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Lookup NU author(s): Emeritus Professor Bill CleggORCiD, Professor Todd Marder
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In order to evaluate the potential for side reactions when using B-chlorocatechol borane (ClBcat) in stoichiometric or catalytic transformations involving metal phosphine complexes, we examined the interaction between ClBcat and a series of PR3 compounds. Reactions of ClBcat with the basic phosphines PMe3, PEt3, PMe2Ph and PBu3t, in exactly 1∶1 stoichiometry, all afforded crystalline adducts of the form R3P . ClBcat, which have been characterised spectroscopically. All display broad singlets at room temperature in both B-11{H-1} and P-31{H-1} NMR spectra with no B-P coupling observed. The low temperature B-11{H-1} and P-31{H-1} NMR spectra, however, do show B-P coupling, suggesting rapid dissociation at room temperature. The compounds ClBcat, BrBcat, and the adducts between ClBcat and PMe3, PEt3 and PBu3t have been characterised by single crystal X-ray diffraction. In ClBcat and BrBcat, the halogen contributes little pi -bonding to boron as the B-O bond lengths are identical in both compounds. The reaction of ClBcat with a small excess of PCy3 yielded Cy3P . ClBcat, which has also been characterised by single crystal X-ray diffraction and shows considerable distortion. The reaction between ClBcat and the less basic phosphines PPh3 and PPh2Me yielded only the redistribution products R3P . BCl3 and B(2)cat(3). In fact, reaction of all of the phosphines with an excess of ClBcat gave only redistribution products, although there was evidence for an intermediate in the B-11{H-1} NMR spectra, with PMe3 and PEt3. The isolated R3P . ClBcat adducts proved unstable, even at low temperature in the solid state, eventually leading to R3P . BCl3 and B(2)cat(3). Reaction of ClBcat with NEt3 afforded Et3N . ClBcat, which was characterised spectroscopically and by single crystal X-ray diffraction. This adduct is stable both in solution and in the solid state.
Author(s): Coapes RB, Souza FES, Fox MA, Batsanov AS, Goeta AE, Yufit DS, Leech MA, Howard JAK, Scott AJ, Clegg W, Marder TB
Publication type: Article
Publication status: Published
Journal: Journal of the Chemical Society: Dalton Transactions
Year: 2001
Issue: 8
Pages: 1201-1209
ISSN (print): 1472-7773
ISSN (electronic): 1364-5447
Publisher: Royal Society of Chemistry
URL: http://dx.doi.org/10.1039/b010025k
DOI: 10.1039/b010025k
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