Representation of 7r-bonding in olefin-transition-metal complexes

Olefin complexes have most often been prepared by displacement of some other ligand by the olefin. Both thermal and photochemical reactions have been observed. Olefins can form complexes with platinum and palladium by displacing solvent or halide molecules from the coordination sphere of the metal  

Displacement of carbon monoxide from metal carbonyls is a common preparative method  

The dimeric ir-allylnickel(I) bromides are prepared readily from allyl bromides and nickel carbonyl. Allylmagnesium bromide reacts with nickel bromide to give bis(ir-allyl)nickel  

Organometallics involving organic ligands having a cyclic array of four carbon 

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Figure 5.1. Representation of 7r-bonding in olefin-transition-metal complexes.

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