701913-42-0Relevant articles and documents
Kinetic and spectroscopic studies of the [palladium(Ar-bian)]-catalyzed semi-hydrogenation of 4-octyne
Kluwer, Alexander M.,Koblenz, Tehila S.,Jonischkeit, Thorsten,Woelk, Klaus,Elsevier, Cornelis J.
, p. 15470 - 15480 (2007/10/03)
The kinetics of the stereoselective semi-hydrogenation of 4-octyne in THF by the highly active catalyst [Pd{(m,m′-(CF3)2C 6H3)-bian}(ma)] (2) (bian = bis(imino)acenaphthene; ma = maleic anhydride) has been investigated. The rate law under hydrogen-rich conditions is described by r = k[4-octyne]0.65[Pd]-[H2], showing first order in palladium and dihydrogen and a broken order in substrate. Parahydrogen studies have shown that a pairwise transfer of hydrogen atoms occurs in the rate-limiting step. In agreement with recent theoretical results, the proposed mechanism consists of the consecutive steps: alkyne coordination, heterolytic dihydrogen activation (hydrogenolysis of one Pd-N bond), subsequent hydro-palladation of the alkyne, followed by addition of N-H to palladium, reductive coupling of vinyl and hydride and, finally, substitution of the product alkene by the alkyne substrate. Under hydrogen-limiting conditions, side reactions occur, that is, formation of catalytically inactive palladacycles by oxidative alkyne coupling. Furthermore, it has been shown that (Z)-oct-4-ene is the primary reaction product, from which the minor product (E)-oct-4-ene is formed by an H2-assisted, palladium-catalyzed isomerization reaction.
Stable Platinum(0) Catalysts for Catalytic Hydrosilylation of Styrene and Synthesis of [Pt(Ar-bian)(η2-alkene)] Complexes
Sprengers, Jeroen W.,De Greef, Michiel,Duin, Marcel A.,Elsevier, Cornelis J.
, p. 3811 - 3819 (2007/10/03)
The use of alkenes and bidentate N-ligands in the platinum(0)-catalyzed hydrosilylation of styrene with triethylsilane has been evaluated. A number of bidentate N-ligands, phen, bpy, dafo, and phenyl-bian, were tested at various reaction temperatures using in situ formed catalysts with [Pt(nbe)3] as a precursor. The main conclusions are: (i) ligands, such as phen, which form stable platinum(0) complexes, give lower catalytic activities compared to the ligands which form less stable complexes; (ii) a small ligand effect is observed with dafo and phenyl-bian compared to [Pt(nbe)3], the precursor complex, displaying the lability of these ligands. The complex [Pt(nbe)3], that only has labile alkene ligands, is an active catalyst at low temperatures. At higher temperatures, the catalyst is no longer stable and a decrease in yield is observed. Several novel complexes have been synthesized: [Pt(m,m-(CF3)2-C6H 3-bian)(tcne)], [Pt(m,m-(CF3)2-C6H3-bian)(ma)], [Pt(p-MeO-C6H4-bian)(ma)], [Pt(p-MeO-C6H 4-bian)(dmfu)] and [Pt(phenyl-bian)(dmfu)]. Whereas the two [Pt(Ar-bian)(ma)] complexes are intrinsically more active than the two [Pt(Ar-bian)(dmfu)] complexes, the latter are much more stable, i.e. the nature of the alkene in these complexes is an important factor in determining their catalytic behavior. Compared to [Pt(Me-nq)(nbe)2], the two [Pt(Ar-bian)(dmfu)] complexes are much more stable resulting in significantly higher overall yields. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
