K2Mg5−xSn3 and K3Mg18Tt11 (Tt=Sn, pb) with two types of Mg–Sn/Pb frameworks

K2Mg5−xSn3 (x=0.28) and K3Mg18Tt11 (Tt=Sn, Pb) have been synthesized by reacting the mixture of the corresponding pure elements at high temperature, and structurally characterized by single-crystal X-ray diffraction studies. K2Mg5−xSn3 (x=0.28) is isostructural with Ni7−xSbQ2 (Q=Se, Te) series and features 2D corrugated [Mg5−xSn3] layers that are separated by K+ cations. The structure of K3Mg18Tt11 (Tt=Sn, Pb) is closely related to the Ho2Rh12As7 structural type and features 3D [Mg18Tt11] framework composed of 1D [Mg18Tt11] columns that are interconnected via Mg–Tt bonds, forming 1D hexagonal tunnels occupied by the K+ cations. Electronic structure calculations indicate that Mg atoms can function as either electron donor or as a participator in the network along with Tt atoms. Magnetic property measurements and band structure calculations indicate that these compounds are metallic.