Synthesis and structure of the alkali-metal amalgams A3Hg20 (A = Rb, Cs), K3Hg11, Cs5Hg19, and A7Hg31 (A = K, Rb)

The synthesis and single-crystal structures of four alkali-metal amalgams, are reported. The compounds A(3)Hg(20) (A = Rb, Cs) are of new structural type (Pm-3n, Z = 2, a = 10.737(1) Angstrom and 10.913(1) Angstrom, for A = Rb and Cs, respectively), while K3Hg11 is the first example of a mercury compound with the alpha-La3Al11-type structure (Immm, Z = 2, a = 5.122(1) Angstrom, b = 10.063(2) Angstrom, c = 14.782(3) Angstrom). The structure of A(7)Hg(31) (A = K, Rb) determined from single crystal (P6/mmm, Z = 1, a = 10.850(2) Angstrom and 11.000(2) Angstrom c = 10.210(2) Angstrom and 10.377(3) Angstrom, for A = K and Rb, respectively) is compared with that of K7Hg31, previously known from powder diffraction only, Cs5Hg19 (I4/m, Z = 2, a = 11.803(3) Angstrom, c = 10.814(5) Angstrom) is isostructural with the known Rb5Hg19. (C) 2000 Academic Press.