Evidence for a reversible 1,2-hydrogen shift (α elimination) in some bis(η-cyclopentadienyl)tungsten compounds
The reaction of [W(η-C5H5)2(C2H4)Me][PF6] with PMe2Ph gives [W(η-C5H5)2(CH2CH2PMe2Ph)Me][PF6](2) which eliminates ethylene when heated to give, in sequence, [W(η-C5H5)2(CH2PMe2Ph)H][PF6](3) and [W(η-C5H5)2Me(PMe2Ph)][PF6](4). Repeating this sequence with the deuteriated methyl analogues shows that the CD3 unit in (2) is reformed quantitatively in (4) and supports the proposal that the mechanism of the reaction involves a reversible 1,2-hydrogen shift equilibrium between the intermediates [W(η-C5H5)2Me]+ and [W(η-C5H5)2(CH2)H]+. The compounds [W(η-C5H5)2L(Me)](L = SEt2 or PPh3) and [W(η-C5H5)2Me(I)] have also been prepared and treated with PMe2Ph to give (3). Some implications of the 1,2-hydrogen shift (α elimination) are discussed.
- This article is part of the themed collection: Malcolm Green FRS: In celebration of his 80th Birthday