Tetrachloroferrate(III) complexes of some organic diammonium cations: Structures and magnetic properties

Article abstract of DOI:10.1002/zaac.200700330

With aqueous acidic iron(III) chloride, the three diamines ethylenediamine (en), tetramethylethylenediamine (tmeda) and 4:4′- tetramethyldiaminodiphenylmethane (ddmp) yield the aquapentachloroferrate(III) and a pair of [FeCl₄]^- Cl^- double salts, respectively. Their structures indicate that N-H...Cl hydrogen bonding is present, but the Fe...Fe distances are all quite long. The magnetic data show that, while all the materials display antiferromagnetic coupling on cooling, in none of the cases was any transition observed above 1.8 K.

Full text of DOI:10.1002/zaac.200700330

DOI: 10.1002/zaac.200700330
Tetrachloroferrate(III) Complexes of some Organic Diammonium Cations:
Structures and Magnetic Properties
Bruce D. Jamesa,*, Jerzy Mrozinskib,*, Julia Klakb, Brian W. Skeltonc, and Allan H. Whitec
a Bundoora/Victoria / Australia, La Trobe University, Department of Chemistry
b Wroclaw/Poland, University of Wroclaw, Department of Chemistry.
c Crawley/Western Australia, University of Western Australia, School of Biomedical, Biomolecular and Chemical Sciences, Chemistry M313
Received July 3rd, 2007.
Abstract. With aqueous acidic iron(III) chloride, the three diamines
ethylenediamine (en), tetramethylethylenediamine (tmeda) and
4:4Ј-tetramethyldiaminodiphenylmethane (ddmp) yield the aqua-
pentachloroferrate(III) and a pair of [FeCl4]Ϫ ClϪ double salts,
respectively. Their structures indicate that NϪH···Cl hydrogen
bonding is present, but the Fe···Fe distances are all quite long. The
magnetic data show that, while all the materials display antiferro-
magnetic coupling on cooling, in none of the cases was any tran-
sition observed above 1.8 K.
Keywords: Iron; Aquapentachloroferrate(III); Ethylenediammon-
ium salt; Tetrachloroferrate(III) double salts; Tetramethylethylene-
diammonium;
4:4Ј-Tetramethyldiammoniumdiphenylmethane;
Crystal structures; Magnetic properties
Introduction
cations, however, may yield other double salts, the struc-
tures of which may depend on the position of substituents
in the heterocyclic system [7].
Tetrachloroferrate(III) compounds are well known [1] and
are of interest because the weak-field chloride ligands per-
mit the maximum spin state for a d5 electronic configura-
tion [2]. It has been found, however, that synthetic results
are not always straightforward and that different coun-
terions may produce compounds having different compo-
sitions. Some of the materials having more unusual anion
compositions such as [Fe2Cl9]3Ϫ can contain the [FeCl4]Ϫ
anion [3], an observation quite consistent with the stability
of that species, particularly in acidic solution [4]. On the
other hand, the classic compound (NH4)2[FeCl5(OH2)] con-
tains a (distorted) octahedral FeIII ion [5], even though it is
also obtained from an acidic solution.
Chloroferrate(III) derivatives of diammonium cations
appear to have received little attention, and structural infor-
mation is consequently sparse. The compound formed from
iron(III) chloride and the simplest diamine, 1,2-diamino-
ethane (ethylenediamine, en) was reported in 1926, albeit
with reservations about the presence of the aqua ligand [8],
while the hexanediammonium system appears to be the
only other one that has been characterized, and this yielded
an interesting mix of ions [9]. Consequently, it was con-
sidered that a comparison of the chloroferrates derived
from diamines having small carbon chains and synthesized
under similar (aqueous acidic) conditions might prove to be
interesting in terms of possible interplay between double
salt formation, increased coordination number about the
iron ion, and any significant influences of hydrogen-bond-
ing in their structures. The diamines chosen were the two-
carbon backbone ethylenediamine (en) and 1,1,2,2-tetra-
methylethylenediamine (tmeda) and the one-carbon, but
phenyl-substituted (and sterically-significant) 4:4Ј-tetra-
methyldiaminodiphenylmethane (ddmp). The structures
and magnetic properties of the materials are described here.
