In my textbook, these reasons are given as of why transition metals form a large number of complex compounds:-
- Smaller size of metal ions
- High ionic charges
- Availability of d orbitals for bond formation
What is the use of the first reason, i.e small size? Shouldn't it be opposite? In interhalogen compounds too, in XYn, X should be of greater size than Y. So why opposite in case of complex compounds?