Magnesium, zinc and aluminium complexes supported by tripodal diaminebis(aryloxido) ligands: synthesis, solid state and solution structure

Abstract

The reactions of the diaminebis(aryloxido) ligand precursors [Me2NCH2CH2N(CH2-4-R-C6H3OH)2] [R = C(CH3)2CH2C(CH3)3, H2L(1); R = CH3, H2L(2)] with Mg(n)Bu2, ZnEt2 and AlEt3 create complexes of general formula [M2(μ-L-κ(4)O,N,N,O)2] (M = Mg, 1a for L(1) and 1b for L(2); M = Zn, 2a for L(1) and 2b for L(2)) and [Al2(μ-L-κ(3)O,N,N,O)2Et2] (3 for L(1)) in good yields. Compounds 1a-3 were characterized by NMR spectroscopy and ESI-MS experiments. The definitive molecular structure of 1b·CH2Cl2, 2a·H2O, 2b·CH2Cl2 and 3 was provided by a single-crystal analysis and revealed their dimeric nature with an M2O2 planar core. The L(1) and L(2) ligands coordinate as the dianions in a tetradentate/bridging manner in 1b, 2a, 2b and in a tridentate/bridging mode in 3. The NMR spectra showed that the solid state of these compounds is essentially retained in solution.

Magnesium amino-bis(phenolato) complexes for the ring-opening polymerization of rac-lactide

“…The solid-state molecular structure with selected bond lengths and angles is shown in Fig. [50][51][52] A brief comparison of the structural properties of magnesium amine-bis( phenolate) complexes follows. Crystallographic and structure refinement data can be found in Table S1 in ESI.…”

“…1. 50 This is manifested in a rhombic Mg 2 O 2 core that is nearly perfectly planar, possessing a sum of angles of 359.9°. † The dimeric structure with chemically distinct phenolate groups is consistent with the NMR studies discussed above.…”

“…[50][51][52][53] In this report, we present the synthesis and characterization of two new magnesium amine-bis(phenolate) complexes that show good lactide ROP activity in both melt and solution conditions. Magnesium complexes of aminophenolate ligands have previously been reported by others but their activity for ROP of lactides was not tested or they showed very low or no activity.…”

Well‐controlled ring‐opening polymerization of cyclic esters catalyzed by aluminum amido complexes: Kinetics and mechanism

“…1,2 Among them, aluminum complexes have attracted significant research focus, especially in the field of isoselective ROP of rac-lactide (rac-LA). [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Although a variety of aluminum complexes have been explored up to date, in principal, only those having at least one alkoxy ligand could initiate the polymerization of cyclic esters in a well-controlled manner. [1][2][3][4][5][6][7] Due to the difficulties encountered in synthesis and/or purification, structurally well-defined aluminum alkoxide complexes are still limited.…”

“…Selected bond lengths [Å ] and angles [ ]: Al1-N1 1.8583(17), Al1-N2 2.0130(19), Al1-C18 1.963(2), Al1-C19 1.968(3). N1-Al1-C18 114.74(10), N1-Al1-C19 113.43(10), C18-Al1-C19 118.61(11), N1-Al1-N2 96.62(7), C18-Al1-N2 103.87(9), C19-Al1-N2 105.99(10), C8-N1-C7 116.38(15), C8-N1-Al1 121.99(13), C7-N1-Al1 121.37(13), C1-N2-C17 109.13(15), C1-N2-C14 114.75(16), C17-N2-C14 102.42(17), C1-N2-Al1 110.20(13), C17-N2-Al1 115.61(14), C14-N2-Al1 104.66(13).ARTICLE initiators ([e2CL] 0 :[Al] 0 hx2009;5 100:1), and the results are summarized in…”