Synthesis, structural characterization and magnetic properties of RE2MgGe2 (RE=rare-earth metal)

Eleven new compounds in the RE–Cd–Ge systems (RE=Pr, Nd, Sm, Gd–Yb; Y): Crystal chemistry of the RE2CdGe2 series

“…Yb 2 CdGe 2 ) monotonically decrease from 7.4589(12) to 7.1829(12)Å and from 4.3456(13) to 4.1273(14)Å, respectively. Similar dependence is also reported for the isostructural RE 2 MgGe 2 [3,4] and RE 2 InGe 2 [5][6][7]. For Yb 2 CdGe 2 , the cell parameter a follows the lanthanide contraction, while its c parameter (4.169(3)Å) is anomalously larger-instead of being smaller than Tm 2 CdGe 2 (c¼4.1273(14)Å), the value is actually between that of Dy 2 CdGe 2 (c¼4.1817(5)Å) and Ho 2 CdGe 2 (c ¼4.1580(19)Å).…”

“…For example, the Cd-Ge separation gradually decrease from 2.9745 (6) in Pr 2 CdGe 2 to 2.8442(12)Å in Yb 2 CdGe 2 . These distances are similar to the In-Ge distances in the RE 2 InGe 2 series (2.855(1)-2.941(1)Å) [5][6][7], as well as the Mg-Ge distances in the RE 2 MgGe 2 series and (2.8093(8)-2.9500(5)Å) [3,4]. They are all little longer than the sum of the Pauling's radii (r Ge ¼1.242Å; r Cd ¼1.382Å; r In ¼1.421Å; r Mg ¼1.364Å) [11] and are characteristic of very weak bonding interactions.…”

“…Such Ge-Ge distances are close to the sum of the Pauling's radius of the Ge atom and typify single Ge-Ge bonds, i.e., they are characteristic of strong covalent interactions [39]. Similar distances are observed many other rare-earth metal germanides containing Ge 2 dumbbells, such as RE 2 MgGe 2 (d Ge-Ge ¼2.5057(18)-2.5483(14)Å) [3,4], RE 2 InGe 2 (d Ge-Ge ¼2.504(5)-2.512(2)Å) [5][6][7], RE 3 Li 4 Ge 4 (d Ge-Ge ¼2.514(2)-2.524(2)Å) and RE 7 Li 8 Ge 10 (d Ge-Ge ¼ 2.528(2)-2.537(2)Å) [40], to name a few.…”

“…Among these, the rareearth metal (RE) containing phases are abundant and can be grouped into several large RE 2 MX 2 classes, where the most commonly seen M-elements are Mg, In, Sn and Pb (main-group), or Cd; the X-elements are typically late transition metals such as Cu, Ni, Au, Pd, Pt, and Rh. In some cases (including the archetype), 'X' can be a non-metallic element -Si or Ge -and several series such as RE 2 MgGe 2 [3,4], RE 2 InGe 2 [5][6][7], RE 2 MgSi 2 [8], RE 2 AlSi 2 [9], and RE 2 AlGe 2 [10] have already been identified. Having studied some of the RE 2 InGe 2 compounds in our own laboratory [5], and having considered the fact that Cd and In are frequently found to form RE 2 InX 2 and RE 2 CdX 2 with the same transition metals, we set out to investigate the possibility to synthesize the up till now unknown RE 2 CdGe 2 phases.…”

Synthesis and Structural Characterization of ACu9Tt4 (A = Ca, Sr, Ba, Eu; Tt = Si, Ge, Sn) – Tetragonally Distorted Ternary Variants of the Cubic NaZn13 Structure Type. Improved Structure Refinement of SrCu2Ge2

“…and indicate strong covalency of the Ge–Ge interactions. Similar distances are observed for many other binary and ternary alkaline‐earth and rare‐earth ( RE ) metal germanides, such as Sm 3 Ge 5 [2.543(1) Å],47 RE 2 MgGe 2 [ d Ge–Ge = 2.506(2)–2.548(1) Å],48 RE 2 InGe 2 [ d Ge–Ge = 2.504(5)–2.512(2) Å],49 the Zintl phases Ca 5 Ge 3 [2.575(2) Å],50 CaGe 2 [2.541(2) Å],51 and EuGe 2 [2.564(4) Å] 52. En contraire, the refined by Schäfer et al Ge–Ge distance in SrCu 2 Ge 2 25 is 2.701 Å – much longer than the one from our refinements, and clearly outside the range for Ge–Ge single bonds.…”