K2Li(NH2)3 and K2Na(NH2)3—synthesis and crystal structure of two crystal-chemically isotypic mixed-cationic amides

K2Li(NH2)3 (1) was the only crystalline product obtained from the reaction of potassium with dilithium decahydro-closo-decaborate Li2B10H10 in liquid ammonia at −38 °C. The compound crystallizes in the space group P42/m with Z=4, a=6.8720(5) Å, c=11.706(1) Å and V=552.81(7) Å3. The investigated crystal-chemically isotypic sodium compound K2Na(NH2)3 (2) was merohedrally twinned and crystallized from a reaction mixture containing potassium and disodium decahydro-closo-decaborate Na2B10H10 in liquid ammonia with a=7.0044(5) Å, c=12.362(1) Å and V=606.48(9) Å3. The compounds contain pairs of edge sharing tetraamidolithium or tetraamidosodium tetrahedra which are interconnected by potassium ions forming three-dimensional infinite networks.