Amidoamine-based dendrimers with end-grafted Pd-Fe units: Synthesis, characterization and their use in the Heck reaction

The synthesis and characterization of novel amidoamine-based metallodendrimers with heterobimetallic end-grafted amidoferrocenyl-palladium-allyl chloride units is described. Dendrimer (Fe((eta(5)-C5H4PPh2) (eta(5)-C5H4))C(O)HNCH2CH2NHC(O)CH2CH2)N[CH2CH2N(CH2CH2C(O)NHCH2CH2NH-C(O)(Fe(eta(5)-C5H4)(eta(5)-C5H4PPh2)))(2)](2) (9-Fe) and the corresponding metal species (Fe((eta(5)-C5H4PPh2(Pd(eta(3)-C3H5)Cl))(eta(5)-C5H4)) C(O)HNCH2CH2NHC(O)CH2CH2)N[CH2CH2N(CH2CH2C(O)NHCH2CH2NHC(O)(Fe(eta(5)-C5H4)(eta(5)-C5H4 PPh2(Pd(eta(3)-C3H5)Cl))))(2)](2) (9-Fe-Pd) were prepared by a consecutive divergent synthesis methodology including additioneamidation cycles, standard peptide coupling, and coordination procedures. For comparative reasons also the monomeric and dimeric molecules (Fe(eta(5)-C5H4PPh2)(eta(5)-C5H4C(O)(NHC3H7)-C-n)) (5-Fe) and [Fe(eta(5)-C5H4PPh2)(eta(5)-C5H4C(O)NHCH2)](2) (6-Fe) as well as N(CH2CH2C(O)NHCH2CH2NHC(O)(Fe(eta(5)-C5H4)(eta(5)-C5H4PPh2)))(3) (7-Fe) and [CH2N(CH2CH2C(O)NHCH2CH2NHC(O)(Fe(eta(5)-C5H4)(eta(5)-C5H4PPh2)))(2)](2) (8-Fe) were prepared from Fe(eta(5)-C5H4PPh2)(eta(5)-C5H4CO2H) (3). Using [Pd(eta(3)-C3H5)Cl](2) (4) as palladium source heterobimetallic metallodendrimers (Fe(eta(5)-C5H4PPh2(Pd(eta(3)-C3H5)Cl))(eta(5)-C5H4C(O)(NHC3H7)-C-n)) (5-Fe-Pd), [Fe(eta(5)-C5H4PPh2(Pd(eta(3)-C3H5)Cl))(eta(5)-C5H4C(O)NHCH2)](2) (6-Fe-Pd), N(CH2CH2C(O)NHCH2CH2NHC(O)(Fe(eta(5)-C5H4)(eta(5)-C5H4PPh2(Pd(eta(3)-C3H5)Cl))))(3) (7-Fe-Pd) and [CH2N(CH2CH2C(O)NHCH2CH2NHC(O)(Fe(eta(5)-C5H4)(eta(5)-C5H4PPh2(Pd(eta(3)-C3H5)Cl))))(2)](2) (8-Fe-Pd) were synthesized. Additionally, seleno-phosphines of 5-Fe-Se and 9-Fe-Se, respectively, were prepared by addition of elemental selenium to 5-Fe or 9-Fe to estimate their s-donor prperties. The palladium-containing amidoamine supports are catalytically active in the Heck-Mizoroki crosscoupling of iodobenzene with tert-butyl acrylate. The catalytic data are compared to those obtained for the appropriate mononuclear and dinuclear compounds 5-Fe-Pd and 6-Fe-Pd. This comparison confirms a positive cooperative effect. The mercury drop test showed that (nano) particles were formed during catalysis, following on heterogeneous carbonecarbon cross-coupling. (C) 2010 Elsevier B.V. All rights reserved.