10.1021/ja052287b.s003 Benjamin G. Harvey Benjamin G. Harvey Charles L. Mayne Charles L. Mayne Atta M. Arif Atta M. Arif Richard D. Ernst Richard D. Ernst Structural and Spectroscopic Demonstration of Agostic C−C Interactions in Electron-Deficient Metallacyclobutanes and Related Cage Complexes:  Possible Implications for Olefin Polymerizations and Metatheses American Chemical Society 2005 dienyl fragment C 8 H 11 ligand electron PhC 2 SiMe 3 C 8 H 11 bond C 5 H 5 allyl interaction PMe 3 coordinations CH 2 group 2005-11-30 00:00:00 Dataset https://acs.figshare.com/articles/dataset/Structural_and_Spectroscopic_Demonstration_of_Agostic_C_C_Interactions_in_Electron_Deficient_Metallacyclobutanes_and_Related_Cage_Complexes_Possible_Implications_for_Olefin_Polymerizations_and_Metatheses/3254038 The reaction of the half-open titanocene, Ti(C<sub>5</sub>H<sub>5</sub>)(<i>c-</i>C<sub>8</sub>H<sub>11</sub>)(PMe<sub>3</sub>) (<i>c-</i>C<sub>8</sub>H<sub>11</sub> = cyclooctadienyl), with two equivalents of PhC<sub>2</sub>SiMe<sub>3</sub> leads to their incorporation and coupling to the dienyl fragment. One alkyne inserts into a C−H bond of the central CH<sub>2</sub> group of the <i>c-</i>C<sub>8</sub>H<sub>11</sub> ligand's edge-bridge, while the second undergoes a 5+2 coupling with the dienyl fragment, yielding coordinated σ-allyl and olefin fragments, as demonstrated by X-ray diffraction. Together with the C<sub>5</sub>H<sub>5</sub> and PMe<sub>3</sub> coordinations, this leads to a 14-electron count. While the very electron-deficient titanium center passes up potential π coordination of the allyl fragment, it instead engages in interactions with one or two C−C bonds, and perhaps a C−H bond, as revealed from the structural and spectroscopic data. Similar interactions have been found in electron-deficient metallacyclobutane complexes of titanium and zirconium, but not in the 18-electron molybdenum and tungsten analogues. These and other observations may have implications relating to metatheses and polymerizations of olefins.