Bisaryl and Bisalkynyl Diruthenium (III,III) Compounds Based on an Electron-Deficient Building Block

Reported herein is a new series of diruthenium(III,III) bisalkynyl and bisaryl diruthenium(III,III) compounds supported with 2-amino-3-(trifluoromethyl)pyridinate (amtfmp). Using Ru2(amtfmp)4Cl2 from a modified preparation, cis 2:2 Ru2(amtfmp)4(C≡CPh)2 (1), cis 2:2 Ru2(amtfmp)4(Ph)2 (2), and 3:1 Ru2(amtfmp)4(Ph)2 (3) were synthesized via a lithium–halogen exchange reaction using LiC2Ph and LiPh, respectively. Compounds 1–3 are all Ru2(III,III) species with a ground-state configuration of π4δ2(π*)4 (S = 0) and were characterized via mass spectrometry, electron absorption and 1H/19F NMR spectroscopies, and voltammetry. The molecular structures of 1–3 were established using single-crystal X-ray diffraction analysis, and preliminary density functional theory analysis was performed to elaborate the electronic structures of 1 and 2. Comparisons of the electrochemical properties of 1–3 against the Ru2(amtfmp)4Cl2 starting material reveal cathodic shifts of the Ru27+/6+ oxidation and the Ru26+/5+ and Ru25+/4+ reduction potentials. In comparison to related Ru2(III,III) bisalkynyl and bisaryl compounds, the electrode potentials for 1–3 are anodically shifted up to ca. 0.95 V, highlighting the strong electron-withdrawing nature of the amtfmp ligand.