π Delocalization in iridathiabenzenes

Fenske–Hall calculations were carried out for (PEt3)3Ir(C7H9) (1), [(PEt3)3Ir(C6H8S)]+ (2), [(S-t-but)(PEt3)2]Ir(C6H8S) (3), and [(S-t-but)(PMet3)3]Ir(C6H8S) (4) in order to compare the degree of π delocalization in the metallathiacycle rings of (2) and (3). In comparison to (1), a true iridabenzene and (4), an iridathiacyclobutadiene, the π ring systems in (2) and (3) are considerably more localized than the π system in (1) but are not totally localized. Strong metal–sulfur bonding in (2) disrupts the π ring system and results in some localization of the ring π bonds. The introduction of the donor thiolate ligand in (3) disrupts the ring of π system even more by destabilizing the metal orbitals used for metal–sulfur interactions. This weakens the metal–sulfur interaction seen in (2) and leads to even more localization of the ring π system in (3).