Manganese(II) and Magnesium(II) Analogies in Iridium Hydride Coordination Chemistry

Overview & Synopsis

Alkane elimination reactions between stable magnesium and manganese dialkyls, [L n M(CH 2 tBu) 2 ] (M = Mg, Mn), and an iridium polyhydride species, [Cp*IrH 4 ] (Cp* = C 5 Me 5 ), provide a variety of heterobimetallic Mg-Ir and Mn-Ir hydride complexes. In several cases, their solid-state molecular structures are shown to be virtually identical despite fundamentally different electronic properties of Mg(II) (2p 6 ) and Mn(II) (3d 5 ). A direct comparison of the paramagnetic Mn with the diamagnetic Mg analog enables a comprehensive characterization based on a combination of analytical techniques (single-crystal X-ray diffraction, IR, and NMR spectroscopies), especially with respect to the hydride ligands, traditionally difficult to identify in open-shell species. Nevertheless, such congruence is not universal: the nuclearity and M:Ir stoichiometry depend on the nature of the Mg and Mn dialkyl precursors, which in turn is determined by the type of coligand L, and on the presence of protondonating reagents in the reaction mixture, revealing subtle differences between the Mg and Mn systems in certain cases.