American Chemical Society
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Synthesis, Structure, and Reactions of Triaryl(methyl)bismuthonium Salts

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journal contribution
posted on 2000-05-06, 00:00 authored by Yoshihiro Matano
Treatment of triarylbismuth difluorides 2 (Ar3BiF2; a, Ar = Ph; b, Ar = 4-MeC6H4; c, Ar = 4-MeOC6H4; d, Ar = 2-MeOC6H4) with methylboronic acid (3) in the presence of BF3·OEt2 in CH2Cl2 afforded the corresponding triaryl(methyl)bismuthonium tetrafluoroborates 4ad ([Ar3MeBi+][BF4-]) in 42−91% yield. X-ray crystallographic analysis of compound 4d revealed that the bismuth center possesses a distorted tetrahedral geometry with C−Bi−C bond angles of 106.1(3)−113.6(3)° and Bi−C bond lengths of 2.182(7)−2.195(8) Å. Compound 4a transferred the methyl group to Ph3E (E = P, As, Sb), tris(4-methylphenyl)bismuthine, ROH (R = Me, Et, i-Pr, PhCH2), water, sodium benzenesulfinate, sodium benzoate, N,N-dimethylformamide (DMF), and thioacetamide to give the corresponding methylated products with a good recovery of triphenylbismuthine. The pseudo-first-order rate constant (kobsd = 2.9 × 10-4 s-1) observed for the reaction between 4a and benzyl alcohol (5d) was about twice as large as that (kobsd = 1.3 × 10-4 s-1) between MeOTf and 5d (in CDCl3 at 23 °C; [4a] or [MeOTf] = 0.062 M; [5d] = 0.97 M). The observed reactivity of 4a clearly demonstrates the high nucleofugality of the triphenylbismuthonio group.