Ruthenium bipyridyl compounds with two terminal alkynyl ligands

Abstract

Compounds of the form Ru(X₂bipy)(PPh₃)₂(–CCC₆H₄NO₂-p)₂ (X₂bipy = 4,4′-X₂-2,2′-bipyridine, X = Me 3a, Br 3b, I 3c) have been synthesised from the mono-alkynyl precursors Ru(X₂bipy)(PPh₃)₂(–CCC₆H₄NO₂-p)Cl (X = Me 2a, Br 2b, I 2c); the former are the first ruthenium bis-alkynyl compounds that also contain a bipyridyl ligand. Spectroelectrochemical investigation of 3a shows that the metal is readily oxidised to form the ruthenium(III) compound 3a⁺, and will also undergo a single-electron reduction at each nitro group to form 3a²⁻. ESR and UV/visible spectra of these redox congeners are presented. We also report the synthesis of [Ru(Me₂bipy)(PPh₃)₂(–CCBu^t)(NN)][PF₆] 4 during the attempted synthesis of Ru(Me₂bipy)(PPh₃)₂(–CCBu^t)₂, and report its X-ray crystal structure and IR spectrum. X-Ray crystal structures of 3b and 3c (as two different solvates) are presented, and the nature of the intermolecular interactions seen therein is discussed. Z-Scan measurements on Ru(Me₂bipy)(PPh₃)₂(–CCR)Cl (R = C₆H₄NO₂-p2a, Bu^t, Ph, C₆H₄Me) are also reported, and show that Ru(Me₂bipy)(PPh₃)₂(–CCR)Cl (R = C₆H₄NO₂-p2a, Ph) exhibit moderate third-order non-linearities.