Tunable Binding of Dinitrogen to a Series of Heterobimetallic Hydride Complexes

The reaction of [Ru­(H)₂(N₂)₂(PCy₃)₂] (<b>1</b>) with β-diketiminate stabilized hydrides of Al, Zn, and Mg generates a series of new heterobimetallic complexes with either H₂ or N₂ ligated to the ruthenium center. Changing the main-group fragment of the <b>M·Ru-N</b>_<b>2</b> (M = Al, Zn, Mg) complexes can subtly alter the degree of binding, and therefore activation, of the diatomic ligand, as evidenced by the ν_NN absorptions in the infrared data. Experimental and computational data rationalize this tunable binding; decreasing the electronegativity of the main group in the order Al > Zn > Mg infers greater ionic character of these <b>M·Ru-N</b>_<b>2</b> complexes, and this in turn results in greater destabilization of the frontier molecular orbitals of ruthenium and therefore greater Ru­(4d) → π*­(N₂) back-donation

Insertion of CO₂ and COS into Bi–C Bonds: Reactivity of a Bismuth NCN Pincer Complex of an Oxyaryl Dianionic Ligand, [2,6-(Me₂NCH₂)₂C₆H₃]Bi(C₆H₂^<i>t</i>Bu₂O)

The reactivity of the unusual oxyaryl dianionic ligand, (C₆H₂^<i>t</i>Bu₂-3,5-O-4)^2–, in the Bi³⁺ NCN pincer complex Ar′Bi­(C₆H₂^<i>t</i>Bu₂-3,5-O-4), <b>1</b>, [Ar′ = 2,6-(Me₂NCH₂)₂C₆H₃] has been explored with small molecule substrates and electrophiles. The first insertion reactions of CO₂ and COS into Bi–C bonds are observed with this oxyaryl dianionic ligand complex. These reactions generate new dianions that have quinoidal character similar to the oxyaryl dianionic ligand in <b>1</b>. The oxyarylcarboxy and oxyarylthiocarboxy dianionic ligands were identified by X-ray crystallography in Ar′Bi­[O₂C­(C₆H₂^<i>t</i>Bu₂-3-5-O-4)-κ²O,O′], <b>2</b>, and Ar′Bi­[OSC­(C₆H₂^<i>t</i>Bu₂-3-5-O-4)-κ²O,S], <b>3</b>, respectively. Silyl halides and pseudohalides, R₃SiX (X = Cl, CN, N₃; R = Me, Ph), react with <b>1</b> by attaching X to bismuth and R₃Si to the oxyaryl oxygen to form Ar′Bi­(X)­(C₆H₂^<i>t</i>Bu₂-3,5-OSiR₃-4) complexes, a formal addition across five bonds. These react with additional R₃SiX to generate Ar′BiX₂ complexes and R₃SiOC₆H₃^<i>t</i>Bu₂-2,6. The reaction of <b>1</b> with I₂ forms Ar′BiI₂ and the coupled quinone, 3,3′,5,5′-tetra-<i>tert</i>-butyl-4,4′-diphenoquinone, by oxidative coupling

Mild sp²Carbon–Oxygen Bond Activation by an Isolable Ruthenium(II) Bis(dinitrogen) Complex: Experiment and Theory

The isolable ruthenium­(II) bis­(dinitrogen) complex [Ru­(H)₂(N₂)₂(PCy₃)₂] (<b>1</b>) reacts with aryl ethers (Ar–OR, R = Me and Ar) containing a ketone directing group to effect sp²C–O bond activation at temperatures below 40 °C. DFT studies support a low-energy Ru­(II)/Ru­(IV) pathway for C–O bond activation: oxidative addition of the C–O bond to Ru­(II) occurs in an asynchronous manner with Ru–C bond formation preceding C–O bond breaking. Alternative pathways based on a Ru(0)/Ru­(II) couple are competitive but less accessible due to the high energy of the Ru(0) precursors. Both experimentally and by DFT calculations, sp²C–H bond activation is shown to be more facile than sp²C–O bond activation. The kinetic preference for C–H bond activation over C–O activation is attributed to unfavorable approach of the C–O bond toward the metal in the selectivity determining step of the reaction pathway

Mild sp²Carbon–Oxygen Bond Activation by an Isolable Ruthenium(II) Bis(dinitrogen) Complex: Experiment and Theory

The isolable ruthenium­(II) bis­(dinitrogen) complex [Ru­(H)₂(N₂)₂(PCy₃)₂] (<b>1</b>) reacts with aryl ethers (Ar–OR, R = Me and Ar) containing a ketone directing group to effect sp²C–O bond activation at temperatures below 40 °C. DFT studies support a low-energy Ru­(II)/Ru­(IV) pathway for C–O bond activation: oxidative addition of the C–O bond to Ru­(II) occurs in an asynchronous manner with Ru–C bond formation preceding C–O bond breaking. Alternative pathways based on a Ru(0)/Ru­(II) couple are competitive but less accessible due to the high energy of the Ru(0) precursors. Both experimentally and by DFT calculations, sp²C–H bond activation is shown to be more facile than sp²C–O bond activation. The kinetic preference for C–H bond activation over C–O activation is attributed to unfavorable approach of the C–O bond toward the metal in the selectivity determining step of the reaction pathway

Mild sp²Carbon–Oxygen Bond Activation by an Isolable Ruthenium(II) Bis(dinitrogen) Complex: Experiment and Theory

The isolable ruthenium­(II) bis­(dinitrogen) complex [Ru­(H)₂(N₂)₂(PCy₃)₂] (<b>1</b>) reacts with aryl ethers (Ar–OR, R = Me and Ar) containing a ketone directing group to effect sp²C–O bond activation at temperatures below 40 °C. DFT studies support a low-energy Ru­(II)/Ru­(IV) pathway for C–O bond activation: oxidative addition of the C–O bond to Ru­(II) occurs in an asynchronous manner with Ru–C bond formation preceding C–O bond breaking. Alternative pathways based on a Ru(0)/Ru­(II) couple are competitive but less accessible due to the high energy of the Ru(0) precursors. Both experimentally and by DFT calculations, sp²C–H bond activation is shown to be more facile than sp²C–O bond activation. The kinetic preference for C–H bond activation over C–O activation is attributed to unfavorable approach of the C–O bond toward the metal in the selectivity determining step of the reaction pathway