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Two manganese(II) complexes each formally containing two cis-tetracyanoethylenide radical anionic ligands (TCNE(super ./-)) are synthesized. Single-crystal X-ray structural analysis reveals unexpected pi stacking of the TCNE ligand in both complexes, rendering the TCNEs effectively diamagnetic, as verified by magnetic measurement.

The synthesis and characterization of two manganese(II) complexes formally each featuring two cis-tetracyanoethylenide radical anionic ligands (TCNE•/-) are reported. In each case, tris(pyrazol-1-ylmethyl)amine serves as a capping ligand, blocking three facial coordination sites. Crystal structures show that the two TCNE anions in each molecule exhibit an intramolecular stacking interaction that forms what can be considered a coordinated (TCNE2)2- moiety. These molecules are presumed to be structural models of some of the local bonding in the family of amorphous, ferrimagnetic, M[TCNE]2·y(solvent) coordination polymer magnets. Magnetic measurements indicate that the (TCNE2)2- bridge is diamagnetic and not a good mediator of magnetic exchange, a result that might explain the observed lower ordering temperatures in some of the polymer magnets. [ABSTRACT FROM AUTHOR]