Carbon–carbon vs. carbon–oxygen bond activation in 2- and 3-furonitriles with nickel

Abstract

The reaction between [(dippe)NiH]₂ (1) (dippe = 1,2-bis(diisopropylphosphino)-ethane) and 2- and 3-furonitrile (2-FN and 3-FN) was carried out at room temperature. Both furonitriles initially react with H₂ loss and coordinating a [Ni(dippe)] fragment to the nitrile substituent in a η²-CN way to yield complexes [(dippe)Ni(η²-C,N-2-FN)] (2) and [(dippe)Ni(η²-C,N-3-FN)] (10), respectively. After monitoring this reaction for 6 days at room temperature in the presence of a slight excess of each nitrile, the C–CN bond activation products [(dippe)Ni(CN)(η¹-C-2-FN)] (7) and [(dippe)Ni(CN)(η¹-C-3-FN)] (11) were observed as the main products. These complexes were fully characterized by ¹H, ³¹P{¹H} and ¹³C{¹H} NMR and by single crystal X-ray determinations. After isolation and characterization of (7) and (11), a thermal stability study was carried out, and it was found that the –C–CN bond activation is reversible at 100 °C for both compounds. Particularly, the thermolysis of complex (7) allowed the further production of a C–O ring opening at the furan to yield complex [(dippe)Ni(κ²-O,C–OCHCH–CHC(CN))] (9), which was also isolated and characterized by multinuclear NMR.