C-(halide) oxidative addition routes to ruthenium carbenes

Ru(H)(2)(H-2)(2)L-2 (L = PCy3) reacts with CHRCl2 (R = H, Ph) to give Ru(CHR)Cl2L2 and H-2. Using Cl2C=CH2 as the gem-dihalide gives Ru(CHCH3)Cl2L2, due to hydrogenation of the C=C bond of the presumed vinylidene primary product by released H-2. Released H-2 also reacts with Ru(CHR)Cl2L2 (R = H, Ph) to give H3CR, HCl and RuHCl(H-2)L-2. This undesirability of H-2 as a coproduct can be diminished by using Ru(H)(2)(N-2)(2)L-2 as the reagent, giving Ru(CHR)Cl2L2 and 1H(2) and 2N(2) as products. Reaction of Ru(H)(2)(N-2)(2)L-2 with Cl2CHEt gives RuCl2(CHEt)L-2 and RuHCl(N-2)L-2, the latter apparently by competitive beta-H migration from an intermediate RuHCl(CHClEt)L-2 species. When Ru(H)(2)(N-2)(2)L-2 is reacted with the monochloride PhCH2Cl, the primary product RuCl(CH2Ph)(H-2)L-2 slowly (hours) evolves further to give RuHCl(N-2)L-2 and PhCH3. Reaction of Ru(H)(2)(N-2)(2)L-2 with C6F6. BrHC=CHPh, and CH3I give RuHX(N-2)L-2 (X = F, Br, I, respectively). The N-2 ligand in RuHCl(N-2)L-2 can be displaced by H-2 and by CO, while H-2 converts RuHF(N-2)L-2 to Ru(H)(2)(H-2)(2)L-2 and HF.