Multinuclear calixarene synthons with covalently linked aryl-palladium(II) complexes

New synthetic procedures have been developed for potentially useful metallacalixarene building blocks. The metal sites were covalently connected to calixn]arenes (n = 4, 6) by oxidative addition of 4-iodobenzyl precursors to either Pd(PPh(3))(4) or Pd(2)(dba)(3)/tmeda (dba = dibenzylideneacetone) to furnish calixarene-modified aryl-Pd(II)I(L(n)()) complexes L(n)() = bis-PPh(3) or N,N,N',N'-tetramethylethylenediamine (tmeda)]. Methods were explored for the selective preparation of mono-Pd(II)-calix4]arene and di-Pd(II)-calixn]arenes (n = 4 or 6) complexes and also for bifunctional calix4]arene synthons with two Pd(II) complexes accompanied by 4-pyridylmethyl or 4-cyanobenzyl groups. The properties of the Pd(II)-calixn]arenes were studied in detail by one- and two-dimensional NMR and mass spectrometric techniques. The X-ray molecular structures of two 4-iodobenzylcalix4]arene precursors were also determined.