Acetylene catalytic hydrochlorination over mechanically pre-activated K2PdCl4 salt: A study of the reaction mechanism

Mechanical pre-grinding of solid K2PdCl4 in a vibratory micromill under acetylene or propylene atmosphere leads to the formation of catalyst for acetylene hydrochlorination by gaseous HCl. The active sites of the heterogeneous catalyst are Pd(II)chloro complexes with a coordination vacancy, capable reversibly form pi-acetylene complexes. The HCl molecules participate in two steps of the reaction: acetylene chloropalladation (rate-limiting step) forming intermediate sigma-chlorovinyl Pd(II) derivative and protonolysis of the last one. (C) 2012 Elsevier Inc. All rights reserved.