STRUCTURES OF HEXAKIS(1-PROPYLTETRAZOLE)IRON(II) BIS(TETRAFLUOROBORATE), [FE(CHN4C3H7)6](BF4)2, HEXAKIS(1-METHYLTETRAZOLE)IRON(II) BIS(TETRAFLUOROBORATE), [FE(CHN4CH3)6](BF4)2, AND THE ANALOGOUS PERCHLORATES - THEIR RELATION TO SPIN CROSSOVER-BEHAVIOR AND COMPARISON OF DEBYE-WALLER FACTORS FROM STRUCTURE DETERMINATION AND MOSSBAUER-SPECTROSCOPY

Single-crystal structure determinations of the spin crossover compounds [Fe(ptz)6]X2 and [Fe(mtz)6]X2 (PtZ = C3H7N4CH, mtz = CH3N4CH, X = BF4, ClO4) have been performed at different temperatures. The temperature dependence of the lattice constants was measured for the two mtz compounds between 300 and 110 K. The two different structure types for the ptz and mtz compounds are compared and discussed in relation to the physical properties associated with the temperature-induced and light-induced spin transitions. In particular, the atomic displacement parameters for the two inequivalent Fe complexes in the mtz structure were found to be significantly different. They are in good accordance with the vibrational amplitudes derived from the Debye-Waller factors measured by Mossbauer spectroscopy. Crystal data, measured with Mo Kalpha radiation, lambda = 0.71069 angstrom: (SI) [Fe(ptz)6](ClO4)2 at 299 K: M(r) = 927.6, R3BAR (Z = 3), D(m) (295 K) = 1.33, D(x) = 1.333 Mg m-3, a = 10.804 (3), c = 34.296 (5) angstrom, V = 3467 (1) angstrom3, F(000) = 1446, mu = 0.461 mm-1, R = 0. 1 15 (1965 unique reflections), isostructural to (S2). (S2) [Fe(PtZ)6](BF4)2 at 297, 250 and 195 K: M(r) = 902.3, R3BAR (Z = 3), D(m) (295 K) = 1.32, D(x) = 1.312 Mg m-3, a = 10.833 (2), c = 33.704 (6) angstrom, V = 3425 (i) angstrom3 at 297 K, a = 10.857 (3), c = 33.053 (13) angstrom, V = 3374 angstrom3 at 250 K and a = 10.890(2), c = 32.330 (10) angstrom, V = 3320(1) angstrom3 at 195 K; F(000) = 1398; mu = 0.368 mm-1 (297 K), 0.373 mm-1 (250 K) and 0.380 mm-1 (I 95 K); R = 0. 125 (2058 unique reflections) at 297 K, R = 0. 1 14 (I 799 unique reflections) at 250 K and R = 0.077 (1695 unique reflections) at 195 K. (S3) [Fe(MtZ)6](ClO4)2 at 298 K: M(r) = 759.2, P2(1)/n (Z = 4), D(m) = 1.55, D(x) = 1.551 Mg m-3, a = 18.270 (4), b = 10. 367 (2), c 18.674 (5) angstrom, beta = 11 3.16 (2)-degrees, V = 3252(1) angstrom3, F(000) = 1544, mu = 0.647 mm-1, R = 0.083 (4529 unique reflections), isostructural to (S4). (S4) [Fe(mtz)6](BF4)2 at 157 and 11 3 K: M(r) = 733.9, P2(1)/n (Z = 4), D(m) = 1.53, D(x) = 1.524 Mg m-3 at 295 K; a = 17.778 (6), b = 10.215 (2), c = 18.625(6) angstrom, beta = 114.03(2)-degrees, V = 3089(2) angstrom3 at 157 K and a = 17.673(7), b = 10.178(5), c = 18.648(8) angstrom, beta = 114.27(3)-degrees, V = 3058(2) angstrom3 at 113 K; F(000) = 1480; mu = 0.535 mm-1 (157 K) and 0. 540 mm-1 (I 13 K); R = 0.090 (4485 unique reflections) at 157 K and R = 0.074 (4625 unique reflections) at 113 K.