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Issue 45, 2006
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Chelating N-pyrrolylphosphino-N′-arylaldimine ligands: synthesis, ligand behaviour and applications in catalysis

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Abstract

Two families of variously-substituted N-pyrrolylphosphino-N′-arylaldimine ligands, 2-(aryl–N[double bond, length as m-dash]CH)C4H3N–PR2 {3a–d R = Ph; 4a–d R = Pri2N}, have been prepared from the corresponding pyrrolylaldimines 2. The donor characteristics/basicity of PN-chelating 3 and 4 have been assessed using a combination of 31P{1H} NMR and IR spectroscopies through study of the magnitudes of 1JSeP for the phosphorus(V) selenides 7 and 8, and measurement of νCO for the complexes [RhCl(CO)(3,42-P,N)] (5, 6), respectively. The synthesis of the palladium(II) complexes [PdCl2(3,42-P,N)] (9, 10) was readily achieved from reaction of 3 or 4 with [PdCl2(MeCN)2] in CH2Cl2. X-Ray crystallographic studies of 13d and 14b confirm the chelating nature of the PN ligands, which adopt a distorted ‘envelope’ conformation, and highlight the potentially significant steric demands of these metal scaffolds. Reaction of equimolar quantities of 3 with [NiBr2(DME)] in MeCN afforded [NiBr2(32-P,N)] (15), while the same reaction undertaken in CH2Cl2 with 3c gave rise to the homoleptic bis(pyrrolatoimine) derivative [Ni{2-(mes–N[double bond, length as m-dash]CH)C4H3N}2] (16) in 45% yield, following PN bond cleavage. Complex 16c was characterised in the solid-state by X-ray crystallography. No identifiable metal-containing complexes could be obtained on reaction of 4 with a variety of sources of Ni(II). The palladium dichloride complexes 13 and 14 proved inactive in combination with MAO or EtAlCl2 for ethylene polymerisation, and with methanesulfonic acid for CO/ethylene co-polymerisation. Contrastingly, the nickel complexes 15 in combination with 4.5 eq. EtAlCl2 catalysed the formation of butenes and hexenes with moderate activity from ethylene at 1 bar.

Graphical abstract: Chelating N-pyrrolylphosphino-N′-arylaldimine ligands: synthesis, ligand behaviour and applications in catalysis

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Publication details

The article was received on 14 Aug 2006, accepted on 19 Sep 2006 and first published on 02 Oct 2006


Article type: Paper
DOI: 10.1039/B611652C
Citation: Dalton Trans., 2006, 5362-5378
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    Chelating N-pyrrolylphosphino-N′-arylaldimine ligands: synthesis, ligand behaviour and applications in catalysis

    C. E. Anderson, A. S. Batsanov, P. W. Dyer, J. Fawcett and J. A. K. Howard, Dalton Trans., 2006, 5362
    DOI: 10.1039/B611652C

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