Clathrochelates meet phosphorus: thiophosphorylation of Fe(ii) dichloroclathrochelate precursor, synthesis of N,S-donor macrobicyclic ligands and their Pd(ii) complexes as potent catalysts of Suzuki cross-coupling reaction†‡§¶
Abstract
Nucleophilic substitution of an iron(II) dichloroclathrochelate with diphenylphosphine sulfide under PTC afforded a monophosphorylated cage complex. This precursor undergoes further nucleophilic substitution with mono- and diamines giving P,N-substituted mono- and bis-clathrochelates; those with thiophosphoryl and pyridyl groups were used as N,S-donor macrobicyclic ligands toward the palladium(II) ion. In the resulting Pd,Fe-binuclear 1 : 1 complexes, the clathrochelate moieties retain the geometry, characteristic of low-spin iron(II) complexes, with a minor distortion caused by intramolecular interactions. The Pd2+ ion has a twisted square-planar N2SCl-environment. The complexes thus obtained proved to be efficient catalysts of the Suzuki cross-coupling reaction.