Assembly of Hybrid Inorganic−Organic Materials from Octahedral Nb₆ Clusters and Metal Complexes

Abstract

The octahedral edge-bridged niobium cyano-chloride cluster [Nb6Cl12(CN)6]4- and the [Mn(salen)]+ metal complex have been used as building units to prepare solid-state materials with extended frameworks at room temperature through self-assembly processes. Three materials with different dimensionalities were prepared and characterized:  (Me4N)4[Nb6Cl12(CN)6]·2MeOH (1) (0D), (Me4N)2[Mn(salen)]2[Nb6Cl12(CN)6] (2) (2D), and (Et4N)2[Mn(salen)(MeOH)]2[Nb6Cl12(CN)6]·2MeOH (3) (1D). 1 was used as cluster precursor for the preparation of 2 and 3. The framework dimensionality seems to be affected by the size of the template-counterion used. Single-crystal X-ray analysis revealed that 1 is based on discrete [Nb6Cl12(CN)6]4- separated by (Me4N)+ and MeOH molecules. 2 has a two-dimensional framework, in which each layer is formed by [Nb6Cl12(CN)6]4- clusters connected through four cyanide ligands to four different [Mn(salen)]+. Each manganese complex connects two clusters through Nb−CN−Mn−NC−Nb bridges, leading to the formation of anionic layers interleaved by (Me4N)+. In 3, every cluster unit [Nb6Cl12(CN)6]4- is linked to two [Mn(salen)(MeOH)]+ units through two apical trans cyanide ligands, leading to the formation of trimeric units {Mn−(NC)[Nb6Cl12(CN)4](CN)−Mn}. Every trimeric unit connects to two neighboring units through hydrogen bonding between OMeOH from coordinated methanol ligand and NCN from two neighboring clusters, resulting in the formation of anionic chains along the crystallographic a axis {[Mn(salen)(MeOH)]2[(Nb6Cl12)(CN)6]}2-. The chains are separated by (Et4N)+ and MeOH. Magnetic properties and thermal behavior of these new hybrid inorganic−organic compounds are presented