Solid-State 91Zr NMR of Bis(cyclopentadienyl)dichlorozirconium(IV)

The first solid-state 91 Zr NMR spectra of an organometallic zirconium complex, bis(cyclopentadienyl)dichlorozirconium(IV) (Cp 2 ZrCl 2 ), are presented. Overlapping static and magic-angle spinning (MAS) 91 Zr NMR spectra of Cp 2 ZrCl 2 and a zirconium oxide NMR rotor are presented to explore the possibility of conducting 91 Zr NMR experiments using standard ZrO 2 rotors. Quadrupolar Carr−Purcell Meiboom−Gill (QCPMG) 91 Zr NMR experiments on static and MAS samples, in combination with analytical and numerical spectral simulations, are used to extract 91 Zr quadrupolar coupling constants and asymmetry parameters. The first example of zirconium chemical shielding anisotropy is reported for Cp 2 ZrCl 2, with a span of Ω = 475(45) ppm and a skew of −0.55(5) (i.e., δ 11 = 306 ppm, δ 22 = −62 ppm, and δ 33 = −169 ppm). Comparison of conventional static and MAS 91 Zr Hahn echo NMR spectra with those acquired using the recently reported double frequency sweep/QCPMG and rotor-assisted population transfer/QCPMG pulse sequences demonstrate an order of magnitude gain in sensitivity for Cp 2 ZrCl 2 . Restricted Hartree−Fock and hybrid density functional theory calculations reveal that anisotropic zirconium chemical shielding tensors can be calculated with good accuracy using non-relativistic theory with large all-electron basis sets. The 91 Zr quadrupolar parameters for Cp 2 ZrCl 2 are C Q = 6.35(10) MHz and η Q = 0.3(1). Reasonable agreement is obtained between calculated 91 Zr electric field gradient tensors and experimental results.