Rhenium oxytetrachloride

Rhenium oxytetrachloride is prepared by reacting rhenium heptoxide with thionyl chloride. Initially a golden-brown complex of perrhenyl chloride with sulfuryl chloride, (ReO₃Cl)₂,SO₂Cl₂ is gradually deposited. Upon prolonged contact, this rhenium(VII) complex redissolves with reduction to rhenium(VI). On vacuum evaporation of the thionyl chloride supernatant, or of the final solution after redissolution of the complex, the dark red rhenium oxytetrachloride is obtained.^[1]

It can also be prepared by heating rhenium pentachloride and dry oxygen in a sealed vessel at 180 °C. Direct chlorination results in an impure product.^{[4]: 44–45}

Rhenium oxytetrachloride is formed quantitatively by heating rhenium metal in sulfuryl chloride at 300 °C.^[2]

Upon reaction with pyridine, an oxotrichlorobispyridinerhenium(V) complex is formed.^{[4]: 52–53}