Structure and Magnetic Properties of Homoleptic Trivalent Tris(alkyl)lanthanides.

Six new solvent-free, homoleptic paramagnetic tris(alkyl)lanthanides Ln{C(SiHMe)} () and Ln{C(SiHMe)Ph} () (Ln = Gd, Dy, and Er) were synthesized to investigate the magnetic properties of 4f organometallic compounds stabilized by secondary Ln↼H-Si and benzylic interactions. The unit cell of contains one independent molecule ( = 2), while and crystallize with four independent isostructural molecules per unit cell ( = 16). In all molecules, as in other compounds, the three tris(dimethylsilyl)methyl ligands form a trigonal planar LnC core, and six secondary interactions involving Ln↼H-Si bonding in Ln{C(SiHMe)} form above and below the equatorial plane.

Suppressing H Spin Diffusion in Fast MAS Proton Detected Heteronuclear Correlation Solid-State NMR Experiments.

Fast magic angle spinning (MAS) and indirect detection by high gyromagnetic ratio (γ) nuclei such as proton or fluorine are increasingly utilized to obtain 2D heteronuclear correlation (HETCOR) solid-state NMR spectra of spin-1/2 nuclei by using cross polarization (CP) for coherence transfer. However, one major drawback of CP HETCOR pulse sequences is that H spin diffusion during the back X→H CP transfer step may result in relayed correlations. This problem is particularly pronounced for the indirect detection of very low-γ nuclei such as Y, Rh, Ag and W where long contact times on the order of 10-30 ms are necessary for optimal CP transfer.

Rare earth arylsilazido compounds with inequivalent secondary interactions.

A new bulky silazido ligand, -N(SiHMe2)Dipp (Dipp = C6H3-2,6-iPr2), supports planar, three-coordinate homoleptic rare earth complexes Ln{N(SiHMe2)Dipp}3 (Ln = Sc, Y, and Lu), each containing three secondary Ln↼HSi interactions and one agostic CH bond. Y{N(SiHMe2)Dipp}3 and acetophenone react via hydrosilylation, rather than by insertion into the Y-N bond or by enolate formation.

Enhancing the Sensitivity of Solid-State NMR Experiments with Very Low Gyromagnetic Ratio Nuclei with Fast Magic Angle Spinning and Proton Detection.

Many transition metals commonly encountered in inorganic materials and organometallic compounds possess NMR-active nuclei with very low gyromagnetic ratios (γ) such as Y, Rh, Ag, and W. A low-γ leads to poor NMR sensitivity and other experimental challenges. Consequently, nuclei with low-γ are often impossible to study with conventional solid-state NMR methods.

Direct O dynamic nuclear polarization of single-site heterogeneous catalysts.

We utilize direct 17O DNP for the characterization of non-protonated oxygens in heterogeneous catalysts. The optimal sample preparation and population transfer approach for 17O direct DNP experiments performed on silica surfaces is determined and applied to the characterization of Zr- and Y-based mesoporous silica-supported single-site catalysts.

Homoleptic organolanthanide compounds supported by the bis(dimethylsilyl)benzyl ligand.

A β-SiH functionalized benzyl anion [C(SiHMe)Ph] is obtained by deprotonation of HC(SiHMe)Ph with KCHPh or by reaction of KOtBu and (MeHSi)CPh; LnI(THF) and three equivalents of this carbanion combine to provide homoleptic tris(alkyl)lanthanide compounds Ln{C(SiHMe)Ph} (Ln = La, Ce, Pr, Nd) containing secondary metal-ligand interactions.