Synthesis and Theoretical Studies of the Stability of Tetrahalide Tungsten Molecular Complexes trans- [WX ₄ (OPPh ₃ ) ₂ ] (X = Cl, Br, or I)

The work is devoted to theoretical and experimental studies of the synthesis and stability of tungsten tetrahalide complexes trans-[WX₄(OPPh₃)₂] (X = Cl, Br, or I). New molecular complexes of tungsten(IV) trans-[WCl₄(OPPh₃)₂] (I) and trans-[WBr₄(OPPh₃)₂] (II) were obtained in the form of polycrystalline powders starting from different tungsten sources: oxotetrahalides, hexahalides, or trioxide, in the presence of triphenylphosphine and triphenylphosphine oxide. The X-ray crystal structures were determined for I and II (I: P-1, a = 9.3841(10) Å, b = 9.6332(10) Å, c = 10.4243(13) Å, α = 101.585(4)°, β = 108.097(4)°, γ = 93.365(4)°, Z = 1, V = 870.03(17) ų; II: P- 1, a = 9.5326(5) Å, b = 9.5946(5) Å, c = 10.7150(7) Å, α = 102.387(2)°, β = 107.898(2)°, γ = 94.308(2)°, Z = 1, V = 900.32(9) ų). Magnetic susceptibility measurements revealed Van Vleck-type paramagnetism for the compounds. In order to estimate the enthalpy of the studied reactions and predict the existence of trans-[WI₄(OPPh₃)₂], DFT calculations were performed. The article discusses the synthesis of new complex compounds I and II, their crystal structures and magnetic properties, and the results of DFT calculations for the reactions involved in the formation of trans-[WX₄(OPPh₃)₂] (X = Cl, Br, or I).