Ru(II) Complexes with a Chemical and Redox-Active S₂N₂ Ligand: Structures, Electrochemistry, and Metal–Ligand Cooperativity

Here we describe the synthesis, structures, and reactivity of Ru complexes containing a triaryl, redox-active S₂N₂ ligand derived from <i>o</i>-phenylenediamine and thioanisole subunits. The coordination chemistry of <i>N</i>,<i>N′</i>-bis­[2-(methylthio)­phenyl]-1,2-diaminobenzene [H₂(^MeSNNS^Me)] was established by treating RuCl₂(PPh₃)₃ with H₂(^MeSNNS^Me) to yield {Ru­[H₂(^MeSNNS^Me)]­Cl­(PPh₃)}Cl (<b>1</b>). Coordinated H₂(^MeSNNS^Me) was sequentially deprotonated to form Ru­[H­(^MeSNNS^Me)]­Cl­(PPh₃) (<b>2</b>) followed by the five-coordinate, square pyramidal complex Ru­(^MeSNNS^Me)­(PPh₃) (<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 NaBH₄ or treatment of <b>3</b> with BH₃·tetrahydrofuran (THF) yielded Ru­[(μ-H)­BH₂]­(^MeSNNS^Me)­(PPh₃) (<b>5</b>) with BH₃ 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 (Ru³⁺/Ru²⁺). Reactions of <b>3</b> with CO, HBF₄, and benzoic acid yielded the new complexes Ru­(^MeSNNS^Me)­(CO)­(PPh₃), {Ru­[H­(^MeSNNS^Me)]­(PPh₃)­(THF)}­BF₄, and Ru­[H­(^MeSNNS^Me)]­(PPh₃)­(PhCO₂), 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

Validating the Biphilic Hypothesis of Nontrigonal Phosphorus(III) Compounds

Constraining σ3-P compounds in nontrigonal, entatic geometries has proven to be an effective strategy for promoting biphilic oxidative addition reactions more typical of transition metals. Although qualitative descriptions of the impact of structure and symmetry on σ3-P complexes have been proposed, electronic structure variations responsible for biphilic reactivity have yet to be elucidated experimentally. Reported here are P K-edge XANES data and complementary TDDFT calculations for a series of structurally modified P(N)3 complexes that both validate and quantify electronic structure variations proposed to give rise to biphilic reactions at phosphorus. These data are presented alongside experimentally referenced electronic structure calculations that reveal nontrigonal structures predicted to further enhance biphilic reactivity in σ3-P ligands and catalysts.NIH NIGMS (Grant GM114547)NSF (Grant CHE-1724505

Validating the Biphilic Hypothesis of Nontrigonal Phosphorus(III) Compounds

Constraining σ3-P compounds in nontrigonal, entatic geometries has proven to be an effective strategy for promoting biphilic oxidative addition reactions more typical of transition metals. Although qualitative descriptions of the impact of structure and symmetry on σ3-P complexes have been proposed, electronic structure variations responsible for biphilic reactivity have yet to be elucidated experimentally. Reported here are P K-edge XANES data and complementary TDDFT calculations for a series of structurally modified P(N)3 complexes that both validate and quantify electronic structure variations proposed to give rise to biphilic reactions at phosphorus. These data are presented alongside experimentally referenced electronic structure calculations that reveal nontrigonal structures predicted to further enhance biphilic reactivity in σ3-P ligands and catalysts.NIH NIGMS (Grant GM114547)NSF (Grant CHE-1724505