[Ni(CN)4]2−
Explanation:
The complex [Ni(CN)4]2− is not expected to absorb visible light because cyanide (CN−) is a strong field ligand, which causes a large splitting of the d-orbitals. This large splitting means the energy gap between the orbitals is too big for visible light to excite electrons, so it absorbs in the ultraviolet region instead.
