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Issue 30, 2015
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Reactions of α-diimine-aluminum complexes with sodium alkynides: versatile structures of aluminum σ-alkynide complexes

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Abstract

Reaction of AlCl3 with the monoanionic α-diimine ligand [NaL] yielded the complex [L˙AlIIICl2] (1, L = [(2,6-iPr2C6H3)NC(Me)]2), and subsequent reduction of 1 by sodium metal afforded the mononuclear [L2−AlIIICl(THF)] (2) and binuclear [L2−(THF)AlII−AlII(THF)L2−] (3). Compounds 2 and 3 exhibit interesting reactivities to sodium alkynides at room temperature. Treatment of dialumane 3 with 1 equiv. of 4-methylphenylacetylene in the presence of sodium metal yielded the asymmetric Al–Al-bonded compound [Na(Et2O)][LAl–Al(C[triple bond, length as m-dash]C(C6H4–Me))L] (4) containing an alkynyl group attached to one of the Al atoms. The reaction of 2 with 4-methylphenylacetylene and Na (or sodium 4-methylphenylacetylide) resulted in the mononuclear product [L(THF)Al(C[triple bond, length as m-dash]C–(C6H4–Me))] (5) containing a single terminal acetylide ligand. Precursor 2 reacted with 2 equiv. of phenylacetylene (or 4-methylphenylacetylene, trimethylsilylacetylene) and Na to give the tweezer “ate” complexes, [Na(THF)(DME)][LAl(C[triple bond, length as m-dash]CR)2] (R = C6H5, 6a; C6H4–Me, 6b; Si(Me)3, 6c), [Na(THF)]2[LAl(C[triple bond, length as m-dash]CPh)2]2(μ-C7H8) (7), [Na(C7H8)][(μ-Na)][LAl(C[triple bond, length as m-dash]CSi(Me)3)2]2 (8), as well as the polymeric [LAl(C[triple bond, length as m-dash]CPh)2Na]n (9). In the products, two alkynyl groups coordinate terminally to one Al center and a sodium ion is embedded between these two alkynyls. Interestingly, both cycloaddition and terminal acetylide coordination of three equiv. of alkyne occurred in the reaction of 2 with 1-hexyne, resulting in the unique dialuminum complex [Na(Et2O)]2[{L(C(C4H9)[double bond, length as m-dash]CH)}Al(C[triple bond, length as m-dash]C(C4H9))2]2 (10). Complexes 1–10 have been characterized by NMR (1H, 13C) and IR spectroscopy, elemental analysis, and X-ray diffraction, and their electronic structures were studied by DFT calculations.

Graphical abstract: Reactions of α-diimine-aluminum complexes with sodium alkynides: versatile structures of aluminum σ-alkynide complexes

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Publication details

The article was received on 05 May 2015, accepted on 10 Jun 2015 and first published on 06 Jul 2015


Article type: Paper
DOI: 10.1039/C5DT01693B
Dalton Trans., 2015,44, 13671-13680

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    Reactions of α-diimine-aluminum complexes with sodium alkynides: versatile structures of aluminum σ-alkynide complexes

    Y. Zhao, Y. Liu, B. Wu and X. Yang, Dalton Trans., 2015, 44, 13671
    DOI: 10.1039/C5DT01693B

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