Convergent and Divergent Noncovalent Synthesis of Metallodendrimers

A new building block is constructed with one pyridine and two kinetically inert complexed Pd(II) ions, for the controlled assembly of metallodendrimers following either a convergent or a divergent route. The double pincer ligand 8 was cyclopalladated with Pd[CH 3 CN] 4 (BF 4 ) 2 and subsequently converted into the neutral bis-palladium chloride complex 3 . The pyridine moiety of 3, that is covalently attached to the spacer bridging the two pincer complexes, coordinates to activated palladium centers. Via a combination of pyridine- ( 3 ) and cyano-based ( 2 ) building blocks, dendrons up to generation three were assembled and characterized with 1 H NMR and FT-IR spectroscopy and MALDI-TOF mass spectrometry. These dendrons can coordinate through a cyano ligand to an activated nucleus 1 forming convergently assembled metallodendrimers. Alternatively, building blocks 3 were used in the divergent assembly of more stable metallodendrimers, because of the stronger coordination of pyridine compared to cyano ligands. The formation of metallodendrimers is evidenced by IR and 1 H NMR spectroscopy and electro spray and MALDI-TOF mass spectrometry.