Supramolecular Interactions of Group VI Metal Carbonyl Complexes: The Facilitating Role of 1,3-Bis(p-isocyanophenyl)urea

An investigation of supramolecular phenomena involving zerovalent transition metal complexes was facilitated by the production of the ditopic isocyanide ligand 1,3-bis(p-isocyanophenyl)urea, which was synthesized via substoichiometric phosgenation of 4-isocyanophenylamine and used to coordinate group VI metal carbonyl fragments. The resulting binuclear organometallic complexes were observed to pack into ladder-like anisotropic arrays in the solid state. Crystallographic and computational evidence suggests that this packing motif can be attributed to a combination of intermolecular II-πand urea-πinteractions. Similar to other N,N′-diarylureas bearing electron-withdrawing groups, 1,3-bis(p-isocyanophenyl)urea and the organometallic complexes prepared therefrom also exhibit an affinity toward anion binding in nonaqueous solution. Equilibrium constants (K) for the formation of host-guest complexes between the organometallic derivatives of 1,3-bis(p-isocyanophenyl)urea and chloride, nitrate, and acetate anions exceed 10³, 10⁴, and 10⁵ M^-1, respectively.