Combined Spectroscopic and Quantum Chemical Study of [trans-Ru(C≡CC6H4R1‑4)2(dppe)2]n+ and [trans-Ru(C≡CC6H4R1‑4)(C≡CC6H4R2‑4)(dppe)2]n+ (n = 0, 1) Complexes:Interpretations beyond the Lowest Energy Conformer Paradigm

S Marques-Gonzalez, M Parthey, D.S Yufit, J.A.K Howard, M Kaupp, Paul Low

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The reaction of trans-RuCl(C≡CC6H4R1-4)(dppe)2 (2: R1 = Me (a), C5H11 (b), OMe (c), CO2Me (d), NO2 (e), C≡CSiMe3 (f), C≡CBut (g), NH2 (h)), prepared in situ from reactions of [RuCl(dppe)2]OTf ([1]OTf) with terminal alkynes in CH2Cl2 solutions containing 1,8-diazabicycloundec-7-ene (DBU) and TlBF4, provides a convenient and rapid route to bis(acetylide) complexes trans-Ru(C≡CC6H4R1-4)2(dppe)2 (3a–h) and trans-Ru(C≡CC6H4R1-4)(C≡CC6H4R2-4)(dppe)2 (4, R1 = C≡CSiMe3, R2 = NH2; 5, R1 = CO2Me, R2 = NH2; 6, R1 = CO2Me, R2 = OMe). However, even in the absence of the chloride abstracting reagent, more strongly electron donating substituents (e.g., R1 = OMe (2c), NH2 (2h)) promote sufficient ionization of the Ru–Cl bond in trans-RuCl(C≡CC6H4R1-4)(dppe)2 to lead to slow conversion to bis(alkynyl) complexes 3c,h in the presence of excess alkyne and DBU. Desilylation of 2f and 3f affords 2i and 3i (R1 = C≡CH), respectively. The molecular structures of 3a–d,f–i have been determined and are reported together with the structures of the monoalkynyl complexes 2f,g,i and compared with related compounds from the literature. Complexes 3a–i and 4–6 undergo one reversible electrochemical oxidation process, which can be attributed to depopulation of an orbital with significant alkynyl ligand character. The one-electron-oxidation products [3f]•+, [3h]•+, [4]•+, and [5]•+, chosen to serve as representative examples of this family of complexes, each exhibit a series of NIR absorptions between 15000 and 5000 cm–1 which on the basis of TDDFT calculations cannot be attributed to a single, static lowest energy molecular structure. Rather, the transitions that are responsible for the absorption band envelope have varying degrees of LMCT and inter-alkynyl ligand IVCT or MLCT character that depend not only on the nature of the Rn groups but also on the ensemble of thermally populated molecular conformers in solution with various relative orientations of the metal fragment and arylethynyl moieties.
Original languageEnglish
Pages (from-to)4947−4963
Issue number18
Publication statusPublished - 22 Sep 2014


Dive into the research topics of 'Combined Spectroscopic and Quantum Chemical Study of [trans-Ru(C≡CC<sub>6</sub>H<sub>4</sub>R<sup>1</sup>‑4)<sub>2</sub>(dppe)<sub>2</sub>]<em><sup>n+</sup> </em>and [trans-Ru(C≡CC<sub>6</sub>H<sub>4</sub>R<sup>1</sup>‑4)(C≡CC<sub>6</sub>H<sub>4</sub>R<sup>2</sup>‑4)(dppe)<sub>2</sub>]<em><sup>n+</sup></em> (<em>n</em> = 0, 1) Complexes:Interpretations beyond the Lowest Energy Conformer Paradigm'. Together they form a unique fingerprint.

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