Methylene transfer from SnMe groups mediated by a rhodium(I) pincer complex: Sn-C, C-C, and C-H bond activation

Christian M. Frech, Linda J W Shimon, David Milstein

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

The PCP-Rh1 complex la based on the [1,3-phenylenebis(methylene) ]bis(diisopropylphosphine) ligand reacts with [diazo-(phenyl)methyl] trimethylstannane (2) at room temperature to give novel pincer-type phenyl(dimethylstannyl)-methylene]hydrazinato complex 3a. The reaction sequence involves a unique combination of Sn-C bond cleavage, C-C bond formation, C-H activation and intramolecular deprotonation of a rhodium hydride intermediate, which results in methylene transfer from an SnMe group to the pincer system and PCP-chelate expansion. A methylene-transfer reaction was also demonstrated with tetramethyltin as the methylene source in the presence of KOC(CH 3)3 at room temperature. The resulting unstable "chelate-expanded" Rh1 complex [(C10H 5-(CH2P/Pr2)2)(CH2)Rh(L)] (L = N2, THF; 4a) was isolated as its carbonyl derivative 5 a. Heating 4 a in benzene yielded an equimolar amount of toluene and la, which demonstrates the ability of the Rh1 pincer complex to extract a methylene group from an unactivated alkyl tin substrate and transfer it, via C-C followed by C-H activation, to an arene. Use of fluorobenzene resulted in formation of fluorotoluene. Catalytic methylene-group transfer mediated by la was not possible, because of formation of o-xylylene complex 8 under the reaction conditions. Steric parameters play a decisive role in the reactivity with tin compounds; while iPrP derivative la underwent facile reactions, tBuP complex lb was inert.

Original languageEnglish
Pages (from-to)7501-7509
Number of pages9
JournalChemistry - A European Journal
Volume13
Issue number26
DOIs
Publication statusPublished - 2007

Fingerprint

Rhodium
Fluorobenzenes
Tin Compounds
Chemical activation
Tin compounds
Derivatives
Deprotonation
Tin
Toluene
Benzene
Hydrides
Ligands
Heating
Hydrogen
Temperature
Substrates
trimethyltin

Keywords

  • C-C activation
  • C-H activation
  • Pincer ligands
  • Rhodium
  • Tin

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Methylene transfer from SnMe groups mediated by a rhodium(I) pincer complex : Sn-C, C-C, and C-H bond activation. / Frech, Christian M.; Shimon, Linda J W; Milstein, David.

In: Chemistry - A European Journal, Vol. 13, No. 26, 2007, p. 7501-7509.

Research output: Contribution to journalArticle

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abstract = "The PCP-Rh1 complex la based on the [1,3-phenylenebis(methylene) ]bis(diisopropylphosphine) ligand reacts with [diazo-(phenyl)methyl] trimethylstannane (2) at room temperature to give novel pincer-type phenyl(dimethylstannyl)-methylene]hydrazinato complex 3a. The reaction sequence involves a unique combination of Sn-C bond cleavage, C-C bond formation, C-H activation and intramolecular deprotonation of a rhodium hydride intermediate, which results in methylene transfer from an SnMe group to the pincer system and PCP-chelate expansion. A methylene-transfer reaction was also demonstrated with tetramethyltin as the methylene source in the presence of KOC(CH 3)3 at room temperature. The resulting unstable {"}chelate-expanded{"} Rh1 complex [(C10H 5-(CH2P/Pr2)2)(CH2)Rh(L)] (L = N2, THF; 4a) was isolated as its carbonyl derivative 5 a. Heating 4 a in benzene yielded an equimolar amount of toluene and la, which demonstrates the ability of the Rh1 pincer complex to extract a methylene group from an unactivated alkyl tin substrate and transfer it, via C-C followed by C-H activation, to an arene. Use of fluorobenzene resulted in formation of fluorotoluene. Catalytic methylene-group transfer mediated by la was not possible, because of formation of o-xylylene complex 8 under the reaction conditions. Steric parameters play a decisive role in the reactivity with tin compounds; while iPrP derivative la underwent facile reactions, tBuP complex lb was inert.",
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N2 - The PCP-Rh1 complex la based on the [1,3-phenylenebis(methylene) ]bis(diisopropylphosphine) ligand reacts with [diazo-(phenyl)methyl] trimethylstannane (2) at room temperature to give novel pincer-type phenyl(dimethylstannyl)-methylene]hydrazinato complex 3a. The reaction sequence involves a unique combination of Sn-C bond cleavage, C-C bond formation, C-H activation and intramolecular deprotonation of a rhodium hydride intermediate, which results in methylene transfer from an SnMe group to the pincer system and PCP-chelate expansion. A methylene-transfer reaction was also demonstrated with tetramethyltin as the methylene source in the presence of KOC(CH 3)3 at room temperature. The resulting unstable "chelate-expanded" Rh1 complex [(C10H 5-(CH2P/Pr2)2)(CH2)Rh(L)] (L = N2, THF; 4a) was isolated as its carbonyl derivative 5 a. Heating 4 a in benzene yielded an equimolar amount of toluene and la, which demonstrates the ability of the Rh1 pincer complex to extract a methylene group from an unactivated alkyl tin substrate and transfer it, via C-C followed by C-H activation, to an arene. Use of fluorobenzene resulted in formation of fluorotoluene. Catalytic methylene-group transfer mediated by la was not possible, because of formation of o-xylylene complex 8 under the reaction conditions. Steric parameters play a decisive role in the reactivity with tin compounds; while iPrP derivative la underwent facile reactions, tBuP complex lb was inert.

AB - The PCP-Rh1 complex la based on the [1,3-phenylenebis(methylene) ]bis(diisopropylphosphine) ligand reacts with [diazo-(phenyl)methyl] trimethylstannane (2) at room temperature to give novel pincer-type phenyl(dimethylstannyl)-methylene]hydrazinato complex 3a. The reaction sequence involves a unique combination of Sn-C bond cleavage, C-C bond formation, C-H activation and intramolecular deprotonation of a rhodium hydride intermediate, which results in methylene transfer from an SnMe group to the pincer system and PCP-chelate expansion. A methylene-transfer reaction was also demonstrated with tetramethyltin as the methylene source in the presence of KOC(CH 3)3 at room temperature. The resulting unstable "chelate-expanded" Rh1 complex [(C10H 5-(CH2P/Pr2)2)(CH2)Rh(L)] (L = N2, THF; 4a) was isolated as its carbonyl derivative 5 a. Heating 4 a in benzene yielded an equimolar amount of toluene and la, which demonstrates the ability of the Rh1 pincer complex to extract a methylene group from an unactivated alkyl tin substrate and transfer it, via C-C followed by C-H activation, to an arene. Use of fluorobenzene resulted in formation of fluorotoluene. Catalytic methylene-group transfer mediated by la was not possible, because of formation of o-xylylene complex 8 under the reaction conditions. Steric parameters play a decisive role in the reactivity with tin compounds; while iPrP derivative la underwent facile reactions, tBuP complex lb was inert.

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