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

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 H-2 loss and coordinating a [Ni(dippe)] fragment to the nitrile substituent in a eta(2)-C N way to yield complexes [(dippe) Ni(eta(2)-C, N-2-FN)] (2) and [(dippe) Ni(eta(2)-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)(eta(1)-C-2-FN)] (7) and [(dippe) Ni(CN)(eta(1)-C-3-FN)] (11) were observed as the main products. These complexes were fully characterized by H-1, P-31{H-1} and C-13{H-1} 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 degrees 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(kappa(2)-O, C-OCH=CH-CH= C(CN))] (9), which was also isolated and characterized by multinuclear NMR.