title: Nature of Si-H interactions in a series of ruthenium silazane complexes using multinuclear solid-state NMR and neutron diffraction.
abstract: 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.
authors.affiliation: LCC (Laboratoire de Chimie de Coordination), CNRS , 205 Route de Narbonne, F-31077 Toulouse, France.
authors.forename: Katharine A
authors.initials: KA
authors.lastname: Smart
authors.forename: Mary
authors.initials: M
authors.lastname: Grellier
authors.forename: Yannick
authors.initials: Y
authors.lastname: Coppel
authors.forename: Laure
authors.initials: L
authors.lastname: Vendier
authors.forename: Sax A
authors.initials: SA
authors.lastname: Mason
authors.forename: Silvia C
authors.initials: SC
authors.lastname: Capelli
authors.forename: Alberto
authors.initials: A
authors.lastname: Albinati
authors.forename: Virginia
authors.initials: V
authors.lastname: Montiel-Palma
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Muñoz-Hernández
authors.forename: Sylviane
authors.initials: S
authors.lastname: Sabo-Etienne