Synthesis and Electronic Structure of Ru2(Xap)4(Y-gem-DEE) Type Compounds: Effect of Cross-Conjugation

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• 作者：William P. Forrest ; Mohommad M. R. Choudhuri ; Stefan M. Kilyanek ; Sean N. Natoli ; Boone M. Prentice ; Phillip E. Fanwick ; Robert J. Crutchley ; Tong Ren
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：August 3, 2015
• 年：2015
• 卷：54
• 期：15
• 页码：7645-7652
• 全文大小：539K
• ISSN：1520-510X

文摘

Reported in this Article are the preparation and characterization of a series of new Ru₂(II,III) compounds bearing one cross-conjugated 蟽-geminal-diethynylethene ligand (gem-DEE), namely, Ru₂(Xap)₄(Y-gem-DEE) (Xap = N,N鈥?anilinopyridinate (ap) or 2-(3,5-dimethoxy)anilinopyridinate (DiMeOap), and Y = SiⁱPr₃ (1) or H (2)) and [Ru₂(ap)₄]₂(渭-gem-DEE) (3). Compounds 1鈥?b>3 were characterized by spectroscopic and voltammetric techniques as well as the single crystal X-ray diffraction study of 2a. The X-ray structural data of 2a and the spectroscopic/voltammetric data of compounds 1 and 2 indicate that the gem-DEE ligands are similar to simple alkynyls in their effects on the molecular and electronic structures of the Ru₂(Xap)₄ moiety. Similar to the previously studied [Ru₂(ap)₄]₂(渭-C_2n) type compounds, dimer 3 exhibits pairwise 1e^{鈥?/sup> oxidations and reductions, albeit the potential splits within the pair (螖E_1/2) are significantly smaller than those of [Ru₂(ap)₄]₂(渭-C₄). The electronic absorption spectra of the reduced and oxidized derivatives of 1a and 3 were determined using spectroelectrochemistry methods. No discernible intervalence charge transfer transition (IVCT) was detected in the near-IR spectrum for either 3鈥?/sup> or 3+, suggesting that the Ru₂鈥揜u₂ coupling in these mixed-valence states is weak. DFT calculations on a model compound of 3 yielded six singly occupied molecular orbitals (SOMOs), which have Ru₂ contributions similar to those previously calculated for the [Ru₂(ap)₄]₂(渭-C_2n) type compounds. Among six SOMOs, SOMO-2 is the only one containing substantial d蟺鈥撓€(gem-DEE) character across the entire Ru₂-渭-gem-DEE-Ru₂ linkage, which explains the weakened Ru₂鈥揜u₂ coupling.}