Extensive studies by Carlin’s group have shown that sys-
tems based on pyridinium and substituted pyridinium cat-
ions (pyHϩ) are able to form hydrogen-bonded ion clusters,
effectively [(pyH)3Cl]2ϩ, that can function as cations to sta-
bilize chloroferrate(III) compounds [6]. Some quinolinium
* Dr. Bruce D. James
Department of Chemistry, La Trobe University
Vic. 3086, Australia.
Tel.: ϩ61 3 9479 2534
Fax.: ϩ61 3 9479 1399
Experimental Section
E-mail: b.james@latrobe.edu.au
Syntheses
4:4Ј-Tetramethyldiaminodiphenylmethane (ddmp) was
a BDH
* Prof. Dr. Jerzy Mrozinski
Faculty of Chemistry, University of Wroclaw, F. Joliot Ϫ Curie 14
PL-50-383 Wroclaw, Poland
Tel.: ϩ48 71 375 7307
Fax.: ϩ48 71 328 2348
E-mail: jmroz@wchuwr.chem.uni.wroc.pl
product, while other reagents were obtained from the Aldrich
Chemical Co. All were employed without further purification.
Syntheses were based on similar ones previously described [3, 5, 7,
9], and generally carried out in about 10Ϫ2 mole quantities. In gen-
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B. D. James, J. Mrozinski, J. Klak, B. W. Skelton, A. H. White
eral, the base was dissolved in ethanol (with warming and ad-
ditional hydrochloric acid where necessary) and the solution added
slowly with constant stirring to an approximately equimolar quan-
tity of hydrated iron(III) chloride dissolved separately in an excess
of aqueous HCl. Sufficient conc. aqueous HCl or ethanol was ad-
ded (with further warming as necessary) to dissolve any precipi-
tated solids, and the resulting solution was allowed to evaporate
slowly in an air stream until crystals appeared (generally several
days). Products: (tmedaH2) [FeCl4]Cl (1), yellow crystals, mp.
195Ϫ197; (ddmpH2)[FeCl4]Cl (2), yellow crystals, m.p. 175Ϫ177;
(enH2) [FeCl5(OH2)] (3), dark red-brown crystals, m.p. 109-110 °C
ϫ 0.30 mm; ‘Tπmin/max ϭ 0.83. 2θmax ϭ 58°; Nt ϭ 27745, N ϭ 5991
(Rint ϭ 0.023), No ϭ 3619; R1 ϭ 0.036, wR2 ϭ 0.110 (a ϭ 0.0638);
S ϭ 1.05. Η∆ρmaxΗ ϭ 0.39 e AϪ3. T ca. 298 K
˚
Variata. The anion was modelled as rotationally disordered about
Fe-Cl(11), site occupancies of the two sets of chlorine atoms re-
fining to 0.57(2) and complement. Data were measured at room-
temperature.
3. (enH2)[FeCl5(OH2)] (3) ϵ C2H12Cl5FeN2O, M ϭ 313.2. Ortho-
rhombic, space groupP212121 (D42, No. 19), a ϭ 6.8796(6), b ϭ
3
˚
˚
10.7140(10), c ϭ 14.3471(9) A, V ϭ 1057 A . Dc (Z ϭ 4) ϭ 1.967 g
cmϪ3. µMo ϭ 2.6 mmϪ1; specimen: 0.32 ϫ 0.30 ϫ 0.24 mm;
Analyses (Campbell Microanalytical Laboratory, University of
Otago, New Zealand):
‘T’min/max ϭ 0.82. 2θmax ϭ 82°; Nt ϭ 77754, N ϭ 6874 (Rint
ϭ
0.025), No ϭ 6436; R1 ϭ 0.023, wR2 ϭ 0.057 (a ϭ 0.0250, b ϭ
0.1435); S ϭ 1.40. xabs ϭ 0.377(7). Η∆ρmaxΗ ϭ 0.69 e AϪ3. T ca.
˚
Calcd for (tmedaH2)[FeCl4]Cl: C, 20.51; H, 5.16; N, 7.97; Cl, 50.46.
Found: C, 20.47; H. 5.08; N, 7.89; Cl, 50.31 %.
100 K
Calcd. for (ddmpH2)[FeCl4]Cl: C, 41.71; H, 4.94; N, 5.72; Cl, 36.22.
Found: C, 41.78; H, 5.22; N, 5.91; Cl, 36.22 %
Variata. The high value of xabs appears to be consequent on the
quasi-centrosymmetric nature of the structure (rather than twin-
ning or other problems).
