Synthesis and structure of the alkali-metal amalgams A(3)Hg(20) (A = Rb, Cs), K3Hg11, Cs5Hg19, and A(7)Hg(31) (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 t ype (Pm-3n, Z = 2, a = 10.737(1) Angstrom and 10.913(1) Angstrom, for A = R b and Cs, respectively), while K3Hg11 is the first example of a mercury com pound with the alpha-La3Al11-type structure (Immm, Z = 2, a = 5.122(1) Angs trom, 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 = 10.8 50(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 R b5Hg19. (C) 2000 Academic Press.