312925-28-3Relevant academic research and scientific papers
Mechanistic information from low-temperature rapid-scan and NMR measurements on the protonation and subsequent reductive elimination reaction of a (diimine)platinum(II) dimethyl complex
Wik, Bror J.,Ivanovic-Burmazovic, Ivana,Tilset, Mats,Van Eldik, Rudi
, p. 3613 - 3621 (2008/10/09)
A detailed kinetic study of the protonation and subsequent reductive elimination reaction of a (diimine)platinum(II) dimethyl complex was undertaken in dichloromethane over the temperature range of -90 to +10°C by stopped-flow techniques. Time-resolved UV-vis monitoring of the reaction allowed the assessment of the effects of acid concentration, coordinating solvent (MeCN) concentration, temperature, and pressure. The second-order rate constant for the protonation step was determined to be 15200 ± 400 M-1 s-1 at -78°C, and the corresponding activation parameters are ΔH? = 15.2 ± 0.6 kJ mol-1 and ΔS? = -85 ± 3 J mol-1 K-1, which are in agreement with the addition of a proton that results in the formation of the platinum(IV) hydrido complex. The kinetics of the second, methane-releasing reaction step do not show an acid dependence, and the MeCN concentration also does not significantly affect the reaction rate. The activation parameters for the second reaction step were found to be ΔH? = 75 ± 1 kJ mol-1, ΔS ? = +38 ± 5 J mol-1 K-1, and ΔV? = +18 ± 1 cm3 mol-1, strongly suggesting a dissociative character of the rate-determining step for the reductive elimination reaction. The spectroscopic and kinetic observations were correlated with NMR data and assisted the elucidation of the underlying reaction mechanism.
The metal is the kinetic site of protonation of (Diimine)Pt dimethyl complexes
Wik, Bror Johan,Lersch, Martin,Tilset, Mats
, p. 12116 - 12117 (2007/10/03)
Protonolysis of (diimine)PtMe2 (1) complexes in CD2Cl2 containing CD3CN at -78 °C yields (diimine)PtMe2(H)(NCCD3)+ (4), (diimine)PtMe(NCCD3)+ (5), and methane. The relative yields of 5 and methane decrease with increasing concentrations of CD3CN. This is consistent with protonation of 1 occurring directly at the metal, rather than at a methyl group. The principle of microscopic reversibility then implies that the deprotonation in Shilov-type C-H activation occurs from a Pt(IV) hydridomethyl intermediate, rather than from a Pt σ-methane complex. Copyright