Calcd. for (enH2) [FeCl5(OH2)]: C, 7.43; H, 3.74; N, 8.66; Cl, 54.84.
Found: C, 7.36; H, 3.80; N, 8.34; Cl, 53.51 %
Magnetic measurements
The magnetization of the powdered samples was measured over the
temperature range 1.8Ϫ300 K using a Quantum Design SQUID-
based MPMSXL-5-type magnetometer. The superconducting mag-
net could be operated at a field strength ranging from 0 to 5 T.
Measurements on the sample compounds were made at magnetic
field 0.5 T. The SQUID magnetometer was calibrated with a
palladium rod sample. Corrections are based on subtracting the
sample-holder signal and contribution χD estimated from
Pascal constants [11] which are Ϫ240ϫ10Ϫ6 cm3molϪ1 for the
complex (tmedaH2)[FeCl4]Cl (1), Ϫ185ϫ10Ϫ6 cm3molϪ1 for
(ddmpH2)[FeCl4]Cl (2), and, finally, Ϫ147ϫ10Ϫ6 cm3molϪ1 for
(enH2)[FeCl5(OH2)] (3). The effective magnetic moment was calcu-
lated from the equation, µeff ϭ 2.83(χMT)1/2 (B.M.).
Structure determinations
Full spheres of CCD area-detector diffractometer data were meas-
ured (ω-scans; monochromatic Mo Kα radiation; λ ϭ 0.71073 A),
˚
yielding Nt(otal) reflections, these merging to N unique (Rint cited)
after ’empirical’/multiscan absorption correction (proprietary
software), No with I > 2σ(I) being considered ’observed’. Full ma-
trix least squares refinement on F2 refined anisotropic displacement
parameters for the non-hydrogen atoms, hydrogen atoms being in-
cluded constrained according to a riding model (reflection weights:
(σ2(F2) ϩ (aP)2 (ϩ bP))Ϫ1 (P ϭ (Fo ϩ 2Fc)/3)). Neutral atom com-
plex scattering factors were employed within the SHELXL-97 pro-
gram [10]. Pertinent results are given below and in the Tables and
Figures, the latter showing 20 % (room-temperature) and 50 %
(low-temperature) probability amplitude displacement ellipsoids
for the non-hydrogen atoms, hydrogen atoms having arbitrary radii
EPR spectra
˚
of 0.1 A. Individual variations in procedure are cited as
EPR spectra were recorded at room temperature and at 77 K on a
Bruker ESP 300 spectrometer operating at X-band, and equipped
with an ER 035M Bruker NMR gaussmeter and HP 5350B Hew-
lett-Packard microwave frequency counter. The spectra at 4.5 K
temperature were measured with an X-band Radiopan SE/X 2543
Spectrometer
’variata’. Crystallographic data for the structures have been
deposited with the Cambridge Crystallographic Data Centre,
CCDC 633029-633030, 643244. Copies can be obtained free of
charge on application to The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (Fax: int.code ϩ (1223)336-033; e-mail
for inquiry: fileserv@ccdc.cam.ac.uk; email for deposition:
deposit@ccdc.cam.ac.uk).
Results and Discussion
Crystal/refinement data
Structures
1. (tmedaH2)[FeCl4]Cl (1) ϵ C6H18Cl5FeN2, M ϭ 351.3. Mono-
clinic, space group P21/n (C52h, No. 14 (variant)), a ϭ 6.7973(2),
The results of the single crystal X-ray structure determi-
nations are all consistent with the proposed compositions
and connectivities implied above, being the salt
[FeCl5(OH2)]2Ϫ (in 3) or double salts ([FeCl4]Ϫ ·ClϪ) (1, 2)
of the relevant organic cations. The structures of the
[FeCl4]Ϫ species are essentially as expected, and are shown
in the figure captions.
1. (tmedaH2)[FeCl4]Cl (1). Here, a full formula unit, de-
void of crystallographic symmetry, comprises the asymmet-
ric unit of the structure (Figure 1(a)). Interactions of the
3
˚
˚
b ϭ 19.0746(4), c ϭ 12.1794(3) A, β ϭ 102.453(2)°, V ϭ 1542 A .
