Methylene- and diamidonaphthalene-bridged diiridium(III) complexes

The reaction of [Ir2(μ-1,8-(NH)2naphth)(CO)2(PiPr3)2] (1) with CH2I2 has led to the sequential formation of complexes [Ir2(μ-1,8-(NH)2naphth)I(CH2I)(CO)2(PiPr3)2] (2) and [Ir2(μ-1,8-(NH)2naphth)(μ-CH2)I2(CO)2(PiPr3)2] (3). The oxidative isomerisation of 2 into 3 takes place with reorganisation of the CO and PiPr3 ancillary ligands from transoid to cisoid relative positions. The activation parameters for this oxidative isomerisation have been estimated in toluene-d8 as ΔS‡=16±2 cal K−1 mol−1 and ΔH‡=30±3 K cal mol−1. The abstraction of iodide ligands from 3 has allowed the preparation of mono- and dicationic compounds with acetonitrile or CO ligands. The latter have been found to be unstable towards CO loss. The reaction of 3 with LiCCPh, followed by iodide abstraction with AgBF4, has afforded the unsaturated complex [Ir2(μ-1,8-(NH)2naphth)(μ-CH2)(CCPh)(CO)2(PiPr3)2][BF4] (9), which has been characterised by X-ray diffraction. The comparison between the stability of the carbonyl adduct of 9, [Ir2(μ-1,8-(NH)2naphth)(μ-CH2)(CCPh)(CO)3(PiPr3)2][BF4] (10) and its isostructural iodide analogue [Ir2(μ-1,8-(NH)2naphth)(μ-CH2)I(CO)3(PiPr3)2][ClO4] (5) suggests that methylene bridges allow the transmission of the trans effects and influences due to the axial iodide and phenylacetylide ligands to the neighbouring metal centres. Compound 9 has also allowed the preparation of the neutral compounds [Ir2(μ-1,8-(NH)2naphth)(μ-CH2)(CCPh)2(CO)2(PiPr3)2] (11) and [Ir2(μ-1,8-(NH)2naphth)(μ-CH2)(CCPh)(CH3)(CO)2(PiPr3)2] (12) by reaction with the appropriate lithium reagents.