involved are summarized in Table 111. In Hg4(A~F6)2, however, the interaction of the Hg: + ion with the AsFC anion in a direction approximately collinear with the terminal Hg-Hg bonds is replaced by the intercation Hga-Hg interaction at 124O to the terminal Hg-Hg bond and several weak Hg-F contacts with the anions. These latter H g F interactions are considerably longer than the short interactions (2.38 A) in Hg3(AsF6)2,2 which are collinear with the Hg-Hg bonds. They resemble in length the interactions in other compounds that are not collinear with the Hg-Hg bonds. For example, the closest H g F contacts in Hg2,,,AsF6 are 2.87 (1) or 2.98 (1)
If the intercation H g -H g contact and one or two of the shortest H g F contacts to Hg( 1) are considered, then the environment of Hg( 1) in Hg4(A~F6)2 is similar to that of the Hg atoms in the two modifications of tetrakis(dipheny1seleno)dimercury(I) perchlorate, [ (C6H5)2Se]4Hg2(C104)2.16
Other interionic interactions of comparable strength in other Hg(1) and Hg(I1) compounds have been observed, and many of these are discussed elsewhere." However, the nature of these additional interactions is still unclear. A recent calcu-lation18 on the mercurous halides Hg,F, and HgzC12 indicated that the closest next-neighbor fluorine and chlorine atoms (15)