INTERCALATION CHEMISTRY OF A MG-AL LAYERED DOUBLE HYDROXIDE ION-EXCHANGED WITH COMPLEX MCL4(2-) (M=NI, CO) IONS FORM ORGANIC MEDIA

The complex anions NiCl42- and CoCl42- were introduced into the interlayers of a Mg-Al layered double hydroxide (LDH) from non-aqueous media. Then the interaction of the metal complexes with adsorbed water or ammonia was studied. When an ethanol (or nitromethane) solution of [Et4N]2[NiCl4] or [Et4N]2[CoCl4] was stirred with a Mg-Al LDH containing NO3-, the anionic metal complex was transferred into the galleries of the LDH. Tetrahedral NiCl42- anions in LDH react with adsorbed water molecules to yield octahedral Ni(H2O)62+ species. This in turn can be reversibly converted back to NiCl42- by heating LDH in a vacuum. Tetrahedral CoCl42- anions in CoCl-LDH are markedly affected by heating under vacuum at 473 K. Thus, a part of the complex was transformed into tetrahedral CoCl42- where Co(II) ions exist under unusually reduced ligand field strengths. Adsorption of water molecules on this sample results in the formation of Co(H2O)62+, regeneration of initial tetrahedral Co(II) species and disappearance of the anomalous tetrahedral Co(II) species. On the other hand, adsorption of ammonia onto LDH does not result in the formation of Co-ammine complexes, but ammonia molecules interact with the interlayered Co(II) complexes through ligand molecules.