Strong π-Backbonding Enables Record Magnetic Exchange Coupling Through Cyanide

• DOI: 10.1021/jacs.9b09445
• Publication Date: 2019-10-11T02:28:54Z
• Authors: Juan A. Valdez-Mo...; Agnes E. Thorarin...; Jordan A. DeGayner; Sean A. Lutz; Chun-Hsing Chen; Yaroslav Losovyj; Maren Pink; T. David Harris; Jeremy M. Smith
• Keywords: Unpaired electron

The paramagnetic cyano-bridged complex PhB(tBuIm)3Fe-NC-Mo(NtBuAr)3 (Ar = 3,5-Me2C6H3) is readily assembled from a new four-coordinate, high-spin (S 2) iron(II) monocyanide and the three-coordinate molybdenum(III) Mo(NtBuAr)3. X-ray diffraction IR spectroscopy reveal that delocalization of unpaired electron density into cyanide π* orbitals leads to reduction C-N bond order. Direct current (dc) magnetic susceptibility measurements, supported by electronic structure calculations, demonstrate presence strong antiferromagnetic exchange between spin centers, with coupling constant J -122(2) cm-1. To our knowledge, this value represents strongest ever be observed through cyanide. These results ability low-coordinate metal fragments engender extremely virtue significant π-backbonding ligand.