Supramolecular assemblies of tungsten complexes with unusual chelating groups

Metal complexes of ligands with η¹-O coordinated carbonyl moieties are well-known throughout the inorganic literature. However, metal complexes containing authentic acid chloride ligands have not previously been isolated. The synthesis and characterization of compounds with the formula W(X)Cl₃(OPh-2-COCl) (2) [X = O (2a), NC₆H₃-2,6-(CH₃)₂ (2b), and Ph₂C₂ (2c)] are reported. The crystal structures of 2a and 2c were solved, showing the interaction of the acid chloride carbonyl moiety with the tungsten center. Complex 2c adopts a channelled structure having six-fold symmetric voids in the solid state. As was anticipated, the coordinated acid chloride of 2a reacts readily with nucleophiles to produce the ester WOCl₃(OPh-2-COPrⁿ) (3) and the amide WOCl₃(OPh-2-CONHBu^t) (4a). A related amide complex WOCl₃(OPh-2-CONH₂) (4b), synthesized by the reaction of WOCl₄ with salicylamide, displays an infinite-chain structure supported by hydrogen bonding between the amide group and the oxo ligand of an adjacent tungsten complex. The η¹-O coordinated nitro compounds W(X)Cl³(OPh-2-NO²) (5) [X = O (5a), NC₆H₃-2,6-(CH₃)₂ (5b), and Ph₂C₂ (5c)] have also been isolated and the crystal structure of 5c is reported.