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

Katharine Smart (1) , Mary Grellier (1) , Yannick Coppel (1) , Laure Vendier (1) , S. A. Mason (2) , S. C. Capelli (2) , A. Albinati (3) , V. Montiel-Palma (4) , M. A. Muñoz-Hernández (4) , Sylviane Sabo-Etienne (1)

1 LCC - Laboratoire de chimie de coordination
2 ILL - Institut Laue-Langevin
3 Dipartimento di Chimica
4 Centro de Investigaciones Químicas

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 (1H wPMLG, 29Si CP MAS, and 2D 1H-29Si dipolar HETCOR experiments) and solution NMR studies. The corresponding intermediate complexes, [Ru{κ-Si,N-(SiMe2-N-heterocycle)}(η4-C8H12)(η3-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)(η2-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.

Domaines: Chimie de coordination; Catalyse

Katharine Smart, Mary Grellier, Yannick Coppel, Laure Vendier, S. A. Mason, et al.. Nature of Si-H Interactions in a Series of Ruthenium Silazane Complexes Using Multinuclear Solid-State NMR and Neutron Diffraction. Inorganic Chemistry, 2014, 53 (2), pp.1156-1165. ⟨10.1021/ic4027199⟩. ⟨hal-00992447⟩