The fixation of bis(2-pyridylimino)isoindolato (BPI) ligands to dendritic carbosilanes

Bis(2-pyridylimino)isoindolato (BPI) ligands, containing an alkynyl linker unit which allows their fixation to carbosilane dendrimers and dendrons, were synthesized by reaction of 4-nitrophthalodinitrile with 4-butynol giving the phthalodinitrile derivative containing the linker. These were subsequently reacted with two molar equivalents of 2-amino-4-methylpyridine and 2-amino-4-(t)butylpyridine yielding the respective BPI protioligands 2a and 2b. Lithiation with LDA and reaction with Si-Cl or Si-OTf (OTf=triflate) end groups in core or peripheral positions of dendritic carbosilanes gave the endodendrally and expdendrally functionalized dendrimers. Among these the first and second generation dendrimers G-1](8-exo)-4-Ctriple bond, length as m-dash]CCH2CH2O]-10-MeBPI (8), G-1]12-exo-4-Ctriple bond, length as m-dash]CCH2CH2O]-10-MeBPI (9) and G-2](16-exo)-4-Ctriple bond, length as m-dash]CCH2CH2O]-10-MeBPI (10) were synthesized and fully characterized. The functional dendrimers were metallated by reaction with (PhCN)2PdCl2] in dichloromethane to give the corresponding pallada-dendrimers.