Albert-Ludwigs-Universität Freiburg Institut für Anorganische und Analytische Chemie Albertstrasse 21 D-79104 Freiburg, Germany.
Inorg Chem. 2010 Apr 5;49(7):3130-40. doi: 10.1021/ic901784k.
Single crystals of the new compounds Sc(3)Al(3)O(5)C(2) and ScAl(2)ONC were obtained by reacting Sc(2)O(3) and C in an Al-melt at 1550 degrees C. Their crystal structures continue the row of transition metal oxide carbides with an ordered distribution of anions and cations with ScAlOC as the first representative. In the structure of Sc(3)Al(3)O(5)C(2) (P6(3)/mmc, Z = 2, a = 3.2399(8) A, c = 31.501(11) A, 193 refl., 23 param., R(1)(F) = 0.024, wR(2)(I) = 0.058) the anions form a closest packing with five layers of oxygen separated by two layers of carbon atoms. Sc is placed in octahedral voids and Al in tetrahedral voids thus forming layers of AlOC(3) tetrahedra and ScC(6)- and ScO(6)-octahedra, respectively. Surprisingly the layers of ScO(6) octahedra are connected by an additional layer of undistorted trigonal bipyramids AlO(5). The structure of ScAl(2)ONC (space group R3m, Z = 3, a = 3.2135(8) A, c = 44.636(1) A, 187 refl., 21 param., R(1)(F) = 0.023, wR(2)(F(2)) = 0.043) can directly be derived from the binary nitrides AlN (wurtzite-type) and ScN (rocksalt-type). The anions form a closest packing with alternating double layers of C and O separated by an additional layer of N. Again, Al and Sc occupy tetrahedral and octahedral voids, respectively. All compositions were confirmed by energy dispersive X-ray spectroscopy (EDXS) measurements on single crystals. According to band structure calculations Sc(3)Al(3)O(5)C(2) is electron precise with a band gap of 0.3 eV. Calculations of charges and charge densities reveal that the mainly ionic bonding contains significant covalent contributions, too. As expected Sc and C show higher covalent shares than Al and O. The different coordinations of O, Al, and Sc are clearly represented in the corresponding p and d states.
新化合物 Sc(3)Al(3)O(5)C(2) 和 ScAl(2)ONC 的单晶通过在 1550°C 的 Al 熔体中反应 Sc(2)O(3) 和 C 获得。它们的晶体结构延续了过渡金属氧化物碳化物的行列，具有阴离子和阳离子的有序分布，以 ScAlOC 为第一个代表。在 Sc(3)Al(3)O(5)C(2) (P6(3)/mmc, Z = 2, a = 3.2399(8) A, c = 31.501(11) A, 193 个反射，23 个参数，R(1)(F) = 0.024, wR(2)(I) = 0.058) 的结构中，阴离子形成具有五层氧和两层碳原子的最密堆积。Sc 位于八面体空隙中，Al 位于四面体空隙中，从而形成 AlOC(3)四面体和 ScC(6)-和 ScO(6)-八面体层。出人意料的是，ScO(6)八面体层通过附加的未扭曲的三角双锥 AlO(5)层连接。ScAl(2)ONC (空间群 R3m, Z = 3, a = 3.2135(8) A, c = 44.636(1) A, 187 个反射，21 个参数，R(1)(F) = 0.023, wR(2)(F(2)) = 0.043)的结构可以直接从二元氮化物 AlN (纤锌矿型)和 ScN (岩盐型)推导出来。阴离子形成具有交替双层 C 和 O 的最密堆积，由附加的一层 N 隔开。同样，Al 和 Sc 分别占据四面体和八面体空隙。所有成分均通过单晶的能量色散 X 射线光谱 (EDXS) 测量得到证实。根据能带结构计算，Sc(3)Al(3)O(5)C(2)是电子精确的，带隙为 0.3 eV。电荷和电荷密度的计算表明，主要的离子键包含显著的共价贡献。不出所料，Sc 和 C 的共价份额高于 Al 和 O。O、Al 和 Sc 的不同配位在相应的 p 和 d 态中得到清晰表示。
