Dendrimer-based multinuclear gold(I) complexes

In model reactions for the synthesis of phosphine-terminated tentacles of polyamine dendrimers, the amides MeNHCOC(2)H(4)PPh(2) (2a) and (CH(2)NHCOC(2)H(4)PPh(2))(2) (2b) were prepared from the spacer phosphine (diphenylphosphino)propionic acid (1) and methylamine or ethylenediamine, respectively, using EDC [N-ethyl-N'-(3-(dimethylamino)propyl)carbodiimide hydrochloride] as a coupling agent. By the same procedure, the dendritic, multifunctional species DAB-PPI-(NHCOC(2)H(4)PPh(2))(16) (5a) and DAB-PPI-(NHCOC(2)H(4)PPh(2))(32) (5b) were obtained from diaminobutane-poly(trimethyleneamine) dendrimers. The purification of products 5a,b was followed by GPC methods, and the compounds were identified by analytical and NMR spectroscopic data. Treatment of the diphenylphosphino-terminated compounds 2a,b and 5a,b with equivalent amounts of (dimethyl sulfide)gold(I) chloride afforded the corresponding mono-, di-, hexadeca-, and dotriacontanuclear gold(I) complexes 3a,b and 6a,b, respectively, with terminal (diphenylphosphine)gold(I) chloride groups (-PPh(2)AuCl) in good yields as stable colorless solids. Full coverage of all omega-phosphine functions was accomplished as confirmed again by NMR spectroscopy. For further delineation of the configuration of the peptide-phosphine spacer tentacles, X-ray structure analyses were performed for MeNHCOC(2)H(4)PPh(2)AuCl (3a, triclinic, space group P (1) over bar) and (CH2-NHCOC(2)H(4)PPh(2)AuCl)(2) (3b, monoclinic, space group C2/c). The conformation of the molecules and their packing can be rationalized on the basis of intermolecular NH...O hydrogen bonds, which in these cases exclude intra- and intermolecular Au-I...Au-I contacts.