Rational construction of functional molybdenum (tungsten)–copper–sulfur coordination oligomers and polymers from preformed cluster precursors
The investigation of heterometallic Mo(W)–M′–S clusters (M′ = transition metals) has its genesis in the late 1970s with the identification of the nitrogenase iron–molybdenum cofactor (FeMoco) featuring a Mo–Fe–S double-cubane cluster core. This has led to the generation of a library of cluster skeletons subsequently used as building blocks for oligomers (OGs) and polymers, merging this field with the fascinating developments in supramolecular chemistry and coordination polymers (CPs). While resembling the general metal–ligand assembly to form CPs in one-pot, cluster-based OGs or CPs are conventionally prepared from Mo(W)–S synthons and Cu(I) salts in the presence of bridging ligands. This review summarizes the synthesis of Mo(W)–Cu–S cluster-supported OGs and CPs through a two-step strategy involving preformed clusters. This stepwise approach facilitates clean conversion, and is amenable to exquisite design protocols and yields products otherwise inaccessible via a direct one-pot method. We review the synthesis of OGs and CPs by cluster core upgrading, downgrading, ligand substitution, and cluster aggregation reactions, together with the optical and host–guest properties of the products. In doing so, we demonstrate the power and generality of this strategy for assembling these unique materials and offer clues on how to adapt this less practiced method to preparing extended molecular assemblies with potentially intriguing properties.