Metals in organic syntheses

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

“…The dependence of the CO insertion reaction on SnCl 2 for P ∧ PS ligand complexes contrasts with the situation for Pt II complexes of diphosphane [18,19,50] or P ∧ N ligands, [24] for which no such requirement is reported. The reluctance of CO to insert into the Pt-alkyl bond in the absence of SnCl 2 provides a ready explanation for the initially surprising inactivity of the cationic complex 4a in olefin hydroformylation in the absence of a co-catalyst (entry 6 of Table 1).…”

Intramolecularly Stabilised Group 10 Metal Stannyl and Stannylene Complexes: Multi‐pathway Synthesis and Observation of Platinum‐to‐Tin Alkyl Transfer

“…It could mean that the role of SnCl 2 as co-catalyst in palladium-and platinum-based catalytic systems may be different from previous propositions in which SnCl 2 is believed to lead to the formation of a SnCl 3 ligand that serves as a weakly coordinating anion and/or as a trans-labilising ligand. [8,[22][23][24][25] Based on the observations in this study, it is conceivable that an alkyl group on palladium can transfer to the tin centre of the trichlorostannyl ligand during a catalytic reaction (analogous to step (iii)) to form a more stable resting state that cannot undergo b-H elimination. To the best of our knowledge, such a possibility has not been previously observed or suggested in the context of catalysis by Group 10 metal complexes.…”

“…[17][18][19][20][21] Although the exact role of SnCl 2 as a co-catalyst is not completely understood, it is believed that it inserts into the MÀCl bond (M = Group 10 metal), forming trichlorostannyl species [MÀSnCl 3 ] where SnCl 3 À serves as a weakly coordinating anion and/or as a trans-labilising ligand. [8,[22][23][24][25] Recently, we reported on the formation of Group 10 diphosphinostannylene complexes consisting of a central SnCl 2 stan-nylene moiety buttressed by two 2-diphenylphosphinopyridine ligands (PyPPh 2 ; a) [Eq. (1)].…”

Mechanistic studies on the formation of Pt(II) hydroformylation catalysts in imidazolium-based ionic liquids

“…In these systems SnCl 2 is usually added to the reaction mixture to act as a co-catalyst. On addition of SnCl 2 to a solution of cis- indicating the formation of the activated complex which is suggested to be cis-[Pt II (PPh 3 ) 2 Cl(SnCl 3 )] or cis-[Pt II (PPh 3 ) 2 (SnCl 3 ) 2 ] depending on the number of SnCl 2 molecules inserted into the Pt-Cl bond (see Scheme 1) [7,8]. This aspect was investigated in detail in the present study based on earlier work performed by Wasserscheid and Waffenschmidt [9], in which they studied the performance of the mentioned hydroformylation catalyst in chlorostannate melts.…”