Reversible cyclometalation of silyl ligands. First X-ray structure of an iridium(I) silyl that is not stabilized by chelation

The iridasilacycle fac-(PMe(3))(3)Ir(o-C(6)H(4)SiMe(2))(H) (1) results from the ortho metalation of the transient (PMe(3))(3)Ir(SiMe(2)Ph) (7), generated from Ir(PMe(3))(4)Cl and PhMe(2)SiLi at ambient temperature. Complex 1 can also be obtained from fac-(PMe(3))(3)Ir(CH3)(H)(SiMe(2)Ph) (6), which, when heated, reductively eliminates methane. 1 and its analog fac-(PMe(3))(3)Ir(o-C(6)H(4)SiPh(2))(H) (2), react with hydrogen at 80 degrees C to yield the dihydridosilyliridium(III) complexes fac-(PMe(3))(3)Ir(SiR(2)Ph)(H)(2) (3, R = Me; 4, R = Ph). The reaction of 1 with deuterium demonstrates that initial opening of the iridasilacycle takes place, followed by D-D oxidative addition to 7. The reaction of 1 with CO allows us to trap the iridium(I) species and provides a synthetic route to Ir(PMe(3))(2)(CO)(2)(SiMe(2)Ph) (5). Complex 5 was identified by spectroscopy and by X-ray crystallography and was synthesized independently from 3 and CO. The chemistry presented shows that metalation of silyl ligands can be a facile reversible process that takes place under mild conditions. It also indicates that iridasilacycles can be used as a masked form of electron-rich Ir(I) silyl complexes, which are not readily accessible species.