SPANphos
From Wikipedia, the free encyclopedia
| SPANphos | |
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| Properties | |
| Molecular formula | C47H46O2P2 |
| Molar mass | 704.814 g/mol |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
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SPANphos is a diphosphine commonly used as a ligand in organometallic compounds. This compound is a rare example of a trans spanning ligand especially helpful in catalysis. By having a compound that only forms pure trans-chelating ligands, certain cis-positions will be inhibited giving way to research of new catalysts. This compound is remarkable for the fact that its trans-chelating bond is rigid in linking two trans-sites. The problem that arises from other trans-chelating compounds is that the length of the linking bond is great causing loss of rigidity, thus forming unwanted complexes such as metal to metal bonds.
[edit] Synthesis
The C2-symmetric trans-diphosphine is easily synthesized from inexpensive reagents. In the first step 4,4,4',4',6,6',-hexamethylspiro-2,2'-bichroman is prepared via an acid-catalyzed reaction between p-cresol and acetone is formed. The spirane is brominated with N-bromosuccinimide, and treated with n-BuLi and chlorodiphenylphosphine to obtain SPANphos. [1]
[edit] Uses
Only a few trans-chelating ligands are known, and with SPANphos there are now opportunities to discover new families of catalysts that act with ligands around the active metal center. Trans-diphosphanes, unlike cis-diphosphanes, have a chiral backbone that works with substituents on the phosphorus atom to contribute to the formation of a chiral cavity around the metal center. In Pd and Pt complexes SPANphos acts only as a trans-coordinating diphosphane ligand, giving complexes of the formula MC12(SPANphos).
[edit] References
- ^ Z. Freixa, M. S. Beentjes, G. D. Batema, C. B. Dieleman, G. P. F. v. Strijdonck, J. N. H. Reek, P. C. J. Kamer, J. Fraanje, K. Goubitz and P. W. N. M. Van Leeuwen (2003). "SPANphos: A C2-Symmetric trans-Coordinating Diphosphane Ligand". Angewandte Chemie 42 (11): 1322-1325. doi:.
