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)H2 with excess Et3N·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), IiPr2Me2 (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(IiPr2Me2)(PPh3)2(CO)HF (6), 1, and Ru(IiPr2Me2)2(PPh3)(CO)HF (7) in a matter of hours. The molecular structures of compounds 1−4 have been determined by X-ray crystallography.