Molecular modeling of the octacoordinated tetracarbonato-Nd(III), [Nd(CO3)4]5−, complex and its nonacoordinated fluoro- and aquo-adducts

Theoretical investigation on the structures of the octacoordinated [Nd(CO3)4]5- and the nonacoordinated [Nd(CO3)4.OH2]5- complexes, using the SPARKLE parameters of the lanthanides within MOPAC, revealed that they possessed dodecahedral and square antiprismatic structures respectively with an average Nd-O distance of 0.249 nm. These structures and the Nd-O distances agreed well with those experimentally found in the crystal structures. Replacing the water molecule with a fluoride ion or a mondentatecarbonato ligand resulted in a nonacoordinated distorted square antiprismatic structures where the trans-carbonato groups were twisted. The corresponding decacoordinated structures with two fluoride ions or a bidentatecarbonato group, [Nd(CO3)4·F2]7- and [Nd(CO3)5]7-, were also investigated. In both cases considerable twisting of the transcarbonato groups was observed.