Bertus A. Markies

Synthesis and structural studies of phenyl(iodo)- and methyl(phenyl)palladium(II) complexes of bidentate nitrogen donor ligands

Phenylpalladium(I1) complexes of the type PdIPh(N-N), with N-N = N,N,N’,N’-tetramethylethylenediamine (tmeda) or 2,2’-bipyridyl (bpy), can be conveniently prepared in 70-95% yield by oxidative addition of iodobenxene to bis(dibenzylideneacetone)palladium(0) in the presence of the appropriate nitrogen donor ligand. The bromo analogues were obtained in only S-12% yield in this way. The complex PdIPh(tmeda) (la) reacts readily with MeLi to give PdMePh(tmeda) (3) in 88% yield, whereas PdIPh(bpy) (la) gives PdMePh(bpy) (4) and PdMe,(bpy) in varying ratios. The formation of PdMe,(bpy) was found to result from the synergistic action of lithium iodide and methyllithium. Pure PdMePh(bpy) (4) was obtained in 82% yield via ligand-exchange from PdMePh(tmeda) (3). The crystal structures of PdIPh(N-N) (la, 2a) and PdMePh(N-N) (3, 4) complexes were determined by X-ray diffraction studies. The results show that the phenyl group is always oriented perpendicular to the coordination plane aroutd palladium, with the largest deviation found for 3 (14.3(2)“). The Pd-N bond distances in the tmeda complexes (2.127(6)-2.210(3) A) are larger than those in the bpy-coordinated complexes (2.870(8)-2.144f8) A). Similarly, the Pd-CfMe) bond distances (2.5703(8) and 2.575(l) & are larger than the Pd-C(Ph) bond distances (1.985(3)-1.996tlO) A)>.

Selectivity in reductive elimination and organohalide transfer from methyl(aryl)benzylpalladium(IV) complexes of bidentate nitrogen donor ligands, PdBrMe(Ar)(CH2Ph)(L2)

Oxidadve addiion of iodoarenes to bis(dibenzylideneacetone)palladium(0) in the presence of N.N. N’,N’-tetramethylethylenediamine (tmeda) affords PdIAr(tmeda) (Ar = 4-MeC6H4, 4-MeOC6H4, 4-Me(O)C6H4, 4-O2NC6H4, 3-MeOC6H4) in high yield. Some of these complexes (Ar = 4-MeC6H4, 4-MeOC6H4, 3-MeOC6H4) react with LiMe to form PdMeAr(tmeda), and the methyl(aryl)palladium(II) complexes react wbb 2,2’-bipyridyl (bpy) or 1,10-phenanthroline (phen) to afford PdMeAr(L2): PdMePh(phen) may be obtained similarly. All of the diorganopalladium(II) complexes of bpy and phen react with benzyl bromide to form PdBrMeAr(CH2Ph)(L2) but a complex could not be isolated for Ar = 3-MeOC6H4, L2 = bpy. The isolated palladium(IV) complexes react wbh PdMe2(bpy) at -20°C in (CD3)2C0 to selectively transfer henzy1 bromide to give PdMeAr(L2) and PdBrMe2(CH2Ph)(bpy) respctively. The complexes PdBrMeAr(CH2Ph)(bpy) (Ar = Pb, 4-MeC6H4. 4MeOC6H4) undergo selective reductive elimination of Ar-Me in CDCl3 to form PdBr(CH2Ph)(L2), but PdBrMeAr(CH2Ph)(phen) (Ar = Ph. 4-MeC6H4, 4-MeOC6H4, 3-MeOC6H4) give mixtures of PdBr(CH2Ph)(phen) and Me-Ar togaher with lesser amounts of PdBrMe(phen) and Ar-CH2Ph (ca. 10-20%).

Insertion of Isocyanides into the Palladium-Carbon Bond of Cyclopalladated Complexes

Insertion of isocyanides into the Pd-C bond has been observed in the reactions of PdBr[C6H3(CH2NMe2)2-2,6] with isocyanides CNR which give the complexes PdBr[C(=NR)C6H3(CH2NMe2)2-2,6-C̲,N̲](CNR) (2a-d). An imino bridged complex 5 is formed on heating the imino complex PdCl[C(=NCH2CO2Et){C6H4(CH2NMe2)-2}](CNCH2CO2Et). The structures of 2c (R = nBu) and 5 have been determined by X-ray crystallography.

Insertion of norbornene into aryl–palladium(II) bonds: mechanistic aspects of the subsequent C–H activation

The insertion of norbornene into the Pd–C bond of the cationic phenylpalladium(II) complex [PdPh(pmdien)]OTf (2, pmdien =N,N,N′,N′,N″-pentamethyldiethylenetriamine, OTf = trifluoromethanesulfonate) yields a 1 : 1 enantiomeric mixture of an ortho 2-exo-norbornyl-substituted phenylpalladium(II) compound via selective, intramolecular C–H activation of the phenyl ring.

Anion-Controlled Oligomerization of Carbon Monoxide and Norbornene on a Palladium(II) Centre

The insersiotion of both norborene and corbon monoxide into the Pd–C bond of 2,2′-bipyridly coordinated palladium(II) complexes can be controlled by the nature of the anions present in soloution, and this allows the stepwise synthesis of a metal-bound CO/norbornene co-oligomer of which an X-ray crystal Structure is presented.

A second polymorph of 2,2'-bipyridyl-(methyl)(phenyl)palladium(II)

The crystal structure of a second polymorph of [Pd(CH 3 )(C 6 H 5 )(C 10 H 8 N 2 )], containing four crystallographically independent molecules, is presented and compared with the structure of the previously reported polymorph [Markies et al. (1994). J. Organomet. Chem. 482, 191-199] containing only one crystallographically independent molecule. In both polymorphs molecules lie in infinite stacks, surrounded by six similar stacks ; the main difference between the two polymorphs is about 23° in the tilt angle of the coordination plane with reference to the stacking direction.

(2-Acetylbicyclo[2.2.1]heptyl-C3,O)(2,2'-bipyridyl)palladium(II) Trifluoromethanesulfonate 0.5-Diethyl Ether Solvate

The norbornyl moiety in the title compound, [Pd(C9HI3- O)(CIoHsN2)]CF3SO3.0.5C4H10 O, is selectively cis, exo substituted on the 2 and 3 positions with the acetyl substituent bonded intramolecularly via its O atom to the palladium(II) centre.