SYNTHESIS, STRUCTURE, MAGNETIC-BEHAVIOR, AND MOSSBAUER-SPECTROSCOPY OF 2 NEW IRON(II) SPIN-TRANSITION COMPOUNDS WITH THE LIGAND 4-ISOPROPYL-1,2,4-TRIAZOLE - X-RAY STRUCTURE OF RIAZOLE)(6)(H2O)(6)](TOSYLATE)(6)CENTER-DOT-2H(2)O

Two new iron(II) compounds with the formula [Fe-3(iptrz)(6)(H2O)(6)]X- 6 . xH(2)O (with iptrz = 4-isopropyl-1,2,4-triazole and X = p-toluenes ulfonate (Tos) or trifluoromethanesulfonate (Trifl)) were synthesized. The crystal structure of [Fe-3(iptrz)(6)(H2O)(6)](Tos)(6) . 2H(2)O (I ) has been solved at room temperature. Crystals of I are triclinic, sp ace group <P(1)over bar> with a = 12.8820(11) Angstrom, b = 15.580(2) Angstrom, c = 24.445(4) Angstrom, alpha = 79.270(12)degrees, beta = 86 .688(11)degrees, gamma = 83.007(8)degrees, Z = 2. The structure of I c onsists of linear trinuclear cations with a +6 charge and noncoordinat ed anions and lattice water molecules. The central iron ion is located on an inversion center and is coordinated by 6 nitrogen atoms of 6 ip trz molecules bridging via the nitrogen atoms in the 1,2-positions. Ea ch external iron atom completes its coordination sphere with three coo rdinated water molecules. The temperature dependent magnetic measureme nts of compound I and [Fe-3(iptrz)(6)(H2O)(6)](Trifl)(6) (II) show tha t both compounds exhibit a gradual spin conversion of the central iron ion centered at T-1/2 = 242 K for I and 187 K for II. Temperature dep endent Mossbauer spectroscopy measurements on I show the behavior expe cted for a compound of this nature. The measurements on II indicate a strong influence of the spin conversion of the central iron ion on bot h external iron ions. The nature of this phenomenon is proposed to be connected to a very rigid lattice structure (ionic, H-bonding) connect ing the trinuclear units.