Use of calix[4]arenes in the redox chemistry of lanthanides: the reduction of dinitrogen by a calix[4]arene-samarium complex.

The synthesis and structural characterization of a samarium-dinitrogen complex supported by a calix[4]arene ligand in which the N-N bond distance has been stretched to 1.611(16) Angstrom are described. The central mu(3)-eta(2):eta(2):eta(2)-hydrazido tetraanion formed is bonded to three Sm(III) centers with an overall butterfly-type arrangement.

Reactivity of a Vanadium(III) Center over an Oxo Surface Modeled by Calix[4]arene.

Metalation of the monomethoxycalix[4]arene [p-Bu(t)-calix[4]-(OMe)(OH)(3)], 1, using [VMes(3).THF] led to the coordinatively unsaturated V(III)-d(2) fragment [p-Bu(t)-calix[4]-(OMe)(O)(3)V] collapsing to the dimer [{&mgr;-p-Bu(t)-calix[4]-(OMe)(O)(3)}V](2), 2, where each calix[4]arene shares a bridging oxygen donor atom. The dimeric complexity remains intact in the reaction with Bu(t)NC and PhCN, which bond to the metal inside the cavity of the calix[4]arene leading to [{&mgr;-p-Bu(t)-calix[4]-(OMe)(O)(3)}(V-L)](2) [L = Bu(t)NC, 3; L = PhCN, 4].