C-scorpionate iron(II) complexes as highly selective catalysts for the hydrocarboxylation of cyclohexane

• Published in: Inorganica Chimica Acta 2019-04, Vol.489, p.269-274
• Main Authors: Matias, Inês A.S., Ribeiro, Ana P.C., Alegria, Elisabete C.B.A., Pombeiro, Armando J.L., Martins, Luísa M.D.R.S.
• Format: Article
• Language: English
• Subjects: Alkanes; Aqueous medium; Carboxylic acid; Catalysis; Catalysts; Coordination compounds; Cyclohexane; Homogeneous catalysis; Hydrocarboxylation; Iron; Iron chlorides; Scorpionate; Selectivity
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2019.02.035

[Display omitted] •Homogeneous C-scorpionate Fe(II) complex catalyze cyclohexane hydrocarboxylation.•Water acts as a source of the hydroxide moiety in the carboxylic acid group.•Cyclohexanecarboxylic acid is selectively produced in good yield. The C-scorpionate iron(II) complexes [FeCl2{κ3-HC(pz)3}] (1) (pz = pyrazol-1-yl), Li[FeCl2{κ3-SO3C(pz)3}] (2) and the new [FeCl2{κ3-HOCH2C(pz)3}] (3) act as catalysts for the hydrocarboxylation of cyclohexane (with CO and H2O) to cyclohexanecarboxylic acid in a remarkable yield (up to 60%) and under mild conditions. The catalysts selectivity for the acid can be tuned by CO pressure, catalyst amount and reaction temperature. Complex [FeCl2{κ3-HC(pz)3}] (1) provides the most effective catalyst requiring low CO pressure. This work constitutes an unprecedented use of iron complexes as catalysts for the hydrocarboxylation of alkanes.