169207-35-6Relevant academic research and scientific papers
Protonation of trans-2-MeCCH)2(Ph2PCH2CH2PPh2)2>: Mechanism of Formation of trans- (X = Cl or Br) or trans-
Henderson, Richard A.,Oglieve, Kay E.,Salisbury, Philip
, p. 2479 - 2488 (1995)
The reaction between trans-2-MeCCH)2(Ph2PCH2CH2PPh2)2> and an excess of anhydrous HX (X = Cl or Br) in tetrahydrofuran gives trans- and the evolution of 1 mol equivalent of MeCCH.Mechanistic studies indicated that initial protonation of trans-2-MeCCH)2(Ph2PCH2CH2PPh2)2> occurs at a propyne ligand to form the vinyl species, trans-2-MeCCH)(Ph2PCH2CH2PPh2)2>(1+), and at low concentrations of acid rate-limiting dissociation of the other trans-propyne, followed by attack of halide ion at the molybdenum, produces trans-.At high concentrations of acid further rapid protonation of the vinyl ligand occurs to give trans-2-MeCCH)(Ph2PCH2CH2PPh2)2>(2+).This second protonation further labilises the trans-propyne which is lost in the rate-limiting step and subsequent attack of halide gives trans-(1+).Dissociation of a proton gives the product, trans-.The reaction between trans-2-MeCCH)2(Ph2PCH2CH2PPh2)2> and HBF4*OEt2 gives a mixture of trans- and the alkylidyne complex: trans-.The alkylidyne complex has been isolated pure by fractional crystallisation.The factors which discriminate between the formation of the vinyl and alkylidyne species are discussed.
