Structure and Magnetism of Heptanuclear Complexes Formed on Encapsulation of Hexacyanoferrate(II) with the Mn(II) and Ni(II) Complexes of 1,4-Bis(2-pyridylmethyl)-1,4,7-triazacyclononane

The reaction of [Mn(dmptacn)OH2]2+ and [Ni(dmptacn)OH2]2+ (dmptacn = 1,4-bis(2-pyridylmethyl)-1,4,7-triazacyclononane) with each cyano ligand on ferricyanide results in the assembly of heteropolynuclear cations around the
cyanometalate core and reduction of FeIII to FeII. In [{Mn(dmptacn)CN}6Fe][ClO4]8·5H2O (1) and [{Ni(dmptacn)CN}6Fe][ClO4]8·7H2O (2), ferrocyanide is encapsulated by either six MnII or NiII dmptacn moieties. These same
products are obtained when ferrocyanide salts are used in the synthesis instead of ferricyanide. A binuclear complex,
[{Mn(dmptacn)}2CN][ClO4]3 (3), has also been formed from KCN and [Mn(dmptacn)OH2]2+. For both MnII and NiII,
the use of the pentadentate dmptacn ligand facilitates the formation of discrete cations in preference to networks
or polymeric structures. 1 crystallizes in the trigonal space group R3̄ (No. 148) with a = 30.073(3) Å, c = 13.303(4) Å, and Z = 3 and is composed of heptanuclear [{Mn(dmptacn)CN}6Fe]8+ cations whose charge is balanced
by perchlorate counteranions. Weak H-bonding interactions between neighboring heptanuclear cations and some
perchlorate counterions generate an infinite 1D chain of alternating [{Mn(dmptacn)CN}6Fe]8+ and ClO4- ions running
along the c-axis. Complex 3 crystallizes in the orthorhombic space group Pbcn (No. 60) with a = 16.225(3) Å,
b = 16.320(2) Å, c = 18.052(3) Å, and Z = 8 and is composed of binuclear [{Mn(dmptacn)}2CN]3+ cations in
which the cyano-bridged MnII centers are in a distorted trigonal prismatic geometry. Variable temperature magnetic
susceptibility measurements have revealed the presence of a weak ferromagnetic interaction between the
paramagnetic MnII centers in 1, mediated either by the −NC−Fe−CN− bridging units or by Mn−NH···ClO4-···NH−Mn intercluster pathways.