title: Rhodium-catalyzed dehydrocoupling of the sterically encumbered phosphine-borane adduct tBu(2)PH.BH(3): synthesis of the linear dimers tBu(2)PH-BH(2)-tBu(2)P-BH(3) and tBu(2)PH-BH(2)-tBu(2)P-BH(2)Cl.
abstract: The dehydrocoupling of the sterically hindered phosphine-borane adduct tBu(2)PH.BH(3) above 140 degrees C is catalyzed by the rhodium complexes [Rh(1,5-cod)(2)][OTf] or Rh(6)(CO)(16) to give the four-membered chain tBu(2)PH-BH(2)-tBu(2)P-BH(3) (1), which was isolated in 60% yield and characterized by multinuclear NMR spectroscopy, mass spectrometry, and elemental analysis. Thermolysis of 1 in the temperature range 175-180 degrees C led to partial decomposition and the formation of tBu(2)PH.BH(3). When the dehydrocoupling of tBu(2)PH.BH(3) was performed in the presence of [[Rh(mu-Cl)(1,5-cod)](2)] or RhCl(3) hydrate, the chlorinated compound tBu(2)PH-BH(2)-tBu(2)P-BH(2)Cl (2) was formed which could not be obtained free of 1. The molecular structures of tBu(2)PH.BH(3), tBu(2)PH-BH(2)-tBu(2)P-BH(3) (1), and tBu(2)PH-BH(2)-tBu(2)P-BH(2)Cl (2) together with 1 were determined by single-crystal X-ray diffraction studies.
authors.affiliation: Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, M5S 3H6, Canada.
authors.forename: H
authors.initials: H
authors.lastname: Dorn
authors.forename: E
authors.initials: E
authors.lastname: Vejzovic
authors.forename: A J
authors.initials: AJ
authors.lastname: Lough
authors.forename: I
authors.initials: I
authors.lastname: Manners