Indium Complexes Supported by 1,ω-Dithiaalkanediyl-Bridged Bis(phenolato) Ligands: Synthesis, Structure, and Controlled Ring-Opening Polymerization ofl-Lactide

Abstract

Indium bis(phenolato) complexes [In(L)R(THF)(n)] (L = 1,4-dithiabutanediylbis(4,6-di-tert-butylphenolato) (etbbp), R = Cl, n = 0, 1; L = 1,3-dithiapropanediylbis(6-tert-butyl-4-methylphenolato) (mtbmp), R = Me, n = 1, 2; L = 1,4-dithiabutanediyl-bis(6-tert-butyl-4-methyl-phenolato) (etbmp), R = Me, n = 0, 3; L = etbbp, R = CH(2)SiMe(3), n = 0, 4; L = 1,4-dithiabutanediylbis{4,6-di(2-phenyl-2-propyl)phenolato} (etccp), R = CH(2)SiMe(3), n = 0, 5) were prepared from indium trichloride or from the corresponding tris(alkyl) complexes and 1 equiv of tetradentate 1,omega-dithiaalkanediyl-bridged bis(phenol) LH(2). The monomeric nature of the alkyl indium complexes was shown by X-ray diffraction studies of the complexes [In(mtbmp)Me(THF)] (2), [In(etbbp)(CH(2)SiMe(3))] (4), and [In(etccp)(CH(2)SiMe(3))] (5). Pseudo-octahedral configuration was found for 2, while square pyramidal structure was observed for 4 and 5. The isopropoxy complexes [In(L)(O(i)Pr)] (L = etbbp, 6; etccp, 7) were synthesized starting with indium tris(isopropoxide). Complex 6 crystallized as homochiral dimer of pseudo-octahedral fragments with bridging mu(2)-alkoxide ligands, but in solution two diastereomers were observed. The isopropoxy complexes efficiently initiated the ring-opening polymerization of L-lactide in toluene to give isotactic poly(L-lactides) with narrow molecular weight distribution (M(w)/M(n) = 1.03-1.18).

Bulk solvent-free melt ring-opening polymerization (ROP) of L-lactide catalyzed by Ni(II) and Ni(II)–Ln(III) complexes based on the acyclic Salen-type Schiff-base ligand

“…Fig. 3 shows the 13 C NMR spectrum of the selected PLLA, in which the peaks at 16.64, 69.01 and 169.62 ppm were observed and should be assigned to methyl carbon, methane carbon and ester carbon, respectively, in agreement with the corresponding carbon atoms of the chemical structure, and the PLLA is isotactic in nature [25]. It is worth noting that the systems 1-8 are active for the bulk ROP of L-Lactide in the absence of normal initiators (alkoxide), and the end methyl groups of PLLA are not from the catalysts, as also checked by the 1 H NMR spectroscopy (as shown in Fig.…”

High activity of an indium alkoxide complex toward ring opening polymerization of cyclic esters

“…2 Of the numerous pre-catalysts developed toward this end, indium complexes have demonstrated high activity and stereoselectivity for a number of monomers. [3][4][5][6][7][8][9][10][11][12][13] Lactide polymerizations have been particularly well examined, but many of the precatalysts [14][15][16][17][18][19][20] often require initiators. β-butyrolactone, 8,21 ε-caprolactone, 20 and trimethylene carbonate 22 polymerizations have also been achieved by indium catalysts.…”

Aluminum Complexes of Tridentate Amine Biphenolate Ligands Containing Distinct N‐alkyls: Synthesis and Catalytic Ring‐opening Polymerization

“…For steric and/or electronic tuning, the phenolate-based ligands may in some cases integrate extra central or peripheral donor(s). [45][46][47][48][49][50][51][52][53][54][55][56][57][58] Figure 1 depicts representative examples of amine bi-phenolate ligands with and without a peripheral donor. Notably, while several reports disclose the influences of ortho-and para-substituents (R 1 and R 2 , respectively) 45,47,59 and additional N-tethered donors 46,59 on ROP catalysis, the effect of N-alkyl substituents (R 3 ) lacking of extra donors is not well established.…”