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

The iridium(I)-aminophosphane complex [Ir{κ 3 C , P , P '-(SiNP-H)}(cod)] has been prepared by reaction of [IrCl(cod)(SiNP)] with KCH 3 COO. DFT calculations show that this reaction takes place through an unexpected outer sphere mechanism (SiNP = SiMe 2 {N(4-C 6 H 4 Me)PPh 2 } 2 ; SiNP-H = CH 2 SiMe{N(4-C 6 H 4 Me)PPh 2 } 2 ). The reaction of [IrCl(cod)(SiNP)] or [Ir{κ 3 C , P , P '-(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 2 (η 3 -C 3 H 5 )(SiNP)], which, in turn, reacts with tert -butyl isocyanide yielding the substitution product [IrCl(η 3 -C 3 H 5 )(CN t Bu)(SiNP)]Cl via the observed intermediate [IrCl 2 (η 1 -C 3 H 5 )(CN t Bu)(SiNP)]. On the other hand, the reaction of [Ir{κ 3 C , P , P '-(SiNP-H)}(cod)] with [FeCp 2 ]X (X = PF 6 , CF 3 SO 3 ), I 2 or CF 3 SO 3 CH 3 results in the metal-centered two-electron oxidation rendering a varied assortment of iridium(III) compounds. [Ir{κ 3 C , P , P '-(SiNP-H)}(cod)] reacts with [FeCp 2 ] + (1 : 2) in acetonitrile affording [Ir{κ 3 C , P , P '-(SiNP-H)}(CH 3 CN) 3 ] 2+ isolated as both the triflato and the hexafluorophosphato derivatives. Also, the reaction of [Ir{κ 3 C , P , P '-(SiNP-H)}(cod)] with I 2 (1 : 1) yields a mixture of iridium(III) derivatives, namely the mononuclear compound [IrI(κ 2 P , P '-SiNP)(η 2 ,η 3 -C 8 H 11 )]I, containing the η 2 ,η 3 -cycloocta-2,6-dien-1-yl ligand, and two isomers of the dinuclear derivative [Ir 2 {κ 3 C , P , P '-(SiNP-H)} 2 (μ-I) 3 ]I, the first species being isolated in low yield. DFT calculations indicate that [IrI(κ 2 P , P '-SiNP)(η 2 ,η 3 -C 8 H 11 )]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 3 C , P , P '-(SiNP-H)}] platform by the newly formed HI. Finally, the oxidation of [Ir{κ 3 C , P , P '-(SiNP-H)}(cod)] by methyl triflate proceeds via a hydride abstraction from the cod ligand, with the elimination of methane and the formation of the η 2 ,η 3 -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.