Chemical reactivity of K xTi 6Se 8 and the crystal structures of (H 2O) 1.5Ti 6Se 8 and Ti 3Se 4-channel compounds with the hexagonal Nb 3S 4 structure

Abstract

The topotactic redox reaction of K 0.52Ti 6Se 8 with molecular iodine in acetonitrile allows the preparation of the binary titanium selenide Ti 3Se 4 with the hexagonal Nb 3S 4-type structure. The species formed during the redox reaction was identified as the complex KI⋅I 2. The reaction of Ti 3Se 4 with water leads to the formation of the new ternary compound (H 2O) 1.5Ti 6Se 8. Simu ltaneous thermogravimetric analysis and mass spectrometry shows the emission of water over a wide temperature range and a weight loss which is in accordance with the content determined by single crystal X-ray work. The shape of the emission peak is indicative for a diffusion-limited reaction. The crystal structures of Ti 3Se 4 and (H 2O) 1.5Ti 6Se 8 are presented. In the water containing sample the oxygen atoms are displaced from the center of the hexagonal channels towards the TiSe 6 octahedra. This displacement leads to the formation of weak TiO and SeO interactions. The average OO distances within the channels are indicative for the formation of hydrogen bonds. The intercalated water exhibits only limited influence on the crystal structure of the host material.