Substitution in Coordination Compounds

Some labile complexes react with alkynes to afford products in which at least one ligand was displaced by an acetylene molecule. Substitution reactions most commonly occur for complexes containing the following ligands CO, halides, phosphines, water, N2, etc. 

Phosphine Pd(0) and Pt(0) complexes react with acetylenes according to the following equations  

Platinum(II) halides readily form alkyne complexes via halogen substitution reac- 

The only stable Pd(II) compound with bis(/ r/-butyl)acetylene may be prepared by reaction of Bu CCBu with bis(benzonitrile)dichloropalladium(II) or di-/x-chloro-dichlorodi (ethylene )dipalladium (II)  

2[PdCl2(PhCN)2] +2 /-BuCCBu-/-[Pd2Cl4(C2H4)2] +2 /-BuCCBu-/- 

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The origin of optical activity in molecules often reduces to the question of how the molecule acquires the electronic properties expected of a chiral object when it is formed from an achiral object. Most often an achiral molecule becomes chiral by chemical substitution. In coordination compounds, chirality commonly arises by the assembly of achiral units. So it is natural to develop ideas on the origins of chiral spectroscopic properties from the interactions of chirally disposed, but intrinsically achiral, units. Where this approach, an example of the independent systems model, can be used, it has obvious economic benefits. Exceptions will occur with strongly interacting subunits, e.g., twisted metal-metal-bonded systems, and in these cases the system must be treated as a whole—as an intrinsically chiral chromophore. ... 

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