- Bonnand, Evan
- Synthesis of iron nitrosyl complexes with carbamate ligands
Formation of first row transition metal complexes that can bind a nitrosyl group (NO) is of interest for understanding how biological systems reduce atmospheric pollutants, and for future chemical reactions. One approach is to construct complexes containing an ancillary ligand bound to the metal first and add the nitrosyl group second. A second approach is to form an iron nitrosyl complex with intermediate H2O ligands first, followed by addition of an ancillary N,N-diethyldithiocarbamate ligand. This method and complex were previously reported to be air-stable, making the chemistry more accessible than typical procedures in the absence of oxygen and moisture. The current work investigated the various components of the reaction to identify the most robust procedure.
FellSO4-7H2O was reacted with NaNO2 in sulfuric acid to form [Fe(NO)(H2O)5]2-, followed by addition of sodium N,N-diethyldithiocarbamate (dtc) to form (dtc)2Fe(NO). Several different trials were conducted by changing the ratios of starting materials to determine the optimal conditions. IR spectroscopy verified the presence of the nitrosyl complex. Additional variants included using Felll starting materials and silver N,N-diethyldithiocarbamate, which both resulted in formation of the desired product. Future work includes further characterization and isolation of the complex in bulk.
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- Henriquez, Brenda
- Nitrous oxide (N2O) is the main contributor to the ozone layer depletion, has almost 300 times the warming potential of carbon dioxide, and lingers in the atmosphere for an average of 114 years. Biological systems can both produce N2O via NO reductive coupling and reduce N2O through reactions at copper and iron centers, but not at sufficient rates to mitigate pollution. The mechanisms are not fully understood, and a more complete understanding would benefit pollution remediation efforts. Hyponitrite (O2N22-) intermediates are proposed, but there are few isolated examples. In the current work, discrete ?-diketiminate (iPrNNFG) copper complexes formed in solution from NO coupling were analyzed by X-ray absorption spectroscopy (XAS) to determine the metal oxidation state, coordination environment, and assess hyponitrite formation. The X-ray absorption near edge structure (XANES) analysis determined the oxidation state of the complexes [(iPrNNF6)CuO2N2][CoCp2] and (iPrNNF6)CuO2N2 to be +1, while
(iPrNNF6)CuO2N2Ph has an oxidation state of +2. The [(iPrNNF6)CuO2N2][CoCp2] complex had a lower rising edge feature making the oxidation state assignment more nuanced. The extended X-ray absorption fine structure (EXAFS) allowed for the copper coordination environment to be determined, using (iPrNNF6)CuO2N2Ph as a comparison for which the 3-D atomic structure is reported. The EXAFS for [(iPrNNF6)CuO2N2][CoCp2] suggest dimer formation. The EXAFS for (iPrNNF6)CuO2N2 are consistent with O2N2 bound to copper, and suggest that the hyponitrite complex was synthesized and isolated. This has implications for understanding reactivity and reduction of N2O and NO and is one of the first examples of an isolated copper hyponitrite complex. Future work includes understanding the mechanism by studying other intermediates formed in NO coupling reactions and has implications for understanding pollutant reduction. This work was
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