Silica-Supported Tungsten Carbynes (≡SiO)_xW(≡CH)(Me)_y (x = 1, y = 2; x = 2, y = 1): New Efficient Catalysts for Alkyne Cyclotrimerization

Abstract

The activity of silica-supported tungsten carbyne complexes (≡SiO)xW(≡CH)(Me)y (x = 1, y = 2; x = 2, y = 1) toward alkynes is reported. We found that they are efficient precatalysts for terminal alkyne cyclotrimerization with high TONs. We also demonstrate that this catalyst species is active for alkyne cyclotrimerization without the formation of significant alkyne metathesis products. Additional DFT calculations highlight the importance of the W coordination sphere in supporting this experimental behaviorA.P. thanks the Spanish MINECO for a Ramón y Cajal contract (RYC-2009-05226) and the European Commission for a Career Integration Grant (CIG09-GA-2011-293900

Unsaturated fatty acid esters metathesis catalyzed by silica supported WMe5

“…We recently discovered that (1) converts terminal alkynes into substituted benzene derivatives via cyclotrimerization mechanism under solvent free conditions. 19 Following the same line of thought, 1 being active for olefins (ISOMET) (Figure 3a) and alkynes (cyclotrimerization) (Figure 3c), catalytic experiments with a molar mixture of 1-decene/1-decyne were carried out ( Figure 3b). Figure 3c displays the GC chromatogram corresponding to the total conversion of 1-decyne, showing only cycloctrimerization products.…”

Simple addition of silica to an alkane solution of a Wilkinson WMe6 or Schrock W alkylidyne complex gives an active complex for saturated and unsaturated hydrocarbon metathesis

“…3 catalyzes also the ISOMET reaction of 1-decene, Figure 5 and Figure S9. 10 The formation of the latter would suggest the formation of 5-octadecyne c4 c5 c6 c7 c8 c9 c11 c12 c13 c14 c15 c16 c17 c18 c19 c20 c21 c22 c23 c24 c25 c26 c27 c28 c29 This one pot protocol was also efficient in converting fatty acid esters (FAE) into the corresponding diesters. 16,24,25 As it is generally assumed that high oxidation state W alkylidyne without pendent alkyl groups catalyze alkyne metathesis and not olefin metathesis, [26][27][28] our result demonstrates thus the importance of the alkyl groups in the W coordination sphere.…”

“…In both cases (linear and cyclic alkanes metathesis), the alkane products distribution is similar to the one observed while starting with pre-catalyst 1 (see Figure 1, for n-decane metathesis, see Figure S1 for cyclooctane metathesis). 10 These previous works highlighted that a silica supported W-carbyne moiety associated with σ-ligand is crucial for the transformation of alkane metathesis to occur. In fact, it is well-known in homogeneous system that these electron-deficient W complexes decompose into inactive species through a dimerization processes.…”

Exploring Basic Components Effect on the Catalytic Efficiency of Chevron-Phillips Catalyst in Ethylene Trimerization

“…Based on the aforementioned catalytic precursors, the active site model (shown in Scheme 1) is considered as an active catalyst in the trimerization process [14,15]. This catalyst mainly consists of a pyrrole ring coordinated to the Cr center, together with a pendant R2AlCl group σ-bonded to the pyrrole ligand, via Al-N linkage, and to the Cr metal, via Cr-Cl linkage.…”