Aluminum complexes incorporating symmetrical and asymmetrical tridentate pincer type pyrrolyl ligands: synthesis, characterization and reactivity study?

Dalton Transactions Pub Date: 2013-07-05 DOI: 10.1039/C3DT51133B

Abstract

A series of aluminum complexes incorporating substituted symmetrical and asymmetrical tridentate pyrrolyl ligands are synthesized conveniently and the treatment of the derivatives with small organic molecules are analyzed. The reaction of lithiated [C4H2NH(2-CH2NHtBu)(5-CH2NR1R2)], where for 1, R1 = R2 = Me; 2, R1 = H, R2 = tBu, with AlCl3 in diethyl ether affords Al[C4H2N(2-CH2NHtBu)(5-CH2NMe2)]Cl2 (3) and Al[C4H2N(2,5-CH2NHtBu)2]Cl2 (4), respectively, in high yields. Furthermore, subjecting 3 and 4 to reaction with one equiv. of LiNMePh in diethyl ether generates Al[C4H2N(2-CH2NHtBu)(5-CH2NMe2)][NMePh]Cl (5) and Al[C4H2N(2,5-CH2NHtBu)2][NMePh]Cl (6), respectively, while eliminating one equiv. of LiCl. The reaction between compound 4 with two equiv. of LiO-Ph-4-Me in diethyl ether yields the aluminum di-phenoxide compound Al[C4H2N(2,5-CH2NHtBu)2](O-Ph-4-Me)2 (7) whereas the combination of 3 and two equiv. of LiNHtBu, produces Al[C4H2N(2-CH2NtBu)(5-CH2NMe2)](NHtBu)(NH2tBu) (8). Additionally, the mixing of 1 and one equiv. of AlMe3 renders Al[C4H2N(2-CH2NHtBu)(5-CH2NMe2)]Me2 (9). Adding one more equiv. of AlMe3 with 9 affords {Al[C4H2N(2-CH2NHtBu)(5-CH2NMe2)AlMe3]Me2} (10), which can also be obtained by treating 1 with two equiv. of AlMe3 directly. The treatment of 9 with one equiv. of 2,6-dimethylphenol in diethyl ether gives the aluminum alkoxide derivative, Al[C4H2N(2-CH2NHtBu)(5-CH2NMe2)](O-C6H3-2,6-Me2)Me (11). Furthermore, the reaction between 9 and one equiv. of 1-ethyl-1-phenyl ketene, initiates the aluminum dimethyl complex Al{C4H2N[2-CH2CEtPh-C([double bond, length as m-dash]O)-NHtBu](5-CH2NMe2)}Me2 (12) with a C–N bond breakage and a C–C bond formation. All the Al-derivatives are characterized by 1H and 13C NMR spectroscopy and the molecular structures are determined by single crystal X-ray diffractometry in solid state.

Graphical abstract: Aluminum complexes incorporating symmetrical and asymmetrical tridentate pincer type pyrrolyl ligands: synthesis, characterization and reactivity study
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