title: Kinetic aspects for the reduction of CO₂ and CS₂ with mixed-ligand ruthenium(II) hydride complexes containing phosphine and bipyridine.
abstract: A new water-soluble ruthenium hydride complex [Ru(H)(bpy)2(PTA)]PF6 (bpy = 2,2'-bipyridine, PTA = 1,3,5-triaza-7-phosphaadamantane) (1a) was prepared. 1a reacted with CO2 and CS2 to give the corresponding formate and dithioformate complexes, respectively. Both the insertions of CO2 and CS2 into the Ru-H bond of 1a followed second-order kinetics. The second-order rate constant (k2) of CO2 insertion reaction varied from (9.40 ± 0.41) × 10(-4) M(-1) s(-1) in acetone to (1.13 ± 0.08) × 10(-1) M(-1) s(-1) in methanol; moreover, the ln(k2) is in good linear relationship with the acceptor number (AN) of the solvent used. Although, the k2 of CS2 insertion reaction ranged from (3.43 ± 0.10) M(-1) s(-1) in methanol to (24.0 ± 0.5) M(-1) s(-1) in N,N-dimethylformamide, which is 1000 times faster than CO2 insertion. Generally, the k2 of CS2 insertion increased with the static dielectric constant (D(s)) of the reaction medium investigated. For comparison purposes, we further investigated the reactivity of [Ru(H)(bpy)2(PPh3)]PF6 (PPh3 = triphenylphosphine) (1b) with CO2 and CS2. 1b reacted with CO2 slowly in the methanol with a k2 of (1.46 ± 0.09) × 10(-3) M(-1) s(-1), yielding a formate complex [Ru(η(1)-OC(H)═O)(bpy)2(PPh3)]PF6 (2b). The reaction of 1b with CS2 is 1000 times faster than that of CO2. The structures of 1a, 1b, and 2b were determined by X-ray crystallographic analysis.
authors.affiliation: CAS Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences , Guangzhou 510640, P. R. China.
authors.forename: Jing
authors.initials: J
authors.lastname: Huang
authors.forename: Jinzhu
authors.initials: J
authors.lastname: Chen
authors.forename: Hui
authors.initials: H
authors.lastname: Gao
authors.forename: Limin
authors.initials: L
authors.lastname: Chen