Effect of phosphane ligands in the nucleophilic additions at iridium allenylidene complexes

The reactivity of allenylidene complexes towards nucleophilic additions has been deeply investigated in ruthenium complexes, however, studies involving iridium complexes are scarce. Thus, several acetonitrile complexes have been synthesized as precursors for the in situ nucleophilic additions of phosphanes and amines at non-isolated allenylidene complexes of formula [IrCp*Cl(=C=C=CPh 2 )(L)]PF 6 (L = PMe 3 , P(OMe) 3, PPh 2 (OMe), PPh 2 Me, PCy 3 , P(3,5-C 6 H 3 (CF 3 ) 2 ) 3 ). Therefore, addition of phosphanes as nucleophiles provided different ratios of the allenyl [IrCp*Cl{C(PR 3 )=C=CPh 2 }(L)]PF 6 ( 4·R ) and alkynyl complexes [IrCp*Cl{C≡C–CPh 2 (PR 3 )}(L)]PF 6 ( 5·R ) (R = Ph, OMe, Me) depending on the phosphane used as nucleophile and the one bonded to the metal center. The regioselectivity mainly arose from steric demand instead of the electronic effect of the phosphanes. The addition of amines led, in most cases, to the first substituted aminocarbene complexes [IrCp*Cl{=C(NRR')–CH=CPh 2 }(L)]PF 6 (R = H, R' = Et ( 6 ); R = R' = Et ( 7 )) with the {IrCp*Cl(PR 3 ) + } fragment; however, using a bulky phosphane such as PCy 3 , formation of a second product was observed, probably an iridanaphthalene derivative [IrCp*{κ 2 C,C -{=C(NRR')–CH=CPh 2 }(PCy 3 )]PF 6 (R = H, R' = Et ( 8 ); R = R' = Et ( 9 )). • The steric demand of phosphane ligands have a higher impact in the reactivity of allenylidenes [IrCp*Cl(=C=C=CPh)L]PF 6 than the electronic parameter. • Substituted aminocarbenes of fragment {IrCp*Cl(L)} + can be obtained by nucleophilic attack at the allenylidene instead of amynolisis reactions. • Combination of steric and electronic properties of PCy 3 leads to a different reactivity.