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Issue 11, 2007
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One electron oxidation of chromium N,N-bis(diarylphosphino)amine and bis(diarylphosphino)methane complexes relevant to ethene trimerisation and tetramerisation

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Abstract

Complexes of the type [(diphosphine)Cr(CO)4] (diphosphine = Ph2PN(iPr)PPh2, Ar2PN(Me)PAr2 or Ar2PCH2PAr2 (Ar = 2-C6H4(MeO)) have been synthesised. In the solid state, these complexes show tight phosphine bite angles in the range 67.82(4)° to 71.52(5)° and the nitrogen atom in N,N-bis(diarylphophino)amine ligands adopts an almost planar (sp2) geometry. All of the complexes are readily oxidised electrochemically or chemically to corresponding Cr(I) species. There is no evidence for coordination of the pendant ether group in derivatives with Ar = 2-MeO-C6H4 in either Cr(0) or Cr(I) species. Treatment of the [(diphosphine)Cr(CO)4] complexes with [NO]BF4 yields [(diphosphine)Cr(NO)(CO)3]BF4. Removal of CO ligands to generate an oligomerisation-active species is not observed with amine oxides but triethyl aluminium is effective in this role, and active catalysts can be produced. The use of weakly coordinating anions seems crucial in achieving oligomerisation catalysis.

Graphical abstract: One electron oxidation of chromium N,N-bis(diarylphosphino)amine and bis(diarylphosphino)methane complexes relevant to ethene trimerisation and tetramerisation

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Publication details

The article was received on 15 Jan 2007, accepted on 31 Jan 2007 and first published on 09 Feb 2007


Article type: Paper
DOI: 10.1039/B700559H
Citation: Dalton Trans., 2007,0, 1160-1168
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    One electron oxidation of chromium N,N-bis(diarylphosphino)amine and bis(diarylphosphino)methane complexes relevant to ethene trimerisation and tetramerisation

    L. E. Bowen, M. F. Haddow, A. G. Orpen and D. F. Wass, Dalton Trans., 2007, 0, 1160
    DOI: 10.1039/B700559H

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