An NMR study of the species produced by the reactions of dialkyl magnesium and HCl with calcined silica and the polymerisation performance of Ziegler–Natta catalysts produced from this support material

Quantitative Investigation of a Hybrid Ziegler–Natta Catalyst Support Prepared by Grafting Di(n‐butyl)magnesium onto Partially Dehydroxylated Silica

“…as determined by 29 Si CP/MAS NMR spectroscopy. [20] The appearance of the signal at around d = À100 ppm changes only slightly because the chemical shifts of the Q 4 (3 Si,1 Mg/Al) sites (i.e., SiA C H T U N G T R E N N U N G (OSi) 3 A C H T U N G T R E N N U N G (OMg/Al)) are expected to be very similar to those of the Q 3 sites that they replace. [20] Therefore, the 29 Si CP/MAS NMR spectrum confirms alkyl transfer to Si and suggests that the major new Figure 1.…”

“…[20] The appearance of the signal at around d = À100 ppm changes only slightly because the chemical shifts of the Q 4 (3 Si,1 Mg/Al) sites (i.e., SiA C H T U N G T R E N N U N G (OSi) 3 A C H T U N G T R E N N U N G (OMg/Al)) are expected to be very similar to those of the Q 3 sites that they replace. [20] Therefore, the 29 Si CP/MAS NMR spectrum confirms alkyl transfer to Si and suggests that the major new Figure 1. Transmission infrared spectra in two spectral regions a) for a thin, self-supporting disk of S2100-500 silica; b) after treatment of the silica with nBu 2 Mg; c) after treatment of the nBu 2 Mg-modified silica with HCl(g), followed by evacuation at RT for 6 h; d) after evacuation at 100 8C for 4 h; e) after evacuation at 200 8C for 4 h. The spectra are vertically offset for clarity.…”

“…[40,41] Consequently, the peak at d = 27 ppm in Figure 3a is assigned to the b-CH 2 and g-CH 2 3 . We note that previous assignments [19,20] of the latter to the a-CH 2 signal of SiOMgA C H T U N G T R E N N U N G (nBu) sites appear to be based on incorrect comparisons with molecular compounds. Stoichiometry of nBu 2 Mg grafting: Information about the mass gain of the silica during grafting, combined with elemental analysis and the total number of silanol groups, allows us to deduce the absolute contribution of each grafting reaction [Eqns.…”

“…Only a handful of previous studies have described the reaction of dialkylmagnesium reagents with silica. [18][19][20] Two…”

“…The alkylmagnesium-modified silica surface is proposed to contain dimers and/or tetramers with the empirical formula Both reactions were proposed to generate the same isolated alkylmagnesium sites, described simply as " SiOMgR". [18][19][20] In two reports, peaks in the 13 C CP/ MAS NMR spectrum of nBu 2 Mg-modified silica in the region of d = 30-35 ppm were assigned to the a-CH 2 signals of [MgnBu] groups, based on their disappearance upon reaction with either HCl or TiCl 4 . [19,20] Changes in the 13 C and…”