ORIGIN OF THE UNEXPECTED SP VS SP(2) HYBRIDIZATION OF CARBON IN THE MB(2)C (M=TH, U) SOLID-STATE PHASES - AN AB-INITIO STUDY OF THE [H2BCBH2](4-) MODEL AND ISOELECTRONIC SPECIES

被引:7
作者
FRAPPER, G
HALET, JF
SAILLARD, JY
VOLATRON, F
机构
[1] UNIV RENNES 1,CHIM SOLIDE & INORGAN MOLEC LAB,CNRS,URA 1495,F-35042 RENNES,FRANCE
[2] UNIV PARIS 11,CHIM THEOR LAB,CNRS,URA 490,F-91405 ORSAY,FRANCE
关键词
D O I
10.1021/j100032a018
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
In the solid-state actinoid-boron-carbon MB(2)C compounds, the nonmetal atoms form two-dimensional planar anionic nets in which the carbon is sp-hybridized, whereas the sp(2) hybridization is expected. This paper describes an ab initio study of the [H2BCBH2](4-) anion and several other isoelectronic systems chosen to modelize the [B2C](4-) repeat unit present in the MB(2)C phases. It is shown that the three-orbital/four-electron interaction pattern usually invoked to explain the bending of triatomic units is still valid. However, the electronegativity difference between B and C forces the system to work in the other way, i.e, favors the linearity or quasi-linearity. Calculations indicate that the potential energy surfaces associated with the bending are extremely flat over a large angle range around linearity. It is likely that in the real MB(2)C compounds crystal forces and the presence of B-B bonds tend to reinforce the preference for BCB linearity. This trend of opposition to bending, which is caused by a large electronegativity difference effect, should be quite general in chemistry.
引用
收藏
页码:12164 / 12169
页数:6
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