196409-86-6Relevant academic research and scientific papers
C-H bond cleavage in thiophenes by [P(CH2CH2PPh2)3Ru]. UV flash kinetic spectroscopy discloses the ruthenium-thiophene adduct which precedes C-H insertion
Bianchini, Claudio,Casares, Juan A.,Osman, Robert,Pattison, David I.,Peruzzini, Maurizio,Perutz, Robin N.,Zanobini, Fabrizio
, p. 4611 - 4619 (1997)
Photolysis of [(PP3)RuH2] (PP3 = P(CH2CH2PPh2)3) (1) in THF at 23 °C under an inert atmosphere (N2, Ar, or He) in the presence of thiophene (T) or ethyl 2-thiophenecarboxylate (2-CO2EtT) gives the (hydride)2-thienyl complexes [(PP3)Ru(H)(2-Tyl)] (5) (Tyl = C4H3S) and [(PP3)Ru(H)(2-CO2EtTyl)] (7) (CO2EtTyl = C4H2(CO2Et)S), respectively. The C-H insertion products 5 and 7 are also selectively obtained by the thermal reaction of the Ru(0) dinitrogen complex [(PP3)Ru(N2)] (4) in THF with T or 2-CO2EtT. Complexes 5 and 7 are both photochemically and thermally stable. Under comparable conditions, the photolysis of the Os derivative [(PP3)OsH2] in THF in the presence of T exclusively yields the C-H insertion product [(PP3)Os(H)(2-Tyl)]. Photolysis of 1 at 23 °C under nitrogen and in the presence of 2,5-dimethylthiophene (2,5-Me2T) gives the complex [(PP3)Ru(η1-S-2,5-Me2T)] (8) containing an S-bound thiophene molecule. Complex 8 is also obtained by reaction of isolated 4 with 2,5-Me2T. The Ru(0) transient, [(PP3)Ru], generated by laser flash photolysis in either cyclohexane or THF solution, has been detected and characterized by UV-vis spectroscopy. [(PP3)Ru] reacts with T (k2 = (1.4 ± 0.2) × 106 dm3 mol-1 s-1), yielding an adduct [(PP3)-Ru(T)]. In cyclohexane, [(PP3)Ru(T)] decays to the C-H insertion product 5 with first-order kinetics (k = 20 ± 1 s-1 at 296 K). In THF, the 16 e- Ru(0) transient forms with THF a short-lived adduct, probably bound through oxygen, [(PP3)Ru(THF)], which reacts with T to give [(PP3)Ru(T)] (kobs = 680 s-1, [T] = 0.3 mol dm-3 under Ar). This T adduct decays to [(PP3)Ru(2-Tyl)H] with first-order kinetics (k = 18 ± 1 s-1). Similar measurements with 2,5-Me2T yield a rate constant for [(PP3)Ru] + 2,5-Me2T in cyclohexane of (1.0 ± 0.3) × 106 dm3 mol-1 s-1. The resulting [(PP3)Ru(2,5-Me2T)] is kinetically stable. Flash photolysis of [(PP3)OsH2] in cyclohexane with added T yields rate constants for [(PP3)Os] + T and for isomerization of [(PP3)Os(T)] of (3.7 ± 0.1) × 105 dm3 mol-1 s-1 and 8 ± 1 s-1, respectively.
