Synthesis of the complexes [PdCIR(cod)] (R = benzyl, ethyl; cod = 1,5-cyclooctadiene). β-Elimination from [PdCIEt(cod)] to give the η¹,η² and η³ isomers of [Pd₂(μ-Cl)₂(C₈H₁₃)₂]

Abstract

Treatment of [PdCl,(cod)] with tetrabenzyltin gives the benzylpalladium complex [PdCI(CH,Ph)(cod)] (cod = 1.5-cyclooctadiene). la, whose structure has been determined by X-ray crystallography. It adopts approximate square-planar geometry, with the double bonds perpendicular to the square plane. The corresponding ethylpalladium derivative l b has been prepared by a similar-method, but it is considerably less stable. It decomposes by p-elimination to produce ethene and a transient Key words: palladium, diene complexes, allyl complexes, isomerization, p-elimination.RCsurnC : Le traitement du [PdCl,(cod)] avec le tCtrabenzylCtain conduit au complexe benzylpalladium [PdCI(CH,Ph)(cod)] (cod = cycloocta-l,5-dikne), la, dont on a dCterminC la structure par diffraction des rayons X. I1 adopte une gComCtrie plan carrC dans laquelle les doubles liaisons sont perpendiculaires au plan carre. On a prCparC le dCrivC Cthylpalladium correspondant, lb, par une mCthode semblable; il est toutefois beaucoup moins stable. I1 se dCcompose par une Climination P pour former de I'Cthkne et un hydrure complexe transitoire qui peut donner lieu soit B une insertion migratoire conduisant au [Pd,(p-CI),(q1,q2-C,H,,),], 2a, soit h une Climination reductrice dinucleaire avec une deuxikme molCcule de l b qui fournit de I'Cthane, du [PdCl,(cod)], du cyclooctadikne libre et du palladium mCtallique. On a aussi prCparC le complexe 2a par rkaction du [PdCl,(cod)] avec le NaBH,. A des tempkratures plus ClevCes, le composC 2a se transforme en un mClange B I'Cquilibre avec I'isomkre q3-allyle 2b. On a aussi CtudiC les rCactions du [PdCl,(cod)] ou du K,PdCI, en solution aqueuse, en prCsence de cyclooctadikne, qui conduisent aux produits 2a ou 2b.

Nucleophilic Attack of Carbonyl-Stabilized Phosphorus Ylides on 1,5-Cyclooctadiene Complexes of Palladium and Platinum

“…Nucleophilic attack at olefinic bonds coordinated to palladium(II) or platinum(II) has been well studied , and found to be the key step in many catalytic reactions. A wide range of nucleophiles including HO - , , RO - , , RCO 2 - , ,, N 3 - , , H - , Cl - , , NR n H 3 - n , , CN - , NCO - , ,, NO 2 - , ,,, aryl, ,,− acetylacetonate, , diethylmalonate, ethyl acetoacetate, and N , N -dimethylaminonaphthalene (Proton Sponge) have been employed, and enhanced electrophilicity of the olefinic moiety in cationic complexes has been observed . Although phosphorus ylides have never been used in these reactions, a couple of examples were reported in which an (ethylene)iron(II) complex was attacked by an ylide to give a metalated phosphonium complex. , In most cases the attack is produced in an exo fashion to give complexes in which the nucleophile is anti with respect to the metal.…”

Room-Temperature Benzylic Alkylation of Benzylic Carbonates: Improvement of Palladium Catalyst and Mechanistic Study

“…To elucidate the structures and dynamic behaviors of the above (benzyl)palladium species, authentic (η 1 - and η 3 -benzyl)palladium complexes bearing L2 were prepared as shown in Scheme . Pd­(η 1 -benzyl)­Cl­( L2 ) ( 6b ) was obtained from the reaction of Pd­(η 1 -benzyl)­Cl­(cod) ( 9 ) with L2 in CH 2 Cl 2 (eq 3, Scheme ). In the 31 P NMR spectrum of 6b , a pair of doublet peaks appeared at 31.6 and 42.4 ppm with 28 Hz of P–P coupling constant.…”

“…Under a nitrogen atmosphere, dry CH 2 Cl 2 (1.0 mL) was added to a mixture of Pd­(η 1 -benzyl)­Cl­(cod) , (34.0 mg, 0.10 mmol) and L2 (42.0 mg, 0.10 mmol). After the solution was stirred at ambient temperature for 5 min, silver triflate (27.3 mg, 0.11 mmol) was added to the mixture.…”

“…[Pd(η 1 -benzyl)(DiPrPF)]OTf (8b) (Scheme 2, Equation 4). Under a nitrogen atmosphere, dry CH 2 Cl 2 (1.0 mL) was added to a mixture of Pd(η 1 -benzyl)Cl(cod) 8,21 (34.0 mg, 0.10 mmol) and L2 (42.0 mg, 0.10 mmol). After the solution was stirred at ambient temperature for 5 min, silver triflate (27.3 mg, 0.11 mmol) was added to the mixture.…”

Oxygenation of a benzyl ligand in SNS-palladium complexes with O2: acceleration by anions or Brønsted acids

“…The selectivity of the main organic products and formed Pd complexes was regulated primarily by a proton (Scheme 1). 21 pysmepy, and AgOTf, was treated with 1 atm of O2 in CD3CN in the absence or presence of additives. The results are shown in Table 1.…”