Аннотация:The reaction of MgCl2 with NaBH4 in 1,2-dimethoxyethane (DME) gave the complex Mg(BH4)2·1.5 DME. Heating this complex in vacuo results in sublimation of Mg(BH4)2·DME. The reaction of Mg(BH4)2· 1.5 DME with tetraphenylphosphonium tetrahydroborate produces the anionic complex (Ph4P)2[Mg(BH4)4]. The compounds were characterized by chemical analysis and IR spectroscopy. The crystal structure of (Ph4P)2[Mg(BH4)4] was determined by X-ray diffraction. The crystals of (Ph4P)[Mg(BH4)4] are monoclinic, a = 11.219(4) Å, b = 19.887(6) Å, c = 20.747(3) Å, β = 91.72(6),V = 4627.2(4) Å3, FW = 762.45, ρcalcd= 1.094 g/cm3, space group C2/c. The (Ph4P)+ cations form supramolecular chain ensembles typical of compounds with tetraphenylphosphonium cations