Dendrimer-phosphine complexes with platinum(0) at the core

Preparation of novel mono- and bidentate phosphine ligands having dendrimer moiety is reported. Monodentate (1a-c) and bidentate ligands (5a,b) were synthesized from bis(4-hydroxyphenyl)phenylphosphine oxide (3) and 1,2-bis(dichlorophosphino)ethane, respectively, in high yields. The defect-free monodisperse nature of these compounds was confirmed by P-31 NMR and elemental analysis as well as by ESI mass spectra. Complexation of these ligands with PtCl2(COD) followed by NaBH4 reduction in a THF/H2O mixture gave Pt(0) complexes 10a,b (having la,b as the ligands) and 13a,b (5a,b as the ligands). Monodentate ligands gave PtL3 complexes (10a,b) and bidentate ligands gave Pt(L-L)(2) complexes (13a,b), respectively. Preliminary studies on oxidative addition of RI (R = CH3 or C6H5) to 10a,b showed that the metal center is easily accessible. Further, molecular modeling of 13b showed nanoscale flattened globular structure of the complex with an approximate diameter of 4.4 nm.