Reaction of the alloy KGeSb with 2,2,2-crypt in ethylenediamine (en) produces a dark red solution from which crystals of both (2,2,2-~rypt-K+)~Sb:-(I) and (2,2,2-~rypt-K+)~Sb?--2en (11) can be isolated. The former has also been obtained from like reactions of KAuSb and KPbSb compositions. Four octants of X-ray diffraction data were collected for each complex on an automated diffractometer using monochromated Mo K a radiation, at room temperature for I and at -80 OC for 11. Compound I crystallizes in the space group Pi with a = 11.555 (1) A, b = 11.795 (1) A, c = 11.067 ( I ) A, a = 97.60 ( 1 ) O , / 3 = 97.80 (1)O, y = 61.24 (1)O, V = 1306.1 (2) A', and Z = 1 and is isostructural with the known (2,2,2-cry~t-K+)~Bi,~-. Refinement of positional and anisotropic thermal parameters for all 29 non-hydrogen atoms by full-matrix least-squares techniques yields R = 0.081 and R, = 0.1 13 for 3909 independent observed reflections. The Sbzanion is effectively square planar (D4,,), with bond lengths of 2.749 (1) and 2.751 (1) 8, and bond an les of 90.05 (3)' and 89.95 (3)O. Compound I1 also occurs in space group Pi with a = 14.589 (2) A, b = 21.753 (3) 1, c = 13.857 (2) A, a = 92.46 (1)O, /3 = 99.63 (2)O, y = 89.12 (2)O, V = 4331 (1) A3, and Z = 2. Positional and thermal parameters (anisotropic for all but carbon) for the 96 non-hydrogen atoms were refined to R = 0.075 and R, = 0.093 for 7281 independent observedreflections. This structure contains the Sb73-anion with approximately C,, symmetry; the anion was previously known (but less well defined) in the (2,2,2-cr~pt-Na+)~Sb~'-salt, but the two compounds are not isostructural.
IntroductionIn the last 10 years, many polyatomic anions of the post transition elements, Bi42-,2 Sb73-,3 and As113-4 in group 5, for example, have been isolated as stable salts by the reaction of their alkali-metal alloys with 2,2,2-crypt, an excellent complexing agent for the metal cation Recent investigations have included reactions to produce heteropolyatomic clusters of group 4 and 5 elements in order to explore new electronic configurations and structures; Sn2Bi2-5 and Pb2Sb2-6 are two examples of such anions that have recently been structurally characterized.As part of this study we explored the reactions of a KGeSb alloy. Instead of the expected heteropolyatomic Ge/Sb anions, two antimony clusters were produced as the K+-crypt salts. One compound contained the new Sb42-anion, and the second, the Sb7j-anion in a new structure.
