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

Timothy A. Shuttleworth, Miguel A. Huertos, Indrek Pernik, Rowan D. Young, Andrew S. Weller

Research output: Contribution to journalArticle

16 Citations (Scopus)

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.
Original languageEnglish
Pages (from-to)12917-12925
Number of pages9
JournalDalton Transactions
Volume42
Issue number36
DOIs
Publication statusPublished - 2013
Externally publishedYes

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