Reactions of π-cyclopentadienyltriphenylphosphinemetal diiodides and π-cyclopentadienylcarbonylmetal diiodides (M = Co,Rh, Ir) with 1,4-dilithio-1,2,3,4-tetraphenylbutadiene

Reactions between π-cyclopentadienyltriphenylphosphinemetàl diiodides (M = Rh and Ir) and 1,4-dilithio-l,2,3,4-tetraphenylbutadiene result in the formation of 1-(π-cyclopentadienyl)-l-triphenylphosphine-2,3,4,5-tetraphenylrhodole and 1-(π-cyclopentadienyl)-1-triphenylphosphine-2,3,4,5-tetraphenyliridole, respectively, in low yield. Reactions between π-cyclopentadienyltriphenylphosphinecobalt diiodide or π-cyclopentadienylcarbonylcobalt diiodide do not produce the expected cobaltacyclopentadiene complexes, but instead a low yield of π-cyclopentadienyl-(π-tetraphenylcyclobutadiene)cobalt. The trimeric rhodium complex (π-C₅H₅Rh)₃(CO)(PhCCPh) has been isolated from a reaction between 1,4-dilithio-l,2,3,4-tetraphenylbutadiene and π-cyclopentadienylcarbonylrhodium diiodide. The importance of metallocyclic intermediates in the formation of polynuclear complexes of this type is discussed.