The title compound is readily prepared from the rhenium carboxylate, (dppe)(CO) 3 ReC(O)OCH 3 , by prolonged stirring of a solution of the carboxylate in benzene/H 2 O or THF/H 2 O. The reaction involves the unusual in situ conversion of Re--C bonds to Re--O bonds. The X-ray structure of the title compound shows that the μ 2 ,η 2 -carbonato ligand is present in the symmetrical syn, syn conformation in the solid state in contrast to the alternate syn, anti geometry reported for the related complex, (diars)(CO) 3 ReOC(O)ORe(CO) 3 (diars).