Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, N9B 3P4 (Canada).
Chemistry. 2013 Sep 9;19(37):12396-414. doi: 10.1002/chem.201301268. Epub 2013 Aug 1.
A series of transition-metal organometallic complexes with commonly occurring metal-chlorine bonding motifs were characterized using (35)Cl solid-state NMR (SSNMR) spectroscopy, (35)Cl nuclear quadrupole resonance (NQR) spectroscopy, and first-principles density functional theory (DFT) calculations of NMR interaction tensors. Static (35)Cl 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 (35)Cl 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. (35)Cl 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 (35)Cl SSNMR spectra. (35)Cl 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 (35)Cl SSNMR spectrum of a transition-metal species (TiCl4) diluted and supported on non-porous silica is presented. The combination of (35)Cl SSNMR and (35)Cl 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.
采用（35）Cl 固态 NMR（SSNMR）光谱、（35）Cl 核四极共振（NQR）光谱和第一性原理密度泛函理论（DFT）计算 NMR 相互作用张量对一系列具有常见金属-氯键合模式的过渡金属有机金属配合物进行了表征。使用 WURST-QCPMG 脉冲序列，在标准（9.4 T）和高（21.1 T）磁场强度下，以分段方式获取（35）Cl 超宽带 NMR 谱。通过对光谱的分析模拟，很容易从（35）Cl 电场梯度（EFG）和化学位移（CS）张量参数中提取出来；特别是，四极参数对结构差异非常敏感，可以很容易地区分桥接和末端键合环境中的氯原子。许多配合物都获得了（35）Cl NQR 光谱，这有助于解析结构相似但结晶学上不同且磁不等价的氯原子，并对（35）Cl SSNMR 谱进行解释和分配。从第一性原理 DFT 计算中获得的（35）Cl EFG 张量与实验结果一致良好，这突出了理论和实验方法相结合用于结构表征的重要性。最后，给出了一个过渡金属物种（TiCl4）在非多孔二氧化硅上稀释和支撑的（35）Cl SSNMR 谱的初步实例。结果表明，（35）Cl SSNMR 和（35）Cl NQR 光谱与 DFT 计算相结合，是一种用于纯、不纯块状和支撑形式的各种含氯过渡金属配合物的特征描述的有前途且简单的方法。
