181804-00-2Relevant articles and documents
Supramolecular assemblies involving organometallic free acids
Baroni, Timothy E.,Heppert, Joseph A.,Hodel, Rolande R.,Kingsborough, Richard P.,Morton, Martha D.,Rheingold, Arnold L.,Yap, Glenn P. A.
, p. 4872 - 4879 (1996)
Reactions between W(η2-Ph2C2)Cl4 and salicylic acid derivatives generate analytically pure free acids of formula W(η2-Ph2C2)Cl3(Hsal-R) (1) in high yields (Hsal = a salicylate monoanion). The products exist as hydrogen-bonded dimers in the solid state. The acid functionality on one molecule hydrogen bonds to one of the cis-chloride ligands of an adjacent complex at a 3.03 A? distance. The more electron-rich tungsten center renders these acetylene complexes less acidic than their oxo and arylimido analogs. As a result, W(η2-Ph2C2)Cl3-(Hsal) exhibits partial dimerization in solution and have relatively weak hydrogen bonds to nitrogen- and oxygen-containing organic molecules. Among a range of possible phenol-phenoxide complexes of the W(η2-Ph2C2)Cl3 subunit, only the ether adduct of the catecholate, W(η2-Ph2C2)Cl3(Hcat-OEt 2) (2), has been isolated and structurally characterized. The weaker hydrogen bond strength of larger chelating bis(phenolates) evidently destabilize the phenol-phenoxide structures in favor of simple chelating bis(phenoxides). The salicylate free acids form various supramolecular complexes in solution and the solid state, including [W(η2-Ph2C2)Cl3(Hsal)] 4(18-Crown-6) (5), one of a family of tetranuclear systems organized around hydrogen bonding to an 18-crown-6 template. This structure is characterized by π-stacking of the Hsal ligands between confacial free acid complexes and the steric screening of the two non-hydrogen-bonded 18-crown-6 oxygens by pairs of antarafacial W(Ph2C2) units.
