Molecular Precursors for CdS Nanoparticles: Synthesis and Characterization of Carboxylate−Thiourea or −Thiosemicarbazide Cadmium Complexes and Their Decomposition

The reactions of cadmium acetate with picolinic (Hpic), 2,6-dipicolinic (H2pydc), or salicylic acid (H2sal) followed by the addition of thiourea (tu) or thiosemicarbazide (ths) yielded six new coordination complexes, including [Cd(Hsal)2(tu)2] (1a), [Cd(pic)2(tu)2]·0.5H2O (2a), [Cd(pic)2(ths)2]·2H2O (2b), [Cd(pydc)(tu)2] (3a), and [Cd(pydc)(ths)2(H2O)]·2H2O (3b). All of the compounds were characterized spectroscopically and by elemental analysis. Compounds 1a, 2a, 2b, 3a, and 3b formed well-defined crystals and were further characterized by single-crystal X-ray diffraction. Additionally, reaction of Cd(Hsal)2 with ths produced a compound 1b of uncertain composition that had bound ths as evidenced by ESI-MS. The most likely formula for this compound was Cd(sal)(ths)x, but Cd(Hsal)2(ths)x was also possible. In compounds 1a and 3a, the Cd(II) ion exhibits penta-coordinated geometry; in 1a, three carboxylate oxygen atoms and two sulfur atoms from thiourea complete the coordination sphere, whereas in 3a, two c...