Seltenerdethenidhalogenide Ln_2n+6(C₂)_n+4X_2n+2: Darstellung, Struktur, Verwachsung und Verzwilligung

Abstract

Preparation, crystal structure, intergrowth and twinning of the compounds La10(C2)6Br6, Ce10(C2)6Br6 and Gd10(C2)6Cl6 are described. The compounds Ln10(C2)6X6 are formed by heating mixtures of LnX3, Ln und C in tantalum capsules under argon with the ratio LnX3:Ln:C = 2:4:6 for La10(C2)6Br6 at 1040 °C, 30 d (yield ca. 20 %), Ce10(C2)6Br6 at 1200 °C, 12 d, (80 %), Pr10(C2)6Br6 at 1140 °C, 5 d, (20 %) and 2:8:12 for Gd10(C2)6Cl6 at 1170 °C, 39 d, (100 %). They crystallize isotypical in a new structure type in C2/m with a = 22.809(5) Å, b = 3.9855(8) Å, c = 16.599(3) Å, β = 123.32(3)° (La10(C2)6Br6), a = 22.483(5) Å, b = 3.9253(8) Å, c = 16.375(3) Å, β = 123.15(3)° (Ce10(C2)6Br6), a = 22.360(10) Å, b = 3.895(2) Å, c = 16.269(8) Å, β = 123.44(3)° (Pr10(C2)6Br6) and a = 21.507(4) Å, b = 3.7193(7) Å, c = 15.331(3) Å, β = 123.34(3)° (Gd10(C2)6Cl6). The structure of Ln10(C2)6X6 is composed of Ln octahedra centered by (C2) groups, which are connected through common edges to form sheets which are further connected perpendicularly by chains of Ln triple octahedra to form tunnels, which contain the X atoms coordinating the triangular faces of the Ln octahedra. The compounds are semiconductors according to ionic formulations (Ln3+)10(C24–)6(X–)6 suggested by the C=C double bond assignment.

Crystal Structure and Electronic Properties of Y3AlC3

“…In fact, the ELF shows little variation over an extended and fully connected region (the aluminum plane). This in other ethenid compounds 10,11 and is similar to the one in YC 2…”

“…The carbon dumbbell has a shorter bonding length than C 2 4– in other ethenid compounds , and is similar to the one in YC 2 8 , where the antibonding C p orbitals are part of the conduction band. The site-resolved partial density of states (Figure ) reveal that this is also the case for Y 3 AlC 3 with a weak contribution of the corresponding states around E F .…”

Synthesis and Characterization of Cerium-Oxo Clusters Capped by Acetylacetonate

“…In addition to previously reported homometallic Ce 10 decamers, 77 which exhibit different arrangements of Ce atoms as compared to Ce-10 , there are few heterometallic assemblies that consist of Ce 10 assemblies together with other metal ions such as Mn and Na. 20 , 82 − 84 These Ce 10 cluster cores vary in the arrangement of the Ce metal centers and range from edge-sharing Ce 6 octahedra to three Ce 3 units surrounding a central Ce site. 20 , 82 − 84 Interestingly, the homo- and heterometallic structures that consist of edge-sharing Ce 6 octahedra, such as (pyH) 8 [Ce 10 O 4 (OH) 4 (O 3 PPh) 12 (NO 3 ) 12 ] and [Ce 10 Mn 14 O 24 (O 2 CPh) 32 ], adopt the same decameric unit that is observed in Ce-12 .…”

“… 20 , 82 − 84 These Ce 10 cluster cores vary in the arrangement of the Ce metal centers and range from edge-sharing Ce 6 octahedra to three Ce 3 units surrounding a central Ce site. 20 , 82 − 84 Interestingly, the homo- and heterometallic structures that consist of edge-sharing Ce 6 octahedra, such as (pyH) 8 [Ce 10 O 4 (OH) 4 (O 3 PPh) 12 (NO 3 ) 12 ] and [Ce 10 Mn 14 O 24 (O 2 CPh) 32 ], adopt the same decameric unit that is observed in Ce-12 . Such units have likewise been observed for the actinides.…”