Hydrogen bonding in tungsten(VI) salicylate free acids1Dedicated to Professor Daryle Busch on the occasion of his 70th birthday.1

Tungsten Oxo Salicylate Complexes from Tungsten Hexachloride Reactions Systems

“…The structural characteristics of [W(O)(Hsal)(sal)] 2 O correspond closely to the structures of other salicylate complexes. − ,− The short average WO distances of 1.654 (9) Å and concomitant long average trans W−O distances of 2.216 (9) Å are characteristic of tungsten oxo salicylate complexes. − ,− The average O Ar −W−O COO bite angle of the salicylate chelates is 81°. This is characteristic of sal ligands, but is significantly larger than the 75° angles that are characteristically observed for chelating catecholate ligands. , This relaxed bite angle accommodates the octahedral coordination geometry of the tungsten center better than the more restricted chelating diolates. , It also accounts for the observation that W−O distances trans to the oxo ligand are 0.1 Å shorter in the salicylate complexes than in their catecholate analogues.…”

“…The intramolecular hydrogen bonding observed in [W(O)(Hsal)(sal)] 2 O is characteristic of intermolecular hydrogen bonds studied in neutral mononuclear tungsten salicylate complexes. ,− The O−O distances of 2.54 Å (average) reflect strong hydrogen bonding . These hydrogen bonds are achieved with 6° less distortion of the W− μ -O−W angle from linearity than is found in structurally related ditungsten catecholate complexes. , The carbonyl and carboxylic acid units have greater radial extension from tungsten than analogous alkoxide and alcohol moieties.…”

“…By comparing the spectra of the original and fractionated mixtures to that of pure W(O)Cl 3 (Hsal) ( 1 ), it is possible to assign one of the three sets of salicylate multiplets to this complex. 1 is a dimeric Brønsted acid in solution and can be prepared in high yield directly from reactions between W(O)Cl 4 and salicylic acid in nonpolar media. ,− …”

“…Like the chemistry of traditional chlorinating reagents, including PCl 5 , the initial oxygen atom transfer step greatly reduces the halogenating aptitude of the tungsten. , There was no evidence for the formation of significant quantities of tungsten dioxo products, even in the presence of a significant excess of salicylic acid. In addition to salicoyl chloride and 1 , W(O)Cl 3 (OC 6 H 4 COCl) ( 4 ) is identifiable in the product mixtures by its distinctive 1 H NMR spectrum …”

“…Six coordinate complexes of tungsten (VI), bearing a range of uni- and dinegative ligands, have been widely studied over the past twenty years. − We have been intrigued by the hydrogen bonding behavior of Brønsted acid complexes of the tungsten oxo, aryl imido, and acetylene derivativesspecifically, complexes containing salicylate (Hsal) or phenol−phenolate (HOArO) monoanions. − Systematic variation of the steric and electronic environment at the metal by changing the identity or substitution pattern of the appended ligands provides an opportunity to study the influence of the high oxidation state metal on the acidity of the metal bound functionality in nonaqueous solvents. These compounds also form building blocks for hydrogen bonded inorganic/organic hybrid materials. − While investigating the synthesis of simple monosalicylate W(=X)Cl 3 (Hsal) (1) complexes, we encountered a surprisingly diverse range of tungsten salicylate derivatives, including 2 and 3 , that derive from reactions employing tungsten hexachloride as the metal precursor. During reactions with salicylic acid (H 2 sal), we repeatedly observed the incorporation of both bridging and terminal oxo ligands at the metal, producing complexes characterized as structures 1 , 2 , and 3 .…”