text: Carbonato complexes are prepared by salt metathesis reactions using alkali metal carbonate salts as precursors.  In some cases, bicarbonate intermediates are implicated since carbonate does not exist in appreciable concentrations near neutral pH. The other chief route to metal carbonato complexes involves addition of  to metal oxides.  Such reactions may be catalyzed by water since the carbonation of metal hydroxides is particularly well established.  Isotope labeling studies show that these reactions can proceed (and perhaps usually proceed) without scission of the M-OH bond (L = generic ligand):
  Many esoteric routes have been demonstrated.  For example, the deoxygenation of peroxycarbonate by tertiary phosphines:
  : (Ph = CH)
  Carbon dioxide undergoes disproportionation upon reaction with low-valence metals.