Rhenium - VII mixed ligand oxofluorooxalato complexes of quinquevalent rhenium

Abstract

A binuclear mixed ligand fluorooxalato complex acid of quinquevalent rhenium with the stoichiometry Re : C₂O₄ : F = 2 : 1 : 2 has been isolated by boiling freshly precipitated rhenium dioxide with oxalic acid and 40 per cent HF. The sodium, potassium and ammonium salts have been obtained by reacting the acid with alkali acetates and precipitating with ethanol. The sparingly soluble Tl⁺, Ba²⁺, Ni²⁺, [Co(NH₃)₆]³⁺ and [Co en₃]³⁺ salts have been isolated by metathesis. The i.r. spectra of the acid and its potassium salt resemble those of typical chelated oxalato complexes and are different from those of sodium oxalate or bridged oxalato complexes. The spectra give ν(O---H) and ν_as(Re---O---Re) bands. The acid and its sodium and potassium salts are weakly paramagnetic. The molecular weight and conductance of the potassium salt, i.r. spectra and analytical data indicate that the acid may be represented as H₂[(C₂O₄)(OH)₃Re.O.Re(OH)₃F₂].