Density-functional computation of 99Ru NMR parameters

Gradient-corrected and hybrid variants of density-functional theory are used to compute the geometries and 99Ru chemical shifts of RuO4, RuCp2], K4Ru(CN)6], Ru3(CO)12], Ru(CO)3X3]- (X=Cl, I), Ru(CO)2Cl4]2-, Ru(bipy)3]2+, and Ru(CO)2(iPr-DAB)(X)(Y)] XY= Cl2, I2, MeCl, MeI, or (SnMe3)2]. For this set of compounds, substituent effects on delta(99Ru) are somewhat underestimated with the BPW91 pure density functional but are described well by the B3LYP hybrid functional, which can also be used to reproduce empirical trends in electric field gradients (EFGs) at the Ru nucleus qualitatively. In the Ru(CO)2(iPr-DAB)XY] series, trends in the computed EFGs parallel those in the observed 99Ru NMR linewidths, in accordance with the quadrupolar relaxation mechanism expected for this nucleus. For this series of compounds, the use of X-ray-derived geometries affords a worse correlation between calculated EFGs and experimental linewidths than does the use of optimized geometries.