N-heterocyclic carbene stabilized trans-dihydrido aqua and ethanol complexes of ruthenium: Precursors to complexes with Ru-heteroatom bonds [Review]

摘要

Attempts to isolate the bis-N-heterocyclic carbene complex Ru(AsPh3)(IMes)(2)(CO)H-2 (IMes bis(1,3-(2,4,6-trimethylphenyl)imidazol-2-ylidene)) by crystallization with either ethanol or hexane yields instead the ethanol and water complexes Ru(IMes)(2)(CO)(EtOH)H-2 (1) and Ru(IMes)(2)(CO)(H2O)H-2 (2), respectively. Both multinuclear NMR spectroscopy and X-ray crystallography demonstrate that these two compounds are isostructural with a trans arrangement of the hydride ligands. Thermolysis of 1 results in decarbonylation of the bound ethanol ligand to yield Ru(IMes)(2)(CO)(2)H-2 (3). Substitution of the coordinated solvent ligands in 1 or 2 occurs readily with p-ethoxyphenol to give Ru(IMes)(2)(CO)(HOC6H4-p-OEt)H-2 (4), while treatment of 2 with 1-propanethiol affords the thiol complex Ru(IMes)(2)(CO)(HSCH2-CH2CH3)H-2 (8). Reaction of 8 with CO gives the thiolate hydride species Ru(IMes)(2)(CO)(2)-(SCH2CH2CH3)H (9), whereas addition of CO to either 1 or 2 affords Ru(IMes)(2)(CO)(3) (5). The hydroxy hydride complex Ru(IMes)(2)(CO)(2)(OH)H (6) has been isolated as an intermediate on the pathway from 2 to 5. Addition Of CO2 or p-HO2CC5H4N to solutions of 2 yields the bicarbonate complex Ru(IMes)(2)(CO)(kappa(2)-O2COH)H (10) and the isonicotinate species Ru(IMes)(2)-(CO)(kappa(2)-O2CC5H4N)H (11), respectively. Addition of CO to 10 affords Ru(IMes)(2)(CO)(2)(eta(1)-O-2-COH)H (7). Treatment of complex 2 with excess acetonitrile yields the N-imidoylimidato complex Ru(IMes)(2)(CO)(NH=C(CH3)N C(CH3)O)H (12), which arises from the formal addition of two molecules of acetonitrile in head-to-tail fashion across the RuO-H bond. Compounds 1, 2, 6, 7, 8, 9, 11, and 12 have been structurally characterized by single-crystal X-ray diffraction. [References: 150]