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 temperat ure. Complex 1 can also be obtained from fac-(PMe(3))(3)Ir(CH3)(H)(SiM e(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 hy drogen at 80 degrees C to yield the dihydridosilyliridium(III) complex es fac-(PMe(3))(3)Ir(SiR(2)Ph)(H)(2) (3, R = Me; 4, R = Ph). The react ion of 1 with deuterium demonstrates that initial opening of the irida silacycle takes place, followed by D-D oxidative addition to 7. The re action of 1 with CO allows us to trap the iridium(I) species and provi des 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 t hat takes place under mild conditions. It also indicates that iridasil acycles can be used as a masked form of electron-rich Ir(I) silyl comp lexes, which are not readily accessible species.