Thermal Stability of Tris(3,5-dimethylpyrazolyl)hydridoboratorhenium(V)(oxo)- (1,2-dithiolate) and -(1,2-monothiodiolate) Complexes and DFT Studies of C-S Bond Cleavage

Organometallics, 21 (5), 929 -933, 2002. 10.1021/om0107385 S0276-7333(01)00738-5
Web Release Date: February 6, 2002

Thermal Stability of Tris(3,5-dimethylpyrazolyl)hydridoboratorhenium(V)(oxo)- (1,2-dithiolate) and -(1,2-monothiodiolate) Complexes and DFT Studies of C-S Bond Cleavage

Kevin P. Gable,* Pitak Chuawong, and Alexandre F. T. Yokochi

Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003

Received August 13, 2001

Abstract:

Rhenium(V) complexes are prepared by reductive cyclocondensation of alkane-1,2-dithiols or alkane-1-thio-1,2-diols with Tp'ReO₃ (Tp' = tris(3,5-dimethylpyrazolyl)hydridoborate) and PPh₃. One complex, Tp'Re(O)(SCH₂CH₂S), was characterized by X-ray crystallography. Unlike the corresponding 1,2-diolato compounds, these sulfur analogues are thermally stable in hydrocarbon solvents for more than one week at 120 C. To evaluate whether the barrier to cycloreversion was thermodynamic or kinetic in origin, DFT calculations were performed at the B3LYP/LACVP** level. Comparison of calculated reaction energies reveals that substitution of each sulfur raises the predicted E_rxn for alkene cycloreversion by about 10 kcal/mol.

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