475563-43-0Relevant academic research and scientific papers
Ruthenium-catalyzed isomerization of allylic alcohols: Oxidation state determines resistance against diene inhibition
Van Der Drift, Robert C.,Sprengers, Jeroen W.,Bouwman, Elisabeth,Mul, Wilhelmus P.,Kooijman, Huub,Spek, Anthony L.,Drent, Eite
, p. 2147 - 2155 (2002)
The novel complex mer-[RuCl3(dmso)(phen)] (1) has been prepared and characterized by X-ray diffraction. The ruthenium center is in a distorted octahedral environment with the three chloride ions coordinated in a mer-fashion and an S-bonded dmso ligand trans to one of the phen nitrogen atoms. Electrochemical experiments show two reversible waves in acetonitrile solution, corresponding to the couples RuIII/II (0.11 V) and RuIV/III (1.73 V). The analogous RuII complex cis, cis-[RuCl2(dmso)2(phen)] (2) shows one reversible wave at 1.08 V, corresponding to the RuIII/II couple. Both complexes exhibit high catalytic activity in the isomerization of 3-buten-2-ol to butanone. The initial turnover frequency (TOF) for 1 in diglyme/water at 130 °C is 295 h-1 with a firstorder kini of 0.6 h-1, while 2 reaches an initial TOF of 260 h-1 and a kini of 0.5 h-1. A cumulative turnover number (TON) of 1025 has been obtained with 1 as a catalyst precursor. The activity of 1 and 2 has been compared to that of in situ mixtures with both RuIII and RuII precursors. All RuII complexes are deactivated before 100% conversion has been attained. RuCl3 is a good catalyst precursor with an initial TOF of 500 h-1. If RuCl3 is mixed in situ with one equivalent of phen, an induction period of 40 min results and the activity thereafter is much lower than without the addition of phen. With 2 equiv. of phen, no reaction is observed in the first 6 h and only a very low activity is obtained after that. An important difference between 1 and 2 becomes apparent when a conjugated diene is added to the reaction mixture; only 1 remains active. The results demonstrate that only RuIII complexes with one phen ligand are active catalyst precursors for the isomerization of allylic alcohols in the presence of conjugated dienes. The consequence of this observation is further demonstrated by applying both catalyst precursors in the direct one-pot conversion of 1,3-butadiene to butanone. In this reaction, complex 1 (TON = 2050, t = 6 h) forms a much more active precursor than complex 2 (TON = 1300, t = 7 h). Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
