Influence of Ligand Polarizability on the Reversible Binding of O2 by trans-[Rh(X)(XNC)(PPh3)2] (X = Cl, Br, SC6F5, C2Ph; XNC = Xylyl Isocyanide). Structures and a Kinetic Study
摘要:
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(SC6F5)(O-2)(XNC)(PPh3)(2)] (7) and [Rh(C2Ph)(O-2)(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 O-2 from the dioxygen adducts of 1-4 were obtained using P-31 NMR to monitor changes in the concentration of [Rh(X)(O-2)(XNC)(PPh3)(2)] (X = Cl, Br, SC6F5, C2Ph) resulting from the bubbling of argon through the respective warmed solutions (solvent chlorobenzene). From data recorded at temperatures in the range 30-70 degrees C, activation parameters were obtained as follows: Delta H double dagger (kJ mol(-1)): 31.7 +/- 1.6 (X = Cl), 52.1 +/- 4.3 (X = Br), 66.0 +/- 15.8 (X = SC6F5), 101.3 +/- 1.8 (X = C2Ph); Delta S double dagger (J K-1 mol(-1)): -170.3 +/- 5.0 (X = Cl), -120 +/- 13.6 (X = Br), -89 +/- 18.2 (X = SC6F5), -6.4 +/- 5.4 (X = C2Ph). The values of Delta H double dagger and Delta S double dagger are closely correlated (R-2 = 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 Delta H double dagger are interpreted in terms of differing polarizabilities of ligands X.
The catalytic substitution of metal carbonyls and substituted metal carbonyls by isonitriles in the presence of rhodium(I) and polymer-supported rhodium(I) complexes
作者:Michel O. Albers、Neil J. Coville、Christakis P. Nicolaides、Ronald A. Webber、Terence V. Ashworth、Eric Singleton
DOI:10.1016/s0022-328x(00)85787-3
日期:1981.9
Metal carbonyls and substituted metal carbonyls, under relatively mild reaction conditions, in the presence of isonitriles, undergo catalytic CO substitution by rhodium(I) and polymer-supported rhodium(I) complexes. The reaction provides a facile route to the synthesis of transition metalisonitrilemetalisonitrilecomplexes.