Pentagonal planar complexes

Table 10 Electronic Energy Calculations for 5-Coordinate Pentagonal Planar Complexes with D51J Symmetry ...

The first pentagonal bipyramidal complex of zinc, ZnLCl2 3H20, was reported in 1973, where L is the planar five-coordinate 2,6-diacetylpyridinebis(semicarbazone).346 The crystal structure determination shows the complex to contain the [LZnG(H2Q)]+ cation, with three bland two O-donor atoms forming a slightly distorted planar pentagon around the metal ion and the chlorine and water in axial positions. 

Figure 6-13. The templated formation of a hydrazone macrocycle. This ligand contains five nitrogen donor atoms and was designed to investigate the properties of metal complexes containing a pentagonal planar donor set. In practice, the complexes of these ligands usually acquire one or two axial ligands to give six- or seven-co-ordinate complexes.

Compounds that appear to contain the [XeF]+ (1) and bent [Xe2F3]+ ions are known although the former is always strongly coordinated to a counterions such as SbF-6. Complex anions include XeF-5, XeF-7 and XeF2-g, the first of which has a unique pentagonal planar structure (3), as expected from VSEPR. 

The only other example of a Schiff base condensation with dipyridine to form a macrocyclic complex has been reported by Tasker et al.112) in which 2,6-diformyl-pyridine or 2,6-diacetylpyridine is condensed with 6,6 -dihydrazmo-2,2 -dipyridine (132) in the presence of zinc(II) to afford a pentagonal bipyramidal complex 133. The rigidity of the system results in an equatorial Ns donor set that is essentially planar water molecules occupy the axial positions. 

Consistent with the original supposition that sapphyrins should be good ligands for large cations, Woodward predicted that sapphyrins might form particularly stable chelate complexes with uranyl cation (U02 ), a species that is known to favor pentagonal planar coordination environments. " Unfortunately,... 

C. Ligand Field Stabilization for Complexes of Molybdenum Hexacarbonyl and Poly(vinylamine) in the Glassy State Quantum Mechanical Model Parameters and Trigonal Bipyramid 5-Coordinate d Complexes of Molybdenum Hexacarbonyl and Poly(vinylamine) with D311 Symmetry Above Tg Square Pyramid 5-Coordinate d Complexes of Molybdenum Hexacarbonyl and Poly(vinylamine) with C4V Symmetry Above Tg Pentagonal Planar 5-Coordinate d Complexes of Molybdenum Hexacarbonyl and Poly(vinylamine) with Ds Symmetry Above Eg... 

F. Pentagonal Planar 5-Coordinate Complexes of Molybdenum Hexacarbonyl and Poly(vinylamine) with Dsh Symmetry Above... 

Table 4.3 indicates that octahedral coordination is a common mode for Li. Less usual is planar 6-fold coordination (Fig. 4.8a), pentagonal pyramidal coordination (Fig. 4.8i) or irregular 6-fold coordination (Fig. 4.9a). Examples of 7-fold coordination are in Fig. 4.9b and c. Lithium has cubic 8-fold coordination in the metallic form and in several of its alloys with metals of large radius. It is also 8-coordinate in the dilithionaphthalene complex shown in Fig. 4.9d here the aromatic... 

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