Organopalladium-functionalized dendrimers: Insertion of palladium(0) into peripheral carbon-iodine bonds of carbosilane dendrimers derived from polyols. Crystal structure of Si{(CH2)(3)O2CC6H4I-4}(4)

A carbosilane dendrimer with 12 peripheral iodoarene groups, Si{(CH 2) 3{Si(CH 2) 3O 2C(C6H 4I-4)} 3} 4 (G 1-ArI, 5), and the corresponding G 0 model compound, Si{(CH 2) 3O 2CC 6H 4I-4} 4 (G 0-ArI, 4) have been prepared from polyol precursors. These compounds react with Pd(dba) 2/ tmeda (dba = dibenzylideneacetone, tmeda = N,N,N',N'-tetramethylethylenediamine) to yield periphery-palladated complexes, Si{(CH 2) 3O 2C(C 6H 4-4)PdI(tmeda)} 4 (G 0-ArPdI(tmeda), 6) and Si{(CH 2) 3{Si(CH 2) 3O 2C(C 6H 4-4)PdI(tmeda)} 3} 4 (G 1-ArPdl(tmeda), 7). Dendrimer 7 represents the first example of an exclusively σ-bonded completely periphery-palladated dendrimer. Reactions of the model palladium(II) complexes PdI(EtO 2C(C 6H 4)-4)(tmeda) (2) and PdI(EtO 2C(C 6H 4)-4)(bpy) (3) (bpy = 2,2′-bipyridyl) with the transmetalation reagents LiMe and SnMe 4 were not successful, while no reaction occurred with the related reagent Sn(C∼N)Me 3 [C∼N = 8-(dimethylamino)-1-naphthyl]. The molecular structure of G 0-ArI (5) has been determined by X-ray crystallography and has C 2v, symmetry in the solid state.