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

作者：O' Keefe Christopher A; Johnston Karen E; Sutter Kiplangat; Autschbach Jochen; Gauvin Regis; Trebosc Julien; Delevoye Laurent; Popoff Nicolas; Taoufik Mostafa; Oudatchin Konstantin; Schurko Robert W^*

来源：Inorganic Chemistry, 2014, 53(18): 9581-9597.

DOI：10.1021/ic501004u

Chlorine ligands in a variety of diamagnetic transition-metal (TM) complexes in common structural motifs were studied using Cl-35 solid-state NMR (SSNMR), and insight into the origin of the observed Cl-35 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 Cl-35 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., %26lt;1 h). Analytical simulations were performed to extract the Cl-35 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 Cl-35 EFG tensor parameters, suggesting that Cl-35 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 Cl-35 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.

• 出版日期2014-9-15