Conversion of alkanenitriles to amidines and carboxylic acids mediated by a cobalt(II)–ketoxime system

Abstract

The conversion of sterically unhindered organonitriles RCN (R = Me, Et, n-Pr, n-Bu) into the corresponding amidines RC(NH)NH2, isolated as the nitrate salts, and carboxylic acids RCO2H proceeds in the appropriate nitrile as solvent in the presence of Co(NO3)2·6H2O or the cobalt(II) complex trans-[Co(MeCN)2(H2O)4](NO3)2 and a ketoxime R′2CNOH (R′2 = Me2 or C5H10) but does not proceed at all with either the cobalt compound or the ketoxime taken alone. The amidinium nitrates were characterized by C, H, N elemental analyses, FAB+-MS, IR, 1H and 13C{1H} NMR spectroscopies and the structures of RC(NH2)NH2+NO3− (R = Et, n-Pr, n-Bu) were determined by X-ray crystallography, while the carboxylic acids were identified by GC and 1H and 13C{1H} NMR spectroscopies. The reaction proceeds differently with sterically hindered organonitriles, e.g.i-PrCN and t-BuCN, and—instead of amidinium salts—ammonium nitrate and the appropriate carboxylic acids were identified. The structure of trans-[Co(MeCN)2(H2O)4](NO3)2, which is anticipated to be an intermediate in the reaction of Co(NO3)2·6H2O, was determined by X-ray diffractometry.