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Phosphorus-based p-tert-butylcalix[5]arene ligands.
Paul Sood1, Mohan Koutha, Maomian Fan
1Department of Chemistry, Southern Methodist University, Dallas, Texas 75275-0314, USA.
Inorganic Chemistry
|April 27, 2004
Summary
New calix[5]arene phosphorus compounds were synthesized as versatile ligands for metal interactions. Their unique structures offer a balance of flexibility and constraint, enabling both soft and hard ligand coordination.
Area of Science:
- Supramolecular Chemistry
- Organophosphorus Chemistry
- Coordination Chemistry
Background:
- Calixarenes are well-established macrocyclic hosts.
- Trivalent phosphorus compounds are versatile ligands in coordination chemistry.
- Calix[4]arenes offer limited cavity size, prompting exploration of larger analogues.
Purpose of the Study:
- To synthesize novel calix[5]arene trivalent phosphorus derivatives.
- To investigate the structural and conformational properties of these new compounds.
- To evaluate their potential as ligands for metal interactions, considering both soft and hard donor sites.
Main Methods:
- Synthesis of calix[5]arene derivatives via reactions with phosphine reagents.
- Structural characterization using X-ray crystallography.
- Conformational analysis of the synthesized molecules.
Main Results:
- Successful synthesis of two calix[5]arene bis(phosphorus) derivatives (1, 2) and a related chloro-derivative (3).
- X-ray crystallography confirmed approximate cone conformations for 1 and 2, and a 1,2-alternate conformation for 3.
- Heating a monophosphorus precursor yielded monomeric and dimeric species with unique geometries.
Conclusions:
- The synthesized calix[5]arene phosphorus derivatives are promising ligands.
- The larger cavity of calix[5]arene provides a tunable balance of constraint and flexibility.
- The arrangement of phosphorus and oxygen atoms allows for diverse coordination modes (soft and hard Lewis acid interactions).