A simple synthesis of [RuCl₂(NHC)(p-cymene)] complexes and their use in olefin oxidation catalysis

Abstract

A simple and efficient synthetic route to [RuCl2(NHC)(p-cymene)] and [Ru(CO3)(NHC)(p-cymene)] complexes making use of a weak base, under aerobic conditions, is reported. This method enables access to a series of...

Simple synthesis of [Ru(CO3)(NHC)(p-cymene)] complexes and their use in transfer hydrogenation catalysis

“…The study was initiated by investigating the reaction of IPr•HBF4 with [RuCl2(p-cymene)]2 based on the conditions we previously reported. 10 Gratifyingly, the targeted [Ru(IPr)(CO3)(p-cymene)] complex 3a was obtained in a moderate yield after 29 hours when the reaction was carried out in acetone at 60 o C (Table 1, entry 1). Subsequently, we optimized the reaction parameters, including solvent, base and temperature, in order to provide the most practical and efficient method to these complexes.…”

“…Among them, 2b can be efficiently transformed into the corresponding 3b in only 3 hours at 70 o C. In addition, compound 3d can also be successfully synthesized in 72% yield by using CPME as solvent. Although ICy•HCl can also be used as a material to obtain the target product 3d, 10 ICy•HCl salt is highly hygroscopic, resulting in partial hydrolysis. Therefore, ICy•HBF4 2d as a material is an effective reaction partner in the above method.…”

“…12 Although the use of K2CO3 in the synthesis of Ru-NHC complex has been described as early as 2006 by Dixneuf and co-workers, this method was limited to one example of Ru complex and was never further explored. 13 Our group also has recently demonstrated the efficiency of the weak base route to synthesis Ru complexes 10 . Both methods use NHC•HCl as starting material (Scheme 1, Route A).…”

“…6 The advantage of this method is that it does not only simplify the synthetic reaction, but also uses ecofriendly reagents instead of strong bases to prepare a wide range of NHC complexes under mild conditions. Recently, we have developed straightforward and sustainable methods for the synthesis of well-defined Au 7 , Cu 6c, 8 , Pt 9 , Ru 10 and Pd-NHC 11 species, using imidazol(idin)ium salts and weak bases. In addition, other research groups have also developed similar methods for Au, Rh,Cu,etc.…”

A green route to platinum N-heterocyclic carbene complexes: mechanism and expanded scope

“…5 Among many known and still widely used synthetic methods of accessing N-heterocyclic carbene metal complexes, 6 such as reacting a metal precursor with a free NHC 2,7 or a carbene generated in situ by deprotonation of the corresponding azolium salt using a strong base (e.g., NaO t Bu, KHMDS, NaH and n-BuLi), 8 or making use of transmetallation reagents (silver(I)-9 and copper(I)-NHC 10 complexes), the recently disclosed weak-base method stands out as the most sustainable and user-friendly. 11 The development of a protocol utilizing a weak base (e.g., K 2 CO 3 , NaOAc or NEt 3 ) and azolium NHC precursors has been a major advance in accessing ubiquitous well-defined NHC complexes, and has recently become the new standard in the synthesis of gold-, 12 copper-, 13 palladium-, 14 rhodium-, 15 iridium-15a and ruthenium-NHC 16 compounds.…”