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. Two and five crystallographically independent molecules of each (, = 8; , = 20) form with three π-coordinated phenyl groups in addition to either one or two secondary Ln↼H-Si interactions per molecule. The packing of these midseries organolanthanide compounds contrasts the single crystallographically unique molecules in previously reported La{C(SiHMe)} (, = 2, ' = 1) and La{C(SiHMe)Ph} (, = 2, ' = 1/3). doped with can adopt the crystallographic structure of , which promotes magnetic properties, namely a higher χ value at low temperatures as well as stronger magnetic anisotropy. The ac susceptibility data for 10% doped into suggests slow relaxation at low temperatures with a relaxation barrier of ∼45 K. The computed saturated magnetization of ( ≈ 4.5 μ) and ( ≈ 6 μ) matches the experimental values, while the computed value for better matches the value measured for diluted in ( ≈ 5 μ). Gas-phase calculations predict that the ground-state and first excited-state multiplet separations are larger for than , while the ordering for dysprosium is > .