Step 1: Recall the bonding
Ligands donate lone pairs to the central metal ion through coordinate bonds.
Step 2: Name the role
The species that accepts an electron pair is a Lewis acid, so the central metal ion is a Lewis acid. The ligands are Lewis bases. Option (C).
Final Answer:
The metal ion is a Lewis acid, option (C).
\[ \boxed{\text{(C)}} \]