SiMe3 groups. For 1-La and 1-Ce cross-peaks were seen between δH(Si(CH3)3) and δSi(Si(CH3)3) for both the group 1 and group 2 SiMe3 groups, whereas for 1-Pr, 1-Nd and 1-U correlations were only observed for the group 1 SiMe3 groups, as the group 2 SiMe3 resonances were not observed by and Supporting Information Table for selected parameters, Figure for the Si ssNMR spectra, and Supporting Information Figures S35-S41 for all other spectra). Magic angle spinning (MAS) conditions were employed with spinning frequencies between 5 and 12 kHz; frequencies were selected depending on the sample to give adequate resolution and signal-to-noise ratios, while shifting the spinning side bands from the spectral regions of interest and limiting excessive spinning rates to avoid rotor crashes. The resolution (FWHM) of the Si ssNMR resonances did not change with MAS frequency (slow (5 kHz) vs. moderate (12 kHz) spinning), but the 1 H ssNMR spectral resolution varied dramatically as expected (see Supporting Information).