Interaction between Anions and Cationic Metal Complexes Containing Tridentate Ligands with exo- C-H Groups: Complex Stability and Hydrogen Bonding

[Re(CO)(3)([9]aneS(3))][BAr4] (1), prepared by reaction of ReBr(CO)(5), 1,4,7-trithiacyclononane ([9]aneS(3)) and NaBAr4, forms stable, soluble supramolecular adducts with chloride (2), bromide, methanosulfonate (3) and fluoride (4) anions. These new species were characterized by IR, NMR spectroscopy and, for 2 and 3, also by X-ray diffraction. The results of the solid state structure determinations indicate the formation of CHX hydrogen bonds between the anion (X) and the exo-CH groups of the [9]aneS(3) ligand, in accord with the relatively large shifts found by (HNMR)-H-1 spectroscopy in dichloromethane solution for those hydrogens. The stability of the chloride adduct contrasts with the lability of the [9]aneS(3) ligand in allyldicarbonyl molybdenum complexes recently studied by us. With fluoride, in dichloromethane solution, a second, minor neutral dimeric species 5 is formed in addition to 4. In 4, the deprotonation of a CH group of the [9]aneS(3) ligand, accompanied by CS bond cleavage and dimerization, afforded 5, featuring bridging thiolates. Compounds [Mo((3)-methallyl)(CO)(2)(TpyN)][BAr4] (6) and [Mo((3)-methallyl)(CO)(2)(TpyCH)][BAr4] (7) were synthesized by the reactions of [MoCl((3)-methallyl)(CO)(2)(NCMe)(2)], NaBAr4 and tris(2-pyridyl)amine (TpyN) or tris(2-pyridyl)methane (TpyCH) respectively, and characterized by IR and H-1 and (CNMR)-C-13 spectroscopy in solution, and by X-ray diffraction in the solid state. Compound 6 undergoes facile substitution of one of the 2-pyridyl groups by chloride, bromide, and methanosulfonate anions. Stable supramolecular adducts were formed between 7 and chloride, bromide, iodide, nitrate, and perrhenate anions. The solid state structures of these adducts (12-16) were determined by X-ray diffraction. Binding constants in dichloromethane were calculated from (HNMR)-H-1 titration data for all the new supramolecular adducts. The signal of the bridgehead CH group is the one that undergoes a more pronounced downfield shift when tetrabutylammonium chloride was added to 7, whereas smaller shifts were found for the 2-pyridyl C(3)H groups. In agreement, both types of CH groups form hydrogen bonds to the anions in the solid state structures.