Solid-State Ru-99 NMR Spectroscopy:  A Useful Tool for Characterizing Prototypal Diamagnetic Ruthenium Compounds

Abstract

The feasibility of (99)Ru NMR spectroscopy as a tool to characterize solid compounds is demonstrated. Results of the first solid-state (99)Ru NMR investigation of diamagnetic compounds are presented for Ru(NH(3))(6)Cl(2), K(4)Ru(CN)(6). xH(2)O (x = 0, 3), LaKRu(CN)(6), and Ru(3)(CO)(12). The sensitivity of the ruthenium magnetic shielding tensor to subtle changes in the local structure about the ruthenium nucleus is highlighted by comparing the (99)Ru isotropic chemical shift of Ru(NH(3))(6)Cl(2) in aqueous solutions and in the solid state. The narrow isotropic (99)Ru NMR peak observed for solid Ru(NH(3))(6)Cl(2) indicates that this compound is an ideal secondary reference sample for solid-state (99)Ru NMR studies. The isotropic (99)Ru chemical shift, (99)Ru nuclear quadrupolar coupling constant, C(Q), and quadrupolar asymmetry parameter of K(4)Ru(CN)(6). xH(2)O (x = 0, 3) are shown to be sensitive to x. For Ru(3)(CO)(12), the magnetic shielding tensors of each of the three nonequivalent Ru nuclei have spans of 1300-1400 ppm, and the (99)Ru C(Q) values are also similar, 1.36-1.85 MHz, and are surprisingly small given that (99)Ru has a moderate nuclear quadrupole moment. Information about the relative orientation of the Ru magnetic shielding and electric field gradient tensors has been determined for Ru(3)(CO)(12) from experimental (99)Ru NMR spectra as well as quantum chemical calculations.

Analysis of electric field gradient tensors at quadrupolar nuclei in common structural motifs

“…The most notable disagreements between experimental and theoretical values of V 33 occur for the EFG calculations in the transition metal complexes. The less than stellar performance of DFT for calculating EFGs of transition metal atoms has previously been noted for molecular (78)(79)(80)(81) and band structure computations (82). For 3d metals the evidence points to deficiencies in the functionals as the main reason for poor agreement with experiment.…”

“…We first discuss three Ru complexes with moderate-to-large field gradients. Calculations and experiments to determine Ru quadrupole coupling constants were previously performed by Bühl et al (87) and Ooms et al (80). (See also Ref.…”

Separation of 47Ti and 49Ti solid-state NMR lineshapes by static QCPMG experiments at multiple fields

“…Previously, the QCPMG experiment has proved valuable when low-c nuclei are of interest [16][17][18][19][20][21][22][23][24][25] and in the present work isotope-selective QCPMG experiments are presented that facilitate observation of either 47 Ti or 49 Ti lineshapes in anatase and rutile with Ti in natural abundance. We envisage that the application of this technique will also facilitate the acquisition of Ti spectra of disordered materials where two isotopic contributions can complicate spectra severely.…”

Density functional computations of 99Ru chemical shifts: relativistic effects, influence of the density functional, and study of solvent effects on fac—[Ru(CO)3I3]−

“…Although the receptivity of 101 Ru is about twice as high as that of 99 Ru, the latter is generally preferred for NMR experiments because of its smaller quadrupole moment (7.9 fm 2 vs 45.7 fm 2 ). 3 According to a recent paper by Ooms and Wasylishen, 3 before late 2004 there were only 17 articles published reporting 99 Ru NMR experiments. 1,2,4 -18 This small number of publications is in marked contrast to the outstanding importance of Ru in modern chemistry.…”