Synthesis and Characterization of a Terminal Iron(II)–PH₂ Complex and a Series of Iron(II)–PH₃ Complexes

Reported is the reaction of a series of iron(II) bisphosphine complexes with PH3 in the presence of NaBArF4 [where BArF4 = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate]. The iron(II) bisphosphine reagents bear two chlorides or a hydride and a chloride motif. We have isolated six different cationic terminal-bound PH3 complexes and undertaken rigorous characterization by NMR spectroscopy, single crystal X-ray diffraction, and mass spectrometry, where the PH3 often remains intact during the ionization process. Unusual bis- and tris-PH3 complexes are among the compounds isolated. Changing the monophosphine from PH3 to PMe3 results in the formation of an unusual Fe7 cluster, but with no PMe3 being ligated. Finally, by using an iron(0) source, we have provided a rare example of a terminally bound iron–PH2 complex

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

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