Dc (Z ϭ 4) ϭ 1.513 g cmϪ3. µMo ϭ 1.82 mmϪ1; specimen: 0.32 ϫ
0.17 ϫ 0.12 mm; ‘Tπmin/max ϭ 0.87. 2θmax ϭ 70°; Nt ϭ 21369, N ϭ
6264 (Rint ϭ 0.033), No ϭ 3783; R1 ϭ 0.033, wR2 ϭ 0.075 (a ϭ
0.0312); S ϭ 1.02. Η∆ρmaxΗ ϭ 0.58 e AϪ3. T ca. 100 K
˚
2. (ddmpH2)[FeCl4]Cl (2) ϵ C17H24Cl5FeN2, M ϭ 489.5. Mono-
clinic, space group P21/n (C52h, No. 14 (variant)), a ϭ 13.184(2),
3
˚
˚
b ϭ 13.832(3), c ϭ 14.636(2) A, β ϭ 116.732(2)°, V ϭ 2384 A . Dc
(Z ϭ 4) ϭ 1.364 g cmϪ3. µMo ϭ 1.20 mmϪ1; specimen: 0.55 ϫ 0.35
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Tetrachloroferrate(III) Complexes of some Organic Diammonium Cations: Structures and Magnetic Properties
protonic hydrogen atoms are with the uncoordinated chlo-
ride ions, forming a strand along and parallel to a:
˚
Cl1···N,H2 3.045(5), 2.2; ···N,H1 (xϪ1, y, z) 3.040(5), 2.1 A
(N-H···Cl 167, 158° respectively, H···Cl···H ca. 132°.) (Fig-
ure 1(b)), the chlorine atoms of the complex ion having no
close contacts. Pairs of the {(tmedaH2)Cl}(ϱΗϱ) columns are
enclosed within a tube of complex ions (Figure 1(a)). The
shortest Fe···Fe distances are 6.0871(3) (2Ϫx, 1Ϫy, 1Ϫz),
1
1
1
˚
6.7973(4) (xϪ1, y, z), and 7.2160(3) A ( /2ϩx, /2Ϫy, /2ϩz).
Figure 2 (a) Unit cell contents of (ddmpH2)(FeCl4)Cl, (2) pro-
jected down a.
(b) A hydrogen-bonded ···HddmpH···Cl···HddmpH···Cl··· strand.
Within the complex anion, Fe-Cl (fragment) distances range bet-
˚
ween 2.142-2.213(7) A.
of the structure, which, overall, is chiral, the chirality some-
what ambiguously defined in the refinement, seemingly in
consequence of the pseudo-centrosymmetric nature of the
structure (Figure 3). The structure of the anion (Table 1),
although similar to those defined in other studies [5, 14],
appears less susceptible to deformation by hydrogen-bond-
ing and other effects than elsewhere. The distances Fe-Cl2-
4, all trans to other Fe-Cl bonds are closely matched but
Fe-Cl1 is aberrantly short; the shortening of Fe-Cl5 may be
ascribable to hydrogen-bonding elsewhere or a trans-influ-
ence arising from the water molecule oxygen atom. The hy-
drogen atoms of the latter interact with chlorine atoms of
neighbouring anions: H1A0···Cl2 (xϪ1/2, 1/2Ϫy, 2Ϫz)
Figure 1 (a) Unit cell contents of (tmedH2)(FeCl4)Cl, (1), pro-
jected down a.
(b) A hydrogen-bonded ···HtmedH···Cl···HtmedH···Cl··· column,
parallel to a.
˚
Fe-Cl2-5 are 2.1919(4), 2.1923(5), 2.2026(5), 2.1862(5) A, Cl2-Fe-
Cl3-5 110.36(2), 107.90(2), 109.50(2); Cl3-Fe-Cl4,5 108.54(2),
110.04(2); Cl4-Fe-Cl5 110.47(2)°.
