Gerardus M. Kapteijn

Influence of fluorine on aromatic interactions

Non-covalent interactions between aromatic ligands influence the conformations of metal complexes, and the system [M(OAr)2L2] has been used to investigate the difference between phenyl–phenyl, phenyl–pentafluorophenyl and pentafluorophenyl–pentafluorophenyl interactions. X-Ray crystal structures show that pentafluorophenyl groups adopt partially stacked orientations with the two aromatic rings close to parallel and with significant π overlap. In contrast, phenyl groups are skewed away from each other with only edge-to-face contacts. Phenyl–pentafluorophenyl interactions adopt a coplanar fully stacked geometry. These results have been rationalised on the basis of energy calculations (carried out blind) using a variety of empirical models for treating weak non-covalent interactions. The major cause of the different behaviour of the three systems lies in the electrostatic interactions between the π systems.

A new mixed alkoxo aryloxo palladium complex with a bidentate nitrogen donor system

Abstract The reaction of [Pd(OPh)2(bpy)] with 1,1,1,3,3,3-hexafluoro- 2-propanol affords a ‘mixed’ aryloxo alkoxo palladium complex, [Pd(OCH(CF3)2)(OPh)(HOPh)(bpy)] (4). A single crystal X-ray diffraction study of 4 shows the presence of an intermolecular OH···O hydrogen bond and an intramolecular CH···O interaction, which could represent the initial stage of a base-assisted β-hydride elimination.

Diamino-ligated platinum(II) and platinum(IV) phenoxide complexes; syntheses and crystal structures

Abstract The reaction of the diamino-ligated dimethylplatinum(II) complex [Pt(Me)2(bpy)] (bpy = 2,2′-bipyridyl) with phenol affords the new complex [Pt(Me)(OPh)(bpy)] (1). The X-ray crystal structure of square-planar 1 is reported: orthorhombic, space group P212121 No. 19), a = 9.1625(12), b = 12.3922(12), c = 13.3181(13) A , Z = 4 . Reaction of complex 1 with MeI or benzyl bromide affords the novel six-coordinate platinum(IV) aryloxide complexes [Pt(Me)2(I)(OPh)(bpy)] (2) and [Pt(Me)(CH2Ph)(Br)(OPh)(bpy)] (3), respectively. The X-ray crystal structure of octahedral 2 is reported: monoclinic, space group P21/c (No. 14), a = 10.0194(6), b = 10.5126(10), c = 17.6596(14) A , β = 104.159(6)°, Z = 4 . The iodide complex 2 exists as a mixture of two isomers in solution (the major one corresponds to that of trans oxidative addition), whereas the bromide complex 3 is found only as the trans oxidative addition product.

Chemistry of diamino-ligated methylpalladium(II) alkoxides and aryloxides (part II): Methoxide formation and carbonylation reactions

Abstract Reaction of N-ligated methylpalladium(II) alkoxide and aryloxide complexes [Pd(Me)(OR)(N ∼ N)] (R = Ph, CH(CF3)2; N ∼ N tmeda (N,N,N′,N′-tetramethylethylenediamine) or bpy (2,2′-bipyridyl)) with carbon monoxide produces the corresponding methylesters in high yields. The insertion takes place either into the PdMe bond (aryloxide complexes) or into the PdOR bond (alkoxide complexes). Methylalladium(II) methoxide complexes [Pd(Me)(OMe)(N∼N)] (N ∼ N = tmeda, bpy) have been generated in situ by aryloxide- or alkoxide-methanol exchange reactions for which the equilibrium constants have been determined. The bpy-ligated methylpalladium methoxide complex undergoes insertion of CO producing either a methylpalladium methoxycarbonyl complex [Pd(ME(CO2Me)(bpy)] at −60°C) or an acylpalladium methoxycarbonyl complex [Pd(COMe)(CO2Me)(bpy)] (at −25°C); both carbonylated species could be isolated nd characterized at low temperature.

Carbonylation of diamino-ligated methylpalladium(II) methoxide complexes

Abstract The methylpalladium(II) methoxide complexes [Pd(Me)(OMe)(N∼N)] (N∼N)=tmeda or bpy) have been synthesized by alkoxidemethanol exchange of [Pd(Me)(OCH)(CF 3 ) 2 )(N∼N)] in MeOH. The bpy complex undergoes insertion of CO to give either a methyl(methoxycarbonyl) complex [Pd(Me)(CO 2 Me)(bpy)] (at −60°C) or an acyl(methoxycarbonyl) complex [Pd(COMe)(CO 2 Me)(bpy)] (at −25°C). Both carbonylated species were isolated and characterized at low temperature.