American Chemical Society
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Molybdenum and Tungsten Alkylidene and Metallacyclobutane Complexes That Contain a Dianionic Biphenolate Pincer Ligand

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journal contribution
posted on 2016-02-22, 00:00 authored by Peter E. Sues, Jeremy M. John, Richard R. Schrock, Peter Müller
Molybdenum imido alkylidene and tungsten oxo alkylidene complexes that contain a tridentate “pincer” [ONO]2– ligand have been prepared and treated with ethylene to give unsubstituted metallacyclobutane complexes that have a 16e count. Both Mo and W metallacyclobutane complexes exchange C2D4 into the metallacyclobutane ring at 22 °C at a rate that is first order in metal and zero order in C2D4. These metallacycles lose ethylene at least 104–105 times slower than reported 14e unsubstituted Mo and W metallacyclobutane complexes that have been explored in the literature that have a TBP geometry with the metallacyclobutane ring bound in the equatorial positions. Our studies suggest that breaking up the metallacyclobutane ring in these 16e d0 Mo or W complexes is slow because a 14e TBP metallacyclobutane complex cannot be accessed readily.