Metal-ligand -bond formation in Mn ₂( CO )₁₀ and [ MnO ₄]^- requires electron-pair donation between metal and ligand orbitals. Which one of the following represents the direction of electron-pair donation?

Step-by-step solution

In Mn ₂( CO )₁₀ , the oxidation state of Mn is 0 . The CO ligand acts as a -acceptor. The -bond is formed by the synergic back-donation of an electron pair from a filled d-orbital of the metal to the empty ^ * antibonding orbital of the CO ligand. Thus, the direction of electron-pair donation for the -bond is metal orbital ligand orbital. In [ MnO ₄]^- , the oxidation state of Mn is +7 , which corresponds to a d^0 electronic configuration. Since the metal has no d-electrons, it cannot donate electrons for -bonding.