ESR of Some M[Pt(mnt)2] and M[Pd(mnt)2] Polycrystalline Complexes

It has been shown that substitution of small cations(e.g., alkali metal ions) for large bulky cations such as the tetra-n-butylammonium ion in salts prepared from the square planar complex, [X(mnt)2]−n, where (X — Ni, Pt, Pd; mnt — 1,2-dicyano-1,2-ethylenedithiolato), leads to a series of highly conducting materials1–6. Briefly, large bulky cations favor the alternate stacking arrangement (i.e., cation/anion/cation/anion/...) in the crystal structure which is an arrangement which is not highly conductive. On-the-other-hand, in some instances, the small cations appear to support segregated stacking patterns in which the square planar transition metal complex anions are stacked pancakewise and which is an arrangement which is much more conducive to high electrical conductivity. We report here an ESR study of a series of the platinum and palladium complexes based on small counterions. A goal of these studies is to better understand those physical properties which lead to better electrical conductivity. A preliminary report of our work on the Cs[Pd(mnt)2].O.5H2O is given reference 6.