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Synlett 2010(20): 3115-3116  
DOI: 10.1055/s-0030-1259048
SPOTLIGHT
© Georg Thieme Verlag Stuttgart ˙ New York

Potassium Hexacyanoferrate(II)

Jun-Tao Hou*
The College of Chemistry & Material Science, Hebei Normal University, Shijiazhuang 050016, P. R. of China
e-Mail: juntaohou@gmail.com;
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Publication History

Publication Date:
17 November 2010 (online)

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Introduction

Potassium hexacyanoferrate(II) has received considerable attention as an environmentally benign cyanaide source for the synthesis of a variety of important aryl nitriles. K4[Fe(CN)6)] is non-toxic {the LD50 of K4[Fe(CN)6] is lower than that for NaCl} and even used in food industry for metal precipitation. It has also been used as anti-agglutinating auxiliary for table salt (NaCl). It is soluble in ­water without decomposition even on addition of hydrochloric acid. [¹] In addition to its nontoxicity, cheapness, and easy handling, it allows for improved catalyst productivity and substrate scope. [²] The lower basicity and nucleophilicity of the hexacyanoferrate(II) anion compared to the free cyanide ion may help to prevent side reactions. [³] It has been extensively used as highly efficient cyanation reagent in the synthesis of benzonitriles [4-¹7] and (oligo)phenothiazinyl nitriles. [¹8] It has also reported to be used as the cyanide source for cyanation of aroyl chlorides, [¹9] heteroaryl halides, [²0] aryl perfluorooctylsulfonates [²¹] and aryl triflates. [²²] It has been employed in the oxidation of N-phenyl-2,5-diarylamino-1,4-benzoquinone imines to 2-(p-tolylamino)-5-(p-tolyl)phenazin-3-one. [²³]

K4[Fe(CN)6)] is commercially available on a ton scale. It can be readily prepared by the reaction of hydrogen ferrocyanide and potassium hydroxide.