1067516-54-4Relevant academic research and scientific papers
Influence of ligand polarizability on the reversible binding of O 2 by trans-[Rh(X)(XNC)(PPh3)2] (X = Cl, Br, SC6F5, C2Ph; XNC = Xylyl isocyanide). Structures and a kinetic study
Carlton, Laurence,Mokoena, Lebohang V.,Fernandes, Manuel A.
, p. 8696 - 8703 (2009/03/11)
The complexes trans-[Rh(X)(XNC)(PPh3)2] (X = Cl, 1; Br, 2; SC6F5, 3; C2Ph, 4; XNC = xylyl isocyanide) combine reversibly with molecular oxygen to give [Rh(X)(O 2)(XNC)(PPh3)2] of which [Rh(SC 6F5)(O2)(XNC)(PPh3)2] (7) and [Rh(C2Ph)(O2)(XNC)(PPh3)2] (8) are sufficiently stable to be isolated in crystalline form. Complexes 2, 3, 4, and 7 have been structurally characterized. Kinetic data for the dissociation of O2 from the dioxygen adducts of 1-4 were obtained using 31P NMR to monitor changes in the concentration of [Rh(X)(O 2)(XNC)(PPh3)2] (X = Cl, Br, SC 6F5, C2Ph) resulting from the bubbling of argon through the respective warmed solutions (solvent chlorobenzene). From data recorded at temperatures in the range 30-70°C, activation parameters were obtained as follows: ΔH? (kJ mol-1): 31.7 ± 1.6 (X = Cl), 52.1 ± 4.3 (X = Br), 66.0 ± 5.8 (X = SC6F5), 101.3 ± 1.8 (X = C2Ph); ΔS? (J K-1 mol-1): -170.3 ± 5.0 (X = Cl), -120 ± 13.6 (X = Br), -89 ± 18.2 (X = SC 6F5), -6.4 ± 5.4 (X = C2Ph). The values of ΔH? and ΔS? are closely correlated (R2 = 0.9997), consistent with a common dissociation pathway along which the rate-determining step occurs at a different position for each X. Relative magnitudes of ΔH? are interpreted in terms of differing polarizabilities of ligands X.
