Self-assembly of polymer and sheet structures from palladium(II) complexesby hydrogen bonding between carboxamide substituents

The self-assembly of supramolecular structures from either neutral or catio nic palladium(II) complexes containing primary or secondary carboxamide gro ups as substituents on pyridine ligands has been explored. The displacement of PhCN in trans-[PdCl2(PhCN)(2)] by L = N-methylnicotinamide (MNA), isoni cotinamide (INA), or nicotinamide (NA) gave the corresponding complexes tra ns-[PdCl2L2] 1-3, respectively. Complex 1 .H2O forms a 2D sheet network via amide-amide hydrogen bonding supported by chloride ligand-to-water hydroge n-bonding interactions. Several cationic complexes, [Pd(L'L')L-2](2+) 4-9 a nd 11-16, containing the above ligands and with PPh3, dppp, dppm, or bu(2)b ipy as ancillary ligand(s) were prepared. Complex 4 (L = MNA, L'L' = dppp) forms dimers through amide-an-dde hydrogen bonding, forming macrocycles whi ch further propagate to form chains via weak C-H . . .O=C hydrogen bonding. Complex 6 (L = NA, L'L' = dppp) forms zigzag chains connected by amide hea d-to-head hydrogen bonds. Complex 8 (L = INA, L'L' = dppm) gives interestin g double-stranded ribbons linked by two types of amide-amide hydrogen-bondi ng interactions. Complex 13 (L' = PPh3, L = NA) forms an infinite chain via complementary amide-amide hydrogen bonds. Complex 14 (L = MNA, LV = bu(2)b ipy) forms infinite ribbons via the combination of amide hydrogen bonding m ediated by a BF4 anion and weak C-H . . .O=C hydrogen bonding. Complex 15 ( L = INA, L'L' = bu(2)bipy) gives a ladder polymer formed through amide-amid e hydrogen bonds. The structure of cis-[Pd(PPh3)(2)(OH2)(2)] (OTf)(2) (10) is also reported.