Effects of a nonligating pendant hydrogen-bonding group in a metal complex: Stabilization of an HF complex

An amino group has been appended to a benzoquinolinato ligand (bq-NH2 or bq-NH(i-Pr)) in such a way that it can hydrogen bond to a ligand that is also bound to the metal. The effects of this two-point binding are studied. The complexes [(bq-NHR)IrH(L)(PPh3)(2)]BF4 (R = H, i-Pr) were synthesized where L = H2O, F, The hydrogen-bonding pattern in the water complex is probed by crystallographic, IR, and NMR studies. The fluoro complexes protonate at -90 degrees C to give unstable hydrogen fluoride complexes, characterized by NMR ((1)J(HF) = 440 Hz, bq-NH2; 430 Hz, bq-NH(i-Pr)). Comparison with results for the corresponding bq-H and bq-CH3 species suggests that the hydrogen bonding provided by the pendant amino group is the key factor that allows stabilization of the HF complex, a previously unknown species. Crystal structures of an aqua and a fluoro derivative are reported.