The d Block

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4

Slide 27

Catalytic Activity

TM’s and their compounds effective and important catalysts

Industrially and biologically!!

The “people in the know” believe

catalysts provide reaction pathway with lower EA than uncatalysed reaction (see CI 10.5)

Once again,

availability of 3d and 4s e-

ability to change OS

among factors which make TM’s such good catalysts

Slide 28

Heterogeneous Catalysis

Catalyst in different phase from reactants

Usually means solid TM catalyst with reactants in liquid or gas phases

TM’s can

use the 3d and 4s e- of atoms on metal surface to from weak bonds to the reactants.

Once reaction has occurred on TM surface, these bonds can break to release products

Important example is hydrogenation of alkenes using Ni or Pt catalyst

Slide 29

Heterogeneous Catalysis

Slide 30

Homogeneous Catalysis

Catalyst in same phase as reactants

Usually means reaction takes place in aqueous phase

Catalyst aqueous TM ion

Usually involves

TM ion forming intermediate compound with ome or more of the reactants

Intermediate then breaks down to form products

Slide 31

31

Homogeneous Catalysis

Above reaction is that used in Activity SS5.2

2,3-dihydroxybutanoate ion with hydrogen peroxide

Reaction catalysed by Co2+

Slide 32

Suggested Mechanism

REACTANTS

H2O2 +

-O2CCH(OH)CH(OH)C02-

Co2+ (pink)

INTERMEDIATE

containing

Co3+ (green)

PRODUCTS

CO2, methanoate, H2O

Co2+ (pink)