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 A3Hg20 (A=Rb, Cs) are of new structural type (Pm-3n, Z=2, a=10.737(1) ? and 10.913(1) ?, for A=Rb and Cs, respectively), while K3Hg11 is the first example of a mercury compound with the -La3Al11-type structure (Immm, Z=2, a=5.122(1) ?, b=10.063(2) ?, c=14.782 (3) ?). The structure of A7Hg31 (A=K, Rb) determined from single crystal (P6/mmm, Z=1, a=10.850(2) ? and 11.000(2) ?, c=10.210(2) ? and 10.377(3) ?, 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) ?, c=10.814(5) ?) is isostructural with the known Rb5Hg19.