The use of control experiments as the sole route to correct the mechanistic interpretation of mercury poisoning test results: The case of P,C-palladacycle-catalysed reactions

In the study of the metallic mercury interaction with cyclopalladated derivatives of tris-ortho-tolylphosphine [{(κ2P,C-L)Pd(μ-X)}2], the redox-transmetallation of palladacycles by metallic mercury with the formation of P,C-chelated benzylmercurials [(κ2P,C-L)HgX] was revealed at moderate temperature in the presence of excess Hg(0). In contrast, the mercury(0) testing of the Suzuki reaction with the same chloride P,C-precatalyst gave a negative result, even at a higher temperature and with a greater excess of Hg(0). The structures of these mercurials have been convincingly confirmed spectrally (1Н, 13С, 31Р and 199Hg NMR), and via X-ray diffraction study and DFT calculations for the chloride mercurial. Our results and the analysis of known data on the mercury diagnostics of catalytic systems with classical and anomalous P,C-precatalysts enable us to assume that the intact state of palladacycle is present in the key anionic intermediate [(κ2P,C-L)Pd0]– of catalytic cycles of the Suzuki and Heck reactions and a lower reactivity of Hg(0) with palladium(0) complexes in comparison with that of palladium(II) analogues. © 2020

Gorunova O.N.1 , Novitskiy I.M.2, 3 , Grishin Y.K.2 , Gloriozov I.P.2 , Roznyatovsky V.A.2 , Khrustalev V.N. 4, 5, 6 , Kochetkov K.A.1, 7 , Dunina V.V.2
  • 1 A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilova St. 28, Moscow, 119991, Russian Federation
  • 2 Department of Chemistry, M.V. Lomonosov Moscow State University, Lenin Hills, Moscow, 119991, Russian Federation
  • 3 Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, United States
  • 4 Inorganic Chemistry Department, Peoples’ Friendship University of Russia, Miklukho-Maklay Street 6, Moscow, 117198, Russian Federation
  • 5 Department of Chemistry, New Mexico Highlands University, Las Vegas, NM 87701, United States
  • 6 Zelinsky Institute of Organic Chemistry RAS, 47 Leninsky Prospect, Moscow, 119991, Russian Federation
  • 7 Mendeleev University of Chemical Technology of Russia, Miusskaya pl. 9, Moscow, 125047, Russian Federation
Chlorine compounds; Design for testability; Mercury compounds; Organometallics; Reaction intermediates; Anionic intermediates; Catalytic cycles; Catalytic system; Control experiments; Mechanistic interpretations; Moderate temperature; Transmetallation; X-ray diffraction studies; Palladium compounds
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