Cyclopentadienylnickel complexes

Abstract

The neutral complexes (η5-C5H5NiXL (X = Cl, L = PPh3 (I); L = PCy3 (II); X = Br, L = PPh3 (III); L = PCy3 (IV); X = I, L = PPh3 (V); L = PCy3 (VI)) have been obtained by treating NiX2L2 with thallium cyclopentadienide. The same reaction in the presence of TlBF4 gives cationic derivatives [(η5-C5H5)NiL2]BF4 (L = 2PPh2Me (VII); L = dppe (VIII)), whereas mononuclear complexes containing two different ligands (L2 = PPh3 + PCy3 (IX)) or dinuclear [(η5-C5H5)Ni(PPh3)]2dppe(BF4)2 (X) are obtained from the reaction of III with TlBF4 in the presence of a different ligand. Reduction of cationic complexes with Na/Hg gives very unstable nickel(I) derivatives (η5-C5H5)NiL2, which could not be isolated purely. Similar reduction of neutral complexes under CO gives a mixture of decomposition products containing [(η5-C5H5)Ni(CO)]2 and nickel(o) carbonyls, whereas in the presence of acetylenes, dinuclear [(η5-C5H5)Ni]2(RCCR′) (R = R′ = Ph; R = Ph, R′ = H) are obtained.