Organometallic complexes frontier orbitals

Binuclear and polynuclear compounds with direct metal-metal interaction constitute a large class of transition metal complexes which play an important role also in organometallic chemistry. Generally, the frontier orbitals of these compounds are engaged in metal-metal bonding. Consequently, redox processes affect the metal-metal interaction. The same is true for the luminescence of such complexes since it involves also thg frontier orbitals. The binuclear complex Pt2(pop) 36) (pop = diphosphonate) and... 

All of the compounds discussed to this point in this chapter are accommodated by this assumption that the three filled t2g orbitals do not constitute part of the frontier-orbital set. However, there are well-known organometallic examples where these metal d functions do participate in bonding. Hoffmann labels this behavior into the t2g set. Let s take a look at some dinuclear metal complexes that provide geometric evidence of the partial utilization of the t2g set in bonding. 

Partially filled external, or frontier, orbitals are available for bonding with the ligands. The presence of the free orbitals allows for the formation of a covalent complex. This is because the electrons that are donated by the ligands are placed in the vacant orbitals, and this is why the d-block atoms form covalent bonds with ligands. And this is why the transition metals form the majority of organometallic complexes that are known. This is important later when talking about d-orbital splitting and crystal field theory. 

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