˚
2.43(2), H1B0···Cl5 (xϪ1, y, z) 2.45(2) A, the NH3 hydro-
gen atoms all interacting with anionic chlorine atoms at dis-
˚
tances (est.) of 2.51-2.69 A, excepting a shorter contact
2. (ddmpH2)[FeCl4]Cl (2). Again, a full formula unit de-
void of crystallographic symmetry, comprises the asymmet-
ric unit of the structure (Figure 2(a)). Again, the role of the
extended diprotonated cation is to link the uncomplexed
chloride ions into a chain across the ac diagonal of the
cell (Cl1···N,H14 (1/2ϩx, 1/2-y, 1/2ϩz) 2.991(3), 2.1;
1
1
˚
H2A···Cl3 ( /2ϩx, 1 /2Ϫy, 2Ϫz) 2.36 A, and noting also
H2B equidistant between Cl1,2 (x, 1ϩy, x) 2.62, 2.66 A, of-
˚
fering no immediate explanation for the shortness of Fe-
Cl1, or the distortions of nearly ten degrees in one of the
trans angles, a concomitant of a more than five degree dis-
tortion in one of the cis. There are four quasi-equivalent
(reflecting the pseudo-symmetry) Fe···Fe distances (to (x 1,
1
1
1
˚
···N,H(24)(xϪ /2, /2Ϫy, zϪ /2) 3.057(2), 2.1 A). (Figure 2b)
The anion has no close hydrogen contacts, and, unsurpris-
ingly, is disordered. The dihedral angle between the aro-
matic planes of the cation is 72.32(8)°; C-N-C angle sums
are 338.1, 336.5°. The shortest Fe···Fe distances are
1
1
˚
y, z), (x /2, /2Ϫy, 2Ϫz) 6.8796(6), 6.8996(4) A.
Magnetic properties
1
1
1
1
˚
7.3799(8) (xϪ /2, 1 /2Ϫy, zϪ /2) and 7.677(1) A ( /2Ϫx,
1
yϪ1/2, /2Ϫz).
The magnetic properties of complexes (tmedaH2)[FeCl4]Cl
(1), [ddmpH2][FeCl4]Cl (2) and (enH2)[FeCl5(OH2)] (3)
were determined over the temperature range 1.8Ϫ300 K.
3. (enH2)[FeCl5(OH2)] (3). A full formula unit, devoid of
crystallographic symmetry, comprises the asymmetric unit
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B. D. James, J. Mrozinski, J. Klak, B. W. Skelton, A. H. White
Figure 3 Unit cell contents of (enH2)[FeCl5(OH2)], (3) projected
down a, showing hydrogen-bonding interactions.
Table 1 Anion structure (enH2) [FeCl5(OH2)] (3)
˚
r is the iron-ligand atom distance /A; other entries in the matrix
are the angles subtended by the relevant atoms at the head of the
row and columns
r
Cl2
Cl3
Cl4
Cl5
O1
Cl1 2.3268(2) 91.60(1) 174.24(1)
89.24(1) 93.08(1)
86.89(3)
86.66(2)
87.59(3)
84.09(2)
178.89(3)
Cl2 2.3742(3)
Cl3 2.3780(3)
Cl4 2.3750(3)
Cl5 2.3439(3)
O1 2.1698(8)
89.73(1) 170.65(1) 94.45(1)
88.55(1) 92.40(1)
94.80(1)
˚
In the cation C1-C2,N1 are 1.516(2), 1.487(1) and C2-N2 1.487(1) A;
˚
N-C-C angles are 109.70(9), 109.81(8)°. O-H1A,B0 are 0.83(2), 0.81(2) A.
Plots of magnetic susceptibility χM and the χMT product
vs. T are given in Figures 4(a), (b) and (c), respectively.
The value of χMT at 300 K for complex 1 equals
4.27 cm3molϪ1K (5.85 B.M.), the value of this product
decreasing only slightly as the temperature is lowered. Be-
low 50 K a more evident decrease in its value is observed
with continuous decrease of the temperature, reaching
2.42 cm3molϪ1K (4.41 B.M.) at 1.8 K. The decrease in
value in the lowest temperature range is caused by antifer-
romagnetic interactions between Fe3ϩ ions, transmitted
through the crystal lattice.
In this situation the magnetic data were fitted using the
susceptibility equation for S ϭ 5/2, (eq.(1)). To elucidate the
significance of exchange between the Fe3ϩ ions in the crys-
tal lattice, a molecular field correction term was also in-
cluded (eq. (2)) [12]):
Figure 4 (a) Temperature dependence of experimental χM(•) and
χMT(᭺) vs. T for (1). The solid line is the calculated curve for χMT.
(b) Temperature dependence of experimental χM(•) and χMT(᭺) vs.
T for (2). The solid line is the calculated curve for χMT.
(c) Temperature dependence of experimental χM(•) and χMT(᭺) vs.
T for (3). The solid line is the calculated curve for χMT.
where N is Avogadro’s number, g is the spectroscopic split-
ting factor, β is the Bohr magneton, k is the Boltzmann
constant, zJЈ is the intermolecular exchange parameter and
z is the number of nearest neighbor FeIII atoms. The least-
squares fit of the experimental data using these equations
was limited from 10 to 300 K and gives zJЈ ϭ Ϫ0.18 cmϪ1
and g ϭ 2.03, as indicated by the solid curve in Figure 4(a).
