IRON(III) AND IRON(II) COMPLEXES OF 1-THIA-4,7-DIAZACYCLONONANE ([9]ANEN(2)S) AND 1,4-DITHIA-7-AZACYCLONONANE ([9]ANENS(2)) - X-RAY STRUCTURAL-ANALYSES, MAGNETIC-SUSCEPTIBILITY, MOSSBAUER, EPR AND ELECTRONIC SPECTROSCOPY

The complexes [Fe([9]aneN(2)S)(2)][ClO4](2), [Fe([9]aneN(2)S)(2)][ClO4 ](3) and [Fe([9]aneNS(2))(2)][ClO4](2) ([9]aneN(2)S = 1-thia-4. 7-diaz acyclononane and [9]aneNS(2) = 1,4-dithia-7-azacyclononane) have been prepared and the latter two characterised by X-ray crystallography. Th e Mossbauer spectra (isomer shift/mm s(-1), quadrupole splitting/mm s( -1), 4.2 K) for [Fe([9]aneN(2)S)(2)][ClO4](2) (0.52, 0.57), [Fe([9]ane N(2)S)(2)][ClO4](3) (0.25, 2.72) and [Fe([9]aneNS(2))(2)][ClO4](2) (0. 43, 0.28) are typical for iron(II) and iron(III) complexes. Variable-t emperature susceptibility measurements for [Fe([9]aneN(2)S)(2)][ClO4]( 2) (2-300 K) revealed temperature-dependent behaviour in both the soli d state [2.95 mu(B) (300 K)-0.5 mu(B) (4.2 K)] and solution (Delta H d egrees 20-22 kJ mol(-1), Delta S degrees 53-60 J mol(-1) K-1). For [Fe ([9]aneN(2)S)(2)][ClO4](3) in the solid state [2.3 mu(B) (300 K)-1.9 m u(B) (4.2 K)] the magnetic data were fit to a simple model (H = -lambd a L . S + mu L-z) to give the spin-orbit coupling constant (lambda) of -260 +/- 10 cm(-1). The solid-state X-band EPR spectrum of [Fe([9]ane N(2)S)(2)][ClO4](3) revealed axial symmetry (g(perpendicular to) = 2.6 07, g(parallel to) = 1.599). Resolution of g(perpendicular to) into tw o components at Q-band frequencies indicated a rhombic distortion. The low-temperature single-crystal absorption spectra of [Fe([9]aneN(2)S) (2)][ClO4](2) and [Fe([9]aneNS(2))(2)][ClO4](2) exhibited additional b ands which resembled pseudotetragonal low-symmetry splitting of the pa rent octahedral (1)A(1g) --> T-1(2g) and (1)A(1g) ---> T-1(1g) transit ions. However, the magnitude of these splittings was too large, requir ing 10Dq for the thioether donors to be significantly larger than for the amine donors. Instead, these bands were tentatively assigned to we ak, low-energy S --> Fe-II charge-transfer transitions. Above 200 K, t hermal occupation of the high-spin T-5(2g) ground state resulted in ob servation of the T-5(2g) --> E-5(g) transition in the crystal spectrum of [Fe([9]aneN(2)S)(2)][ClO4](2). From a temperature-dependence study , the separation of the low-spin (1)A(1g) and high-spin T-5(2g) ground states was approximately 1700 cm(-1). The spectrum of the iron(III) c omplex [Fe([9]aneN(2)S)(2)][ClO4](3) is consistent with a low-spin d(5 ) configuration.