Virginia Montiel-Palma

Nature of Si–H Interactions in a Series of Ruthenium Silazane Complexes Using Multinuclear Solid-State NMR and Neutron Diffraction

Three new N-heterocyclic-silazane compounds, 1a-c, were prepared and employed as bidentate ligands to ruthenium, resulting in a series of [Ru(H){(κ-Si,N-(SiMe2-N-heterocycle)}3] complexes (3a-c) featuring the same RuSi3H motif. Detailed structural characterization of the RuSi3H complexes with X-ray diffraction, and in the case of triazabicyclo complex [Ru(H){κ-Si,N-(SiMe2)(C7H12N3)}3] (3a), neutron diffraction, enabled a reliable description of the molecular geometry. The hydride ligand of (3a) is located closer to two of the silicon atoms than it is to the third. Such a geometry differs from that of the previously reported complex [Ru(H){(κ-Si,N-(SiMe2)N(SiMe2H)(C5H4N)}3] (3d), also characterized by neutron diffraction, where the hydride was found to be equidistant from all three silicon atoms. A DFT study revealed that the symmetric and less regular isomers are essentially degenerate. Information on the dynamics and on the Ru···H···Si interactions was gained from multinuclear solid-state ((1)H wPMLG, (29)Si CP MAS, and 2D (1)H-(29)Si dipolar HETCOR experiments) and solution NMR studies. The corresponding intermediate complexes, [Ru{κ-Si,N-(SiMe2-N-heterocycle)}(η(4)-C8H12)(η(3)-C8H11)] (2a-c), involving a single silazane ligand were isolated and characterized by multinuclear NMR and X-ray diffraction. Protonation of the RuSi3H complexes was also studied. Reaction of 3a with NH4PF6 gave rise to [Ru(H)(η(2)-H -SiMe2)κ-N-(C7H12N3){κ-Si,N-(SiMe2)(C7H12N3)}2](+)[PF6](-)(4aPF6) which was isolated and characterized by NMR spectroscopy, X-ray crystallography, and DFT studies. The nature of the Si-H interactions in this silazane series was analyzed in detail.

Phosphinodi(benzylsilane) PhP{(o-C6H4CH2)SiMe2H}2: A Versatile “PSi2Hx” Pincer-Type Ligand at Ruthenium

The synthesis of the new phosphinodi(benzylsilane) compound PhP{(o-C6H4CH2)SiMe2H}2 (1) is achieved in a one-pot reaction from the corresponding phenylbis(o-tolylphosphine). Compound 1 acts as a pincer-type ligand capable of adopting different coordination modes at Ru through different extents of Si-H bond activation as demonstrated by a combination of X-ray diffraction analysis, density functional theory calculations, and multinuclear NMR spectroscopy. Reaction of 1 with RuH2(H2)2(PCy3)2 (2) yields quantitatively [RuH2{[η(2)-(HSiMe2)-CH2-o-C6H4]2PPh}(PCy3)] (3), a complex stabilized by two rare high order ε-agostic Si-H bonds and involved in terminal hydride/η(2)-Si-H exchange processes. A small free energy of reaction (ΔrG298 = +16.9 kJ mol(-1)) was computed for dihydrogen loss from 3 with concomitant formation of the 16-electron species [RuH{[η(2)-(HSiMe2)-CH2-o-C6H4]PPh[CH2-o-C6H4SiMe2]}(PCy3)] (4). Complex 4 features an unprecedented (29)Si NMR decoalescence process. The dehydrogenation process is fully reversible under standard conditions (1 bar, 298 K).

Bonding Mode of a Bifunctional P∼Si−H Ligand in the Ruthenium Complex “Ru(PPh2CH2OSiMe2H)3”

The phosphinosilane compound PPh 2CH 2OSiMe 2H is potentially a bifunctional P approximately Si-H ligand. By treatment with the Ru (II) precursor RuH 2(H 2) 2(PCy 3) 2, the complex Ru(PPh 2CH 2OSiMe 2H) 3 ( 2), resulting from the coordination of three ligands and the displacement of two PCy 3 and two dihydrogen ligands, was formed. The different bonding modes for each of the three bifunctional P approximately Si-H ligands are discussed on the basis of multinuclear NMR, X-ray diffraction, and density functional theory studies. One ligand acts as a monodentate phosphine ligand with a pendant Si-H group, whereas the two others act as bidentate ligands with different Si-H bond activations. Indeed, an intermediate structure between two arrested forms 2a and 2b can be proposed: a dihydrido(disilyl)ruthenium(IV) species (form 2a) resulting from two Si-H oxidative additions or a hydrido(silyl)ruthenium(II) species (form 2b) presenting an agostic Si-H bond and only one oxidative addition.

Semirigid Pincer-Like SiPSi Ligands

Abstract While the majority of the reported transition metal systems bonded to silylphosphines have focused on the combination of one Si with either one, two or three phosphorus atoms, semirigid multi-silyl phosphine designs remain largely unexplored. This chapter focuses on a pincer-like silylphosphine system, SiPSi , in which the flexibility of the ligand is increased by adding two extra methylene groups on the otherwise rigid phosphine. These changes furnish upon complexation either non classical agostic M-η 2 -(Si-H) bonds or proceed via oxidative addition to κ 1 -Si-M-H core structures. The semirigid pincer-like SiPSi ligand [Ph P ( o -C 6 H 4 -CH 2 Si Me 2 H) 2 ] and its related tetradentade SiPSi-Si ligand [ P ( o -C 6 H 4 -CH 2 Si Me 2 H) 3 ] can adopt either meridional (Pt) as in pincer complexes or facial (Ru, Rh, Ir) arrangements depending on the choice of ancillary ligands and the metal. Full oxidative addition of the Si-H bonds or non classical coordination modes can be achieved.

CCDC 947557: Experimental Crystal Structure Determination

Related Article: Katharine A. Smart, Mary Grellier, Laure Vendier, Sax A. Mason, Silvia C. Capelli, Alberto Albinati, Virginia Montiel-Palma, Miguel A. Munoz-Hernandez, Sylviane Sabo-Etienne|2014|Inorg.Chem.|53|1156|doi:10.1021/ic4027199

Two photochemical pathways in competition: matrix isolation, time-resolved and NMR studies of cis-[Ru(PMe3)4(H)2]

cis-[Ru(PMe3)4(H)2] (1) reacts by two distinct photochemical pathways resulting in the formation of [Ru(PMe3)4] and [Ru(PMe3)3(H)2]; derivatives of these intermediates are generated in the presence of CO and Ph2SiH2.