文摘
The chemical bonding of the M2 dimers (M = Ag, Au, Hg) present in Yb3Ag2, Ca5Au4 and Ca3Hg2 was examined on the basis of first principles electronic band structure calculations. In these compounds, the 6s- and 5d-block bands of M are completely filled while the frontier levels of M are given by partially filled 6p-block bands such that the transition metal atoms M are best described as anions with electron configuration (5d)10(6s)2(6p)1. Thus, the M2 dimers (M = Ag, Au, Hg) of Yb3Ag2, Ca5Au4 and Ca3Hg2 are present as [Ag−Ag]4−, [Au−Au]4−, and [Hg−Hg]2− Zintl-anions, respectively, in these compounds in which the M2 dimers have a single bond formed by the pc3;−pc3; interaction between the 5p and 6p orbitals of M atoms. The anions of late transition metal elements are different from those of late main group elements in their tendency for covalent bond formation.