1 research outputs found
Ru(II) Complexes with a Chemical and Redox-Active S<sub>2</sub>N<sub>2</sub> Ligand: Structures, Electrochemistry, and Metal–Ligand Cooperativity
Here we describe
the synthesis, structures, and reactivity of Ru
complexes containing a triaryl, redox-active S<sub>2</sub>N<sub>2</sub> ligand derived from <i>o</i>-phenylenediamine and thioanisole
subunits. The coordination chemistry of <i>N</i>,<i>N′</i>-bisÂ[2-(methylthio)Âphenyl]-1,2-diaminobenzene [H<sub>2</sub>(<sup>Me</sup>SNNS<sup>Me</sup>)] was established by treating
RuCl<sub>2</sub>(PPh<sub>3</sub>)<sub>3</sub> with H<sub>2</sub>(<sup>Me</sup>SNNS<sup>Me</sup>) to yield {RuÂ[H<sub>2</sub>(<sup>Me</sup>SNNS<sup>Me</sup>)]ÂClÂ(PPh<sub>3</sub>)}Cl (<b>1</b>). Coordinated
H<sub>2</sub>(<sup>Me</sup>SNNS<sup>Me</sup>) was sequentially deprotonated
to form RuÂ[HÂ(<sup>Me</sup>SNNS<sup>Me</sup>)]ÂClÂ(PPh<sub>3</sub>) (<b>2</b>) followed by the five-coordinate, square pyramidal complex
RuÂ(<sup>Me</sup>SNNS<sup>Me</sup>)Â(PPh<sub>3</sub>) (<b>3</b>). Single-crystal X-ray diffraction (XRD) studies revealed that the
ligand structurally rearranged around the metal at each deprotonation
step to conjugate the adjacent aryl groups with the <i>o</i>-phenylenediamine backbone. Deprotonation of <b>2</b> with
NaBH<sub>4</sub> or treatment of <b>3</b> with BH<sub>3</sub>·tetrahydrofuran (THF) yielded RuÂ[(ÎĽ-H)ÂBH<sub>2</sub>]Â(<sup>Me</sup>SNNS<sup>Me</sup>)Â(PPh<sub>3</sub>) (<b>5</b>) with
BH<sub>3</sub> bound across a Ru–N bond in a metal–ligand
cooperative fashion. The cyclic voltammogram of <b>3</b> in
THF revealed three redox events consistent with one-electron oxidations
and reductions of the <i>o</i>-phenylenediamine backbone
and the metal (Ru<sup>3+</sup>/Ru<sup>2+</sup>). Reactions of <b>3</b> with CO, HBF<sub>4</sub>, and benzoic acid yielded the new
complexes RuÂ(<sup>Me</sup>SNNS<sup>Me</sup>)Â(CO)Â(PPh<sub>3</sub>),
{RuÂ[HÂ(<sup>Me</sup>SNNS<sup>Me</sup>)]Â(PPh<sub>3</sub>)Â(THF)}ÂBF<sub>4</sub>, and RuÂ[HÂ(<sup>Me</sup>SNNS<sup>Me</sup>)]Â(PPh<sub>3</sub>)Â(PhCO<sub>2</sub>), indicating broader suitability for small molecule
binding and reactivity studies. Subsequent nuclear magnetic resonance
spectroscopy, infrared spectroscopy, and mass spectrometry data are
reported in addition to molecular structures obtained from single-crystal
XRD studies