Density-functional computation of Nb-93 NMR chemical shifts

作者：Buehl Michael; Wrackmeyer Bernd

来源：Magnetic Resonance in Chemistry, 2010, 48: S61-S68.

DOI：10.1002/mrc.2624

• NMR
• Nb-93
• density-functional calculations
• chemical-shift computations
• electric field gradient

Nb-93 chemical shifts of [NbX6](-) (X = Cl, F, CO), [NbXCl4](-) (X = O, S), Nb-2(OMe)(10), Cp*Nb-2(kappa(2)-BH4), (Cp*Nb)(2)(mu-B2H6)(2), CpNb(CO)(4), and Cp2NbH3 are computed at the GIAO (gauge-including atomic orbitals)-, BPW91- and B3LYP-, and CSGT (continuous set of gauge transformations)-CAM-B3LYP, -omega B97, and -omega B97X levels, using BP86-optimized or experimental (X-ray) geometries. Experimental chemical shifts are best reproduced at the GIAO-BPW91 level when delta(Nb-93) values of inorganic complexes are referenced directly relative to (NbC16)- and those of organometallic species are first calculated relative to [Nb(CO)(6)](-). An inadvertent error in the reported delta(Nb-93) values of cyclopentadiene borane complexes (H. Brunner et al., J. Organomet. Chem. 1992, 436, 313) is corrected. Trends in the observed Nb-93 NMR linewidths for anionic niobates [Nb(CO)(5)](3-), [Nb(CO)(5)H](2-), and [Nb(CO)(5)(NH3)](-) are rationalized in terms of computed electric field gradients at the metal.

• 出版日期2010-12