THE ELECTRONIC-STRUCTURE OF BA7GA4SB9, A COMPOUND SEEMINGLY PROBING THE LIMITS OF THE ZINTL CONCEPT
THE ELECTRONIC-STRUCTURE OF BA7GA4SB9, A COMPOUND SEEMINGLY PROBING THE LIMITS OF THE ZINTL CONCEPT
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DOI：
10.1021/ic00342a004
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发表时间：
1990-08-22
影响因子：
4.6
通讯作者：
HOFFMANN, R
中科院分区：
文献类型：
--
作者：
ALEMANY, P;ALVAREZ, S;HOFFMANN, R
在最近合成的化合物Ba_7 Ga_4Sb_9中，存在一个Ga_4Sb_（14）~-二维网络，它探测了Zintl概念的极限。它由一维交替的四元和八元Ga-Sb环组成，通过长而键合的Sb-Sb接触连接在一起形成二维结构。能带计算显示出相当局域化的成键和半填充的Sb-Sb a* 带。Zintl的概念1· 2在固态化学家对大范围晶体结构中的成键作用的描述中起着重要的作用。在这个简单的方案中，正电性元素仅仅作为电子供体，将电子贡献给它们的结合的、电负性更强的键合伙伴。后一种元素则形成键以满足八隅体规则。尽管津特尔的概念在理解各种晶体结构方面非常有用，但有时候它会失效。这些限制性的情况本质上是有趣的，因为它们告诉我们从一种成键类型到另一种成键类型的转变。其中一种化合物是Ba 7 Ga 4Sb 9，最近由Schafer、Cordier及其同事合成。3这种化合物具有金属光泽，但其电性能至今未见报道。如果人们试图按照Zintl规则将电荷分配给该化合物中的Ga和Sb原子，则不可能找到承载-14电荷的常规共价网络，由于结构中存在7个Ba 2+阳离子，因此需要取消+14电荷。
In Ba7Ga4Sb9, a recently synthesized compound, there is a Ga4Sbg14~ two-dimensional net that probes the limits of the Zintl concept. It is made up of one-dimensional alternating four-and eight-membered Ga-Sb rings, linked together into a two-dimensional structure by long but bondingSb-Sb contacts. Band calculations reveal quite localized bonding and a half-filled Sb-Sb a* band. A pairing distortion is indicated and should be sought experimentally.Zintl’s concept1· 2 plays an important rolein the description that solid-state chemists give to bonding in a large range of crystal structures. In this simple scheme, electropositive elements act merely as electron donors, donating electrons to their conjoined, more electronegative, bonding partners. The latter elements then form bonds to satisfy the octet rule. Although tremendously usefulin understanding a great variety of crystal structures, Zintl’s concept sometimes fails. These lim-iting cases are inherently interesting in that they inform us of the transition from one bonding type to another. One such compound is Ba7Ga4Sb9, which has been synthesizedrecently by Schafer, Cordier, and co-workers. 3 This compound has a metallic luster, but its electrical properties have not been reported so far. If one tries to assign charges to the Ga and Sb atoms in this compound following Zintl’s rule, it is impossible, as we will see, to find a conventional covalent network bearing a charge of-14, necessary to cancel the+ 14 charges due to the seven Ba2+ cations present in the structure.