Synthesis and Spectroscopic and Magnetic Characterization of Tris(3,5-dimethylpyrazol-1-yl)borate Iron Tricyanide Building Blocks, a Cluster, and a One-Dimensional Chain of Squares

The synthesis and spectroscopic and magnetic characterization of several hydridotris(3,5-dimethylpyrazol-1yl)borate (Tp*) iron(II) and iron(III) tricyanide complexes, a rectangular cluster, and a one-dimensional chain of squares are described. Treatment of [NEt4][(Tp*)FeIII(CN)3] (3) with manganese(II) triflate in dimethylformamide (DMF) affords rectangular clusters (6, {[(Tp*)Fe(CN)2(μ-CN)Mn(DMF)4]2[OTf]2}·2DMF), while tosylate salts afford one-dimensional networks (5, {MnII(DMF)2(μ-OTs)(μ-NC)2(NC)FeIII(Tp*)} n ) containing embedded [(Tp*)2FeIII 2MnII 2(CN)6]2+ clusters via in situ trapping; the cluster and network crystallize in the monoclinic (6, P21/n) and triclinic (5, P1̄) space groups, respectively. The 1-D network (5) appears to be derived from {cis-(μ-O3SC6H4Me)2MnII(DMF)4} n (4, P21/n), which is obtained via crystallization of Mn(OTs)2 from DMF/Et2O mixtures. For 4, magnetic studies indicate that the MnII centers are magnetically isolated, with calculated J, g, and θ constants of 6.7 × 10-3 cm-1, 2.03, and −0.52 K. Additional magnetic studies of 5 and 6 indicate that the [(Tp*)FeIII(CN)3]- centers are highly anisotropic (g = 2.9) and are antiferromagnetically coupled to adjacent MnII centers. For 5 and 6, fitting of the χT vs T data via the Curie−Weiss expression affords Curie (6.25 and 10.8 cm3 K mol-1) and Weiss (−14.37 and −8.80 K) constants that are consistent with antiferromagnetically coupled low-spin FeIII and high-spin MnII centers; least-squares fitting of the χT vs T data using molecular field theory affords g avg., J 1, J 2, and J‘ values of 2.25, −1.72, −0.58, and −0.12 cm-1 for 5. Overall, bridging tosylates appear to be poor communicators of spin information. For 6, the g, J 1, and J 2 (2.15, −2.02, and −0.78 cm-1) values were obtained via least-squares fitting of the χT vs T data using an expression derived using the Kambe vector coupling method; simulations of the data via MAGPACK afford g avg. and J iso values of 2.1 and −2.1 cm-1.