Synthesis and characterization of one- and two-dimensional octacyanometalate(V) networks: {[trans-MII(DMF)4][cis-MII(DMF)4]2[MV(CN)8]2} n (MII =Mn, Fe, Ni; MV =Mo, W)

Abstract: Treatment of several binary transition metal p-toluenesulfonates [MII(OTs)2] with tri(butyl)ammonium octacyanomolybdate(V) or -tungstate(V) in DMF readily affords a series of one- and two-dimensional crystalline octacyanometalate networks of [MII(DMF)4]3[MV(CN)8]2 (MV =Mo, W; MII =Mn, 5, 6; Ni, 7, 8) stoichiometry. Treatment of Fe(OTs)2 with [HBu3N]3[WV(CN)8] in DMF affords amorphous precipitates while FeCl3 affords crystalline [FeII(DMF)6]2[WIV(CN)8] (9) salts; two-dimensional [FeII(DMF)4]3[WV(CN)8]2 (10) lattices are obtained from 9 after standing several months. The structures of 5 and 8 contain [cis-MII(DMF)4(μ-NC)2]2+ and [trans-MII(DMF)4(μ-NC)2]2+ units that are linked via cyanides to three-connected [MV(CN)5(μ-CN)3]3− centers, forming a one-dimensional chain of squares that crystallize in the monoclinic (5, P21/n) and triclinic (8,) space groups; 6 (P21/n) and 10 (P21/c) crystallize as two-dimensional corrugated sheets containing [cis-MII(DMF)4(μ-NC)2]2+, [trans-MII(DMF)4(μ-NC)2]2+, and [MV(CN)5(μ-CN)3]3− units in a 4:2:6 ratio. Magnetic measurements indicate that 6 is a ferrimagnet (T N =8K) that exhibits frequency-dependent behavior in χ″ that is qualitatively similar to 1- and 2-D lattices reported by Tang and Holmes, respectively; dc magnetic measurements suggest that 5, 7, and 8 exhibit incipient magnetic ordering while ac measurements show no frequency-dependent behavior in χ″. Surprisingly, conversion of 5 to 6 in the presence of counterions occurs while heating crystalline samples introduces additional magnetic phases without linkage isomerism; two-dimensional phases containing MnII centers appear to be the sole product when wet DMF is used as a reaction solvent. The experimental evidence suggests that coordinated DMF ligands are labile and the MII(μ-NC)MV linkages are susceptible to fragmentation. [Copyright &y& Elsevier]