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-NH 2 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)(PPh 3 ) 2 ]BF 4 (R = H, i -Pr) were synthesized where L = H 2 O, F. The hydrogen-bonding pattern in the water complex is probed by crystallographic, IR, and NMR studies. The fluoro complexes protonate at −90 °C to give unstable hydrogen fluoride complexes, characterized by NMR ( 1 J HF = 440 Hz, bq-NH 2; 430 Hz, bq-NH( i -Pr)). Comparison with results for the corresponding bq-H and bq-CH 3 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.