A range of 1,1′-bi-2-naphthol (H2BINO) derivatives react with WCl6 in toluene to generate a new family of W(R2BINO)3−nCl2n derivatives. Reactions between excess 3,3′-diphenyl-1,1′-bi-2-naphthol (H2Ph2BINO) and WCl6 generate only the monosubstituted W(Ph2BINO)Cl4 product. The less sterically demanding H2Me2BINO ligand produces minor quantities of various bis-Me2BINO-substituted isomers, together with trans-(R*,R*)-W(Me2-BINO)2Cl2, which is the overwhelmingly favored product. The parent H2BINO ligand generates two of four possible W(BINO)3 diastereomers, with (S*,S*,S*)-W(BINO)3 and (S*,S*,S*)-W(BINO)3 diastereomers being produced in statistically predicted quantities. Molecular modeling and spectroscopic studies indicate that the S*,S*,S* and S*,S*,R* isomers prefer to adopt Δ* rather than Λ* overall complex stereochemistry. This preference stems from a minimization of interligand interactions between (S)-BINO ligands in Δ diastereomers. There is relatively little difference between the stereochemistry of polynorbornene prepared employing the W(R2BINO)3−nCl2n complexes as precatalysts. This may arise, in part, from the ability of the catalysts to engage in secondary metathesis reactions. The (BINO)3W complexes are not activated for ring opening metathesis polymerization catalysis at −70 °C, apparently because the slow rate of ligand exchange at this temperature does not allow the metal to open a coordination site.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry