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 pi-allyliridium(I) complexes, Ir(eta(3)-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(eta(3)-CH2CHCHX)(CO)(PPh3)(3). An equimolar reaction of phenylacetylene with Ir(eta(3)-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 pi-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. (C) 2000 Elsevier Science S.A. All rights reserved.