Why Does NH3 Form Complex Ions with Transition Elements But NH4 Does Not?

[amesalot57]

I am taking this correspondence course, i ran into this question and I think i know the answer but I'm not sure.
Why is it that NH3 readily forms complex ions with the transition elements but NH4 does not?
I think it is because of the extra bond with Hydrogen, therefore there is less unpaired d electrons but I'm not sure.

 

[chemisttree]

Try this...

https://www.physicsforums.com/showthread.php?t=175130