Mechanistic insight into novel sulfoxide containing SABRE polarisation transfer catalysts

Signal Amplification By Reversible Exchange (SABRE) is a hyperpolarisation technique that commonly uses [Ir(H)(2)(carbene)(substrate)(3)]Cl complexes to catalytically transfer magnetisation from para-hydrogen derived hydride ligands to coordinated substrates. Here, we explore the reactivity of a novel class of such catalysts based on sulfoxide containing [IrCl(H)(2)(carbene)(DMSO)(2)], which are involved in the hyperpolarisation of pyruvate using SABRE. We probe the reactivity of this species by NMR and DFT and upon reaction with sodium pyruvate establish the formation of two isomers of [Ir(H)(2)(eta(2)-pyruvate)(DMSO)(IMes)]. Studies with related disodium oxalate yield [Ir-2(H)(4)(IMes)(2)(DMSO)(2)(eta(2)-kappa(2) -Oxalate)] that is characterised by NMR and X-ray diffraction.