Undistorted linear Bi chains with hypervalent bonding in La3TiBi5 from single‐crystal X‐ray diffraction

The crystal structure of the lanthanum titanium bismuthide La₃TiBi₅ (Pearson code hP18, Wyckoff sequence b d g2) has been established from single‐crystal X‐ray diffraction data and analyzed in detail using first‐principles calculations. There are no anomalies pertaining to the atomic displacement parameter of the Ti site, previously reported based on a powder X‐ray diffraction analysis of this compound. The anionic substructure contains columns of face‐sharing TiBi₆ octahedra and linear Bi chains. Due to a significant La(5d) and Bi(6p) orbital mixing, a perfectly one‐dimensional character of the Bi chains is not realised, while a three‐dimensional electronic structure is established instead. The latter fact explains the stability of the polyanionic pnictide units against Peierls distortions. The hypervalent bonding in the Bi chains is reflected in a rather long Bi—Bi distance of 3.2264 (4) Å and a typical pattern of bonding and antibonding interactions, as revealed by electronic structure calculations.