Activation of Propargyl Alcohols by TpRu Complexes Bearing a Bidentate NHC Ligand

The complex [TpRuCl(COD)] reacts with L·Ag2Cl2 (L = bis(3-methylimidazol-2-ylidene)) in dichloroethane at 120 °C for a period of 20 h, furnishing the bis(carbene) derivative [TpRuCl(L)] (1). This compound reacts with NaBAr′4 in FPh under dinitrogen to yield the cationic dinitrogen complexes [TpRu(N2)(L)][BAr′4] (2′) and [{TpRu(L)}(μ-N2)][BAr′4]2 (2). The terminal dinitrogen complex 2′ is labile and spontaneously converts into 2, which was structurally characterized. The reaction of 2 with CO is slow and affords [TpRu(CO)(L)][BAr′4] (3). The kinetics of the substitution of coordinated dinitrogen in 2 by CD3CN has been studied. The value of 25 ± 4 kcal mol–1 determined for ΔG⧧298 for the substitution reaction is consistent with the observation that the dinitrogen ligand is strongly bound to ruthenium in 2. Complex 1 reacts with propargyl alcohols HC≡CC(OH)RR′ (RR′ = Me2, (CH2)5, MePh, HPh) and NaBPh4 in MeOH at 50–60 °C, yielding the corresponding γ-methoxyvinylidene complexes [TpRu═C═CHC(OMe)RR′(L)][BPh4] ...