Radical Salts of Bis(ethylenediseleno)tetrathiafulvalene with Paramagnetic Tris(oxalato)metalate Anions

The synthesis, crystal structure, and physical characterization of five new radical salts formed by the organic donor
bis(ethylenediseleno)tetrathiafulvalene (BEST) and the paramagnetic tris(oxalato)metalate anions [M(C2O4)3]3- (M
= FeIII and CrIII) are reported. The salts isolated are (BEST)4[M(C2O4)3]·PhCOOH·H2O with MIII = Cr (1) or Fe (2)
(crystal data:  1, triclinic, space group P1̄ with a = 14.0999(4) Å, b = 15.3464(4) Å, c = 19.5000(4) Å, α =
76.711(5)°, β = 71.688(5)°, γ = 88.545(5)°, V = 3893.5(2) Å3, and Z = 2; 2, triclinic, space group P1̄ with a =
14.0326(3) Å, b = 15.1981(4) Å, c = 19.4106(4) Å, α = 76.739(5)°, β = 71.938(5)°, γ = 88.845(5)°, V =
3824.9(2) Å3, and Z = 2), (BEST)4[M(C2O4)3]·1.5H2O with MIII = Cr (3) or Fe (4) (crystal data:  3, monoclinic,
space group C2/m with a = 33.7480(10) Å, b = 12.3151(7) Å, c = 8.8218(5) Å, β = 99.674(5)°, V = 3614.3(3)
Å3, and Z = 2; 4, monoclinic, space group C2/m with a = 33.659(6) Å, b = 12.248(2) Å, c = 8.759(2) Å, β =
99.74(3)°, V = 3558.9(12) Å3, and Z = 2), and (BEST)9[Fe(C2O4)3]2·7H2O (5) (crystal data:  triclinic, space group
P1̄ with a = 12.6993(3) Å, b = 18.7564(4) Å, c = 18.7675(4) Å, α = 75.649(5)°, β = 107.178(5)°, γ =
79.527(5)°, V = 3977.5(3) Å3, and Z = 1). The structures of all these salts consist of alternating layers of the
organic donors and tris(oxalato)metalate anions. In 1 and 2 the anionic layers contain also benzoic acid molecules
H-bonded to the terminal oxygen atoms of the anions. In all salts the organic layers adopt β-type packings. Along
the parallel stacks the donors form dimers in 3 and 4, trimers in 5, and tetramers in 1 and 2. All the compounds
are paramagnetic semiconductors with high room-temperature conductivities and magnetic susceptibilities dominated
by the Fe- or Cr-containing anions.