Author : Pitak Chuawong
Publisher :
ISBN 13 :
Total Pages : 190 pages
Book Rating : 4.:/5 (519 download)
Book Synopsis Synthesis, Characterization, and Reactivity of Rhenium Dithiodiolate and Monothiodiolate Complexes by : Pitak Chuawong
Download or read book Synthesis, Characterization, and Reactivity of Rhenium Dithiodiolate and Monothiodiolate Complexes written by Pitak Chuawong and published by . This book was released on 2001 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: The rhenium dithiodiolate, Hydrido-tris-(3,5-dimethyl- 1 -pyrazol yl) borato(ethane- 1,2-dithiodiolato)(oxo)rheni um(V), and Hydrido-tris-(3,5-dimethyl- 1 -pyrazolyl)borato(phenylethanedithiodiolato)(oxo)rhenium(V), were synthesized by reductive cyclocondensation of alkane-1,2-dithiols with Tp'Re03 in a one pot fashion. The rhemium monothiodiolate, Hydrido-tris-(3,5-dimethyl- 1 -pyrazolyl) borato(ethane- 1,2-monothiodiolato)(oxo)rhenium(V), and Hydrido-tris-(3,5- dimethyl- 1 -pyrazolyl)borato(propanemonothiodiolato)(oxo)rhenium(V), were also synthesized by using the same procedure. The syn and anti isomers of rhenium phenylethanedithiodiolate and rhenium propanemonothiodiolate were characterized by using COSY, nOe, and HSQC experiments. An X-ray crystal structure of the rhenium ethanedithiodiolate was obtained, and an unusually small dihedral angle (S-C-C-S) of about 12° was observed. The solution conformation of these compounds was investigated by using a Karplus relationship between vicinal coupling constants and dihedral angle. The dihedral angle for the ethanedithiodiolate appeared to be 38° indicating a staggered geometry for the ring. All of these complexes failed to cyclorevert to any detectable extent at 120°C after 7 days. This observation reflects the thermal stability of rhenium dithiodiolate and monothiodiolate complexes. Energetics of ethylene addition to tetrathioperrhenate anion (ReS4−) and addition of hydrogen sulfide to the alkene adduct were calculated by DFT calculation using LACVP** basis set with B3LYP functionals. The heat of reaction of ethylene addition to ReS4− was 15.4 kcal/mol, and 111.1 kcal/mol for addition of hydrogen sulfide to the alkene adduct. These results are consistent with the stability of the dithiodiolate complex toward cycloreversion reaction. Reaction of Tp'Re03 and ethylene sulfide led to the rhenium ethanedithiolate complex both with and without acid catalysis. This observation led to a proposed multi step mechanism.
