The Synthesis, Structure, and H/D Exchange Reactions of Water-Soluble Half-Sandwich Ruthenium(II) Hydrides of Indenyl and Dihydropentalenyl

Two new water-soluble ruthenium hydrides Cp′Ru­(PTA)₂H, Cp′ = C₉H₇^– (Ind, 1) or C₈H₉^– (Dp, 2), along with IndRu­(PTA)₂Cl (3) have been synthesized. DpRu­(PTA)₂H was synthesized by refluxing DpRu­(PTA)₂Cl with NaCO₂H in methanol. IndRu­(PTA)₂H was unable to be generated in a similar manner due to complications in the synthesis of IndRu­(PTA)₂Cl. IndRu­(PTA)₂H was synthesized by conversion of the mixed-phosphine ruthenium complex IndRu­(PTA)­(PPh₃)Cl into IndRu­(PTA)­(PPh₃)H followed by ligand substitution of PPh₃ with 1,3,5-triaza-7-phosphaadamantane (PTA). Complexes 1 and 2 are stable and moderately soluble in water (S_25°C = 16 mg/mL for 1 and ∼20 mg/mL for 2). The Ru hydrides react with chlorinated solvents, in the case of 1 yielding the challenging synthesize IndRu­(PTA)₂Cl (3) (S_25°C = 17 mg/mL). The synthesis, isolation, and reactivity of 1–3 are described including crystal structures of 1, 2, 3, and [IndRu­(PTA)₃]­(Cl). H/D exchange reactions of 1 with D₂O were monitored by ³¹P NMR spectroscopy as a function of temperature: ΔH^‡ = 92 ± 3 kJ/mol, ΔS^‡ =–22 ± 2 J/mol·K. In addition, H/D exchange reactions of the 1,2-dihydropentalenyl (η⁵-C₈H₉^–, Dp) analogue, 2, with D₂O are also described along with the effects of pH on the ³¹P NMR spectra.