Discrete Rectangles, Prisms, and Heterometallic Cages from a Conjugated Cp*Rh-Based Building Block.

By carefully selecting an existing synthetic strategy and suitable coordination subunits, constructing desired coordination geometries is no longer that difficult to accomplish. Herein, a new strategy to construct a series of unprecedented structures by using conjugated Cp*Rh-based complex BN-OTf (Cp* = η(5)-C5Me5) as the building block is proposed. DFT calculations revealed extensive delocalized π bonds in the subunit. With BN-OTf, rectangular macrocycles TN-bpy and TN-bpe were controllably synthesized. Single-crystal XRD studies confirmed one-dimensional stacking channels for the tetranuclear structure. Notably, the starting ligand imidazole-4,5-dicarboxylate was found to act not only as a tetradentate but also as a hexadentate ligand that can coordinate to further metal ions. Subsequently, [4 Rh+1 M] heterometallic complexes HMZ (M = Cu and Zn) were accessed by chelating borderline hard/soft Lewis acids. With TN-Linker or HMZ, two routes resulted in the [8 Rh+2 M] heterometallic cages HMC (M = Cu and Zn) with excellent crystallinity and stability. Surprisingly, when BN-OTf bonded to rhodium itself, triangular prisms TP-Linker were obtained with high solubility after being linked by bipyridine linkers. Both the X-ray structure and (1)H NMR spectrum confirmed the novel isomerization of the triangular structures. All of the compounds were obtained in high yields and were fully characterized by (1)H NMR spectroscopy, elemental analysis, IR spectroscopy, and in most cases single-crystal X-ray structure determination.

Octadecanuclear macrocycles and nonanuclear bowl-shaped structures based on two analogous pyridyl-substituted imidazole-4,5-dicarboxylate ligands.

Two types of unprecedented Cp*Rh-based (Cp* = η(5)-C5Me5) complexes, two octadecanuclear macrocycles, and a nonanuclear bowl-shaped complex have been synthesized from two analogous pyridyl-functionalized imidazole-4,5-dicarboxylate ligands, 2-(pyridin-4-yl)-1H-imidazole-4,5-dicarboxylate ligand and 2-(pyridin-3-yl)-1H-imidazole-4,5-dicarboxylate ligand, respectively.

Construction of iridium and rhodium cyclometalated macrocycles based on p-carborane and N,N'-donor bridging ligands.

Six tetranuclear half-sandwich iridium and rhodium complexes bridged by neutral N,N'-donor pyridyl-imine ligands and 1,12-dicarbadodecaborane(12)-1,12-dicarboxylate (p-CDC) were controllably synthesized and fully characterized. The results revealed that the precursors, binuclear complexes [(Cp*M)2{1,4-bis(2-pyridylmethyleneamino)benzene}Cl2][OTf]2 (Cp* = η(5)-pentamethylcyclopentadienyl, M = Ir (2a), Rh (2b)), have different preferential configurations, and tetranuclear complexes [(Cp*M)4{1,4-bis(2-pyridylmethyleneamino)benzene}2(p-CDC)2][OTf]4 (M = Ir (3a), Rh (3b)), which were prepared using monodentate p-carborane dicarboxylate and 2a or 2b, showed highly twisted backbones. Likewise, homologous regular rectangular compounds [(Cp*M)4{1,4-{(2-C5H4N)HC=N}2-2,3,5,6-Me4C6}2(p-CDC)2][OTf]4 (M = Ir (4a), Rh (4b)) and [(Cp*M)4{1,4-{(2-C5H4N)HC=N}2-1,5-naphthalene}2(p-CDC)2][OTf]4 (M = Ir (5a), Rh (5b)) were obtained following a similar synthetic route. X-ray determination confirmed that 4b and 5b have stacking channels as well.