Diphenyllead(IV) thiosemicarbazonates and pyrazolonates: Synthesis and characterization

摘要

Cyclization of thiosemicarbazones derived from beta-keto esters and beta-keto amides (HTSC) in the presence of diphenyllead(IV) acetate was explored in methanol solution at room temperature and under reflux. All beta-keto ester TSCs underwent cyclization to give the corresponding pyrazolone (HL), which, except in one case, deprotonated and coordinated the PbPh22+ moiety to form homoleptic [PbPh2(L)(2)] or heteroleptic [PbPh2(OAc)(L)] derivatives. Cyclization did not occur with beta-keto amide TSCs and only [Pbph(2)(TSC)(2)] or [PbPh2(OAc)(TSC)] thiosernicarbazonates were isolated. The complexes were characterized by IR spectroscopy in the solid state and by H-1, C-13 and Pb-207 NMR spectroscopy in DMSO-d(G) solution, in which they evolve and decompose with time. Additionally, crystals of p-acetoacetanisidide thiosemicarbazone (HTSC10), [PbPh2(OAc)(L-5)] center dot MeOH (HL5 = 2,5-dihydro-3,4-dimethyl-5-oxo-1H-pyrazolone-1-carbothioamide), [PbPh2Cl(L-2)] (HL2 = 2,5-dihydro-5-oxo-3-phenyl-1H-pyrazolone-1-carbothioamide), [PbPh2(OAc)(TSC8)]center dot 2MeOH (HTSC8 = acetoacetanilide thiosemicarbazone), [PbPh2(OAc)(TSC10)]center dot H2O and [PbPh2(OAc)(TSC11)] center dot 0.75MeOH (HTSO11 = o-acetoacetotoluidide) were studied by X-ray crystallography. The complexes, monomers or dimers with almost linear C-Pb-C moieties, are compared with the corresponding derivatives of Pb(II).