PI-OLEFIN-IRIDIUM COMPLEXES .23. REACTION S OF CYCLOOCTA-1,5-DIENE RHODIUM AND IRIDIUM COMPOUNDS WITH ALKYNES

A detailed study of the reaction of [{(cod)IrCl}(2)] (cod=eta(4)-cyclo octa-1,5-diene) with MeLi led to an improved synthesis of [{(cod)Ir(mu -CH2)}(2)] (1). Reaction of 1 with 3-hexyne yields a mixture of produc ts from which the iridacyclopentadienyl complex [eta(5){1-(cod)-1,1-H- 2-IrCH=CEtCEt=CH}(cod)Ir] (2) as well as a compound of formal composit ion [(cod)(2)Ir-2(hexyne)(3)] (5) were isolated; 2 was characterized b y X-ray crystal analysis. On the other hand, direct interaction betwee n [{(cod)IrCl}(2)] and MeLi in the presence of 2-butyne affords [(Cod) (eta(5)-C(6)Me(7))Ir] (6). The latter may be alternatively synthesized by reaction of [{(cod)IrCl}(2)] with AgBF4 and 2-butyne and successiv e treatment of the resulting [(cod)(eta(6)-C(6)Me(6))Ir](+) cation (7) with MeLi. Reaction of [{(cod)RhCl}(2)] with 2-butyne in the presence of n-PrLi afforded the trinuclear rhodacyclopentadienyl complex 5){1- (cod)-1-(mu-H)-RhCMe=CMeCMe=CMe}{(cod)Rh}(2)] (8).