Mechanism of Addition of Aryltrimethyl-silanes and -stannanes to Tricarbonyl(cyclohexadienyl)ruthenium(II) Cation

Article abstract of DOI:10.1039/DT9850001049

Kinetic studies of the reaction between the organometallic complex BF4 (1) and aryltrimethyl-silanes and -stannanes of the type XC6H4M'Me3 (M' = Si or Sn; X = H, 4-NMe2, 4-OMe, 1-OMe, 4-Me, 4-SMe, 4-F, 4-Cl, 4-Br, 3-F, or 3-CF3) reveal the rate law, rate = k.This rate law has been rationalised in terms of a rate-determining electrophilic attack by complex (1) on the XC6H4M'Me3 substrates to form Wheland type ?-complex intermediates of the type (2) followed by cleavage of the Me3M-C(dienyl) bond to give the new compunds (3).These reactions are of considerable synthetic interest as they offer useful routes to otherwise inaccessible substituted benzenoid derivatives.For the Sn reactions, a Hammett plot of log (k_X/k_H) versus ? (the standard Hammett substituent constant) is linear with a slope of -2.9 suggesting a common mechanism for each of the reactions.A plot of log (k_X/k_H) for the reactions of (1) with XC6H4SnMe3 in MeNO2 (at 45 deg C) versus log(k_X/k_H) for the protiodemetallation of XC6H4Sn(cyclo-C6H11)3 by HClO4 in aqueous ethanol (at 50 deg C) is also linear indicating that organometallic complexes such as (1) behave in a similar manner to more classical electrophiles.

Full text of DOI:10.1039/DT9850001049

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