Interaction in solution between W(CO)5L (L = CO, PPh5, P(n-C4H9)3) and AlX3 (X = Cl, Br) has been studied in order to obtain some insight into the coordination sphere of the resulting catalyst for metathesis. When L is sufficiently basic (L = PPh3, P(n-C4H9)3) there is formation of an addition compound L(CO)4WCO AlBr3 detected by infrared and 31P NMR spectroscopy. The result of this adduct formation is a strong decrease of electron density on the tungsten followed by the easy dissociation of the ligand L as detected by infrared and 31P NMR spectroscopy. Coordinatively unsaturated tungsten is thus obtained and is relatively stable in solution. The free phosphine is complexed to the excess Lewis acid. This coordinatively unsaturated tungsten favors ligand interchange (formation of W(CO)6) as well as oxidation of zerovalent tungsten to divalent tungsten W(CO)4x2 (X = Cl, Br). The results are compared with those already published with other catalytic systems derived from hexavalent or zerovalent complexes of tungsten.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry
- Materials Chemistry