Studies of high-valent vanadium complexes binding with non-innocent thiolato ligands / the cleavage of strong C-O and O-H bonds with assistance of hydrogen bonds

• Main Authors: Chun-KangLo, 羅淳剛
• Other Authors: Hua-Fen Hsu
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/02628105393853398997

碩士 === 國立成功大學 === 化學系 === 103 === In our effort to understanding high-valent vanadium sulfur chemistry, two tris(thiolato)phosphine ligands, [PS3”]H3 and [PS3*]H3 has been untilized to interact with high-valent vanadium species.([PS3”]H3=[P(C6H3-3-Me3Si-2-S)3]3-. [PS3*]H3=[P(C6H3-3-Ph-2-S)3]3-). At this work, several five vanadium-thiolate complexes have been obtained and characterized. They are [V(PS3”)2][NEt4] (1a), [V(PS3*)2][NPr4] (1b),[VIV(PS2”SH)(PS3”)][PPh4] (2a), [VIV(PS3*)(PS2*SH)][NPent4] (2b), and [VIV(PS3*)2] [(NPr4)2] (3). The reactivity of them with air has been explored. The evidences were supported by Ultraviolet-visible spectroscopies and ESI-MS studies. The hepta-coordinated [VIV(PS2”SH)(PS3”)]- (2a), and [VIV(PS3*)(PS2*SH)]- (2b) proceed air oxidation to form the octa-coordinated [V(PS3”)2]- (1a) and [V(PS3*)2]- (1b), respectively. The octa-coordinated [VIV(PS3*)2]2- (3) can be oxidized via one electron oxidation to form complex 1b by air oxidation or [Fe(C5H5)2][BF4] oxidation. From ESI-MS studies, complex 1a and 1b, species with resonance forms between V(V)-thiolate and V(IV)-thiyl radical, can reacted with H2O and form 2a and 2b by homolytic cleavage of the O-H bond. In addition, complex 1a and 1b also reacted with methanol via homolytic cleavage of O-H bond and C-O bond. Consequently, it led to the formation of 2a, [VIV(PS3”)(PS2SCH3”)]- (4a), and 2b, [VIV(PS3*)(PS2SCH3*)]- (4b), respectively. The kinetic studies of 1a with a series of substrates, such as H2O, toluene, CH3CN, fluorene and THF, have been investigated. From the kinetic isotope effect (KIE), O-H bond cleavage in H2O is an important component of the rate-determining step. It is interesting that 1a prefers to cleave stronger O-H bonds rather than C-H bonds. This finding was proposed that the preorganization step via the assistant of the hydrogen bonding interaction between substrates and 1a plays a key role which reduces the activation energy barrier.