Crystal structure of the Hofmann-dma type clathrate

Abstract

Seven new Hofmann-dma type clathrates Cd(dma)2Ni(CN)4-xG (x = 1, G = aniline, 2,3-xylidine, 2,4-xylidine, 2,5-xylidine, 2,6-xylidine, 3,5-xylidine and x = 2, G = 2,4,6-trim ethylaniline) were prepared by replacing the amine in a Hofmann type clathrate Cd(NH3)2Ni(CN)4-2G by dimethylamine (dma). The structure of the Hofmann-dma type clathrate is formed with stacked host two-dimensional metal complexes of Cd(dma)2 Ni(CN)4 and guest molecules accommodated in the space between the stacked host complexes. This basic structure scheme is the same as that of the Hofmann type clathrate. However, the guest species accommodated in the Hofmann-dma type clathrate are more various than those of the Hofmann type clathrate, and their crystal structures are classified into four types depending on the geometry of the guest species. In order to clarify the structure of the Hofmann-dma type clathrate, single crystal X-ray diffraction experiments were canied out on the seven new clathrates, and the crystal structures of the o-, m- and p- toluidine clathrates were refined. The X-ray structure analyses showed that the host two-dimensional metal complex of the Hofmann-dma tvpe clathrate has stmctural flexibility to form a puckered structure, which results from the angular distortion of the bond between Cd and N of the cyanide bridge in the host two-dimensional complex. This stmctural flexibility of the host complex leads to the diversity of crystal structures and guest species in Hofmann-dma type clathrates.