pt(norbornene)(P,S)] complex 34 and [Pt(P,S)₂] complex 36 has been investigated, resulting in the complexes [PtH{CH(SO₂CF₃)₂}(P,S)] (39), [Pt(norbornyl)(P,S)] (40), [Pt(ethyne)(P,S)] (41) and [Pt(O₂)(P,S)₂] (42). The reactivity of P,S ligand 14a was investigated with Pd(II) and Pd(0) precursors, resulting in the identification of five coordination modes of this ligand. Monodentate binding was observed in [Pd(P,S)₂] complex 44, and chelation in the [Pd(alkene)(P,S)] complexes 47 (alkene = norbornene) and 48 (alkene = dba). Reaction of ligand 14a with [PdCl₂(NCBut)₂] at raised temperature resulted in S−C bond cleavage and the formation of palladium dimer 43 with bidentate coordination of the ligand through phosphine and bridging thiolate moieties. Reaction of ligand 14a with [Pd(OAc)₂] resulted in C−H activation of the aryl backbone and formation of [Pd(μ-OAc)(P,C)]₂ dimer 46. In the presence of excess [Pd(OAc)₂], palladium hexamer 45 was formed, with a combination of P,C palladacycle and monodentate thioether binding resulting in bridging P,C,S coordination of ligand 14a. The Sonogashira cross-coupling of 4-bromoanisole and phenylethyne was performed with 3 mol% of a pre-catalyst mixture containing P,S ligand 14a, [Pd(OAc)₂] and CuI, resulting in quantitative conversion to 4-(phenylethynyl)anisole in four hours. Two enyne by-products were also identified from the reaction. Variations to the pre-catalyst mixture and catalyst loading indicated there was a significant ligand dependence on the yield and selectivity of the reactions. Mercury drop tests and dynamic light scattering experiments confirmed the presence of palladium nanoparticles in the reaction solution; however, the active catalytic species in these reactions has not been identified.</p>

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S-Demethylation catalysed by the Formation of Metal Complexes

Cited by 15 publications

References 2 publications

A Menschutkin type amine alkylation involving methyl transfer to benzylamine from palladium(II) chelate complexes of o-(diphenylphosphino)thioanisole

A Menschutkin type amine alkylation involving methyl transfer to benzylamine from palladium(II) chelate complexes of o-(diphenylphosphino)thioanisole

Palladium‐mediated Cleavage of S–C Bonds: Preparation and Characterization of Palladium(II) Complexes of 2, 6‐Diformyl‐4‐tert‐butylthiophenol Dioxime

Hybrid P,E Ligands: Synthesis, Coordination Chemistry and Catalysis

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