Reactions of cis-dihydrido complex [Ir(H) 2 (NCCH 3 ) 2 (PPh 3 ) 2 ] + (1) with HCtCH and RCt CH (R ) C 6 H 5 , p-C 6 H 4 CH 3 , cyclohex-1-enyl, C(CH 3 )dCH 2 , C(CH 3 ) 3 ) produce cross-conjugated hexatrienes (RCHdC(CHdCH 2 ) 2 , R-HEX) and octatetraenes (H 2 CdCH-CRdCH-C(-CHd CH 2 )dCHR, R 2 -OCT). Two molecules of HCtCH are inserted into Ir-H bonds of 1 to give cis-bis (ethenyl) from which R-HEX-d 1 are obtained in the presence of a base. Di-and trinuclear alkynyl-bis(alkenyl) complexes [L 5 Ir-CtCp-C 6 H 4 -CtC-IrL 5 ] (7, L 5 ) (-CHdCH 2 ) 2 (CO)(PPh 3 ) 2 ) and [L 5 Ir-CtC-m,m-C 6 H 3 -(CtC-IrL 5 ) 2 ] (8, L 5 ) (-CHdCH 2 ) 2 (CO)(PPh 3 ) 2 ) react with H + to produce extended cross-conjugated olefins, p-C 6 H 4 -(HEX) 2 and m,m-C 6 H 3 -(HEX) 3 , respectively, in high yields. Plausible reaction pathways involve alkenyl-vinylidene complexes that undergo the C-C bond formation reaction between the two hydrocarbyl ligands to produce the cross-conjugated olefins.