Modulation of Electronic Couplings within Ru_2-Polyyne Frameworks

摘要

Dimers of [Ru_2(Xap)_4] bridged by 1,3,5-hexa-triyn-diyl (Xap are 2-anilinopyridinate and its aniline substituted derivatives), [Ru_2(Xap)_4]_2(μ-C_6) (1), were prepared. Compounds 1 reacted with 1 equiv of tetracyanoethene (TCNE) to yield the cydo-addition/insertion products [Ru_2(Xap)_4]_2-{μ-C=CC(C(CN)_2)-C(C(CN)_2)O≡C} (2) and 1 equiv of Co_2(dppm)(CO)_6 to yield the η~2-Co_2 adducts to the middle C≡C bond, [Ru_2(Xap)_4]_2(μ-C_6)(Co_2(dppm)(CO)_4) (3). Voltammetric and spectroelectrochemical studies revealed that (i) two Ru_2 termini in 1 are sufficiently coupled with the mono- anion (1~-) as a Robin-Day class II/III mixed valence species; (ii) the coupling between two Ru_2 is still significant but somewhat weakened in 3; and (iii) the coupling between two Ru2 is completely removed by the insertion of TCNE in 2. The attenuation of electronic couplings in 2 and 3 was further explored with both the X-ray diffraction study of representative compounds and spin-unrestricted DFT calculations.