Systematic Preparation of Mo₂⁴⁺ Building Blocks for Supramolecular Assemblies

The preparation of additional and useful building blocks for the construction of supramolecular entities with quadruply bonded Mo24+ units has been explored, and five new mixed-ligand complexes with three types of ligands and various basicities are reported. The ligands used were the DAniF (N,N‘-di-p-anisylformamidinate) anion, the acetate anion, and neutral acetonitrile molecules. The formamidinate ligands are the least labile, and the acetonitrile molecules are the most labile. This difference as well as a relatively strong trans directing influence by the formamidinate anions in ligand substitution reactions allows designed synthesis of various mixed-ligand building blocks, including rare pairs of cis and trans isomers. The new compounds are cis-Mo2(DAniF)2(O2CCH3)2 (1), trans-Mo2(DAniF)2(O2CCH3)2 (2), trans-[Mo2(DAniF)2(O2CCH3)(CH3CNeq)2]BF4 (3), trans-[Mo2(DAniF)2(CH3CNeq)4](BF4)2 (4), and [Mo2(O2CH3)(CH3CNeq)6(CH3CNax)](BF4)3 (5), where eq and ax designate equatorial and axial ligands, respectively. A comparison with some previously synthesized complexes is given along with a discussion of the overall reactivity of all compounds.