Olefin substitution in (silox)3M(olefin) (silox = (t)Bu3SiO; M = Nb, Ta): the role of density of states in second vs third row transition metal reactivity

Journal of the American Chemical Society
Kurt F HirsekornThomas R Cundari

Abstract

The substitution chemistry of olefin complexes (silox)3M(ole) (silox = (t)Bu3SiO; M = Nb (1-ole), Ta (2-ole); ole = C2H4 (as 13C2H4 or C2D4), C2H3Me, C2H3Et, cis-2-C4H8, iso-C4H8, C2H3Ph, cC5H8, cC6H10, cC7H10 (norbornene)) was investigated. For 1-ole, substitution was dissociative (deltaG(double dagger)(diss)), and in combination with calculated olefin binding free energies (deltaG(o)(bind)), activation free energies for olefin association (deltaG(double dagger)(assoc)) to (silox)3Nb (1) were estimated. For 2-ole, substitution was not observed prior to rearrangement to alkylidenes. Instead, activation free energies for olefin association to (silox)3Ta (2) were measured, and when combined with deltaG(o)(bind) (calcd), estimates of olefin dissociation rates from 2-ole were obtained. Despite stronger binding energies for 1-ole vs 2-ole, the dissociation of olefins from 1-ole is much faster than that from 2-ole. The association of olefins to 1 is also much faster than that to 2. Linear free energy relationships (with respect to deltaG(o)(bind)) characterize olefin dissociation from 1-ole, but not olefin dissociation from 2-ole, and olefin association to 2, but not olefin association to 1. Calculated transition states for olefin di...Continue Reading

References

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Citations

Jun 28, 2013·Inorganic Chemistry·Olayinka A Olatunji-Ojo, Thomas R Cundari
Aug 2, 2008·Journal of the American Chemical Society·Neil C TomsonRobert G Bergman
Mar 27, 2009·Chemical Communications : Chem Comm·Peter T Wolczanski
Aug 13, 2015·Journal of the American Chemical Society·Malik H Al-AfyouniPatrick L Holland
Nov 19, 2011·Dalton Transactions : an International Journal of Inorganic Chemistry·Matthew E O'ReillyAdam S Veige
Feb 8, 2018·Dalton Transactions : an International Journal of Inorganic Chemistry·T J MorrowE B Hulley
May 20, 2015·Accounts of Chemical Research·Patrick L Holland

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