Poly(benzyl ether) Dendrimers Functionalized at the Core with Palladium Bis(N-Heterocyclic Carbene) Complexes as Catalysts for the Heck Coupling Reaction.

Bis(imidazolylidene)palladium complexes 9-12 containing a sterically hindered aryl group (mesityl or 2,6-diisopropylphenyl) and a poly(benzyl ether) dendron as N-substituents of the NHC ligand are accessible up to the third generation by transmetalation of the corresponding silver complexes. Complexes 9-12 are soluble, active, and very stable catalysts under Heck reaction conditions. The NHC ligand appears to be stably coordinated to the Pd during catalysis.

Dendronized scorpionate complexes of molybdenum in low and high oxidation states.

Tridentate (L(3)) and bidentate (L(2)) poly(pyrazolyl)methane ligands (Gn-dend)OCH(2)C(pz)(3) (1-4) and (Gn-dend)CH(3,5-Me(2)pz)(2) (pz = pyrazol-1-yl) have been used to synthesize the molybdenum(0) complexes [Mo(CO)(3)(L(3))] (G0-G3, 5-8), [Mo(CO)(4)(L(2))] (G0-G1, 13-14), and [Mo(CO)(3)(NCMe)(L(2))] (G0, 15), and the molybdenum(VI) complexes [MoCl(2)O(2)(L(2))] (9-12). The G0-G3 prefixes represent the generation of poly(aryl ether) dendrons in which the metal complexes are embedded. The molecular structures of compounds 13 and 15 have been determined by X-ray diffraction studies and the hydrodynamic radii of tricarbonyl complexes 5-8 calculated by diffusion-ordered NMR spectroscopy (DOSY).

Crystal structures of poly(aryl ether) dendrons with palladium scorpionate complexes at their focal point.

Novel palladium(II) complexes with bis(pyrazol-1-yl)methane ligands at the focal point of G0-G3 poly(aryl ether) Fréchet-type dendrons are reported. The molecular structures of the metallodendrimer series G0, G1, and G2 [(dend)CH(3,5-Me2pz)2(PdCl2)] have been determined by X-ray diffraction methods. The three structures show a similar three-dimensional organization of the metal complex, which is progressively engulfed by the branches with increasing dendrimer generation.