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Issue 36, 2013
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Bis(phosphine)boronium salts. Synthesis, structures and coordination chemistry

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Abstract

The synthesis of a range of bis(phosphine)boronium salts is reported [(R2HP)2BH2][X] (R = Ph, tBu, Cy) in which the counter anion is also varied (X = Br, [OTf], [BArF4], ArF = 3,5-(CF3)2C6H3). Characterization in the solid-state by X-ray diffraction suggests there are weak hydrogen bonds between the PH units of the boronium cation and the anion (X = Br, [OTf]), while solution NMR spectroscopy also reveals hydrogen bonding occurs in the order [BArF4] < [OTf] < Br. [(Ph2HP)2BH2][BArF4] reacts with RhH(PPh3)3, by elimination of H2, forming [Rh(κ1,η-PPh2BH2·PPh2H)(PPh3)2][BArF4] which shows a β-B-agostic interaction from the resulting base stabilised phosphino–borane ligand. Alternatively such ligands can be assembled directly on the metal centre by reaction of in situ generated {Rh(PPh3)3}+ and Ph2HP·BH3 to afford [Rh(κ1,η-PPh2BH2·PPh3)(PPh3)2][BArF4], which was characterised by X-ray crystallography. Addition of H3B·PPh2H to the well-defined 16-electron “T-shaped” complex [Rh(PiBu3)2(PPh3)][BArF4] (characterised by X-ray crystallography) formed of a mixture of base-stabilised phosphino borane ligated complexes [Rh(κ1,η-PR2BH2·PR3)(PR3)2][BArF4] (R = iBu or Ph). These last observations may lend clues to the formation of bis(phosphine)boronium salts in the catalytic dehydrocoupling reaction of phosphine boranes as mediated by Rh(I) compounds.

Graphical abstract: Bis(phosphine)boronium salts. Synthesis, structures and coordination chemistry

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Publication details

The article was received on 26 Mar 2013, accepted on 15 May 2013 and first published on 16 May 2013


Article type: Paper
DOI: 10.1039/C3DT50817J
Citation: Dalton Trans., 2013,42, 12917-12925
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    Bis(phosphine)boronium salts. Synthesis, structures and coordination chemistry

    T. A. Shuttleworth, M. A. Huertos, I. Pernik, R. D. Young and A. S. Weller, Dalton Trans., 2013, 42, 12917
    DOI: 10.1039/C3DT50817J

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