The Ternary Titanium Transition Metal Bismuthides Ti4TBi2withT=Cr, Mn, Fe, Co, and Ni

• Published in: Journal of solid state chemistry Vol. 133; no. 2; pp. 400 - 406
• Main Authors: Richter, Carolin G., Jeitschko, Wolfgang, Künnen, Bernd, Gerdes, Martin H.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-11-1997
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1006/jssc.1997.7487

The title compounds were prepared by reaction of the elemental components and with the exception of the isotypic chromium compound their tetragonal V4SiSb2-type crystal structures (I4/mcm, Z=4) were determined and refined from single-crystal X-ray data. Ti4CrBi2:a=1051.6(1),c=506.7(1) pm; Ti4MnBi2:a=1049.1(1),c=497.8(1) pm,R=0.031 for 176 structure factors; Ti4FeBi2:a=1048.6(1),c=493.3(1) pm,R=0.013 (274Fvalues); Ti4CoBi2:a=1050.6(2),c=488.2(1) pm,R=0.038 (472Fvalues); Ti4NiBi2:a=1055.4(1),c=481.4(1) pm,R=0.020(373Fvalues), and 14 variable parameters each. The compounds are isotypic with V4SiSb2, a structure which is isopointal with U6Mn and closely related to the structures of W5Si3and TlTe. All atoms have high coordination numbers. Unusual features of the structure are channels formed solely by the bismuth atoms and linear chains of the heavier transition metal ions with bond distances varying between 253.3 (Cr–Cr) and 240.7 pm (Ni–Ni). The electrical conductivities of Ti4TBi2(T=Fe, Co, Ni)—determined with a four-probe technique for sintered polycrystalline samples between 4 K and room temperature—indicate metallic behavior. The magnetic susceptibilities of the five compounds were determined with a SQUID magnetometer. Ti4CrBi2, Ti4FeBi2, and Ti4NiBi2are Pauli paramagnetic. The magnetic susceptibilities of Ti4MnBi2and Ti4CoBi2are strongly temperature dependent. The evaluation of these data according to a modified Curie–Weiss law suggests that both compounds contain one unpaired electron per formula unit. A brief discussion of chemical bonding in these compounds leads to the conclusion that considerable Ti–Ti bonding must be present in these bismuthides, in spite of the fact that the shortest Ti–Ti bonds are as long as 299 pm.