A comparison of low and high activity precatalysts: Do the calculated energy barriers during the self‐metathesis reaction of 1‐Octene correlate with the precatalyst metathesis activity?

Abstract

The self-metathesis reaction of 1-octene with several well-known Grubbs-type precatalysts and the new Z-selective Grubbs precatalyst were studied with molecular modeling. The obtained Gibbs-free energy values for all the steps during the productive metathesis of 1-octene were compared to the values obtained for some low catalytic activity precatalysts. Determining how the Gibbs-free energy values of highly active precatalysts compare to that of low catalytic activity precatalysts gave a deeper insight into the mechanism. The questionable correlation of the theoretically observed trends with those obtained experimentally does point to the need to be very cautious when making assumptions from theoretical results without a sufficiently large dataset.

A Molecular modeling study of the changes of some steric properties of the precatalysts during the olefin metathesis reaction

“…It was also previously shown that in all the systems investigated (except A4 and A6), the rate limiting step of the catalytic cycle might be the formation of the methylidene. [48] The electron donating ability of the ligands on their own did not provide a satisfactory answer for the observed energy difference between the various precatalysts. [48] It was therefore decided to investigate the steric influence of these ligands on the metal with the Solid-G program of Guzei and Wendt.…”

“…As was stated elsewhere we feel it is essential to look at both high and low activity precatalysts in as much detail as possible to avoid drawing wrong conclusions from false assumptions. [48] Methodology The quantum-chemical calculations were performed, by density functional theory (DFT) since it usually gives realistic geometries, relative energies, and vibrational frequencies for transition metal compounds. All calculations were performed with the DMol3 DFT code [50][51][52] as implemented in Accelrys Materials StudioV R 5.0.…”

Towards a better understanding of alkene metathesis: elucidating the properties of the major metal carbene catalyst types

“…Furthermore, most theoretical studies done in alkene metathesis base their predictions of the activity of the catalysts on calculated energy barriers in the electronic reaction pathway [31][32][33][34][35][36][37][38][39][40][41][42]. However, a recent study done by Marx et al [43] highlights the fact that conclusions derived from electronic energy reaction pathways should be done with caution. They found that the energy pathway of experimentally observed low activity catalysts correlated very well with that of high activity catalysts [43].…”

“…However, a recent study done by Marx et al [43] highlights the fact that conclusions derived from electronic energy reaction pathways should be done with caution. They found that the energy pathway of experimentally observed low activity catalysts correlated very well with that of high activity catalysts [43].…”

The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2014

“…Tungsten catalysts of general structure 40 were highly effective in promoting Z-selective and stereoregular polymerization of norbornadiene diester derivative 39 [242]. Severally computationally-based studies of olefin metathesis were reported in 2014, including publications that focus on the following topics: (1) the feasibility of iron olefin metathesis catalysts (the pathway involving the iron analog of catalyst 2 is slightly less endothermic than ruthenium catalyst 2) [275,276]; (2) a comparison of various computational techniques (comparison of time and accuracy) for the complete ruthenium-catalyzed olefin metathesis pathway [277]; (3) orbital symmetry in the [2+2] cycloaddition step of olefin metathesis [278]; (4) the electronic effect of various alkylidene groups on the carbon-metal double bond strength (=CH 2 vs =CHF vs =CF 2 ), plus a comparison of Group 8 metals and similar studies on ruthenium metallacyclobutanes using coupled cluster theory [279]; (5) the cross metathesis of propene and styrene focused on the energies and interconversions of metallacyclobutane intermediates [280]; (6) 1-octene self metathesis [281,282]; (7) the ring opening of 3,3-dimethylcyclopropane using W(NH)(CH 2 )(OMe) 2 [283]; (8) olefin metathesis focusing on cis/trans olefin substrate coordination issues [284]; (9) microwave assisted RCM…”