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dc.contributor.authorGowda, Ravikumar R.
dc.contributor.authorCaporaso, Lucia
dc.contributor.authorCavallo, Luigi
dc.contributor.authorChen, Eugene You Xian
dc.date.accessioned2015-08-03T12:06:55Z
dc.date.available2015-08-03T12:06:55Z
dc.date.issued2014-08-11
dc.identifier.issn02767333
dc.identifier.doi10.1021/om500661y
dc.identifier.urihttp://hdl.handle.net/10754/563700
dc.description.abstractGroup 4 tetrabenzyl compounds MBn4 (M = Zr, Ti), upon protonolysis with an equimolar amount of the tetradentate amine-tris(phenol) ligand N[(2,4-tBu2C6H2(CH 2)OH]3 in toluene from -30 to 25 °C, unexpectedly lead to amine-bis(phenoxy) dibenzyl complexes, BnCH2N[(2,4- tBu2C6H2(CH2)O] 2MBn2 (M = Zr (1), Ti (2)) in 80% (1) and 75% (2) yields. This reaction involves an apparent cleavage of the >NCH2-ArOH bond (loss of the phenol in the ligand) and formation of the >NCH 2-CH2Bn bond (gain of the benzyl group in the ligand). Structural characterization of 1 by X-ray diffraction analysis confirms that the complex formed is a bis(benzyl) complex of Zr coordinated by a newly derived tridentate amine-bis(phenoxy) ligand arranged in a mer configuration in the solid state. The abstractive activation of 1 and 2 with B(C6F 5)3·THF in CD2Cl2 at room temperature generates the corresponding benzyl cations {BnCH2N[(2,4- tBu2C6H2(CH2)O] 2MBn(THF)}+[BnB(C6F5) 3]- (M = Zr (3), Ti, (4)). These cationic complexes, along with their analogues derived from (imino)phenoxy tri- and dibenzyl complexes, [(2,6-iPr2C6H3)N=C(3,5- tBu2C6H2)O]ZrBn3 (5) and [2,4-Br2C6H2(O)(6-CH2(NC 5H9))CH2N=CH(2-adamantyl-4-MeC 6H2O)]ZrBn2 (6), have been found to effectively polymerize the biomass-derived renewable β-methyl-α-methylene- γ-butyrolactone (βMMBL) at room temperature into the highly stereoregular polymer PβMMBL with an isotacticity up to 99% mm. A combined experimental and DFT study has yielded a mechanistic pathway for the observed unusual C-C bond cleavage in the present protonolysis reaction between ZrBn4 and N[(2,4-tBu2C 6H2(CH2)OH]3 for the formation of complex 1, which involves the benzyl radical and the Zr(III) species, resulting from thermal and photochemical decomposition of ZrBn4, followed by a series of reaction sequences consisting of protonolysis, tautomerization, H-transfer, oxidation, elimination, and radical coupling. © 2014 American Chemical Society.
dc.description.sponsorshipThis work was supported by the National Science Foundation (NSF-1300267) for the study carried out at Colorado State University. L.C. thanks the HPC team of Enea (www.enea.it) for using the ENEA-GRID and the HPC facilities CRESCO (www.cresco.enea.it) in Portici, Italy. We thank Boulder Scientific Co. for the research gift of B(C<INF>6</INF>F<INF>5</INF>)<INF>3</INF> and Dr. Brian Newell for assistance on X-ray structural analysis.
dc.publisherAmerican Chemical Society (ACS)
dc.titleUnusual C-C bond cleavage in the formation of amine-bis(phenoxy) group 4 benzyl complexes: Mechanism of formation and application to stereospecific polymerization
dc.typeArticle
dc.contributor.departmentKAUST Catalysis Center (KCC)
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Division
dc.contributor.departmentChemical Science Program
dc.identifier.journalOrganometallics
dc.contributor.institutionDepartment of Chemistry, Colorado State University, Fort Collins, CO 80523-1872, United States
dc.contributor.institutionDipartimento di Chimica e Biologia, Università di Salerno, Via Giovanni Paolo II, I-84084, Fisciano, Italy
kaust.personCavallo, Luigi
dc.relation.isSupplementedByGowda, R. R., Caporaso, L., Cavallo, L., & Chen, E. Y.-X. (2014). CCDC 999630: Experimental Crystal Structure Determination [Data set]. Cambridge Crystallographic Data Centre. https://doi.org/10.5517/cc12k64z
dc.relation.isSupplementedByDOI:10.5517/cc12k64z
dc.relation.isSupplementedByHANDLE:http://hdl.handle.net/10754/624317


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