The electrochemical synthesis of eta(5)-cyclopentadienylcobalt-eta(5)-tetraphenylbutadiene and its reaction with iodine in the presence of electron donor ligands

eta(5)-Cyclopentadienylcobalt-eta(4)-tetraphenylbutadienes RC5H4CoC4H2Ph4 (IIa-d: a R=H; b R=Et; c R=Pr-i; d R=PhCH2) have been prepared by simultaneous electrolysis of a respective substituted cyclopentadiene RC5H5 and diphenylacetylene in acetonitrile containing up to 0.5% water, using a cobalt anode. The action of iodine on IIa-d results in the elimination of the tetraphenylbutadiene ligand and the formation of diiodides (RC5H4CoI2)(2) (IIIa-d). The reaction of IIa with iodine in the presence of electron donor ligands leads to the formation of complexes CpCoI2L, (L=Ph,P, Py, Me2S, dppe), [CpCoIL2]+I-3(-) (L-2=dipy, phen), (CpCoI2)(2)L (L=dppe). (C) 1997 Elsevier Science S.A.