Syntheses and Reductions of C-Dimesitylboryl-1,2-dicarba-closo-dodecaboranes

Kahlert, J.; Böhling, L.; Brockhinke, A.; Stammler, H.-G.; Newmann, B.; Rendina, L.M.; Low, P.J.; Weber, L.; Fox, M.A.

Abstract

Two C-dimesitylboryl-1,2-dicarba-closo-dodecaboranes, 1-(BMes2)-2-R-1,2-C2B10H10 (1, R = H, 2, R = Ph), were synthesised by lithiation of 1,2-dicarba-closo-dodecaborane and 1-phenyl-1,2-dicarba-closo-dodecaborane, respectively, with n-butyllithium and subsequent reaction with fluorodimesitylborane. These novel compounds were structurally characterised by X-ray crystallography. Compounds 1 and 2 are hydrolysed on prolonged exposure to air to give mesitylene and boronic acids 1-(B(OH)2)-2-R-1,2-C2B10H10 (3, R = H, 4, R = Ph respectively). Addition of fluoride anions to 1 and 2 resulted in boryl-carborane bond cleavage to give dimesitylborinic acid HOBMes2. UV absorption bands at 318–333 nm were observed for 1 and 2 corresponding to local π–π*-transitions within the dimesitylboryl groups while visible emissions at 541–664 nm with Stokes shifts of 11920–16170 cm−1 were attributed to intramolecular charge transfer transitions between the mesityl and cluster groups. Compound 2 was shown by cyclic voltammetry to form a stable dianion on reduction. NMR spectra for the dianion [2]2− were recorded from solutions generated by reductions of 2 with alkali metals and compared with NMR spectra from reductions of 1,2-diphenyl-ortho-carborane 5. On the basis of observed and computed 11B NMR shifts, these nido-dianions contain bowl-shaped cluster geometries. The carborane is viewed as the electron-acceptor and the mesityl group is the electron-donor in C-dimesitylboryl-1,2-dicarba-closo-dodecaboranes.

Citation

Kahlert, J., Böhling, L., Brockhinke, A., Stammler, H., Newmann, B., Rendina, L., …Fox, M. (2015). Syntheses and Reductions of C-Dimesitylboryl-1,2-dicarba-closo-dodecaboranes. Dalton Transactions, 44(21), 9766-9781. https://doi.org/10.1039/c5dt00758e

• Journal Article Type: Article
• Acceptance Date: Apr 24, 2015
• Publication Date: Jun 7, 2015
• Deposit Date: Apr 30, 2015
• Publicly Available Date: May 6, 2015
• Journal: Dalton Transactions
• Print ISSN: 1477-9226
• Electronic ISSN: 1477-9234
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 44
• Issue: 21
• Pages: 9766-9781
• DOI: https://doi.org/10.1039/c5dt00758e
• Public URL: https://durham-repository.worktribe.com/output/1406510