does the pairing take place in complexes with different types of ligands in one coordination sphere for ex.

Cr(NH3)4(Cl)2

here a strong ligand nh3 and weak ligand cl2 is present so will paring of electrons take place?

Pls answer urgently!!!

Dear student,

Everything in the brackets is ligands bonded to the central Cr atom. NH3 has a 0 charge. Cl- has a -1 charge. So the complex ion INSIDE the brackets looks like this....

.............Cl....NH3
..............|.. ⁄
.H3N ---- Cr ---- NH3..... "cis".... violet in color
...........⁄..|
.......Cl...NH3

and

.............Cl....NH3
..............|.. ⁄
.H3N ---- Cr ---- NH3..... "trans".... green in color
...........⁄..|
..H3N....Cl

either case, Cr is in the +3 state giving the [Cr(NH3)4Cl2] a "+1" charge. that combines ionically with Cl- OUTSIDE the brackets... like this...
+..............................+.+1
¦.............Cl....NH3....¦
¦..............|.. ⁄ ...........¦
¦.H3N ---- Cr ---- NH3.¦......Cl -1
¦...........⁄..|................¦
¦.......Cl...NH3...........¦
+..............................+