An Investigation of Chlorine Ligands in Transition-Metal Complexes via 35Cl Solid-State NMR and Density Functional Theory Calculations

35Cl solid state NMR (SSNMR), in tandem with 35Cl NQR and density functional theory calculations, was used to characterize chlorine ligands in a series of transition-metal complexes exhibiting structural motifs common to organometallic catalysts. The differentiation of the various chlorine environments was possible, and insight into the origins of the 35Cl electric field gradient tensor parameters was provided. The applicability of 35Cl SSNMR to the study of surface supported transition-metal complexes was demonstrated, validating the use of this technique in the characterization of heterogeneous catalysts

A Study of Transition-Metal Organometallic Complexes Combining 35 Cl Solid-State NMR Spectroscopy and 35 Cl NQR Spectroscopy and First-Principles DFT Calculations

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A Study of Transition-Metal Organometallic Complexes Combining 35Cl Solid-State NMR Spectroscopy and 35Cl NQR Spectroscopy and First-Principles DFT Calculations

A series of transition-metal organometallic complexes with commonly occurring metal-chlorine bonding motifs were characterized using 35Cl solid-state NMR (SSNMR) spectroscopy, 35Cl nuclear quadrupole resonance (NQR) spectroscopy, and first-principles density functional theory (DFT) calculations of NMR interaction tensors. Static 35Cl ultra-wideline NMR spectra were acquired in a piecewise manner at standard (9.4 T) and high (21.1 T) magnetic field strengths using the WURST-QCPMG pulse sequence. The 35Cl electric field gradient (EFG) and chemical shielding (CS) tensor parameters were readily extracted from analytical simulations of the spectra; in particular, the quadrupolar parameters are shown to be very sensitive to structural differences, and can easily differentiate between chlorine atoms in bridging and terminal bonding environments. 35Cl NQR spectra were acquired for many of the complexes, which aided in resolving structurally similar, yet crystallographically distinct and magnetically inequivalent chlorine sites, and with the interpretation and assignment of 35Cl SSNMR spectra. 35Cl EFG tensors obtained from first-principles DFT calculations are consistently in good agreement with experiment, highlighting the importance of using a combined approach of theoretical and experimental methods for structural characterization. Finally, a preliminary example of a 35Cl SSNMR spectrum of a transition-metal species (TiCl4) diluted and supported on non-porous silica is presented. The combination of 35Cl SSNMR and 35Cl NQR spectroscopy and DFT calculations is shown to be a promising and simple methodology for the characterization of all manner of chlorine-containing transition-metal complexes, in pure, impure bulk and supported forms. Fast and furious: A series of transition-metal organometallic complexes with commonly occurring metal-chlorine bonding motifs were characterized using a combination of 35Cl solid-state NMR (SSNMR) spectroscopy, 35Cl nuclear quadrupole resonance (NQR) spectroscopy and first-principles density functional theory (DFT) calculations. Static 35Cl ultra-wideline NMR spectra were rapidly acquired in a piecewise manner at high magnetic field strengths. Copyright \ua9 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Peer reviewed: YesNRC publication: Ye

An Investigation of Chlorine Ligands in Transition-Metal Complexes via ³⁵Cl Solid-State NMR and Density Functional Theory Calculations

Chlorine ligands in a variety of diamagnetic transition-metal (TM) complexes in common structural motifs were studied using ³⁵Cl solid-state NMR (SSNMR), and insight into the origin of the observed ³⁵Cl NMR parameters was gained through first-principles density functional theory (DFT) calculations. The WURST-CPMG pulse sequence and the variable-offset cumulative spectrum (VOCS) methods were used to acquire static ³⁵Cl SSNMR powder patterns at both standard (9.4 T) and ultrahigh (21.1 T) magnetic field strengths, with the latter affording higher signal-to-noise ratios (S/N) and reduced experimental times (i.e., <1 h). Analytical simulations were performed to extract the ³⁵Cl electric field gradient (EFG) tensor and chemical shift (CS) tensor parameters. It was found that the chlorine ligands in various bonding environments (i.e., bridging, terminal-axial, and terminal-equatorial) have drastically different ³⁵Cl EFG tensor parameters, suggesting that ³⁵Cl SSNMR is ideal for characterizing chlorine ligands in TM complexes. A detailed localized molecular orbital (LMO) analysis was completed for NbCl₅. It was found that the contributions of individual molecular orbitals must be considered to fully explain the observed EFG parameters, thereby negating simple arguments based on comparison of bond lengths and angles. Finally, we discuss the application of ³⁵Cl SSNMR for the structural characterization of WCl₆ that has been grafted onto a silica support material. The resulting tungsten-chloride surface species is shown to be structurally distinct from the parent compound