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Layered Zn₂[Co(CN)₆](CH₃COO) double metal cyanide: a two-dimensional DMC phase with excellent catalytic performance.

ABSTRACT: Double metal cyanides (DMCs) are well known, industrially applied catalysts for ring opening polymerization reactions. In recent years, they have been studied for a variety of catalytic reactions, as well as other applications, such as energy storage and Cs sorption. Herein, a new, layered DMC phase (L-DMC), Zn₂[Co(CN)₆](CH₃COO)·4H₂O, was synthesized. The structure, which crystallizes in the monoclinic space group P2₁/m, consists of positively charged {Zn₂Co(CN)₆}⁺ DMC layers linked through acetate groups and presents a new layered structure to the family of double metal cyanides. L-DMC proved to be a reusable and stable catalyst that exhibited a higher activity than the benchmark DMC catalyst in two important applications: hydroamination of phenylacetylene with 4-isopropylaniline and polymerization of 1,2-epoxyhexane.

SUBMITTER: Marquez C

PROVIDER: S-EPMC6520920 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:We have combined results from several spectroscopic techniques to investigate the aerobic reactions of Rh2(AcO)4 (AcO- = CH3COO-) with l-cysteine (H2Cys) and its derivatives d-penicillamine (3,3'-dimethylcysteine, H2Pen), with steric hindrance at the thiol group, and N-acetyl-l-cysteine (H2NAC), with its amino group blocked. Previous investigations have shown that antitumor active dirhodium(II) carboxylates may irreversibly inhibit enzymes containing a thiol group at or near their active sites. Also, cysteine, the only thiol-containing proteinogenic amino acid, interacts in vivo with this class of antitumor compounds, but structural information on the products of such reactions is lacking. In the present study, the reactions of Rh2(AcO)4 and H2L were carried out in aqueous solutions at the pH of mixing (acidic) and at physiological pH, using the different mole ratios 1:2, 1:4, and 1:6, which resulted in the same products in increasing yields. Electrospray ionization mass spectrometry (ESI-MS) indicates formation of dimeric [RhIII 2Pen4]2- or oligomeric {RhIII 2L4} n (L = Cys, NAC) complexes with bridging thiolate groups. Analyses of Rh K edge extended X-ray absorption fine structure (EXAFS) data reveal 3-4 Rh-S and 2-3 Rh-(N/O) bonds around six-coordinated Rh(III) ions at mean distances of 2.33 ± 0.02 and 2.09 ± 0.02 Å, respectively. In the N-acetyl-l-cysteine compound, the RhIII···RhIII distance 3.10 ± 0.02 Å obtained from the EXAFS spectrum supports trithiolate bridges between the Rh(III) ions, as was also found when using glutathione as ligand. In the cysteine and penicillamine complexes, double thiolate bridges join the Rh(III) ions, with the nonbridging Cys2- and Pen2- ligands in tridentate chelating (S,N,O) mode, which is consistent with the ΔδC = 7.3-8.4 ppm shift of the COO- signal in their carbon-13 cross polarization magic angle spinning (CPMAS) NMR spectra. For the penicillamine complex, the 2475.6 eV peak in its S K edge X-ray absorption near edge structure (XANES) spectrum shows partial oxidation, probably caused by peroxide generated from reduction of dissolved O2, of thiolato to sulfenato (S=O) groups, which were also identified by ESI-MS for all three {RhIII 2L4} n compounds.

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Layered Zn₂[Co(CN)₆](CH₃COO) double metal cyanide: a two-dimensional DMC phase with excellent catalytic performance.

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Layered Zn2[Co(CN)6](CH3COO) double metal cyanide: a two-dimensional DMC phase with excellent catalytic performance.

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Layered Zn₂[Co(CN)₆](CH₃COO) double metal cyanide: a two-dimensional DMC phase with excellent catalytic performance.