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

Abstract

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)>.

Synthesis and Reactivity of 2-Aminophenylpalladium(II) Complexes: Insertion Reactions of Oxygen and Carbon Monoxide into Carbon−Palladium Bonds—New Examples of “Transphobia”

“…[79±81] and in some [PdI(R)(bpy)] complexes are in the range 2.575 ± 2.591 . [82,83] The CÀO bond lengths in (Figure 4, right). The last ones lead to a polymeric structure.…”

Synthesis and reactions of heterodinuclear organopalladium–cobalt complexes acting as copolymerization catalyst for aziridine and carbon monoxide

“…Probably CO, which was produced by partial decomposition of tetracarbonylcobalt anion, is considered to insert into the Pd-C bond. In fact, under carbon monoxide atmosphere, pure acylpalladium-cobalt complex, L 2 (RCO)Pd-Co(CO) 4 (L 2 = bpy, R = Me (5), Ph (6); L 2 = tmeda, R = Me (7), Ph (8); L 2 = phen, R = Me (9), Ph (10)) was obtained by the reactions of PdRIL 2 with anionic cobalt complex Na + [Co(CO) 4 ] À in THF (Eq. (1)).…”

“…Large negative values of the entropy change probably suggest strong solvation in the ionic products. Table 3 Selected bond lengths and angles for (bpy)(PhCO)Pd-Co(CO) 4 (6), (tmeda)(PhCO)Pd-Co(CO) 4 (8), and (phen)(MeCO)Pd-Co(CO) 4 (9) Bond lengths (Å ) for (bpy)(PhCO)Pd-Co(CO) 4 (6) Pd(1)-Co (1) 2.569 (5) Pd (1) (14) 2.452(4) Pd(1)-C(17) 2.521 (5) Co (1)-C(14) 1.758 (5) Co(1)-C(15) 1.781 (6) Co (1)-C(16) 1.770 (5) Co (1) (2) Unfortunately no relation between the polymer yield after 3 h catalyzed by complex 1 and the free energy difference DG for aziridine coordination to 1 was observed. This suggests the importance of the successive following process such as C-N bond cleavage and CO insertion in the catalytic copolymerization.…”

Peripherally Metallated Porphyrins: the First Examples of meso‐η1‐Palladio(II) and ‐Platinio(II) Complexes with Chelating Diamine Ligands

“…It is well-known that aromatic iodo groups undergo palladium(0)-catalysed coupling reactions at a much greater rate than those of bromo analogues. [21] This has also been shown to be true for 5-bromo-15-iodo-10,20-diarylporphyrins, which are found to undergo palladium(0)-catalysed coupling reactions at the iodo-substituted position preferentially over the bromo-substituted position. [17,22] With this in mind, the oxidative addition reactions of the platinum(0) diphosphane precursors were repeated with a range of iodoporphyrins; unfortunately, these also failed to give the desired η 1 -organometallic porphyrins.…”