Allylic C-H bond activation and functionalization mediated by tris(oxazolinyl)borato rhodium(I) and iridium(I) compounds

TitleAllylic C-H bond activation and functionalization mediated by tris(oxazolinyl)borato rhodium(I) and iridium(I) compounds
Publication TypeJournal Article
Year of Publication2011
AuthorsHo HA, Gray TS, Baird B, Ellern A, Sadow AD
Journal TitleDalton Transactions
Volume40
Pages6500-6514
Date Published05
Type of ArticleArticle
ISBN Number1477-9226
Accession NumberISI:000291385700026
Keywordsaddition, amido-complexes, carbon-hydrogen-bond, complexes, nmr coordination shifts, organic azides, oxidative, pt(ii) chloride, ray crystal-structure, saturated-hydrocarbons, transfer dehydrogenation, xpcp pincer complexes
Abstract

Allylic C-H bond oxidative addition reactions, mediated by tris(oxazolinyl) borato rhodium(I) and iridium(I) species, provide the first step in a hydrocarbon functionalization sequence. The bond activation products To(M)MH(eta(3)-C8H13) (M=Rh (1), Ir (2)), To(M)MH(eta(3)-C3H5) (M=Rh (3), Ir (4)), and To(M)RhH(eta(3)-C3H4Ph) (5) (To(M) = tris(4,4-dimethyl-2-oxazolinyl)phenylborate) are synthesized by reaction of Tl[To(M)] and the corresponding metal olefin chloride dimers. Characterization of these group 9 allyl hydride complexes includes H-1-N-15 heteronuclear correlation NMR experiments that reveal through-metal magnetization transfer between metal hydride and the trans-coordinated oxazoline nitrogen. Furthermore, the oxazoline N-15 NMR chemical shifts are affected by the trans ligand, with the resonances for the group trans to hydride typically downfield of those trans to eta(3)-allyl and tosylamide. These group 9 oxazolinylborate compounds have been studied to develop approaches for allylic functionalization. However, this possibility is generally limited by the tendency of the allyl hydride compounds to undergo olefin reductive elimination. Reductive elimination products are formed upon addition of ligands such as CO and (CNBu)-Bu-t. Also, To(M)RhH(eta(3)-C8H13) and acetic acid react to give To(M)RhH(kappa(2)-O2CMe) (8) and cyclooctene. In contrast, treatment of To(M)RhH(eta(3)-C3H5) with TsN3 (Ts = SO2C6H4Me) gives the complex To(M)Rh(eta(3)-C3H5)NHTs (10). Interestingly, the reaction of To(M)RhH(h(3)-C8H13) and TsN3 yields To(M)Rh(NHTs)(H)OH2 (11) and 1,3-cyclooctadiene via beta-hydride elimination and Rh-H bond amination. Ligand-induced reductive elimination of To(M)Rh(h(3)-C3H5) NHTs provides HN(CH2CH=CH2)Ts; these steps combine to give a propene C-H activation/functionalization sequence.

URL<Go to ISI>://000291385700026
DOI10.1039/c1dt10249d
Alternate JournalDalton Trans.