Probing the Electronic Structure of Dinuclear Carbon-Rich Complexes Containing an Octa-3,5-diene-1,7-diyndiyl Bridging Ligand
oleh: Michael R. Hall, Stephen A. Moggach, Paul J. Low
| Format: | Article |
|---|---|
| Diterbitkan: | MDPI AG 2024-01-01 |
Deskripsi
One electron oxidation of the monometallic alkenylacetylide complexes [Ru{C≡CC(R)=CH<sub>2</sub>}(dppe)Cp*] (<b>1</b>) and [Ru{C≡CC(R)=CH<sub>2</sub>}Cl(dppe)<sub>2</sub>] (<b>2</b>) (R = Ph (<b>a</b>); R = 4-MeS-C<sub>6</sub>H<sub>4</sub> (<b>b</b>)) generates in each case a dinuclear bis(allenylidene) complex [{Ru}<sub>2</sub>{μ-C=C=C(R)–CH<sub>2</sub>–H<sub>2</sub>C–(R)C=C=C}][PF<sub>6</sub>]<sub>2</sub> ({Ru} = Ru(dppe)Cp* ([<b>3a</b>,<b>b</b>][PF<sub>6</sub>]<sub>2</sub>); {Ru} = RuCl(dppe)<sub>2</sub> ([<b>4a</b>,<b>b</b>][PF<sub>6</sub>]<sub>2</sub>), containing an unsaturated ethane bridge between both allenylidene moieties. Deprotonation of this ethane bridge results in the formation of the previously reported octa-3,5-diene-1,7-diyndiyl-bridged bimetallic species [{Ru}<sub>2</sub>{μ-C≡CC(R)=CH–HC=(R)CC≡C}] ({Ru} = Ru(dppe)Cp* (<b>5a</b>,<b>b</b>); {Ru} = RuCl(dppe)<sub>2</sub> (<b>6a</b>,<b>b</b>). The isolation of these complexes illustrates a general synthetic route to these conjugated bimetallic species from monomeric alkenylacetylide precursors. Electrochemical and spectroelectrochemical investigations evince the ready formation of the representative redox series [<b>5a</b>]<i><sup>n+</sup></i>, and TD-DFT calculations performed on optimised structures featuring the simplified {Ru(dmpe)Cp} coordination sphere [{Ru(dmpe)Cp}<sub>2</sub>{μ-C≡CC(Ph)=HC–CH(Ph)CC≡C}]<i><sup>n</sup></i><sup>+</sup> ([<b>5a</b><sup>†</sup>]<i><sup>n</sup></i><sup>+</sup>) (<i>n</i> = 0, 1, 2) reveal significant delocalisation of the unpaired charge in the formally mixed-valent species (<i>n</i> = 1), consistent with Class III assignment within the Robin–Day classification scheme.