Dimolybdenum-containing molecular triangles and squares with diamidate linkers: Structural diversity and complexity

By employing cis-Mo-2(DAniF)(2)(2+) (DAniF = N,N'-di(p-anisyl)formamidinate) as the vertex building block and terephthaloyldiamidate as the linker, four dimolybdenum-containing cyclic oligomers have been synthesized and structurally characterized. In these compounds, described by the general formula [CiS-Mo-2(DAniF)(2)((ArNOC)(2)C6H4)(2)](n), n = 3 and 4, the geometry and composition of the products are affected by the identity of the aromatic groups of the linker. When Ar = phenyl, n = 3 (1a and 1b); however, n = 4 for Ar = p-trifluoromethylphenyl (2) and when Ar = m-trifluoromethylphenyl (3). All these compounds have a central cavity, shaped by the diamidate linker, that is capable of serving as host to guest molecules in a selective manner. For compounds 2 and 3, self-assembly that takes place in the crystalline state entails intermolecular C-(HF)-F-...-C interactions. Such interactions generate a one-dimensional network with a tunnel cross section of 10 x 10 angstrom(2) in 2, whereas in 3, they result in a cage in which two THF molecules are encapsulated. The (FH)-H-... distances vary in a broad range from 2.38 to 2.70 angstrom.