Synthesis, spectral characterization, crystal structures and catalytic activity of a series of lanthanide(III) azepane dithiocarbamate complexes

Synthesis, spectral characterization, crystal structures of lanthanide(III) pyrrolidine dithiocarbamate complexes and their catalytic activity

“…A nephelauxetic ratio ( β) of less than one and positive values of Sinha's parameter (δ%) and the bonding parameter (b 1/2 ) suggest some covalent character in the metal-ligand bond. Also, the magnitudes of the bonding parameter (b 1/2 ) and Sinha's parameter (δ%) decrease from Pr(III) to Sm(III), indicating that the extent of the covalent character of the metal-ligand bond decreases with increasing atomic number of the metal ion, consistent with the observation made by us [12] and by Su et al [19,20].…”

“…Similar trend was exhibited for S-C-S bite angles also. The crystal structures investigated are comparable with their analogs [12][13][14]. The average bond length (Å) of C-S bond in these complexes is 1.72, which is significantly shorter than the C-S single bond length (1.81) and higher than the C=S distance (1.69).…”

“…In the case of lanthanide catalyzed reactions, a catalyst loading of 10 mol% was routinely used; lanthanide derived systems are proving to be a very fruitful area of research. Recently, the use of lanthanide dithiocarbamate complexes as catalyst in such reaction giving good yields of the product was demonstrated by us [12] and by Vale et al [26,27].…”

“…The small but evident peak that corresponds to the 3 H 4 → 1 I 6 transition in the spectrum of the Pr(III) complex is hardly observable in the spectrum of the Pr(III) aquo ion. This particular transition is hypersensitive to the environment about the Pr(III) ion [11,12,18,19]. The presence of the easily polarizable sulfur donors allows one to expect more covalent character between the soft ligand and the hard lanthanide ions.…”

“…The first band (shorter wavelength band) in the spectrum is attributed to the π→π* transition of the bidentate aromatic ligand. The very intense band at 267 nm is a result of overlapping absorption peaks of the aromatic ligands and the NCS 2 chromophore of the dithiocarbamate[12]. In the visible region, weak and narrow peaks characteristic of the Laporte-forbidden f-f transitions of the lanthanide ions are observed [figure 2(b)].…”