Reactions of acetylenes with noble-metal halides. VIII. Palladium cgloride catalyzed trimerization of 2-butyne and 1-phenyl-1-propyne

Abstract

Reaction of methylphenylacetylene with bis(benzonitrile)palladium chloride (1) in chloroform gave 1,2,4-trimethy 1-3,5,6-triphenylbenzene (2, 58%), l,3,5-trimethyl-2,4,6-triphenylbenzene (3, 39%), and 1,2,3-trimethyl-4,5,6-triphenylbenzene (4, 3%). In benzene, a complex [(PhC2Me)3PdCl2]2 was isolated which readily decomposed to palladium chloride, 2, and 3. 2-Butyne reacted with 1 in benzene to give a complex [Cl(MeC2Me)3-PdCl]2 (6) and in chloroform to give [Cl(MeC2Me)3PdClPdCl2]" (7) and some complex 6. On spectroscopic evidence, both 6 and 7 are assigned structures involving a 2-chloro-3,4,5,6-tetramethyl-2-ira/u,4-cw,6-ira/w-octa-2,4,6triene -bonded at C7 and -bonded at C2,3 to palladium(II). The ligand can take up two positions with respect to the metal, with the coordinated double bond parallel or perpendicular to the coordination plane. Both complexes 6 and 7 decomposed readily to palladium chloride and hexamethylbenzene. A new mechanism for the trimerization of acetylenes is proposed.In 1962 one of us reported3 4a reinvestigation of the reaction, originally described by Malatesta, et al.,* in which diphenylacetylene was dimerized to an ethoxytetraphenylcyclobutenylpalladium chloride complex in the presence of palladium chloride in ethanol. Under slightly different conditions (aprotic solvents) from those used by Malatesta, et al., we observed that diphenylacetylene could also be catalytically trimerized to hexaphenylbenzene. In addition, a tetraphenylcyclobutadienepalladium chloride complex ([Ph4C4( PdCl2)"]z) was formed which eventually deactivated the catalyst.5 These results have been confirmed by a number of workers.6-8These reactions of diphenylacetylene and closely related acetylenes did not readily lend themselves to a more detailed investigation and, since the generality of the reaction was of considerable interest particularly as a very easy route to cyclobutadiene-metal complexes, we began an investigation of the reactions of some other acetylenes with palladium chloride.Our first attempts, using acetylene, propyne, and monophenylacetylene, did not lead to characterizable products. Reactions always proceeded very easily to give mixtures of metal complexes. However, the latter were polymeric and nonstoichiometric in nature and not easily handled. It is probable that the ligands in these complexes are linear polyenes; however, hydrogen-transfer and cyclization reactions are by no means excluded.9

The oligomerization of acetylenes induced by metals of the nickel triad

“…was formed 27 . This same complex was generated by working under very carefully controlled conditions in chloroform.…”

Remarkable features of intermediates in the early transition metal catalyzed conversion of monosubstituted alkenes, dienes and alkynes

“…to regenerate the initial complex. This mechanism has been proposed for the PdCl 2 catalyzed reaction [89] and it is probably applicable to the alkyne conversion promoted by high oxidation state metal compounds such as TaCl 5 and NbCl 5. However, the stoichiometric reactions of TaCl 5 with l-butyne (i:l and 1:3) at 0°C gave no useful information on the reaction pathway since they gave only cyclic trimers in quantitative yield even under such mild conditions.…”

Preparation of bio-polymeric materials, their microstructures and physical functionalities

“…[19][20][21][22] Segmented polyurethanes are elastomeric block copolymers that generally exhibit a phase-segregated morphology made up of soft rubbery segments and hard glassy or semi-crystalline segments. 23,24 The soft segment usually consists of polyether or polyester diols, whereas the hard segment consists of the diisocyanate component and a low molecular weight consists of the diisocyanate component and a low-molecular-weight chain extender.…”

“…Guo et al applied the epoxidation of the double bonds of fatty acids, followed by nucleophilic ring opening of the epoxide to make polyols for producing polyurethanes. [19][20][21][22][23] To further expand applications of the bio-based polymeric materials, previous studies were focusing on converting vegetable oils into useful PUs. Based on these studies, now it has become a main research field to functionalize vegetable oils by the introduction of aromatic co-monomers into the polymer structure, which could be suitable in the search for new viable polymeric materials.…”