Structures and properties of ferromagnetically coupled bis(μ-halo)diiron(II) complexes

Abstract

Three bis(μ-halo)diferrous complexes, [Fe 2(TLA) 2F 2](BF 4) 2 ( 1), [Fe 2(TMPzA) 2Cl 2](BPh 4) 2 ( 2) and [Fe 2(TPA) 2Cl 2](BPh 4) 2 ( 3), have been synthesized and crystallographically characterized. The crystallographic data are as follows: 1, triclinic system, space group P 1 (No. 2), with cell dimensions a=8.746(7), b=11.386(4), c=12.018(6) Å, α=64.44(3), β=81.54(5), γ=87.90(5)°, V=1067(2) Å 3, R=0.046, R w=0.063; 2, triclinic system, space group P 1 (No. 2), with cell dimensions a=10.440(5), b=11.610(8), c=16.98(1) Å, α=77.55(6), β=79.63(5), γ=88.90(5)°, V=1977(4) Å 3, R=0.042, R w=0.050; 3, monoclinic system, space group C2/ c (No. 15), with cell dimensions a=19.211(6), b=15.264(9), c=24.52(2) Å, β=105.57(3)°, V=6926(4) Å 3, R=0.049, R w=0.053. All three complexes have Fe 2X 2 cores with FeFe distances of 3.198(3) Å for 1, 3.563(3) Å for 2 and 3.494(3) Å for 3, and FeXFe angles of 101.72(9)° for 1, 91.94(6)° for 2 and 90.67(3)° for 3. Magnetization studies over the temperature range of 2 to 200 K indicate that the high spin ferrous centers are ferromagnetically coupled in all three complexes. The parameter sets of the best fit ( H ex= JS 1· S 2) are for 1: J=−1.2(2) cm −1, ¦ D i ¦=7.2(5) cm −1, g i =2.12(3); for 2: J=−2.6(2) cm −1, ¦ D i ¦=7.2(5) cm −1, g i =2.15(3); and for 3: J=−10.0(2) cm −1, ¦ D i ¦=13.2(5) cm −1, g i =2.15(3). The EPR signals near g=18 also indicate ferromagnetic coupling between the iron(II) centers.