Pentagonal bipyramids seven-coordinate compounds

The unusual complex p-F-[MoO(02)(pydca)]j (see 5) is formed as the NEt4 salt upon treatment of Mo(02)(pydca)(OH2) with F 418 in the presence of NEt4. The complex, shown in Figure 21, is a centrosymmetric dinuclear ion with each Mo atom possessing pentagonal bipyramidal seven-coordination.307 The linear OtMoVIFMoVIOt unit is to date unique to this complex. The Mo—O, distance is 1.659(3) A and the Mo—F trans to it has the very long distance of 2.135(1) A. The O—O distance of 1.43 A is similar to that found in mononuclear peroxo compounds of Mo . 

The three most common geometries for seven-coordinate compounds (a) the pentagonal bipyramid, (b) the capped octahedron, and (c) the capped trigonal prism. 

To explore the influence of coordination environment on rates and mechanisms of electron transfer reactions at molybdenum centers, we have investigated [17-20] the electrochemical behavior of several families of oxomolybdenum (VI) complexes. The compounds are illustrated in Figure 4. The first three examples are seven-coordinate complexes and exhibit pentagonal bipyramidal geometry. These compounds contain a... 

Pentahalides are known only to neptunium. All of these compounds are very water sensitive. The pentafluorides and PaCls are polymeric seven-coordinate compounds. The geometry is that of a distorted pentagonal bipyramid with double bridging occurring through four of the equa-... 

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