The gadolinium nitride selenides Gd3NSe3 and Gd23N5Se27: Three connectivity types of [NGd4]9+ tetrahedra and fivefold coordinated Gd3+ cations

The A-Type Ln4N2S3 Series: New Nitride Sulfides of the Light Lanthanoids (Ln = Ce–Nd)

“…Thus, a single strand is surrounded by a total of six more in the manner of a hexagonal rod packing. In analogy to all the rare-earth metal(III) nitride chalcogenides and their halide derivatives known to date [1][2][3], the N 3− anions are again surrounded by a more or less distorted tetrahedron of Ln 3+ cations, in which the four N 3− -Ln 3+ distances (228-241 pm) differ by a maximum of 13 pm and the angles range between 97° and 114° (Table 4). In fact, the typical characteristic of the structural construction is actually created by the individual linkage of these [NLn4] 9+ tetrahedra.…”

“…Unlike the crystal structure of the A-type Ln 4 N 2 S 3 members (Ln = La, Pr), in which linear chains are built by linkage of [N 2 Ln 6 ] 12+ bitetrahedra, in the B-type structure layers are produced by their cross-linkage via common vertices according to 2 ∞ {[N(Ln3/4) e 2/2 (Ln1/2) v 2/2 ] 3+ } with four-and eight-fold pores ( Figure 5). Accompanied by a quadruplication of the cell volume for the B-type (Z = 8) as compared to the A-type (Z = 2), the unit cell of the B-Ln 4 N 2 S 3 representatives contains four times the total number of cations and anions, but only twice the number of crystallographically different unkind particles owing to the doubling of the respective Wyckoff positions (8f and 4c or 4e as compared to 4g and 2a).…”

“…The crystal structures of all ternary lanthanide(III) nitride chalcogenides known so far (Ln 3 NCh 3 , Ln 4 N 2 Ch 3 , Ln 5 NCh 6 , Ln 23 N 5 Ch 27 , and Ln 13 N 5 Ch 12 ) and their halide derivatives (Ln 3 N 2 ChX, Ln 4 NCh 3 X 3 , Ln 5 N 2 Ch 4 X, Ln 5 N 3 Ch 2 X 2 , and Ln 6 N 3 Ch 4 X; Ln = La-Nd, Sm, Gd-Ho; Ch = S, Se, Te; X = Cl, Br) are dominated by N 3− anions in a tetrahedral coordination of Ln 3+ cations [1][2][3]. A very interesting structural behavior is exhibited by the nitride chalcogenides with the composition Ln 4 N 2 Ch 3 , which occur in seven different crystal structure types.…”

“…In contrast, the linkage via trans-oriented edges of [NLn 4 ] 9+ tetrahedra builds up undulated chains in the orthorhombic Ce 4 N 2 Te 3 -type structure [5] (Ln = La-Nd; Pnma, Z = 4), the orthorhombic Tb 4 N 2 Te 3 -type structure [6] (Ln = Gd, Tb; Pnna, Z = 4), and the monoclinic Dy 4 N 2 Te 3 -type structure [6] (P2 1 /c, Z = 4). As the main structural feature of the orthorhombic A-La 4 N 2 S 3 -type structure [7] (Pnnm, Z = 2), N 3− -centered (Ln 3+ ) 4 tetrahedra, which first arrange as pairs [N 2 Ln 6 ] 12+ of two edge-shared [NLn 4 ] 9+ units, occur. These are further connected via their four free vertices to form double chains 1 ∞ {([NLn 2 ] 2 ) 6+ }.…”

“…For the first time, an arrangement of interconnected [NLn 4 ] 9+ tetrahedra fused to layers is observed in the monoclinic Nd 4 N 2 Se 3 -type structure [8][9][10][11] (Ln = La-Nd; C2/c, Z = 4). In these compounds the [NLn 4 ] 9+ units are first edge-linked to congonial bitetrahedra [N 2 Ln 6 ] 12+ again, and they then become cross-connected to 2 ∞ {[NLn 2 ] 3+ } layers via their remaining four free vertices. Finally, a second layered arrangement is found in the monoclinic B-Pr 4 N 2 S 3 -type structure [9] (Ln = La, Pr; C2/c, Z = 8 [7,12] is found in the A-La 4 N 2 S 3 -and in the B-Pr 4 N 2 S 3 -type structures, while Ce 4 N 2 Se 3 is observed either with the Nd 4 N 2 Se 3 -or with the Ce 4 N 2 Te 3 -type arrangement.…”