Crystal Structure and ESR Study of a Bimetallic Copper/Iron Crown Ether Inclusion Complex

Bimetallic inclusion complexes have been synthesized by a secondary coordination interaction between the guest complex [Fe(η5-C5H5)(CO)2(NH3)][PF6] and copper(II) complex 1a or nickel(II) complex lb containing crown-ether hosts. The X-ray crystal-structure analysis established that the Cu,Fe inclusion complex 2 crystallize as a centrosymmetric dimer with a CuCu separation of 3.73 A and a novel out-of-plane CuN interaction. The magnetic parameters for 2 were obtained by ESR and ENDOR spectroscopy. ESR susceptibility measurements down to 6 K exclude the presence of any antiferromagnetic coupling interaction between the CuIIcenters of the dimer.