Valence bound theory (VBT) basically defines the covalent bind formation within co ordination compounds. It tells the electron of atoms occupy atomic orbital and electron of one at one attract the other.

According to VBT,

M(Cl6)3 is an inner orbital complex. The orbital involved in the bond formation us 3d , 4s , 4p and they for d2sp3 orbitals that results in covalent bond formation.

You can refer to NCERT co-ordination compound chapter for more detailed regarding VBT theory.

Hope that helps

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