One-dimensional molybdenum thiochlorides and their use in high surface area MoS_x chalcogels

New molybdenum thiochlorides, α-MoSCl₃ and β-MoSCl₃, have been synthesized by chemical vapor transport. A selenium analog, MoSeCl₃, could also be prepared in the same way. The crystal structures consist of infinite chains stabilized by weak van der Waals forces. For the α-phase an infinite chain of _∞¹[Mo₂(S₂)Cl₄Cl_4/2] runs along the crystallographic c axis, while for the β-phase _∞¹[Mo₂(S₂)Cl₃Cl_6/2] chain passes through the b-axis. MoSeCl₃ is isostructural to α-MoSCl₃. The formal charge on molybdenum in these thiochlorides have been assigned by X-ray photoelectron spectroscopy (XPS) to be +IV. β-MoSCl₃ and already known Mo₃S₇Cl₄ and MoS₂Cl₃ are weakly paramagnetic. Thermal decomposition of molybdenum thiochlorides leads to MoS₂. Red MoS₂Cl₃ and Mo₃S₇Cl₄ exhibit band gaps of ∼2.07 and ∼2.11 eV, while black α-MoSCl₃, β-MoSCl₃, and MoSeCl₃ exhibit band gaps of ∼1.2, 1.24, and 1.18 eV, respectively. The new thiochlorides can serve as precursors in the synthesis of molybdenum-sulfide gels and aerogels. The MoS_x chalcogels have a BET surface area of 353 m²/g and a band gap of 1.5 eV.