PCl₃Br₂ dipole moment not =0 while that of PCl₂Br₃ dipole moment =0,why???

both compounds are sp3d2 hybridised but in pcl3br2 the 2 br occupy the equitoriall positions along with 1cl but in pcl2br3 2 cl occupy the axial postions therefore dipole moment is0

 

The answer lies in structure.According to bent’s rule more electronegative element occupies axial postion in sp3d