Palladium-based telomerization of 1,3-butadiene with glycerol using methoxy-functionalized triphenylphosphine ligands.
Glycerol is considered a potential renewable building block for the synthesis of existing as well as new chemicals. A promising route is the telomerization of 1,3-butadiene with glycerol leading to C8 chain ethers of glycerol with applications in, for example, surfactant chemistry. Recently, we reported a new set of palladium-based homogeneous catalytic systems for the telomerization of 1,3-butadiene with glycerol and found that palladium complexes bearing methoxy-functionalized triphenylphosphine ligands are highly active catalysts capable of converting crude glycerol without any significant loss of activity. Herein, we present a detailed account of these investigations by reporting on the influence of the butadiene/glycerol ratio, temperature, and reaction time on product selectivity and activity allowing further optimization of catalyst performance. Maximum activity and yield were reached for high 1,3-butadiene/glycerol ratios at a temperature of 90 degrees C, whereas the selectivity for mono- and diethers of glycerol could be optimized by combining high reaction temperatures and short reaction times with low butadiene/glycerol ratios. Variation of the PdII metal precursors and the metal/ligand ratio showed that palladium precursors with halogen ligands gave unsatisfying results, in contrast to precursors with weakly coordinated ligands such as [Pd(OAc)2] and [Pd(acac)2]. [Pd(dba)2], the only Pd0 precursor tested, gave the best results in terms of activity, which illustrates the importance of the ability to form a Pd0 species in the catalytic cycle. Finally, base addition resulted in a shortening of the reaction time and most likely facilitates the formation of a Pd0 species. Based on these results, we were able to realize the first attempts towards a rational ligand design aimed at a high selectivity for mono- and diether formation.
Palkovits
Regina
R
Inorganic Chemistry and Catalysis group Department of Chemistry, Utrecht University, Sorbonnelaan 16, 3584CA Utrecht (The Netherlands), Fax: (+31) 30-251-1027.|Max-Planck-Institut für Kohlenforschung, Department of Heterogeneous Catalysis and Functional Materials, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, (Germany).
Nieddu
Ilenia
I
Chemical Biology & Organic Chemistry, Debye Institute for Nanomaterials Science, Faculty of Science, Utrecht University, Padualaan 8, 3584CH Utrecht (The Netherlands).
Kruithof
Cornelis A
CA
Chemical Biology & Organic Chemistry, Debye Institute for Nanomaterials Science, Faculty of Science, Utrecht University, Padualaan 8, 3584CH Utrecht (The Netherlands).
Klein Gebbink
Robertus J M
RJM
Chemical Biology & Organic Chemistry, Debye Institute for Nanomaterials Science, Faculty of Science, Utrecht University, Padualaan 8, 3584CH Utrecht (The Netherlands).
Weckhuysen
Bert M
BM
Inorganic Chemistry and Catalysis group Department of Chemistry, Utrecht University, Sorbonnelaan 16, 3584CA Utrecht (The Netherlands), Fax: (+31) 30-251-1027.
D002070:Butadienes / Q000737:chemistry*; D002384:Catalysis; D005990:Glycerol / Q000737:chemistry*; D008024:Ligands; D015394:Molecular Structure; D009943:Organophosphorus Compounds / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D013696:Temperature; D013997:Time Factors
D002070:Butadienes; D008024:Ligands; D009943:Organophosphorus Compounds; C061896:triphenylphosphine; D010165:Palladium; C031763:1,3-butadiene; D005990:Glycerol