Homogeneous catalysis by platinum(II)—tin(II) chloride complex. Part 3.—Kinetics of isotopic exchange reaction of methanol with hydrogen

Abstract

The isotopic exchange reaction of CH₃OH, containing a Pt^II—Sn^II chloride complex, with D₂ has been studied in the temperature range 0–20°C and deuterium pressures up to 100 Torr. The reaction is first-order in deuterium. The rate exhibits a maximum at a Sn/Pt ratio of about 5.5, predicting the effective complex to be penta-coordinated. The comparison of the rate with that of exchange between CH₃OD and H₂ indicates that the kinetic isotope effect, [–dP(H₂)/dt]/[–dP(D₂)/dt], is straight-forward. The fraction of HD produced in hydrogen decreases with incrasing Sn/Pt and temperature. The reaction mechanism is discussed on the basis of these results.