%0 Journal Article %A Natoli, Sean N. %A Azbell, Tyler J. %A Fanwick, Phillip E. %A Zeller, Matthias %A Ren, Tong %D 2016 %T A Synthetic Approach to Cross-Conjugated Organometallic Complexes Based on geminal-Diethynylethene and CoIII(cyclam) %U https://acs.figshare.com/articles/journal_contribution/A_Synthetic_Approach_to_Cross-Conjugated_Organometallic_Complexes_Based_on_i_geminal_i_-Diethynylethene_and_Co_sup_III_sup_cyclam_/4010124 %R 10.1021/acs.organomet.6b00657.s001 %2 https://acs.figshare.com/ndownloader/files/6453231 %K Co III %K analysis %K acyclic cross-conjugated complexes %K DEE %K orbital %K ligand %K PF %K DFT %K OTf %K Cross-Conjugated Organometallic Complexes %K gem %K σ- %K Cl %K cyclam %K geminal %X A series of CoIII(cyclam) complexes ([1a,b]­Cl, [2ac]­PF6, [3]­Cl2, [4a]­(OTf)4, [4b]­(PF6)2, and [5]­Cl2) (cyclam = 1,4,8,11-tetraazacycloctetradecane) bearing a geminal-diethynylethene ligand (gem-DEE) is reported. Syntheses of these acyclic cross-conjugated complexes were accomplished in satisfactory yields, and structural characterizations established that the geometrical feature of gem-DEE is largely preserved upon metalation. Combined structural and electrochemical studies suggest that the gem-DEE ligand, as a σ-donor, is weaker than phenylethynyl but stronger than butadiynyl in CoIII(cyclam) complexes. Voltammetric analysis indicated a weak but discernible Co–Co coupling across the gem-DEE bridge in [3]­Cl2 and [4a]­(OTf)4, while the addition of a second acetylide in the trans position diminished such coupling in [4b]­(PF6)2. DFT analysis revealed significant dπ–π mixing around the cobalt centers with extended π-overlap in the highest occupied orbitals and substantial σ-based mixing in the lowest unoccupied orbitals of [3]­Cl2 and [4a]­(OTf)4, the latter of which likely contributes to the weak Co–Co coupling. %I ACS Publications