The reactivity of the molecular magnesium hydride cation in [(Me4TACD)2Mg2(μ-H)2][B(3,5-Me2-C6H3)4]2 (Me4TACD = 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane) toward Brønsted acids, the mild oxidant diphenyldisulfide as well as heterocumulenes CO2, phenyl isocyanate, and carbodiimide has been investigated. While the hydridic character of the Mg–H bond is evident in reactions with Brønsted acids or an oxidant to give dihydrogen, hydrometallation of double bonds occurred smoothly to give insertion (hydromagnesiation) products.

A magnesium hydride cation [(L)MgH]⁺ supported by a macrocyclic ligand (L = Me₄TACD; 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane) has been prepared by partial protonolysis of a mixed amide hydride [(L)MgH₂Mg{N(SiMe₃)₂}₂] and shown to undergo a variety of reactions with unsaturated substrates, including pyridine.