Eu₂(CN₂)₃ and KEu[Si(CN₂)₄]: Missing Members of the Rare Earth Metal Carbodiimide and Tetracyanamidosilicate Series

Abstract

Compounds (III) and (V) are prepared by solid state metathesis reactions and characterized by powder XRD, photoluminescence, and nonlinear optical measurements.

Missing Carbodiimide and Oxide Carbodiimide of Scandium: Sc2(CN2)3 and Sc2O2(CN2)

“…Tm 2 (CN 2 ) 3 is dimorphic, and the monoclinic modification was obtained by applying mechanical pressure on the rhombohedral phase of Tm 2 (CN 2 ) 3 . Structures of the rhombohedral modifications with RE = Tm, Yb and Lu exhibit significantly larger unit cell volumes and the lower coordination number six of cations, compared to their monoclinic homologues with coordination numbers of seven . The unit cell volume of Sc 2 (CN 2 ) 3 is smaller than the other trigonal‐rhombohedral RE 2 (CN 2 ) 3 (RE = Tm, Yb, Lu) members.…”

“…The majority of the rare earth carbodiimides RE 2 (CN 2 ) 3 were synthesized by a SSM reaction of Li 2 (CN 2 ) with RECl 3 . Analogous to the previously reported syntheses of carbodiimides, Sc 2 (CN 2 ) 3 was prepared according to the following Equation (1): …”

“…Over the last two decades, numerous rare earth metal (RE) carbodiimides were discovered and structurally characterized . Compounds having formulas like RE 2 (CN 2 ) 3 , RE 2 O 2 (CN 2 ), RE 2 O(CN 2 ) 2 , REX(CN 2 ), RE 2 X 2 (CN 2 ) with X = F, Cl or I and more are known. Due to the mild conditions of solid‐state metathesis (SSM) reactions, it was possible to synthesize various new rare earth carbodiimides, even those that are thermally labile …”

Crystallization of the Fundamental Tetracyanamidometallates Li4[Si(CN2)4] and Li4[Ge(CN2)4] from Polymeric Li‐T‐(NCN)‐I Precursors (T=Si, Ge)

“…Representative pseudo-binary members are characterized as M(CN 2 ) and M 2 (CN 2 ) 3 with M being a main group metal (e. g. Ca, [7] In, [8] Sn, [6] or Bi [9] ), a transition metal (e. g. Zr, Hf, [10,11] Cr, [12] Mn, [13] Fe, [14] Co, Ni [15] or Zn [16] ), or a rare-earth (RE) [1] metal. An attractive but less-common field of compounds within the chemistry of (NÀ C�N) 2À ions are tetracyanamidometallate compounds, evidenced by the [T(NCN) 4 ] nÀ ion, in which T represents a main group element such as Si, [17,18,19] Ge, [20] Al [21,22] or Ga. [23] The compounds ARE[Si(NCN) 4 ] (A = K, Rb, Cs; RE = rare earth) were reported to exhibit outstanding optical properties (photoluminescence and/or second harmonic generation = SHG) and to behave stable in air. So far, their preparations depart from appropriate mixtures of a hexafluorometallate, e. g. K 2 SiF 6 plus RECl 3 and Li 2 (CN 2 ) to yield KRE[Si(NCN) 4 ].…”

Layered Carbodiimides A2M(CN2)3 with Tetravalent Cations M = Sn, Zr, and Hf

“…Moreover, it was in question whether their larger ionic radii allowed a tetrahedral environment as in the [T(CN 2 ) 4 ] 4– compounds, and if the reducing nature of the carbodiimide ion would cause partial or full reduction of T 4+ ions in solid‐state metathesis reactions. We note that Zn forms divalent Zn(CN 2 )[3f] and the reaction of EuCl 3 yields Eu(CN 2 ), although Eu 2 (CN 2 ) 3 can be observed on moderate reaction conditions.…”