Structural trends Metal carbon dioxide complex

illustrative structures of transition metal carbon dioxide complexes, left: ni(η-co2)(pcy3)2, rh(η-co2)cll4 (l4 = (diars)2), metallacarboxylic ester cpfe(co)2(η:η-co2)re(co)5, , dimetalla-ester.

carbon dioxide binds metals in few ways. bonding mode depends on electrophilicity , basicity of metal centre. common η-co2 coordination mode illustrated aresta s complex, ni(co2)(pcy3)2, first reported complex of co2. square-planar compound derivative of ni(ii) reduced co2 ligand. in rare cases, co2 binds metals lewis base through oxygen centres, such adducts weak , of theoretical interest. variety of multinuclear complexes known involving lewis basic , lewis acidic metals, e.g. metallacarboxylate salts (c5h2)fe(co)2co2k. in multinuclear cases (compounds containing more 1 metal), more complicated , more varied coordination geometries observed. 1 example unsymmetrical compound containing 4 rhenium centres, [(co)5reco2re(co)4]2. carbon dioxide can bind ligands on metal complex (vs metal), e.g. converting hydroxy ligands carbonato ligands.