Synthesis and reactivity of Ru(PPh3)3(CO)HF and the N-heterocyclic carbene derivatives Ru(NHC)(PPh3)2(CO)HF

The reaction of Ru(PPh3)(3)(CO)H-2 with excess Et3N center dot 3HF at elevated temperature affords the hydride fluoride complex Ru(PPh3)(3)(CO)HF (1). This reacts with a series of N-heterocyclic carbenes (NHCs) at ambient temperature to form the mono-NHC products Ru(NHC)(PPh3)(2)(CO)HF (NHC = IMe4 (2), IEt2Me2 (3), ICy (4), (IPr2Me2)-Pr-i (5)). Complexes 2-4 convert from the trans- to cis-phosphine isomers in solution over weeks (relative rates 2 > 3 >> 4), while 5 undergoes both isomerization and disproportionation to yield cis-Ru((IPr2Me2)-Pr-i)(PPh3)(2)(CO)HF (6), 1, and Ru((IPr2Me2)-Pr-i)(2)(PPh3)(CO)HF (7) in a matter of hours. The molecular structures of compounds 1-4 have been determined by X-ray crystallography.