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Issue 34, 2012
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Nickel complexes supported by quinoline-based ligands: synthesis, characterization and catalysis in the cross-coupling of arylzinc reagents and aryl chlorides or aryltrimethylammonium salts

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Abstract

Lithium and nickel complexes bearing quinoline-based ligands have been synthesized and characterized. Reaction of 8-azidoquinoline with Ph2PNHR (R = p-MeC6H4, But) affords N-(8-quinolyl)iminophosphoranes RNHP(Ph2)[double bond, length as m-dash]N(8-C9H6N) (1a, R = p-MeC6H4; 1b, R = But. C9H6N = quinolyl)). Reaction of 1a with (DME)NiCl2 generates a nickel complex [NiCl2{N(8-C9H6N)[double bond, length as m-dash]P(Ph2)NH(p-MeC6H4)}] (2a). Treatment of 1b with (DME)NiCl2 and following with NaH produces [NiCl{(1,2-C6H4)P(Ph)(NHBut)[double bond, length as m-dash]N(8-C9H6N)}] (4). Complex 4 was also obtained by reaction of (DME)NiCl2 with [Li{(1,2-C6H4)P(Ph)(NHBut)[double bond, length as m-dash]N(8-C9H6N)}] (5) prepared through lithiation of 1b. Reaction of 2-PyCH2P(Ph2)[double bond, length as m-dash]N(8-C9H6N) (6, Py = pyridyl) and PhN[double bond, length as m-dash]C(Ph)CH2P(Ph2)[double bond, length as m-dash]N(8-C9H6N) (8), respectively, with (DME)NiCl2 yields two five-coordinate N,N,N-chelate nickel complexes, [NiCl2{2-PyCH2P(Ph2)[double bond, length as m-dash]N(8-C9H6N)}] (7) and [NiCl2{PhN[double bond, length as m-dash]C(Ph)CH2P(Ph2)[double bond, length as m-dash]N(8-C9H6N)}] (9). Similar reaction between Ph2PCH2P(Ph2)[double bond, length as m-dash]N(8-C9H6N) (10) and (DME)NiCl2 results in five-coordinate N,N,P-chelate nickel complex [NiCl2{Ph2PCH2P(Ph2)[double bond, length as m-dash]N(8-C9H6N)}] (11). Treatment of [(8-C9H6N)N[double bond, length as m-dash]P(Ph2)]2CH2 (12) [prepared from (Ph2P)2CH2 and 2 equiv. of 8-azidoquinoline] with LiBun and (DME)NiCl2 successively affords [NiCl{(8-C9H6N)NP(Ph2)}2CH] (13). The new compounds were characterized by 1H, 13C and 31P NMR spectroscopy (for the diamagnetic compounds), IR spectroscopy (for the nickel complexes) and elemental analysis. Complexes 2a, 4, 7, 9, 11 and 13 were also characterized by single-crystal X-ray diffraction techniques. The nickel complexes were evaluated for the catalysis in the cross-coupling reactions of arylzinc reagents with aryl chlorides and aryltrimethylammonium salts. Complex 7 exhibits the highest activity among the complexes in catalyzing the reactions of arylzinc reagents with either aryl chlorides or aryltrimethylammonium bromides.

Graphical abstract: Nickel complexes supported by quinoline-based ligands: synthesis, characterization and catalysis in the cross-coupling of arylzinc reagents and aryl chlorides or aryltrimethylammonium salts

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Publication details

The article was received on 24 Apr 2012, accepted on 08 Jun 2012 and first published on 20 Jul 2012


Article type: Paper
DOI: 10.1039/C2DT30886J
Citation: Dalton Trans., 2012,41, 10453-10464
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    Nickel complexes supported by quinoline-based ligands: synthesis, characterization and catalysis in the cross-coupling of arylzinc reagents and aryl chlorides or aryltrimethylammonium salts

    Q. Zhang, X. Zhang and Z. Wang, Dalton Trans., 2012, 41, 10453
    DOI: 10.1039/C2DT30886J

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