Activation and Coordination of Ammonia at [Cp*Ir(H)2]: NMR and Matrix Isolation Studies

Abstract

(1)H NMR exchange spectroscopy of a reaction mixture of [Cp*Ir(H)(4)] (1; Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) and ammonia suggests an exchange of hydrogen atoms between the hydrido ligands and ammonia. Treatment of 1 with ND(3) led to an H/D exchange between ND(3) and the hydrido ligands of 1. Subsequent studies showed that photolysis of 1 isolated in frozen argon matrices leads to the formation of the iridium compounds [Cp*Ir(H)(2)] (2) and [Cp*Ir(H)(3)] (4), as it was confirmed by IR spectroscopy. In the presence of water the aqua complex [Cp*Ir(H)(2)(OH(2))] (3) was generated simultaneously. Accordingly, photolysis of 1 in an argon matrix doped with ammonia gave rise to the ammine complex [Cp*Ir(H)(2)(NH(3))] (5). IR assignments were supported by calculations of the gas-phase IR spectra of 1-5 by DFT methods.