THE STRUCTURALLY FLEXIBLE BICYCLIC BIS(2-HYDROXYETHANETHIOLATO)BISMUTH(III) COMPLEX - A MODEL FOR ASYMMETRIC MONOANIONIC CHELATION OF BISMUTH(III)

Reaction of Bi(NO3)(3) With 2-mercaptoethanol gives [Bi(SCH2CH2OH)(2)] [NO3], 5(NO3), independent of stoichiometry. Other salts or derivative s of 5, 5(Cl) and 5(Br), are readily prepared by anion exchange reacti ons and can also be obtained by reaction of BiX3 (X = Cl, Br) with 2-m ercaptoethanol. Reaction of Bi(CH3COO)3 with 2-mercaptoethanol gives t he conjugate base of 5 which is readily protonated with glacial acetic acid to give the acetate salt 5(CH3COO). The compounds have been char acterized by IR, Raman, and NMR spectroscopies and APCI mass spectrome try. X-ray crystallographic studies of 5(NO3) [crystal data: C4H10O2Bi S2N . H2O, I4(1)/a, a 20.337(6) Angstrom, b = 20.337(6) Angstrom, c = 11.303(7) Angstrom, Z = 16], 5(NO3) [crystal data: C4H10O2BiS2Cl, P2(1 )/n, a = 8.653(2) Angstrom, b = 10.618(3) Angstrom, c = 10.564(2) Angs trom, beta = 100.51(2)degrees, Z = 4], and S(CH3COO) [crystal data: C6 H13O4-BiS2, P2(1)/c, a = 8.089(2) Angstrom, b = 16.313(3) Angstrom, c = 8.708(2) Angstrom, beta = 98.37(3)degrees, Z = 4] show them to each contain the bicyclic bis(2-hydroxyethanethiolato)bismuth framework 5. The conformational features of 5 are dramatically different in each of the structures, perhaps reflecting the relative donor capabilities of the anions. The observations reveal a substantial thermodynamic prefe rence for the thiolate-alcohol chelate in a 2:1 stoichiometry over oth er possible structural arrangements, which is interpreted in terms of hard and soft acid-base theory and mediation of the acidity of the bis muth site by the double hydroxyl coordination.