Vibrational spectroscopic study of thiophenolate-capped nanoclusters of CdS and of cadmium thiophenolate complexes

Thiophenolate-capped nanoclusters of cadmium sulfide and the cadmium thiophenolate compounds Cd(SPh)(2), [Cd(SPh)(4)](Me4N)(2), [Cd-4(SPh)(10)](Me4N)(2), and [Cd4X4(SPh)(6)](Et4N)(2) (X = C1, Br, I) have been studied by low-frequency FT-IR and Raman spectroscopy. In the spectrum of the cluster [S4Cd10(SPh)(16)](Me4N)(4) a band at 288 cm(-1) was assigned to the nu(Cd-S) stretching modes of the (Cd-S) bonds of the S4Cd6 cluster core. The nu(Cd-S) stretching frequencies of the bridging and terminal SPh- ligands which cap the cluster core were assigned to bands in the region 150-187 cm(-1). The nu(Cd-S) core band for [S4Cd17-(SPh)(28)](Me4N)(2) With tetracoordinated sulfides, as in bulk CdS, was observed at 270 cm(-1) The far-infrared nu(Cd-S) core band showed a progressive broadening and shift from 270 cm(-1) toward the peak position of 241 cm(-1) in bulk (wurtzite) CdS with increasing cluster size up to ca. 40 Angstrom. This shift is interpreted in terms of an increase in the average Cd-S bond length. Far-infrared spectroscopy has been shown to be a valuable technique for the characterization of thiolate-capped metal chalcogenide clusters.