Generating and Dimerizing the Transient 16‐Electron Phosphinidene Complex [Cp*IrPAr]: A Theoretical and Experimental Study

The properties of the 16‐electron phosphinidene complex [CpRIrPR] were investigated experimentally and theoretically. Density functional theory calculations show a preferred bent geometry for the model complex [CpIrPH], in contrast to the linear structure of [CpIrNH]. Dimerization to give [{CpIrPH} 2 ] and ligand addition to afford [Cp(L)IrPH] (L=PH 3 , CO) were calculated to give compounds that were energetically highly favorable, but which differed from the related imido complexes. Transient 16‐electron phosphinidene complex [Cp*IrPAr] could not be detected experimentally. Dehydrohalogenation of [Cp*IrCl 2 (PH 2 Ar)] in CH 2 Cl 2 at low temperatures resulted in the novel fused‐ring systems 17 (Ar=Mes*) and 20 (Ar=Mes), with dimeric [{Cp*IrPAr} 2 ] being the likely intermediate. Intramolecular CH bond activation induced by steric factors is considered to be the driving force for the irreversible formation of 17 and 20 . ONIOM calculations suggest this arises because of the large steric congestion in [{Cp*IrPAr} 2 ], which forces it toward a more reactive planar structure that is apt to rearrange.