π-Allyliridium(I) complexes, Ir(η3-CH2CHCHAr)(CO)(PPh3)2 (Ar=Ph, C6H4Me-p, C6H4Br-p). Comparison of their structures and chemical properties with analogous Rh complexes

Arylallenes such as (4-methylphenyl)allene, phenylallene, and (4-bromophenyl)allene react with IrH(CO)(PPh3)3 to give the π-allyliridium(I) complexes, Ir(η3-CH2CHCHAr)(CO)(PPh3)2 (Ar=C6H4Me-p, Ph, and C6H4Br-p). Crystallographic studies of the complexes showed a similar coordination geometry to that of Rh(η3-CH2CHCHX)(CO)(PPh3)2. An equimolar reaction of phenylacetylene with Ir(η3-CH2CHCHC6H4Me-p)(CO)(PPh3)2 gives a mixture of trans-Ir(CCPh)(CO)(PPh3)2 and trans,trans-IrH(CCPh)2(CO)(PPh3)2 accompanied by the liberation of 1-(4-methylphenyl)-1-propene. The Ir(III) acetylide complex is obtained separately from the reaction of excess phenylacetylene with the π-allyliridium(I) complex. The respective square-planar and octahedral structures of these complexes are determined by X-ray and NMR analyses. The NMR spectra of the reaction mixture indicate concurrent formation of the Ir(I) and Ir(III) complexes having the phenylethynyl ligands.