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Bavi M, Nabavizadeh SM, Hosseini FN, Niknam F, Hamidizadeh P, Hoseini SJ, Raoof F, Abu-Omar MM. Ligand-Mediated C-Br Oxidative Addition to Cycloplatinated(II) Complexes and Benzyl-Me C-C Bond Reductive Elimination from a Cycloplatinated(IV) Complex. ACS OMEGA 2020; 5:28621-28631. [PMID: 33195914 PMCID: PMC7658948 DOI: 10.1021/acsomega.0c03573] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Accepted: 09/01/2020] [Indexed: 06/11/2023]
Abstract
Reaction of the Pt(II) complexes [PtMe2(pbt)], 1a, (pbt = 2-(2-pyridyl)benzothiazole) and [PtMe(C^N)(PPh2Me)] [C^N = deprotonated 2-phenylpyridine (ppy), 1b, or deprotonated benzo[h]quinoline (bhq), 1c] with benzyl bromide, PhCH2Br, is studied. The reaction of 1a with PhCH2Br gave the Pt(IV) product complex [PtBr(CH2Ph)Me2(pbt)]. The major trans isomer is formed in a trans oxidative addition (2a), while the minor cis products (2a' and 2a″) resulted from an isomerization process. A solution of Pt(II) complex 1a in the presence of benzyl bromide in toluene at 70 °C after 7 days gradually gave the dibromo Pt(IV) complex [Pt(Br)2Me2(pbt)], 4a, as determined by NMR spectroscopy and single-crystal XRD. The reaction of complexes 1b and 1c with PhCH2Br gave the Pt(IV) complexes [PtMeBr(CH2Ph)(C^N)(PPh2Me)] (C^N = ppy; 2b; C^N = bhq, 2c), in which the phosphine and benzyl ligands are trans. Multinuclear NMR spectroscopy ruled out other isomers. Attempts to grow crystals of the cycloplatinated(IV) complex 2b yielded a previously reported Pt(II) complex [PtBr(ppy)(PPh2Me)], 3b, presumably from reductive elimination of ethylbenzene. UV-vis spectroscopy was used to study the kinetics of reaction of Pt(II) complexes 1a-1c with benzyl bromide. The data are consistent with a second-order SN2 mechanism and the first order in both the Pt complex and PhCH2Br. The rate of reaction decreases along the series 1a ≫ 1c > 1b. Density functional theory calculations were carried out to support experimental findings and understand the formation of isomers.
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Affiliation(s)
- Marzieh Bavi
- Professor Rashidi
Laboratory of Organometallic Chemistry, Department of Chemistry, College
of Sciences, Shiraz University, Shiraz 71467-13565, Iran
| | - S. Masoud Nabavizadeh
- Professor Rashidi
Laboratory of Organometallic Chemistry, Department of Chemistry, College
of Sciences, Shiraz University, Shiraz 71467-13565, Iran
| | | | - Fatemeh Niknam
- Professor Rashidi
Laboratory of Organometallic Chemistry, Department of Chemistry, College
of Sciences, Shiraz University, Shiraz 71467-13565, Iran
| | - Peyman Hamidizadeh
- Professor Rashidi
Laboratory of Organometallic Chemistry, Department of Chemistry, College
of Sciences, Shiraz University, Shiraz 71467-13565, Iran
| | - S. Jafar Hoseini
- Professor Rashidi
Laboratory of Organometallic Chemistry, Department of Chemistry, College
of Sciences, Shiraz University, Shiraz 71467-13565, Iran
| | - Fatemeh Raoof
- Professor Rashidi
Laboratory of Organometallic Chemistry, Department of Chemistry, College
of Sciences, Shiraz University, Shiraz 71467-13565, Iran
| | - Mahdi M. Abu-Omar
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States
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Liu X, Liu C, Yang J, Zhang R, Zeng Q, Wang L. Detection and FEM studies of dichromate (Cr2O72−) by allyltriethoxysilane modified nanochannel. J Electroanal Chem (Lausanne) 2020. [DOI: 10.1016/j.jelechem.2020.113818] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Puddephatt RJ. Selectivity in carbon–carbon coupling reactions at palladium(IV) and platinum(IV). CAN J CHEM 2019. [DOI: 10.1139/cjc-2019-0015] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The isomerization and reductive elimination reactions from octahedral organometallic complexes of palladium(IV) and platinum(IV) usually occur through five-coordinate intermediates that cannot be directly detected. This paper reports a computational study of five-coordinate complexes of formulae [PtMe3(bipy)]+, [PtMe2Ph(bipy)]+, and [PtMe(CH2CMe2C6H4)(bipy)]+ (M = Pd or Pt, bipy = 2,2′-bipyridine), particularly with respect to reactivity and selectivity in reductive elimination. All of the complexes are predicted to have square pyramidal structures with the bipy and two R groups in the equatorial positions and one R group in the axial position, and axial–equatorial exchange occurs by a pairwise mechanism, with the transition state having a pinched trigonal bipyramidal (PTBP) stereochemistry, with one nitrogen and two R groups in the trigonal plane. The activation energy for isomerization is lower than that for reductive elimination in all cases. For the complexes [MMe2Ph(bipy)]+, the activation energies for reductive elimination with Me–Me or Me–Ph coupling are similar. For the complexes [MMe(CH2CMe2C6H4)(bipy)]+, the reductive elimination with Me–C6H4 bond formation from the isomer with the methyl group in the axial position is predicted and is attributed to it having the best conformation of the Me and C6H4 groups for C–C bond formation. In all cases, the selectivity for reductive elimination is similar for M = Pd or Pt, but reactivity is higher for M = Pd. The relevance of this work to selectivity in catalysis is discussed.
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Affiliation(s)
- Richard J. Puddephatt
- Department of Chemistry, University of Western Ontario, London, ON N6A 5B7, Canada
- Department of Chemistry, University of Western Ontario, London, ON N6A 5B7, Canada
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Fatemeh NH, Farasat Z, Nabavizadeh SM, Wu G, Abu-Omar MM. N-methylation versus oxidative addition using MeI in the reaction of organoplatinum(II) complexes containing pyrazine ligand. J Organomet Chem 2019. [DOI: 10.1016/j.jorganchem.2018.11.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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