Synthesis and Reactivity of Rhodium(I) and Iridium(I) Chloride Complexes of a Trisphosphinine^†

The SiMe2 linked tris(phosphinine) 1 reacts with [M(COD)Cl]2 (M = Rh, Ir) to give the corresponding [M(1)Cl] complexes 2 and 3. The X-ray crystal structure of 2 reveals a highly twisted geometry of 1 around the rhodium center. Abstraction of the chloride ligand with AgOtf in the presence of CH3CN yields the corresponding cationic complexes 4 and 5. The CH3CN ligand can be quantitatively displaced from 4 by CO to form a cationic carbonyl complex 6 in which the Rh center is highly Lewis acidic. It was also shown that, upon reaction with HCl, 3 equilibrates with the [Ir(1)HCl2] complex 7.