LnP''3_Research Data.zip

Lanthanide (Ln) magnetic resonance imaging and chiral shift reagents generally exploit ¹H NMR shifts, as paramagnetic broadening tends to preclude the use of heavier, less sensitive nuclei. Here we report the solution and solid-state ³¹P NMR shifts of an isostructural series of distorted trigonal bipyramidal Ln(III) <i>tris</i>-silylphosphide complexes, [Ln{P(SiMe₃)₂}₃(THF)₂] (1-Ln; Ln = La, Ce, Pr, Nd, Sm); 1-Ln were also characterized by elemental analysis, single crystal and powder X-ray diffraction, multinuclear NMR, EPR, ATR-IR, and UV-Vis-NIR spectroscopy, and SQUID magnetometry. Breaking assumptions, we observed paramagnetic broadened ³¹P NMR shifts for the Ln-bound P atoms for all the 1-Ln family; in solution 1-Nd showed the most downfield chemical shift (δ{³¹P} = 2570.14 ppm) and 1-Sm the most upfield value (δ{³¹P} = –259.21 ppm). We determined the span of the chemical shift anisotropies (CSA) for solid 1-Ln using magic angle spinning NMR spectroscopy; the CSA was largest for 1-Pr ({³¹P} ≈ 2000 ppm), consistent with a combination of paramagnetism and the relatively large differences in pyramidalization of the three P atoms in the solid-state. Density functional theory calculations on 1-La were in excellent agreement with the experimentally-determined ³¹P NMR shift and CSA. We find good agreement of experimental ¹H NMR chemical shifts with <i>ab initio</i>-calculated values for paramagnetic 1-Ln, whilst the shifts and CSA of heavier ¹³C, ²⁹Si and ³¹P nuclei are not well-reproduced due to the current limitations of paramagnetic NMR calculations for heavier nuclei with large contact shifts.