Palladium Metal Center Research Articles

C—H...F, C—F...π and C—F...F—C interactions in a palladium(II) benzenethiolate complex

The title compound, [1,1′-bis­(diphenyl­phosphino)ferrocene-κ2P,P′]bis­(2,3,4,5,6-penta­fluoro­benzene­thiol­ato-κS)palladium(II­), [FePd(C6F5S)2(C17H14P)2], crystallizes with two independent mol­ecules in the asymmetric unit. The complex has the palladium metal center in a slightly distorted square-planar environment with the 1,10-bis(diphenylphosphino)ferrocene (dppf) ligand coordinated in a bidentate fashion and, completing the coordination environment, the two –SC6F5 thiol­ates in a cis configuration. The mol­ecules are linked by weak C—F⋯π, C—F⋯F—C and C—H⋯F stacking inter­actions.

Synthesis, characterization, and reactivity of monomeric, arylpalladium halide complexes with a hindered phosphine as the only dative ligand.

We report the isolation and structural characterization of several monomeric arylpalladium(II) halide complexes containing tri-tert-butyl phosphine, 1-adamantyl-di-tert-butylphosphine, or 2-adamantyl-di-tert-butylphosphine. X-ray diffraction, IR spectroscopy, and theoretical studies indicated that the complexes may be stabilized by agostic interactions. For example, the distance from the closest hydrogen atom to the palladium metal center in the X-ray structure of the 1-adamantyl-phenylpalladium bromide complex 1 was 2.26(3) A. The calculated Pd-H distance of 2.28 A and harmonic vibrational frequencies were in agreement with the measured distance, but Wiberg bond indices indicated only weak M-H-C interactions. Addition of 2-adamantyl-di-tert-butyl phosphine to 1 led to ligand exchange and formation of 2-adamantyl-di-tert-butyl phosphine complex 2. Addition of P(t-Bu)(3) generated free aryl bromide and Pd[P(t-Bu)(3)](2). Reactivity of complex 1 with nucleophiles provided evidence of the intermediacy of these complexes in palladium-catalyzed cross-coupling reactions. Complex 1 reacted with amine and base to form the corresponding arylamine, with tert-butoxide to form the corresponding ether, with boronic acid and fluoride to form the corresponding biaryl, and with styrene to form stilbene. This complex also catalyzed the reaction of bromobenzene with diphenylamine in the presence of base to produce 94% of the amination product in 45 min at room temperature. This rate is comparable to the reaction rate of in situ generated catalysts.

Ligand effect on the cationic palladium complexes in polymerization of vinyl ethers

A series of cationic palladium complexes have been used as catalysts on the polymerization of vinyl ethers in excellent yields. The key feature of this study indicates how the ligand donors as well as the cationic nature influence the reactivity of the palladium center in the polymerization of vinyl ethers. It was found that the π-acidic character of imine donors does increase the activity of palladium metal center which catalyzes the cationic polymerization of vinyl ether, whereas the palladium center coordinated with bis-phosphine ligand is completely inactive for the polymerization.

Coordination Chemistry of ADPO

Abstract The hypervalent phosphorus compound, 3,7-di-t-butyl-5-aza-2,8-dioxa-1-phosphabicyclo-[3.3.0]octa-2,4,6-triene (ADPO) forms adducts with chromium, tungsten, nickel and palladium metal centers. All four new adducts contain tetrahedral phosphorus atoms as a result of folding of the ADPO unit. This folding of the planar 10-P-3 ADPO molecule to provide an 8-P-3 center for coordination to the transition metal center is the result of the close energy balance between 10-P-3 ADPO and 8-P-3 ADPO and the strength of the phosphorus-metal interaction. In the case of a homoleptic palladium(II) complex, dimerizati on of the coordinated ADPO unit was observed.