TM7TM′6B8 (TM = Ta, Nb; TM′ = Ru, Rh, Ir): New Compounds with [B6] Ring Polyanions

摘要

The ternary boron compounds TM7TM′6B8 (TM = Ta, Nb; TM′ = Ru, Rh, Ir) were prepared by high-temperature thermal treatment of mixtures of the elements. An analysis of the chemical bonding by the electron density/electron localizability approach reveals formation of covalently bonded polyanions [B6] and [TM′6B2]. The cationic part of the structure contains separated TM cations. In agreement with the chemical bonding analysis and band structure calculations, all TM7TM′6B8 compounds are metallic Pauli-paramagnets (TM′ = Ru, Rh) or diamagnets (TM′ = Ir).