Speciation of Be2+ in acidic liquid ammonia and formation of tetra- and octanuclear beryllium amido clusters

摘要

The hexa-μ _(2) -amido-tetraammine-tetraberyllium compounds [Be _(4) (NH _(2) ) _(6) (NH _(3) ) _(4) ]X _(2) (X = Cl, Br, I, CN, SCN, N _(3) ) have been prepared from beryllium metal and NH _(4) X or [Be(NH _(3) ) _(4) ]X _(2) in liquid ammonia at ambient temperature. The obtained compounds feature an adamantyl shaped complex cation, which was examined via X-ray diffraction, IR, Raman and NMR spectroscopy. The speciation in solution was studied via ~(15) N labeling experiments supplemented with quantum chemistry. Hereby, the intermediates [Be _(2) (NH _(2) )(NH _(3) ) _(6) ] ~(3+) and [Be _(3) (NH _(2) ) _(3) (NH _(3) ) _(6) ] ~(3+) were identified. Reactivity studies provided bis( N -acetimidoylacetamidinato- N , N ′)-beryllium( II ), when [Be _(4) (NH _(2) ) _(6) (NH _(3) ) _(4) ] ~(2+) was treated with acetonitrile. While the unprecedented octa-nuclear complex cation [Be _(8) O(NH _(2) ) _(12) (C _(5) H _(5) N) _(4) ] ~(2+) was received from pyridine. This cluster proves that the [Be _(4) O] ~(6+) core can be stabilized without bidentate O -donor ligands.