η 2-acrylonitrilecyclopentadienyldicarbonyliron(II) tetrafluoroborate: an unusual high-valent transition metal complex

Abstract

Fp(η 2-vinyl ether)BF 4 complexes ( 2a–d) (Fp = η-C 5H 5Fe(CO) 2) are useful starting materials for the preparation of thermodynamically unstable Fp(η 2-acrylonitrile)BF 4 complexes ( 3a–d). Treatment of 2a–d with tetraethylammonium cyanide at 0°C gave the neutral adducts 4a–d which were transformed, in the presence of fluoroboric acid etherate at −78°C, to the acrylonitrile complexes 3a–d. These salts are unstable at room temperature, but they add carbon and heteroatomic nucleophiles at −78°C to give (α-cyano-alkyl)Fp complexes 5a–c, 6 and 7.