TETRARUBIDIUM NONAGERMANIDE(4-) ETHYLENEDIAMINE, RB-4[GE-9][EN]

Orange crystals of Rbd(4)[Ge-9][en] are obtained after the exchange re action of a solution of 'NaGe2.25' (precursor) in ethylenediamine (en) with solid RbI at 363 K, followed by slow cooling. The compound is ve ry sensitive to oxidation and hydrolysis. The thermal decomposition in dynamic vacuum starts at 350 K with the complete loss of en followed by the sublimation of Rb in four steps (Rb8Ge25, Rb8Ge44, RbxGe136 wit h x less than or equal to 16, Ge). The Raman spectrum shows the charac teristic bands of the [Ge-9](4-) anion (151, 163, 185 and 222 cm(-1)). Rb-4[Ge-9][en] crystallizes in a new structure type (space group P2(1 )/m; a=15.353 Angstrom, b = 16.434 Angstrom, c = 15.539 Angstrom, beta =113.75 degrees; Z = 6; Pearson code mP198-40), which can be describe d as a hierarchical derivative of the structures of Al4YbMo2 and CrB4 (initiators) formed by partial atom-to-aggregate replacement: B-4[squa re 1][Cr] (=) over cap Al-4[Yb][Mo](2) (=) over cap Rb-4[Ge-9][en](1-2 ). Three crystal lographic independent [Ge-9](4-) clusters with differ ent orientations are embedded in a Lt-connected 46(5) net formed by th e Rb atoms, a network of condensed tetraasteranes. The clusters are di storted monocapped tetragonal antiprisms with D-1(Ge-Ge) = 2.57 Angstr om (16 x) and D-2(Ge-Ge) = 2.84 Angstrom (4x). The atoms of clusters w ith D1 and D2 lie at the surface of a rotational ellipsoid (a=b=2.136 Angstrom, c=2.431 Angstrom). The en molecules are located in open chan nels along [(1) over bar 0 1]. The coordinations [Ge-9] Rb-12/14 and R b [Ge-9](4/12) en(2/8) show that the first step of solvation do not se parate the cations from the cluster anions.