Experimental and DFT investigation of the 1-octene metathesis reaction mechanism with the Grubbs 1 precatalyst

Using density functional theory the metathesis reactions of 1-octene in the presence of Grubbs 1 [RuCl2(PCy3)2(CHPh)] is investigated. At the GGA-PW91/DNP level, the complete geometry optimization and the activation energy of various activation steps and catalytic cycles in the dissociative mechanism are performed. The formation of the catalytically active heptylidene species is kinetically and thermodynamically favoured, while the formation of trans-tetradecene is thermodynamically favoured. The computational results are in agreement with the experimental results obtained with NMR and GC/MSD experiments. Grubbs 1 is active for the metathesis of 1-octene at 25 °C yielding trans-7-tetradecene as the major product. The formation of by-products, i.e. styrene isomers and PCy3, is consistent with the dissociative metal carbene mechanism. The rapid formation of the heptylidene derivative of Grubbs 1 is observed by in situ NMR.

Graphical abstractUsing density functional theory (Accelrys DMol3 GGA-PW91/DNP) and experimental techniques (NMR and GC/MSD) the metathesis of 1-octene in the presence of Grubbs 1 [RuCl2(PCy3)2(CHPh)] is investigated. Grubbs 1 is an active metathesis precatalyst yielding the kinetically favoured trans-7-tetradecene as the major product. The rapid formation of the kinetically and thermodynamically favoured heptylidene species is observed by NMR. The dissociative metal carbene mechanism is supported. Figure optionsDownload full-size imageDownload as PowerPoint slide