Coordination Complexes with cis-TCNE Radical Anion Ligands. Models
of M[TCNE]2 Magnets
Guangbin Wang,Huifang Zhu,Jian Fan,Carla Slebodnick, andGordon T. Yee*
Department of Chemistry, Virginia Polytechnic Institute and State University,
Blacksburg, Virginia 24061
Received May 26, 2005
Abstract:
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.
/-) 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. 
