An Unusual Dynamic Fe-Hg-Pd Cluster with a
Palladium(0) Fragment Stabilized by d10–d10
Heterometallic Bonding
Walter Schuh, Pierre Braunstein,* Marc Benard,
Marie-Madeleine Rohmer, and Richard Welter
Heterometallic cluster
• According to a definition by F. A. Cotton,
cluster compounds are those in which ‘two
or more metal atoms, in addition to being
bonded to other non-metals, are bonded to
each other.’
Angew. Chem. 2003, 115, 2211 – 2214
Example
possible usefulness of the metallic
clusters?
• This type of mixed metal clusters displays unusual
chemical reactivity such as reversible electron transfer
and activation of small organic molecules.
• They are important precursor materials for preparing
bimetallic nanoparticle catalysts for organic reactions.
• catalysis, have potential to promote new homogeneous
catalytic reactions which are not established by
mononuclear center
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Usefulness contd..
• molecular magnets
• Green chemistry
They can be used to get rid of toxic metals
from the environment
• pharmaceuticals.
- are used in chelation therapy
• e.g. They can mimic active centre of
metalloenzymes
Back to the paper
• Synthesis of
with [Pd2(dba)3] ·
CHCl3 as Pd(0) precursor
[Hg{Fe[Si(OMe)3](CO)3(mdppm)} 2Pd]
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Characterization of the product
More about the complex
The complex by analyzed through extended Huckel calculations that
were carried out in the model system
• Fe-Hg-Fe array is essentially linear (179.97 degrees)
•
• The Fe-Hg-Pd bonding result from
*Pd will behave as poor electron acceptor but can attach to metallic
complexes by back bonding
*donation of Fe-Hg sigma to the PdL2 serving as a third “ligand”
* Mostly form the back bonding from the d10 Pd(0 )centre to the d10
Hg(II) center and to a semi bridging CO group
• Semibridging CO provides further stability
IR vibration of CO @ 1821 /cm
Pd has high energy 5s/5p orbital but 4d is easily accessible ( at-12eV)
•
Population increase of Py orbital of Pd from 0.05 to 0.14 es ( sigma
donation)
•
Depopulation of 4d orbital in the order of 0.48e indicates the occurrence of
back bonding
•
Py population of Hg increases from 0.06 to 0.18 e but to a lesser extent for
Fe
•
The largest share of the electron lost by Pd is donated to Pi * orbital of the
semi bridging C1O1 bond ( +0.09e to -0.11e)
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Conclusion
• A heteropolymetallic complex was prepared by capture
of Pd(0) center by trimettalodiphosphane.
• Direct interaction between Pd and Hg (II) has been
detected for the first time
• The complex fluxional behavior of compound has been
shown to consists of apparent “sliding” of the Pd along
the trimetallic chain
Stabilization of the complex
multicentered anchoring of the PdL2 fragments
• Pt does not form the analogue of Pd which emphasizes
the delicate energetic balance of these kind of
complexes.
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