The molecular structure of -dichlorotetraphenoxytungsten(VI)

Synthesis, Structural Studies, and Application of Aluminum Aryloxides for Ring-Opening Metathesis Polymerization

“…Nevertheless, complex 8 was successfully isolated from the reaction between p -cresol and WCl 6 in toluene as dark red-brown crystals in a yield of 43% (Figure a). Single-crystal X-ray diffraction study for 8 revealed the trans -configuration and geometrical parameters, similar to those previously found in the related dichlorotetraphenoxytungsten­(VI) complex (Figure b) . The NMR spectroscopy study for 8 in CDCl 3 exhibited only the presence of the D 4 symmetric specie in the solution at the NMR time scale.…”

“…Single-crystal Xray diffraction study for 8 revealed the trans-configuration and geometrical parameters, similar to those previously found in the related dichlorotetraphenoxytungsten(VI) complex (Figure 4b). 27 The NMR spectroscopy study for 8 in CDCl 3 exhibited only the presence of the D 4 symmetric specie in the solution at the NMR time scale. Notably, the isolated complex 8 and its in situ generated version, obtained by the treatment of WCl 6 with 4 equiv of p-cresol, do not show any ROMP activity under the polymerization conditions employed for aluminum aryloxides 1−7 (Table 1, entries 13 and 14).…”

“…This observation is consistent with the crystallization of 1 from the THF solution in the form of 1• THF adduct with a strong dative Al−O THF bond. The 27 Al NMR spectra measured for heteroleptic complexes 4−7 exhibit a narrower resonance at ca. δ( 27 Al) = 50 ppm.…”

“…Al NMR spectra for the solutions of aluminum aryloxides in THF-d 8 were recorded at 25 °C using a Bruker 500 MHz Avance IIIHD NMR spectrometer operating at 130.33 MHz for 27 Al and using a 5 mm broadband BBFO probe. A single pulse experiment with a 90°pulse, 1 s delay, and 64 transients was used for measuring the 27 Al NMR spectra. The blank was a tube of solvent (THF-d 8 ) with equivalent conditions to measure the aluminum background of the probe.…”