Lanthanide-Centered Polyoxoalkoxide Complexes Provide a Platform for Systematic Room- and Variable-Temperature Nuclear Magnetic Resonance Studies

High Resolution Image Download MS PowerPoint Slide A single, high-yielding approach was employed to synthesize the complete series of lanthanide (Ln) containing polyoxoalkoxide sandwich-type complexes (TBA) 3 [M{Mo 5 O 13 (OMe) 4 NO} 2 ] (M = La–Lu, except Pm ). The complexes were characterized by solution-state 1 H/ 17 O NMR spectroscopy, infrared spectroscopy, cyclic voltammetry, and electronic absorption spectroscopy, while the new derivatives (M = Tm, Yb, Lu, and Y) were also characterized using single crystal X-ray diffraction experiments. Compared to similar [Ln(W 5 O 18 ) 2 ] 9– or [Ln(PW 11 O 39 ) 2 ] 11– series, the presence of large noncoordinating tetrabutylammonium cations makes this series unique in that all (TBA) 3 [M{Mo 5 O 13 (OMe) 4 NO} 2 ] complexes are isostructural in the solid-state, with no changes in crystal packing or polymorph across the series. Solution-state NMR investigations reveal large Ln induced shifts (ca. 100–2000 ppm) for 17 O nuclei directly bound to the Ln center. Variable temperature 17 O NMR spectroscopy reveals that the chemical shift these oxygen nuclei show significant temperature dependence, opening the door to 17 O NMR thermometry with Ln containing polyoxometalates.