Reaction of Tp(PPh_3)Ru(η^2-O_2CCHPh_2) with Carbene and Vinylidene Precursors

Abstract

Tp(PPh_3)Ru(η^2-O_2CCHPh_2) (1) [Tp = tris(pyrazolyl)borate] has been prepared by the reaction of TpRu(Cl)(PPh_3)_2 with 1.2 equiv of NaO_2CCHPh_2. Complex 1 reacts with diphenylcyclopropene to generate the metallacycle Tp(PPh_3)Ru[κ^2-(C,Ο)-C(═CHCHPh_2)OC(CHPh_2)═O] (2). A trace of the carbene Tp(PPh_3)(η^1-O_2CCHPh_2)Ru═CHCH═C(Ph)_2 (3) is also observed in the crude reaction mixture. Compound 1 reacts with phenyldiazomethane to form the benzylidene Tp(PPh_3)(η^1-O_2CCHPh_2)Ru═CHPh (4). A similar species is also available by the reaction between AgO_2CCHPh_2 and Tp(PCy_3)(Cl)Ru═CHCH═C(CH_3)_2 (5), which affords Tp(PCy_3)(η^1-O_2CCHPh_2)Ru═CHCH═C(CH_3)_2 (6). With the addition of an excess of HCl, complexes 4 and 6 release free HO_2CCHPh_2 and are converted to Tp(PPh_3)(Cl)Ru═CHPh (7) and complex 5, respectively. The reaction of 1 with phenylacetylene yields the five-membered chelate Tp(PPh_3)Ru[κ^2-(C,Ο)-C(═CHPh)OC(CHPh_2)═O] (8). Complex 8 is also formed in the reaction of Tp(PPh_3)(Cl)Ru═C═CHPh with 1.2 equiv of AgO_2CCHPh_2. Compounds 1, 2, and 8 have been characterized by X-ray crystallography. Complexes 2, 5, 6, 7, and 8 do not catalyze olefin metathesis reactions, while 4 is an active initiator for the ring-opening metathesis polymerization of norbornene.