17 research outputs found
Structure and Magnetic Properties of Homoleptic Trivalent Tris(alkyl)lanthanides
Six new solvent-free, homoleptic paramagnetic tris(alkyl)lanthanides
Ln{C(SiHMe2)3}3 (1Ln) and Ln{C(SiHMe2)2Ph}3 (2Ln) (Ln = Gd, Dy, and Er) were synthesized to investigate the magnetic
properties of 4f organometallic compounds stabilized by secondary
LnâŒHâSi and benzylic interactions. The unit cell of 1Gd contains one independent molecule (Z =
2), while 1Dy and 1Er crystallize with four
independent isostructural molecules per unit cell (Z = 16). In all molecules, as in other 1Ln compounds,
the three tris(dimethylsilyl)methyl ligands form a trigonal planar
LnC3 core, and six secondary interactions involving LnâŒHâSi
bonding in Ln{C(SiHMe2)3}3 form above
and below the equatorial plane. Two and five crystallographically
independent molecules of each 2Ln (2Gd, Z = 8; 2Dy, Z = 20) form with
three Ï-coordinated phenyl groups in addition to either one
or two secondary LnâŒHâSi interactions per molecule.
The packing of these midseries organolanthanide compounds contrasts
the single crystallographically unique molecules in previously reported
La{C(SiHMe2)3}3 (1La, Z = 2, ZâČ = 1) and La{C(SiHMe2)2Ph}3 (2La, Z = 2, ZâČ = 1/3). 2La doped with 2Dy can adopt the crystallographic structure of 2La, which promotes magnetic properties, namely a higher ÏmT value at low temperatures as well as stronger
magnetic anisotropy. The ac susceptibility data for 10% 2Dy doped into 2La suggests slow relaxation at low temperatures
with a relaxation barrier of âŒ45 K. The computed saturated
magnetization of 1Er (M â 4.5
ÎŒB) and 1Dy (M â
6 ÎŒB) matches the experimental values, while the
computed value for 2Dy better matches the value measured
for 2Dy diluted in 2La (M â 5 ÎŒB). Gas-phase calculations predict
that the ground-state and first excited-state multiplet separations
are larger for 1Er than 2Er, while the ordering
for dysprosium is 1Dy > 2Dy