Reactivity of Ir(I)-aminophosphane platforms towards oxidants.

The iridium(I)-aminophosphane complex [Ir{κ,,'-(SiNP-H)}(cod)] has been prepared by reaction of [IrCl(cod)(SiNP)] with KCHCOO. DFT calculations show that this reaction takes place through an unexpected outer sphere mechanism (SiNP = SiMe{N(4-CHMe)PPh}; SiNP-H = CHSiMe{N(4-CHMe)PPh}). The reaction of [IrCl(cod)(SiNP)] or [Ir{κ,,'-(SiNP-H)}(cod)] with diverse oxidants has been explored, yielding a range of iridium(III) derivatives. On one hand, [IrCl(cod)(SiNP)] reacts with allyl chloride rendering the octahedral iridium(III) derivative [IrCl(η-CH)(SiNP)], which, in turn, reacts with -butyl isocyanide yielding the substitution product [IrCl(η-CH)(CNBu)(SiNP)]Cl the observed intermediate [IrCl(η-CH)(CNBu)(SiNP)]. On the other hand, the reaction of [Ir{κ,,'-(SiNP-H)}(cod)] with [FeCp]X (X = PF, CFSO), I or CFSOCH results in the metal-centered two-electron oxidation rendering a varied assortment of iridium(III) compounds. [Ir{κ,,'-(SiNP-H)}(cod)] reacts with [FeCp] (1 : 2) in acetonitrile affording [Ir{κ,,'-(SiNP-H)}(CHCN)] isolated as both the triflato and the hexafluorophosphato derivatives. Also, the reaction of [Ir{κ,,'-(SiNP-H)}(cod)] with I (1 : 1) yields a mixture of iridium(III) derivatives, namely the mononuclear compound [IrI(κ,'-SiNP)(η,η-CH)]I, containing the η,η-cycloocta-2,6-dien-1-yl ligand, and two isomers of the dinuclear derivative [Ir{κ,,'-(SiNP-H)}(μ-I)]I, the first species being isolated in low yield. DFT calculations indicate that [IrI(κ,'-SiNP)(η,η-CH)]I forms as the result of a bielectronic oxidation of iridium(I) followed by the deprotonation of the cod ligand by iodide and the protonation of the methylene moiety of the [Ir{κ,,'-(SiNP-H)}] platform by the newly formed HI. Finally, the oxidation of [Ir{κ,,'-(SiNP-H)}(cod)] by methyl triflate proceeds a hydride abstraction from the cod ligand, with the elimination of methane and the formation of the η,η-cycloocta-2,6-dien-1-yl ligand with the concomitant two-electron oxidation of the iridium centre. The crystal structures of selected compounds have been determined.