DFT calculations with the B3LYP functional are carried out on the systems [Cp(PH₃)Ir(SiHR₂)]+ and [Cp(PH₃)Ir(SiR₃)]+ (Cp = C₅H₅, R = H, CH₃, SiH₃, Cl), which are representative examples of experimental complexes where the silylene ligand can exist. Geometry optimization for the different systems gives a large variety of structures, including the conventional silyl and hydrido silylene isomers, but also other less usual bridged structures, with a variety of groups taking a bridging position. Analysis of the large amount of data, together with those previously reported for [(dhpe)Pt(SiHR₂)]+ and [(dhpe)Pt(SiR₃)]+ (dhpe = H₂P-CH₂-CH₂-PH₂), leads to a better understanding of the general factors governing the relative stabilities of the possible isomeric forms.