A well-defined silica-supported dinuclear tungsten(iii) amido species: synthesis, characterization and reactivity

Abstract

Grafting of [W(2)(NMe(2))(6)] onto dehydroxylated silica affords the well-defined surface species [([triple bond, length as m-dash]Si-O)W(2)(NMe(2))(5)], characterized by elemental analysis, and infrared, Raman and NMR spectroscopies, and the catalytic reactivity of this supported tungsten(III) d(3)-d(3) dimer and of its alkoxide derivatives towards alkynes has been probed.

Expanding the scope of metathesis: a survey of polyfunctional, single-site supported tungsten systems for hydrocarbon valorization

“…68 An alternative to the direct grafting of the organometallic carbyne complex is found in the immobilization of a binuclear d 3 -d 3 tungsten amido derivative onto SiO 2-700 . 105 The resulting well-defined species [(SiO)W 2 (NMe 2 ) 5 ] was characterized by a combination of elemental analysis, IR, Raman and MAS NMR spectroscopy, supported by DFT calculations (Scheme 22). 105 The precatalyst XIII proved to be unreactive toward 4-nonyne.…”

“…105 The resulting well-defined species [(SiO)W 2 (NMe 2 ) 5 ] was characterized by a combination of elemental analysis, IR, Raman and MAS NMR spectroscopy, supported by DFT calculations (Scheme 22). 105 The precatalyst XIII proved to be unreactive toward 4-nonyne. 105 Bearing in mind that the alcoholysis of the dimethylamido ligands by tert-butanol leads to [W 2 (O t Bu) 6 ], a precursor for metathesis catalysts of the [( t BuO) 3 WRC-R] type, [106][107][108] in situ activation was performed with 5 equivalents of t BuOH per W 2 to XIII.…”

A New Donor‐Stabilized Ditungsten Amido Alkoxido Species: Synthesis, Crystal Structure, Fluxionality, and Grafting onto Silica

“…Indeed, the 13 C CP MAS NMR spectrum of ϵSi-O-[W 2 (NMe 2 ) 5 ] comprises three peaks at δ = 58.2, 47.8, and 37.6 ppm. [9] Other WNMe signals may be hidden under the broad peak centered at δ = Figure 8. 13 C CP MAS spectrum of 4 (100.6 MHz; * denotes rotation peaks).…”

“…Aromatic protons resonate at δ = 7.2 and 9.3 ppm, the latter being assigned to C-Hs in the ortho position of the pyridine www.eurjic.org 1 H 2D double-quantum MAS spectrum of 4 using excitation/reconversion pulse train of one rotor period (50 μs) (800.13 MHz, 20 kHz spinning speed, pulse radio frequency 80 kHz). [9] The other three signals at 1.2, 0.8, and 0.1 ppm are assigned to either NMe or diastereotopic CMe groups. [20] The high number of signals is in line with the lowering of the symmetry and increased rotation barriers due to the increased bulk resulting from the silica surface.…”

“…[9] As the supporting of organometallic species plays a significant role in this chemistry, this prompted us to probe the effect of grafting on other (potential) catalysts.…”