Polymerization of Methyl Methacrylate Catalyzed by Co(II), Cu(II), and Zn(II) Complexes Bearing N‐Methyl‐N‐((pyridin‐2‐yl)methyl)cyclohexanamine

Abstract

Transition metal complexes containing N,N 0 -bidentate pyridylmethylamines ligands continue to receive attention since these ligands can be synthesized with high coordination versatility by introducing various substituents on the amine and/or pyridyl unit. [1][2][3][4][5] Several structural variations in pyridylmethylamines and their complexes have been reported, [6][7][8] and the resultant steric and electronic properties are important for specific chemical applications. The majority of transition metal complexes bearing these ligands have been used in a number of investigations including synthetic, structural analysis and spectroscopic applications, 9-12 as well as for electronic materials, 4,5 catalysts for organic transformation, 13-15 biological applications, 16 and olefin polymerization. 17,18 In contrast, poly(methyl methacrylate) (PMMA) is a universal polymer with optical applications, and its improved optical properties are dependent on the higher glass transition temperature (T g ) and syndiotacticity of PMMA. Radical-mediated polymerization of methyl methacrylate (MMA) cannot achieve sufficiently high T g or a high syndiotacticity in PMMA. Thus, non-radicalmediated MMA polymerization that can result in a higher T g up to 140C is an active and promising field of research.19-22 Recently, we have explored various transition metal complexes as catalysts for homogeneous polymerization of MMA to produce syndiotactic PMMA with high T g up to 130C. 23,24 Considering the versatility of the pyridylbased ancillary ligands and their ability to fine-tune steric and electronic properties, we extended our investigations to the synthesis of novel Co(II), Cu(II), and Zn(II) complexes supported by specific N-methyl-N-((pyridin-2-yl)methyl) cyclohexanamine (nmpc), which shows unique activity and selectivity with several transition metals during MMA polymerization.The complexation reactions proceeded smoothly at room temperature by treating with EtOH solution of (nmpc) with stoichiometric amounts of metal starting material and afforded [M(nmpc)Cl 2 ] n (M = Co and Zn, n = 1; M = Cu, n = 2) in high yields (91-96%) (Scheme 1). The results of 1 H NMR, 13C NMR, IR, and elemental analysis were consistent with the ligands and corresponding complex formation. Particularly, the 1 H NMR spectra of Zn(II) confirmed complexation of the respective ligand; as expected, the majority of the ligand proton signals were observed at a lower field for the complexes relative to the corresponding free ligand. In addition, the incorporation of Me substituents on the N atoms of the ligand architecture resulted in enhanced solubility of corresponding complexes in organic solvents.X-ray diffraction analysis revealed that [Co(nmpc)Cl 2 ] and [Zn(nmpc)Cl 2 ] crystallized in the monoclinic system with space group P2 1 /c and existed as monomeric and solvent-free complexes. [Cu(nmpc)(μ-Cl)Cl] 2 existed as a dimer with space group P-1. The structures for [Co(nmpc)Cl 2 ], [Zn (nmpc)Cl 2 ], and [Cu(nmpc)(μ-Cl)Cl] 2 at a 50% probability level, along with ...

Zinc (II), palladium (II) and cadmium (II) complexes containing 4‐methoxy‐N‐(pyridin‐2‐ylmethylene) aniline derivatives: Synthesis, characterization and methyl methacrylate polymerization

“…Our current system is superior in terms of activity and resulted in syndio‐enriched high molecular weight PMMA compared with N ‐methyl‐ N ‐(pyridin‐2‐ylmethyl) aniline‐based Pd (II) complexes in our earlier report. Similarly, compared with previous Zn (II) complexes with N ‐(pyridin‐2‐ylmethylene) aniline and N ‐phenyl‐(pyridin‐2‐yl)methanimine, current Zn (II) systems effectively catalyzed MMA polymerization. The Cd (II) complexes, [(L‐c)Cd(μ ‐ Br)Br] 2 and [(L‐c)Cd(μ ‐ Br)Br] 2 , exhibited lower activities compared with our previously reported Cd (II) complexes bearing N , N ‐di(2‐picolyl) amine ligand, but resulted in high molecular weight PMMA with improved T g (Table ).…”

“…Recently, we have studied Zn (II), Cd (II), Co (II), Pt (II) and Pd (II) complexes with N , N ‐di(2‐picolyl) amine, 2‐iminomethylpyridine, N ‐methyl‐ N ‐((pyridin‐2‐yl)methyl) cyclohexanamine, N ‐(pyridin‐2‐ylmethyl) aniline and N , N ‐di(2‐picolyl) cycloalkylamine ligands in MMA polymerization with promising results, as a slight difference in ligand architecture is able to influence the stereoregular outcomes during polymerization reactions. Thus, suitable ligand architecture around the metal center is vital for achieving a high degree of polymerization as these complexes/initiators regulate various steps involved in polymerization .…”

Well-Controlled Emulsion Polymerization of Methyl Methacrylate Using (Hg,Cd)-Diphenylcarbazone Catalysts: An attempt to Create Hg-free, Nontoxic, γ-Radiation and thermal Stable Films

“…Organometallic compounds that comprise of IIB metals are amusing because they own interesting coordination forms and structural features which come from d 10 conformation [9]. Several Cd and Zn complexes have been investigated in the eld of MMA polymerization [10][11][12][13][14][15][16]. Previously the effectiveness of alkyl-and aryl-Zn and Cd compounds in polymerization of MMA was investigated [10].…”

“…Previously the effectiveness of alkyl-and aryl-Zn and Cd compounds in polymerization of MMA was investigated [10]. Recently, Cd and Zn complexes containing ancillary ligands, pyridyl-imines and N-substituted 2-iminoalkylpyridines have been applied for MMA polymerization [11][12][13][14][15][16]. N,N-di(2-picolyl) cyclohexylamine based Zn (II), and Cd(II) complexes were found to be active catalysts for the MMA polymerization to produce syndiotactic PMMA [11].…”

“…N,N-di(2-picolyl) cyclohexylamine based Zn (II), and Cd(II) complexes were found to be active catalysts for the MMA polymerization to produce syndiotactic PMMA [11]. Nayab and his coworkers have also been investigated the performance of Cd(II) and Zn (II) complexes with bispyridylamine, iminopyridine and 2-iminoalkylpyridines derivatives in MMA polymerization [12][13][14][15]. Moreover, they have been synthesized Cd (II) and Zn(II) containing 4-bromo-N-(2-pyridinylmethylene) benzenamine and N-methyl-N-((pyridine-2-yl)methyl) benzeneamine ligands [15,16].…”