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 calix[n]arenes (n = 4, 6) by oxidative addition
of 4-iodobenzyl precursors to either Pd(PPh3)4 or Pd2(dba)3/tmeda (dba = dibenzylideneacetone) to
furnish calixarene-modified aryl-Pd(II)I(Ln) complexes [Ln = bis-PPh3 or N,N,N‘,N‘-tetramethylethylenediamine (tmeda)]. Methods were explored for the selective preparation of mono-Pd(II)-calix[4]arene and di-Pd(II)-calix[n]arenes (n = 4 or 6) complexes and also for bifunctional
calix[4]arene synthons with two Pd(II) complexes accompanied by 4-pyridylmethyl or 4-cyanobenzyl
groups. The properties of the Pd(II)-calix[n]arenes were studied in detail by one- and two-dimensional NMR and mass spectrometric techniques. The X-ray molecular structures of two
4-iodobenzylcalix[4]arene precursors were also determined.