Question

When I took inorganic classes, I was told that halide is a pi donor. Assume I am using metal hexahalide why I can't put the pz

orbital of the halides directing to the metal centre? With that halide will just act as a sigma donor.

Answer 1

The pz orbitals of halide ions in an octahedral metal hexahalide complex cannot directly overlap with the metal center due to electron repulsion. Halide ions can only act as sigma donors, not pi donors, in this complex. The sp³ orbitals of halide ions have a tetrahedral geometry, with one forming a sigma bond and the others occupied by lone pairs of electrons.

Step-by-step explanation:

The pz orbital of halide ions in an octahedral metal hexahalide complex cannot directly overlap with the metal center because of the repulsion between the electrons of the ligands and the electrons of the metal ion.

The sp³ orbitals of halide ions have a tetrahedral geometry, with one orbital forming a sigma bond and the other three being occupied by lone pairs of electrons. Thus, the halide ions can only act as sigma donors, not pi donors, in an octahedral metal hexahalide complex.

Therefore, in an octahedral metal hexahalide complex, the halide ions do not directly contribute their pz orbital electrons to the metal center.