Direct Transformation of Ethylene to Propylene by Cascade Catalytic Reactions under Very Mild Conditions

Ring Contraction of a Tungstacyclopentane Supported on Silica: Direct Conversion of Ethylene to Propylene

The reaction of W(NAr)(¹³C₄H₈)(OSiPh₃)₂ (1) (NAr = 2,6-diisopropylphenylimido) with silica partially dehydroxylated at 700 °C (SiO_2-700) is highly dependent on the reaction conditions. The primary product of this reaction is W(NAr)(¹³C₄H₈)(OSiPh₃)(OSi(O-)₃) (2) when the reaction is carried out in the dark. Grafting 1 onto SiO_2-700 in ambient lab light results in the formation of 2, W(NAr)(¹³CH₂¹³CH₂)(OSiPh₃)(OSi(O-)₃) (4), and one isomer of square-pyramidal W(NAr)(¹³CH₂¹³CH(¹³Me)¹³CH₂)(OSiPh₃)(OSi(O-)₃) (3). Heating 2 to 85 °C for 6 h results in the formation of 3, 4, W(NAr)(¹³CH(¹³Me)¹³CH₂¹³CH₂)(OSiPh₃)(OSi(O-)₃) (5), and W(NAr)((¹³CH₂)₂¹³CH(¹³Me)(¹³CH₂)₂)(OSiPh₃)(OSi(O-)₃) (6). Photolysis of 2 with blue LEDs (λ_max = 450 nm) produces 4, both isomers of 3, 5, and free ethylene. In the presence of excess ethylene and blue LED irradiation at 85 °C, 1/SiO_2-700 catalyzes the direct conversion of ethylene to propylene.

Kinetic and mechanistic insights into Ni-AlKIT-6 catalyzed ethylene oligomerization

An experimental study of the ethylene dimerization and isomerization performed on a mesoporous 2 wt% Ni-AIKIT-6 showed that the kinetically determining step is the insertion of ethylene in the metal–alkyl bond at the nickel site neighborhood.