Square-planar five-atom molecules

TETRAHEDRAL AND SQUARE-PLANAR FIVE-ATOM MOLECULES 2.6.1. Tetrahedral XY4 Molecules (Tj,)... 

TETRAHEDRAL AND SQUARE-PLANAR FIVE-ATOM MOLECULES... 

In the solid state, the metal atoms in bis(salicylaIdoximato)copper(II) show two additional contacts with the oxime oxygens of adjacent molecules, resulting in a distorted octahedral structure. However, the axial Cu—O distance (2.66 A) is much longer than the metal—ligand distances in the square-planar array (Cu—O, 1.92 A and Cu—N, 1.94 A).154 Studies by ESR of copper(II) extracts of the commercial reagent SME 529 (14 R = Me, R = C9H)9) have shown that the copper complex exists as a square-planar species in hydrocarbon solutions, but that five-coordinate adducts are formed in the presence of ammonia or pyridine.155... 

The possible structures may be classified in terms of the coordination number of the central atom and the symmetry of the resulting molecule (Fig. 6.17). Two groups about a central atom will form angular (p2 orbitals, C, symmetry) or linear sp hybrid, D , symmetry) molecules three will form pyramidal (p, C3,) or trigonal planar (sp, Dy) molecules four will usually form tetrahedral (sp, Tj) or square planar (dsp, five usually form a trigonal bipyramidal (Dy,), more rarely a square pyramidal (C4,) molecule (both dsp hybrids, but using different orbitals, see Table 6.2) and six groups will usually form an octahedral molecule (d sp, O,). 

In addition to tetrahedral, another common shape for AB4 molecules is square planar. All five atoms lie in the same plane, with the B atoms at the corners of a square and the A atom at the center of the square. Which shape in Figure 9.3 could lead to a square-planar shape upon removal of one or more atoms ... 

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