Allenyl to Alkenylcarbyne Tautomerization at the Ru–Si Bond of Ru(κP,P,Si) Pincer Complexes

The reactions of the dimer [Ru­(μ-Cl)­{κP,P,Si-Si­(Me)­(C6H4-2-PiPr2)2}]2 (1) with 2-methyl-3-butyn-2-ol and 3-chloro-3-methyl-1-butyne are reported. The former stops at the reagent coordination step forming the mononuclear η2 alkyne complex [Ru­{κP,P,Si-Si­(Me)­(C6H4-2-PiPr2)2}­Cl­{η2-HCCC­(OH)­Me2}] (2), while the latter sequentially produces the allene derivative [Ru­(Cl)2{κP,P-Si­(Me)­(1,2-η-CHCCMe2)­(C6H4-2-PiPr2)2}] (3) and its alkenylcarbyne isomer [Ru­{κP,P,Si-Si­(Me)­(C6H4-2-PiPr2)2}­(Cl)2(CCHCMe2)] (4). The structures of complexes 3 and 4 indicate that the allenyl fragment that results from the activation of the propargylic chloride uses the Ru–Si bond of the pincer complex to tautomerize into an alkenylcarbyne ligand.