Polyhydride (Fluoroalkyl)phosphine Complexes of Iridium. Synthesis, Dynamics, and Reactivity Properties of (dfepe)2Ir2(μ-H)3(H)

Abstract

The synthesis and reactivity properties of new dimeric iridium polyhydrides incorporating the acceptor ligand (C2F5)2PCH2CH2(C2F5)2 (dfepe) are reported. Hydrogenolysis of (dfepe)Ir(η3-C3H5) (prepared by metathesis of [(dfepe)Ir(μ-Cl)]2 with allylmagnesium chloride) afforded (dfepe)2Ir2(μ-H)3(H) (3) in high yield as an air-stable red crystalline solid. A triply bridged ground-state geometry for 3 was deduced from low-temperature NMR data and was confirmed by X-ray crystallography. Hydride site exchange mechanisms are proposed which are consistent with VT 1H and 31P NMR data. Although 3 is formally coordinatively saturated, hydride bridge dissociation readily occurs and leads to ligand addition reactions. Thus, treatment of tetrahydride 3 with 1 atm of H2 at 20 °C quantitatively affords the hexahydride dimer [(dfepe)Ir(μ-H)2(H)2]2 (5). In the absence of H2, 5 rapidly loses H2 in solution at 20 °C to re-form 3. The structure of 5 has been determined by X-ray crystallography. 3 also reacts with CO to give (d...