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Issue 4, 2009
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Weakly coordinating counter-ions for highly efficient catalysis of intramolecular hydroamination

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Abstract

A series of cationic rhodium(I) and iridium(I) complexes of the type [M(LL)(C2)]BArF24 (where M = Rh or Ir, LL = bis(pyrazol-1-yl)methane (bpm), bis(N-methylimidazol-2-yl)methane (bim) or 1-(2-(diphenylphosphino)ethyl)-3,5-diphenylpyrazole (Ph2PyP), C2 = 1,5-cyclooctadiene (COD) or (CO)2 and BArF24 = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) were synthesised in good yields. The solid-state structure of a number of complexes, including [Ir(Ph2PyP)(COD)]BArF24, [Ir(bpm)(COD)]BArF24 and [Ir(bim)(COD)]BArF24 was determined using X-ray crystallography. The efficiency of the complexes as catalysts for the intramolecular hydroamination of 4-phenyl-3-butyn-1-amine, 4-pentyn-1-amine and 2-(2-phenylethynyl)aniline was established. The incorporation of the BArF24 counter-ion in the Rh(I) and Ir(I) complexes was found to significantly improve the catalytic activity of the complexes, compared to the analogous Rh(I) and Ir(I) complexes containing BPh4 as the counter-ion. Excellent conversions were achieved for the cyclisation of 2-(2-phenylethynyl)aniline to 2-phenylindole using [Rh(bpm)(CO)2]BArF24 as a catalyst. The use of a microwave reactor for enhancing the catalysed reactions was also investigated.

Graphical abstract: Weakly coordinating counter-ions for highly efficient catalysis of intramolecular hydroamination

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Publication details

The article was received on 14 Aug 2008, accepted on 19 Sep 2008 and first published on 18 Nov 2008


Article type: Paper
DOI: 10.1039/B814168A
Dalton Trans., 2009, 634-642

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    Weakly coordinating counter-ions for highly efficient catalysis of intramolecular hydroamination

    S. L. Dabb, J. H. H. Ho, R. Hodgson, B. A. Messerle and J. Wagler, Dalton Trans., 2009, 634
    DOI: 10.1039/B814168A

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