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.

Reversible Encapsulation of Xenon and CH2Cl2 in a Solid‐State Molecular Organometallic Framework (Guest@SMOM)

“…This resonance also shows across peak at d 3.05 in the 1 Hprojection of the 13 C/ 1 HFSLG HETCOR SSNMR [18] spectrum ( Figure S7). This resonance also shows across peak at d 3.05 in the 1 Hprojection of the 13 C/ 1 HFSLG HETCOR SSNMR [18] spectrum ( Figure S7).…”

J(Si,H) Coupling Constants in Nonclassical Transition‐Metal Silane Complexes

“…However,t he transition between classical and nonclassical silane complexes is ar ather continuous one and is mainly controlled by the electronic influence of the substituents at the silicon atom and the local electronic situation at the transition metal. [10] As pointed out by Corriou and co-workers, [13] the situation is further complicated by the fact that the observed total coupling constants J(Si,H) = 1 J(Si,H) + 2 J(Si,M,H) can be considered the result of two competing mechanisms,w hich provide coupling contributions of opposite sign to the total J(Si,H) values.I ndeed, as ac onsequence of the negative gyromagnetic ratio of the 29 Si nucleus (g = À53.2 10 6 rads À1 T À1 ), the corresponding signs of 1 J(Si,H) and 2 J(Si,M,H) are assumed to be negative and positive,r espectively,i nt he simple Dirac vector model. [10] As pointed out by Corriou and co-workers, [13] the situation is further complicated by the fact that the observed total coupling constants J(Si,H) = 1 J(Si,H) + 2 J(Si,M,H) can be considered the result of two competing mechanisms,w hich provide coupling contributions of opposite sign to the total J(Si,H) values.I ndeed, as ac onsequence of the negative gyromagnetic ratio of the 29 Si nucleus (g = À53.2 10 6 rads À1 T À1 ), the corresponding signs of 1 J(Si,H) and 2 J(Si,M,H) are assumed to be negative and positive,r espectively,i nt he simple Dirac vector model.…”

A Rhodium–Pentane Sigma‐Alkane Complex: Characterization in the Solid State by Experimental and Computational Techniques

“…Interestingly,[ 1b][BAr Figure S4) spectrum shows the disappearance of signals in the 100-60 ppm region, consistent with the hydrogenation of the diene.W eh ave previously shown the utility of 1 [13] following the use of similar techniques to identify agostic Ru···H À Si interactions in the solid state. [19] Calculations using the periodic GIPAW methodology indicate that the sÀRh···HÀCi nteractions (C2/4) correspond to d( 1 H) = À1.6/À2.5 ppm, and correlate to d( 13 C) = 7.3/9.9 ppm, respectively.T he central methylene group (C3) experiences ar ing current shift from proximal [BAr Figure S5-7). On temperature cycling between 223 Ka nd 158 K, there are no significant changes in the 31 P{ 1 H} NMR spectra.…”

“…, reflecting the lack of crystallographic symmetry in the molecule and that the two orientations of the diene do not interchange in the solid state on the SSNMR timescale (that is,s tatic disorder). Likewise,t he 13 C{ 1 H} SSNMR spectrum shows 7alkene resonances between d = 104 and 60 ppm, with the lowest field signal assigned to a1+ 1coincidence.Nohigh field signals,w hich would signal Rh···HÀCo rC ÀH···aryl interactions, [13,19] were observed in the 1 HNMR projection from af requency-switched Lee-Goldburg (FSLG) SSNMR experiment ( Figure S2 Figure 1B). Remarkably,t he refined structure of [3][BAr , R(2s) = 5.6 %).…”