Simultaneous Determination of Structural and Kinetic Parameters Characterizing the Interconversion of Highly Dispersed Species: the Interaction of NO with Rh^I(CO)₂/γ-Al₂O₃

Abstract

Energy-dispersive EXAFS (EDE), combined with mass spectrometry and a flow microreactor system, has been used to investigate the reaction of an Al2O3-supported RhI(CO)2 species with NO. This combined in situ approach uniquely permits a priori analysis of the structures of the species involved (on a time scale of ca. 2 s) and simultaneous determination of reaction mechanism and kinetic parameters. In the current case, it is found that the Al(O)RhI(CO)2Cl species reacts to form an intermediate Al(O)Rh(NO)2Cl Cl species (ν ≈ 0.357 ± 0.125 s-1, Eact ≈ 11 ± 1.25 kJ mol-1), which subsequently forms an (AlO)2Rh(NO)-Cl species and N2O(g) (ν ≈ 2 ± 0.5 × 104 s-1, Eact ≈ 40 ± 3.5 kJ mol-1) showing a bent (134°) RhNO bond. This combination of rapid and complementary techniques should be applicable to a wide range of disciplines where quantitative structural and kinetic determinations are of importance.