Edwin Van Der Eide - Generation and Spectroscopic Characterization of Ruthenacyclobutane and Ruthenium Olefin Carbene Intermediates Relevant to Ring Closing Metathesis Catalysis

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      Publication Details (including relevant citation   information):

      Edwin F. van der Eide, Patricio E. Romero and Warren E. Piers

      Journal   of the American Chemical Society   2008, 130, 4485-4491

      doi:   10.1021/ja710364e

      Abstract:

      The reaction of phosphonium alkylidenes   [(H2IMes)RuCl2=CHPR3]+[A]-  (R = C6H11, A = OTf or   B(C6F5)4, 1-Cy;   R = i-C3H7, A =   ClB(C6F5)3 or OTf,   1-iPr) with   1 equiv of ethylene at −78 °C, in the presence of 2−3 equiv of a   trapping olefin substrate, yields intermediates relevant to   olefin metathesis catalytic cycles. Dimethyl   cyclopent-3-ene-1,1-dicarboxylate gives solutions of a   substituted ruthenacyclobutane 3 of relevance to   ring closing metathesis catalysis. 1H and   13C NMR data are fully consistent with its assignment   as a ruthenacyclobutane, but 1JCC  values of 23 Hz for the CαH2−Cβ  bond and 8.5 Hz for the CαH−Cβ bond point   to an unsymmetrical structure in which the latter bond is more   activated than the former. In contrast, trapping with   acenaphthylene leads to an olefin carbene complex   (6) in which the putative ruthenacyclobutane has   opened; this species was also fully characterized by NMR   spectroscopy and compared to related species reported previously.

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