Koch Klaus R, Engelbrecht Leon
Department of Chemistry and Polymer Science, Stellenbosch University, P. Bag X1, Matieland, 7602, South Africa.
Dalton Trans. 2017 Jul 25;46(29):9303-9315. doi: 10.1039/c7dt01722g.
Well-resolved intrinsic ΔM(Cl) and ΔM(O) isotope shifts (where M = Pt or Rh) are visible in the Pt NMR peak profiles of relatively kinetically inert [PtCl(HO)] (n = 1-6) complexes, their corresponding hydroxido [PtCl(OH)] (n = 1-5/6) anions, and [RhCl(HO)] (n = 3-6) complexes in aqueous solutions at ca. 293 K. Although some such isotope effects have been previously reported, there are very limited published data in the open literature, and the first systematic studies of such intrinsic ΔM(Cl) and ΔM(O) isotope effects are reviewed in this perspective. In high magnetic-field NMR spectrometers, the Pt and Rh NMR peak profiles acquired within a relatively narrow temperature range (288-300 K) constitute unique 'spectroscopic fingerprints', which allow unambiguous structural assignment in solution. Available data for Pt(iv) and Rh(iii) complexes give rise to intrinsic isotope ΔδPt/Rh(Cl) profiles, which are extraordinarily sensitive to the structure of a particular complex or its geometric isomer. The profiles of aquated Pt(iv) and Rh(iii) complexes in acidic solutions may be resolved at either an isotopologue level only or at both an isotopologue and an isotopomer level depending on the structure. By contrast, in the series of [PtCl(OH)] (n = 1-6) anions, ΔδPt(Cl) isotope shifts are resolved only at an isotopologue level. Relatively larger ΔPt(O) isotope shifts obtained by the partial O enrichment of both the [PtCl(HO)] (n = 1-6) and [PtCl(OH)] (n = 1-6) series give rise to remarkable Pt NMR peak profiles showing both Cl and O shifts. In the [PtCl(OH)] (n = 1-5/6) anions a typical NMR peak profile spanning ∼2 ppm only may be resolved at both the isotopologue and isotopomer levels, depending on whether OH ions are coordinated trans to chloride ions or not. The potential utility of such ΔPt(Cl) and ΔPt(O) isotope shifts in selected practical applications involving such complexes is briefly illustrated.
在约293 K的水溶液中，相对动力学惰性的[PtCl(HO)]（n = 1 - 6）配合物、其相应的羟基[PtCl(OH)]（n = 1 - 5/6）阴离子以及[RhCl(HO)]（n = 3 - 6）配合物的Pt NMR峰谱中，可以看到分辨良好的本征ΔM(Cl)和ΔM(O)同位素位移（其中M = Pt或Rh）。尽管此前已报道过一些此类同位素效应，但公开文献中的已发表数据非常有限，本文将对此类本征ΔM(Cl)和ΔM(O)同位素效应的首次系统研究进行综述。在高磁场NMR光谱仪中，在相对较窄的温度范围（288 - 300 K）内采集的Pt和Rh NMR峰谱构成了独特的“光谱指纹”，这使得在溶液中能够明确进行结构归属。Pt(iv)和Rh(iii)配合物的现有数据产生了本征同位素ΔδPt/Rh(Cl)谱，其对特定配合物或其几何异构体的结构异常敏感。酸性溶液中水解的Pt(iv)和Rh(iii)配合物的谱可能仅在同位素异构体水平或在同位素异构体和同位素分子水平上都能分辨，这取决于结构。相比之下，在[PtCl(OH)]（n = 1 - 6）阴离子系列中，ΔδPt(Cl)同位素位移仅在同位素异构体水平上得以分辨。通过对[PtCl(HO)]（n = 1 - 6）和[PtCl(OH)]（n = 1 - 6）系列进行部分O富集获得的相对较大的ΔPt(O)同位素位移，产生了显示Cl和O位移的显著Pt NMR峰谱。在[PtCl(OH)]（n = 1 - 5/6）阴离子中，仅约2 ppm的典型NMR峰谱在同位素异构体和同位素分子水平上都可能分辨，这取决于OH离子是否与氯离子反位配位。本文简要说明了此类ΔPt(Cl)和ΔPt(O)同位素位移在涉及此类配合物的选定实际应用中的潜在用途。
