Tetrahedral ML4 complexes

In a complex of this type, the metal is placed at the centre of a tetrahedron whose vertices are occupied by the four ligands. There are at least two ways to derive the d-block orbitals for a tetrahedral complex. In the direct method, we allow the d orbitals of the metal to interact with the symmetry-adapted combination of ligand orbitals (Chapter 6, 6.6.2.2 

This is not the only way to move from one structure to the other. One can, for example, rotate one ML2 unit by 90° with respect to the other, progressively adjusting the values of the bond angles Di symmetry is conserved). 

The separation between the e and tz levels of the d block is sufficiently small (the tz orbitals are only weakly antibonding) that all five orbitals can be occupied. Diamagnetic complexes with a electronic configuration are thus obtained (2-55), such as [Ni(H)4] , [Ni(CO)4], [M(Pp3)4] (M=Ni, Pd), [Pt(dppe)2] (dppe=diphenylphosphino-ethane), [Ni(CN)4] -, [ 0(00)4] , [Pe(CO)4] , [Cu(CN)4] , [Cu(PMe3)4] , [Ag(PPh3)4] , or [Zn(Cl)4] . These are 18-electron complexes, since eight additional electrons are associated with the four metal-ligand bonds. 

It is straightforward to understand the structural preference for d ° complexes in the tetrahedral geometry, all five d orbitals are 

2-57 Square planar (d high-spin) Tetrahedral (d high-spin) 

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Fig. 11.52 Molecular orbital diagram for a tetrahedral ML4 complex, showing possible Kgand-to-metal charge transfer (LMCT) transitions...

Figure 4 An orbital interaction diagram for the valence orbitals of a tetrahedral ML4 complex...

Fig. 20.7 The relationship between a tetrahedral ML4 complex and a cube the cube is readily related to a Cartesian axis set. The ligands lie between the x, y and z axes compare this with an octahedral complex, where the ligands lie on the axes.

Figure 2.9. Correlation diagram linking the d-block orbitals of a square-planar ML4 complex and those of a tetrahedral ML4 complex, following the deformation shown in 2-55...

Square Planar, Tetrahedral ML4 Complexes and Electron Counting... 

Figure I6.3. Distortion of a square planar to tetrahedral ML4 complex maintaining Dj,/ l mmetty.

SQUARE PLANAR, TETRAHEDRAL ML4 COMPLEXES AND ELECTRON COUNTING... 

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