Neutral and Cationic Palladium Complexes of P‐Stereogenic Phosphanes Bearing a Heterocyclic Substituent

Abstract

The coordination chemistry of 13 optically pure P‐stereogenic diarylmonophosphanes P(Het)PhR [Het = 4‐dibenzofuranyl (DBF), 4‐dibenzothiophenyl (DBT), 4‐dibenzothiophenyl S,S‐dioxide (DBTO2) and 1‐thianthrenyl (TA); R = OMe, Me, iPr, Fc (ferrocenyl)] to Pd‐allyl moieties is described. Both neutral [PdCl(η3‐(2‐methylallyl)(κP‐P)] and cationic [Pd{η3‐(2‐methylallyl)(κP‐P)2}]PF6 complexes have been prepared. Coordination of the heteroatom of the heterocycle was only possible in the case of TA‐based phosphanes; these furnished complexes of the type [Pd{η3‐(2‐methylallyl)(κ2P,S‐P)}]PF6 after chloride abstraction with TlPF6. The crystal structure of the complex [Pd(η3‐2‐methylallyl)(κ2P,S‐PPh(OMe)(1‐TA)]PF6 is reported. The neutral Pd complexes were found to be highly active in the hydrovinylation of styrene after activation with AgBF4, except for the TA‐based phosphanes. The cationic Pd complexes were evaluated in allylic alkylation and amination with the model substrate rac‐trans‐1,3‐diphenylprop‐2‐enyl acetate (rac‐I), achieving total conversions and up to 70 % ee.

Cyclometallated ruthenium complexes with P-stereogenic monophosphines containing a polycyclic aromatic substituent

“…The results of conversion and enantioselectivity obtained with cyclometallated precursors C, along with those with C' [15,16] for comparison are given in Table 1.…”

“…Our group has worked with several types of chiral phosphines and with the corresponding palladium and ruthenium complexes that have been used in catalytic hydrovinylation (Pd) [13], allylic substitution (Pd) [13d,14], cyclopropanation (Ru) [15] and transfer hydrogenation (Ru) [13d, 15,16] reactions.…”

Formation of Allylpalladium Complexes and Asymmetric Allylation Involving Modular Bridging Diamidophosphite-Sulfides Based on 1,4-Thioether Alcohols

“…The C form is represented by two resonances of equal intensity due to the nonequivalence of two phosphorus nuclei. Note that this type of isomerism for η 3 -allylic P,S -chelate complexes in solution is a well-known phenomenon. ,, The 13 C­{ 1 H} NMR spectra show that the chemical shifts for the terminal η 3 -allylic carbons in the cis and trans positions relative to the P atoms differ significantly. The existence of the Pd­(allyl)-P,S fragments is also confirmed by the difference in multiplicity for these nuclei: trans -located methylene carbons are doublets with large C–P coupling constants, while the cis -located carbons are singlets.…”

Digold(I) Thianthrenyl Complexes. Effect of Diphosphine Ligands on Molecular Structures in the Solid State and in Solution

“… 10 − 12 Pd complexes containing a phosphine ligand bearing a thianthrenyl substituent have been reported to form a cyclic compound with a Pd–S bond. 13 An Fe complex with η 6 -coordinated thianthrene has also been prepared and reported to show electrochemical responses from the ligand and Fe centers. 14 However, studies on transition-metal complexes with C-bonded thianthrenyl ligands are scarce.…”

“…Thus, we attempted the synthesis of digold­(I) complexes with polyaromatic ligands in order to stabilize the U-shaped structure by the π–π interaction of the two aromatic ligands. Thianthrene has been reported to form complexes with Ag­(I), Au­(I), and Pd­(II) as neutral S-ligands. − Pd complexes containing a phosphine ligand bearing a thianthrenyl substituent have been reported to form a cyclic compound with a Pd–S bond . An Fe complex with η 6 -coordinated thianthrene has also been prepared and reported to show electrochemical responses from the ligand and Fe centers .…”