The metal ion that does not form a stable metal carbonyl complex is

• Correct answer
  A

  $\mathrm{Ti}^{4+}$
• B

  $\mathrm{V}^{3+}$
• C

  $\mathrm{Cr}^{3+}$
• D

  $\mathrm{Mn}^{4+}$

Hence, the correct answer is option: 'A'.