摘要:
Tridentate Schiff base-ruthenium(II) complexes containing soft phosphorus or sulfur donor atoms were prepared, and their bidirectional thermal and photo substitution reactions were investigated. In acetonitrile, the chloro ligands of trans(CI,Cl)-[RuCl2(ppb-etol)(PPh3)] (1, ppb-etol = 2-(Ph2P)C6H4CH=N(CH2),OH) were substituted by acetonitrile molecules stepwise to yield [RuCl(CH3CN)(ppb-etol)(PPh3)]Cl (2) (first step) and [Ru(CH3CN)(2)(ppb-etol)(PPh3)]Cl-2 (3) (second step). Complexes 2 and 3 reverted to complex I in acetonitrile upon irradiation with UV-Vis light. Similar thermal and photo substitution reactions were also observed for trans (Cl,Cl)-[RuCl2(btb-etol)(PPh3)] (4, btb-etol = 2-((BuS)-Bu-t)C6H4CH=N(CH2)(2)OH). The substitution rates were measured for the first-step reactions of complexes I and 4 over the temperature range of 19.5-29.5 OC in acetonitrile. Kinetic parameters were determined to be k(obsd) = (1.13 +/- 0.04) x 10(-4) s(-1) (25.0 degreesC), DeltaH double dagger = 83.1 +/- 1.7 kJ mol(-1) and DeltaS double dagger = -41.9 +/- 5.6 kJ mol(-1) for complex 1, and k(obsd) = (1.57 +/- 0.06) x 10(-3) s(-1) (25.0 degreesC) DeltaH double dagger = 88.8 +/- 1.9 kJ mol(-1) and DeltaS double dagger = -0.9 +/- 6.5 kJ mol(-1) for complex 4. Accordingly, the substitution reaction of complex 4 proceeded faster than that of complex 1. The structures of [RuCl2{ppb-(1R,2S)-ephe}(PPh3)] (5, ppb-(1R,2S)-ephe=2-(Ph2P)C6H4CH=NCH(Me)-CH(Ph)OH), complex 2, and [Ru(CH3CN)(2){ppb-(R)-btol}(PPh3)](BF4)(2) (6, ppb-(R)-btol = 2-(Ph2P)C6H4CH=NCH(Et)CH2OH) were determined by X-ray analyses. In each complex, the geometry around the ruthenium atom is distorted octahedral, and the tridentate Schiff base and triphenylphosphine ligands occupy the equatorial positions. (C) 2001 Elsevier Science B.V. All rights reserved.