Picolyl–NHC Hydrotris(pyrazolyl)borate Ruthenium(II) Complexes: Synthesis, Characterization, and Reactivity with Small Molecules

Ruthenium­(II) hydrotris­(pyrazolyl)­borate chloro complexes bearing picolyl-functionalized N-heterocyclic carbenes [TpRu­(κ2-C,N-picolyl-RI)­Cl] (picolyl-MeI = 3-methyl-1-(2-picolyl)­imidazol-2-ylidene) (1a), picolyl-iPrI = 3-isopropyl-1-(2-picolyl)­imidazol-2-ylidene (1b), picolyl-Me45DClI = 3-methyl-1-(2-picolyl)-4,5-dichloroimidazol-2-ylidene (1c), picolyl-PhI = 3-phenyl-1-(2-picolyl)­imidazol-2-ylidene (1d), picolyl-MeBI = 3-methyl-1-(2-picolyl)­benzoimidazol-2-ylidene (1e)) have been synthesized and characterized. Furthermore, cationic carbonyl derivatives 2a–e have been prepared, characterized, and used to study the donor properties of the picolylcarbene ligands (picolyl-RI) via infrared spectroscopy. Also, the reactivity of the 16-electron species [TpRu­(κ2-C,N-picolyl-RI)]+, in situ generated using NaBArF4 (ArF = 3,5-bis­(trifluoromethyl)­phenyl) as a halide scavenger, toward N2, CH3CN, H2, CH2CH2, S8, and O2 was studied indicating a strong influence of the NHC wingtip and backbone substituents in the product distribution. The crystal structures of [TpRu­(κ2-C,N-picolyl-iPrI)­Cl] (1b), [TpRu­(κ2-C,N-picolyl-MeI)­CO]­[BArF4] (2a), [TpRu­(κ2-C,N-picolyl-PhI)­CO]­[BArF4] (2d), [{TpRu­(κ2-C,N-picolyl-MeI}2(μ-N2)]­[BArF4]2 (3′a), [{TpRu­(κ2-C,N-picolyl-PhI)}2(μ-N2)]­[BArF4]2 (3′d), [TpRu­(κ2-C,N-picolyl-iPrI)­(η2-CH2CH2)]­[BArF4] (5b), and [{TpRu­(κ2-C,N-picolyl-MeI)}2(μ-S2)]­[BArF4]2 (6) are reported.