Mechanism and Origins of Z Selectivity

In a subsequent report, Wang et al. [77] performed a DFT investigation on the homodimerization of 3-phenyl-l-propene, an experimentally used substrate, with a similar chelated ruthenium catalyst. These computations also agreed with the previous report in that the side-bound mechanism is favored. The same authors later reported a computational study on the same reaction, only using a chelated nitrato catalyst in place of the carboxylate-bound catalysts used in earlier calculations [78]. This study also found the reaction to occur via a side-bound mechanism. 

Wang et al. [54, 79] also investigated the mechanism of initiation of the chelated ruthenium catalyst to form the active ruthenium alkylidene complex. 

The first step in the initiation pathway was found to be similar to the dissociative initiation mechanism of non-chelated catalysts the isopropoxy chelating group dissociated from Ru via rotation of the o-isopropoxyphenyl. Metathesis with a substrate olefin molecule then replaces the o-isopropoxybenzylidene with alkylidene to form the active metathesis catalyst. The metathesis step during initiation of the chelated catalysts was also found to occur via a side-bound mechanism. 

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