Bonding in Metal Carbonyls 🌈

1. Meet the carbonyl family 🤗

Most transition metals happily bond to carbon monoxide alone (these are homoleptic carbonyls). Because every metal–CO set-up is tidy, you can memorise their shapes fast: 🔍:contentReference[oaicite:0]{index=0}

  • Ni(CO)4 – tetrahedral 🔶
  • Fe(CO)5 – trigonal-bipyramidal 🔺
  • Cr(CO)6 – octahedral 🛑

2. Double-metal specials 👫

  • [Mn2(CO)10] – two Mn(CO)5 square pyramids held by an Mn–Mn bond 🤝
  • [Co2(CO)8] – a Co–Co bond bridged by two CO groups 🌉

These linked units pop up often in questions about metal–metal bonding. :contentReference[oaicite:1]{index=1}

3. How each M–C bond forms 🛠️

Every metal–carbon link mixes two friendly interactions: :contentReference[oaicite:2]{index=2}

  • σ donation: the lone pair on carbon hands electrons to a vacant orbital on the metal.
    \( \text{C}\!\!\equiv\!O \;\rightarrow\; M \)
  • π back-donation: a filled \( d \) orbital on the metal sends electrons back into the empty \( \pi^{*} \) orbital of CO.
    \( M \;\rightarrow\; \pi^{*}(\text{C}\!\!\equiv\!O) \)

4. The “synergic hug” 🤗✨

Because σ donation and π back-donation help each other, the overall metal-CO grip tightens — chemists call this the synergic effect. Stronger overlap means sturdier complexes that pop up in labs, industry, and exam papers alike! :contentReference[oaicite:3]{index=3}

High-Yield Ideas for NEET 🔑

  1. Metal–CO bonding always mixes σ donation and π back-donation (synergic effect).
  2. Remember the signature shapes: Ni(CO)4 (tetrahedral), Fe(CO)5 (trigonal-bipyramidal), Cr(CO)6 (octahedral).
  3. Metal-metal bonds plus bridging CO groups show up in Mn2(CO)10 and Co2(CO)8.
  4. CO acts as both an electron donor (σ) and an electron acceptor (π*), stabilising low-oxidation-state metals.