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Metal Incorporation into Copper Aluminum Borates
Published in John R. Kosak, Thomas A. Johnson, Catalysis of Organic Reactions, 2020
Larry C. Satek, Patrick E. McMahon
How do these observations fit into our thoughts of the active site of the catalyst? The structure of the catalyst is very difficult to envision; x-ray and neutron diffraction work reported previously resolved the structure [4a]. The overall structure is shown in Figures 10 and 11. The striking features include the small pores (about 2.5 A free diameter) and the square planar oxygen surrounded by four disordered trigonal bipyramidal metal sites (half occupied by copper and half occupied by aluminum). Although stretching the analogy somewhat, this square planar site is very similar to what could be considered an “inverse porphyrin.” That is, the center is a square planar oxygen atom surrounded by four metal atoms, all tied together with an inorganic framework; this is opposed to a square planar metal atom surrounded by four O or N atoms, all tied together with a carbon framework as in a porphyrin structure. A schematic of this concept appears in Figure 12.
Organometallic and Inorganic–Organic Polymers
Published in Charles E. Carraher, Carraher's Polymer Chemistry, 2017
Bailar listed a number of principles that can be considered in designing coordination polymers. Briefly, these are as follows: (1) Little flexibility is imparted by the metal ion or within its immediate environment; thus, flexibility must arise from the organic moiety. Flexibility increases as the covalent nature of the metal–ligand bond increases. (2) Metal ions only stabilize ligands in their immediate vicinity; thus, the chelates should be strong and close to the metal ions. (3) Thermal, oxidative, and hydrolytic stabilities are not directly related; polymers must be designed specifically for the properties desired. (4) Metal–ligand bonds have sufficient ionic character to permit them to rearrange more readily than typical “organic bonds.” (5) Polymer structure (such as square planar, octahedral, linear, network) is dictated by the coordination number and stereochemistry of the metal ion or chelating agent. (6) Lastly, the solvents used should not form strong complexes with the metal or chelating agent or they will be incorporated into the polymer structure and/or prevent reaction from occurring.
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Published in Joseph C. Salamone, Polymeric Materials Encyclopedia, 2020
Another method for the preparation of low molecular weight poly(alkylene carbonate)s is the copolymerization of alkylene oxide and carbon dioxide with aluminum porphyrins as coordination catalysts. Aluminum porphyrins such as (5,10,15,20-tetraphenylporphinato) aluminum chloride, derived from the reaction of 5,10,15,20-tetraphenylporphyrin with diethylaluminum chloride, when complexed with an appropriate organic quaternary salt (e.g., ethyltriphenylphosphonium bromide) are affective catalysts for the living alternating copolymerization of alkylene oxide (propylene oxide, cyclohexene oxide) and carbon dioxide.24 The mechanism of this copolymerization was proposed to involve an activation of the anion of the quaternary salt as the nucleophile by the metalloporphyrin; the structure of the growing active species was found to be a novel six-coordinate aluminum porphyrin carrying one reactive axial ligand on both sides of its square-planar A1N4 skeleton.25 The propylene oxide ring-opening by the aluminum porphyrin catalyst was found to proceed with inversion of the configuration at the carbon atom of the ring where cleaved (Cβ). This proves for the rearward nucleophilic attack on the coordinating epoxide which needs a participation of two aluminum porphyrin molecules.26 More detailed mechanism of the copolymerization of epoxide and carbon dioxide with the porphinatoaluminum catalyst–organic quaternary salt system has been proposed to involve a nucleophilic attack of the axial ligand at the six-coordinate aluminum anionic species onto the epoxide coordinated at cationic aluminum species.27 When the copolymerization of propylene oxide and carbon dioxide was carried out with the porphinatoaluminum catalyst in the absence of the organic quaternary salt, the copolymer was found to contain ether linkages to some extent, apart from the predominant carbonate linkages in the chain.28–30
Coordination chemistry and magnetic properties of copper(II) halide complexes of quinoline
Published in Journal of Coordination Chemistry, 2022
Christopher P. Landee, Firas F. Awwadi, Brendan Twamley, Mark M. Turnbull
Compound 1 crystallizes in the monoclinic space group C2/c. The molecular structure is shown in Figure 1 and selected bond lengths and angles are listed in Table 2. The Cu(II) is located on an inversion center, rendering the coordination sphere planar, and all trans-bond angles are 180°, as required by symmetry. The Cl1-Cu-N11 bond angle is 89.34(16)° making the complex very nearly square planar. The Cu-Cl1 bond (2.2319(18) Å) is shorter than observed in the corresponding Cu(py)2Cl2 complex [3], while the Cu-N11 (2.027(5) Å) bond is slightly longer than the corresponding bond (2.009 Å) in the pyridine complex, presumably due to steric pressure from the larger quinoline ligand. The quinoline ring is nearly planar (mean deviation of constituent atoms = 0.011 Å) and lies almost perpendicular (85.7°) to the copper coordination plane.
Bio-conjugated N-(2-hydroxy-1-naphthaldehyde)-glucosamine Cu(II) complex: Bacterial sensitivity and superoxide dismutase-like activity
Published in Journal of Coordination Chemistry, 2018
Jan Mohammad Mir, Deepak Kumar Rajak, Ram Charitra Maurya
The optimized structure of [Cu(2-hnd-gls)(H2O)] is given in Figure 3. The various bond lengths, bond angles and dihedral angles generated from the optimized structure of complex are given in Table S1. The computed bond lengths, such as Cu–N(44), Cu–O(42)(enolic), Cu–O(41)(ketonic) and Cu–O(38)(water), are 1.9252 Å, 1.9004 Å, 1.901 Å and 2.0054 Å, respectively. The four bond angles converging toward the metal center are almost 90° and hence describe the square planar geometry of the compound. The two diagonal angles, viz., O(38) Cu(37)–N(44) and O(42)–Cu(37)–O(41) are 176.2770 and 155.4070°, respectively. While four angles converging toward metallic center; O(42)–Cu(37)–O(38), O(41)–Cu(37)–O(38), O(41)–Cu(37)–N(44) and O(42)–Cu(37)–N(44) have been found to be 93.9275, 87.5401, 93.4370 and 86.6353°, respectively. The DFT can be used to calculate the dipole moment (μ) and the respective polarizability tensors. The calculated values are given in Table 1. The calculated electric dipole moment μ (Debye), isotropic polarizability (α in a.u.), anisotropy of the polarizability (Δα in a.u.), all hyperpolarizability (β) components (in a.u.) values of [Cu(2-hnd-gls)(H2O)] can again be described in characterizing the molecular charge delocalization in the square planar complex and its stability. Under such explanation, one can predict the polarization extent within a molecule, which is of prime importance in medicinal as well as the industrial field. The property can be manifested to design materials of desirable properties.