On the mechanism of platinum(II)/SnCl2 catalyzed hydroformylation of olefins. Studies of the reactivity of alkyl complexes containing chelating diphosphines

Xantphos as cis- and trans-chelating ligand in square-planar platinum(II) complexes. Hydroformylation of styrene with platinum–xantphos–tin(II)chloride system

“…The role of tin(II)halide (in most cases tin(II)chloride) is crucial, but not fully cleared up considering all steps of the catalytic cycle. It can act as a SnCl À 3 counter-ion, a Lewis acid and a trichlorostannato-ligand bonded to platinum by forming a Pt-Sn bond [9,12,13]. In case of generally used bidentate ligands, coordinated in cis-manner exclusively, ionic mechanism has been postulated for the CO activation step, its insertion into the Pt-alkyl bond forming Pt-acyl complexes and that of the product forming step.…”

(Diphosphane monosulfide)platinum(II) Complexes for Hydroformylation Reactions: Their Catalytic Activity and a High‐Pressure NMR Mechanistic Study

“…The correlation of activity with ring size is consistent with a chelating structure being maintained in the rate-determining steps of the catalysis, although it has been suggested that the dppb may, alternatively, form oligomeric/polymeric metal species. [23] The presence of SnCl 2 is essential to the generation of effective catalyst systems from both neutral and cationic precursors, thus indicating that the role of SnCl 2 is more than simply the generation of an active site at Pt by removal of Cl -. However, the presence of excess SnCl 3 -is detrimental to the catalysis under our conditions.…”

“…This effect has previously been reported and ascribed to a lowering in the activation energy for the hydrogenolysis step. [22,23] …”

“…The use of chelating diphosphanes brings about considerable activity enhancement, especially in the case of dppb, [22] and Scrivanti et al have performed a mechanistic study intended to explain why the sevenmembered metallacycle is the most efficient. [23] Heteroditopic ligands are chelating compounds endowed with different chemical functionalities capable of coordinating to a metal centre. The very different trans effects produced by the dissimilar donor atoms in these ligands offer the potential to introduce widely different activity and selectivity at selected coordination sites in metal complexes and has resulted in such ligands receiving increasing attention in the field of organometallic chemistry and catalysis.…”

Platinum–alkyl–B(C6F5)3 (or BF3) ‘in situ’ systems as tin(II) halide-free enantioselective hydroformylation catalysts

“…Most of these investigations were focused on the necessity of tin(II) chloride in the catalytic system [16,17]. The crucial role of the trichlorostannato ligand as a facile leaving group, formed upon 'carbene-like' insertion of tin(II) chloride into the platinum-chloride bond, has been shown by HP NMR investigations as well [18].…”