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Reactions of octahedral complexes: the stereochemical consequences

Reactions of octahedral complexes: the stereochemical consequences

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Reactions of octahedral complexes: the stereochemical consequences. Stereochemistry of a dissociation reaction at an O h complex. X is cis to A, and A is a  donor. vacant metal d 2 sp 3 orbital.  donation stabilises the square pyramidal intermediate. - PowerPoint PPT Presentation

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Page 1: Reactions of octahedral complexes: the stereochemical consequences

Reactions of octahedral complexes:the stereochemical consequences

Page 2: Reactions of octahedral complexes: the stereochemical consequences

Stereochemistry of a dissociation reaction at an Oh complex

A

X

A A

Y

A

Y

Y

Y

Y

Y

A

A

Y

Berry pseudo rotation

100% trans

cis transcis:trans 2:1

Page 3: Reactions of octahedral complexes: the stereochemical consequences

The nature of A will control the nature of the intermediate, and hence the stereochemistry of the products

• X is cis to A, and A is a donor A

+ X-

Hence get retention of stereochemistry – close to 100% cis

A Y

Avacant metal d2sp3 orbital

donation stabilises the square pyramidal intermediate

Page 4: Reactions of octahedral complexes: the stereochemical consequences

trans product

• X is trans to A, and A is a donor

A

Y

A

A

Xviewed down the z axis Y

YYA

A

donation stabilises the trigonal bipyramidal intermediateLeads to a mixture

of cis and trans

Page 5: Reactions of octahedral complexes: the stereochemical consequences

The better the donor ability of A, the more the trigonal bipyramidal structure is formed, and the more of the cis product will be produced.

Page 6: Reactions of octahedral complexes: the stereochemical consequences

e

f

ba

d

c

e

f

ba

d

c

Racemisation of tris-chelate complexes

Three pathways

Bailar twist

a

e

b

f

cd

lambda isom er

Page 7: Reactions of octahedral complexes: the stereochemical consequences

a

e

b

f

cd

a

eb

fc

d

a

e

b

f

c

d

Page 8: Reactions of octahedral complexes: the stereochemical consequences

a

e

b

f

c

d

e

f

b

a

d

c

delta isom er

Page 9: Reactions of octahedral complexes: the stereochemical consequences

Ray-Dutt twist

f

a

d c

delta isom er

Page 10: Reactions of octahedral complexes: the stereochemical consequences

f

a

d c

f

ad

c

f

a

d c

Page 11: Reactions of octahedral complexes: the stereochemical consequences

f

a

d c

lambda isom er

Page 12: Reactions of octahedral complexes: the stereochemical consequences

Dissociation/Reformation