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Published on: August 12, 2019
Formation of a diiron-(μ-η1:η1-CN) complex from acetonitrile solution
Tim P Schlachta1, Michael J Sauer1, Leon F Richter1
1Technical University of Munich, School of Natural Sciences, Department of Chemistry and Catalysis Research Center, Molecular Catalysis, Lichtenbergstrasse 4, 85748 Garching, Germany.
Abstract:
The activation of C-C bonds by transition-metal complexes is of continuing interest and acetonitrile (MeCN) has attracted attention as a cyanide source with comparatively low toxicity for organic cyanation reactions. A diiron end-on μ-η1:η1-CN-bridged complex was obtained from a crystallization experiment of an open-chain iron-NHC complex, namely, μ-cyanido-κ2C:N-bis{[(acetonitrile-κN)[3,3'-bis(pyridin-2-yl)-1,1'-(methylidene)bis(benzimidazol-2-ylidene)]iron(II)} tris(hexafluorophosphate), [Fe2(CN)(C2H3N)2(C25H18N6)2](PF6)3. The cyanide appears to originate from the MeCN solvent by C-C bond cleavage or through carbon-hydrogen oxidation.
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Acidity of 1-Alkynes
The acidic strength of hydrocarbons follows the order: Alkynes > Alkenes > Alkanes. The strength of an acid is commonly expressed in units of pKa — the lower the pKa, the stronger the acid. Among the hydrocarbons, terminal alkynes have lower pKa values and are, therefore, more acidic. For example, the pKa values for ethane, ethene, and acetylene are 51, 44, and 25, respectively, as shown here.