The agreement factor R is equal to 6.68ϫ10Ϫ5. The
criterion used in determination of the best fit was based
Nβ2g2
χM
ϭ
S(S ϩ 1)
(1)
(2)
3kT
χM
χcMorr
ϭ
· χM
2zJЈ
1 Ϫ
Nβ2g2
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Tetrachloroferrate(III) Complexes of some Organic Diammonium Cations: Structures and Magnetic Properties
on minimization of the sum of squares of the deviations
[(χMT)obsd Ϫ (χMT)cald]2 / [(χMT)obsd 2
]
The complexes 2 and 3 have similar magnetic behavior.
For 2, the value of χMT at 300 K equal 4.32 cm3molϪ1K
(5.88 B.M.) and the value of the χMT product decreases
with temperature lowering to 0.55 cm3molϪ1K (2.09 B.M.)
at 1.8 K. For complex 3 the value of χMT at 300 K equals
4.05 cm3molϪ1K (5.70 B.M.). The value of the χMT product
decreases with temperature lowering to 0.441 cm3molϪ1K
(1.88 B.M.) at 1.8 K.
The susceptibility curves of all complexes exhibit no max-
ima indicating the presence of antiferromagnetic ordering
´
with a Neel temperature (TN), but in the cases of 2 and 3,
some slight curvature in the plots may suggest that a maxi-
mum can appear below 1.8 K.
Similarly, the magnetic data for 2 and 3 were fitted using
the simplest susceptibility equation for S ϭ /2 with a mo-
Figure 5 Field dependence of the magnetization at 2 K for com-
plexes (1), (2) and (3).
5
lecular field correction (Eq.(1) and (2)) [12]. The best-fit
parameters in the 10 to 300 K range are zJЈ ϭ Ϫ0.94 cmϪ1
and g ϭ 2.02 (R ϭ 3.43ϫ10Ϫ5) for complex 2, as indicated
by the solid curve in Figure 4(b), and for (3) these are zJЈ ϭ
Ϫ2.04 cmϪ1 and g ϭ 1.98 (R ϭ 3.07ϫ10Ϫ6), as indicated in
Figure 4(c).
The values for the Curie and Weiss constants determined
from the relation 1/ χMT ϭ f(T) over the temperature range
50 Ϫ 300 K are equal to 4.30 cm3molϪ1 and Ϫ0.73 K for
complex 1, 4.45 cm3molϪ1 and Ϫ6.92 K for complex 2, and
4.28 cm3molϪ1 and Ϫ16.6 K for complex 3 (Table 2). The
negative values of Weiss constants and intermolecular ex-
change parameters obtained from the calculation confirm
the occurrence of weak antiferromagnetic interactions be-
tween the iron centers in the crystal lattice.
The foregoing results of the magnetic susceptibility meas-
urements of the compounds show some differences in mag-
netic properties dependent on the kind of organic coun-
terion. The presence of the bulky cations results in a dia-
magnetic dilution due to increasing distance between the
paramagnetic FeIII atoms, and the magnetic interaction
might be transmitted by the crystal lattice. This manifests
itself in a decrease in the intermolecular exchange param-
eter and the value of the Weiss constant. In the case of the
(ddmpH2)2ϩ ion complex 2, a stronger antiferromagnetic
interaction is observed between the Fe3ϩ ions than for the
complex with the tetramethylethylenediammonium cation.
The small values of the intermolecular exchange parameters
suggest only weak antiferromagnetic interactions between
the magnetic atoms of FeIII. Although the ethylenediam-
monium cation is less bulky and unhindered (and leads to
a different structure) than is the case for (ddmpH2)2ϩ and
(tmedaH2)2ϩ,the FeIII atoms are still quite far apart. The
Table 2 Magnetic data for complexes 1Ϫ3.
Compound
g
zJЈ
R
TN
K
Curie
Weiss
constant
K
cmϪ1
constant
cm3molϪ1K
´
Neel temperature for the ammonium ion analogue is re-
(tmedH2)[FeCl4]Cl (1) 2.03 Ϫ0.18 6.68ϫ10Ϫ5
(ddmpH2)[FeCl4]Cl (2) 2.02 Ϫ0.94 3.44ϫ10Ϫ5
(enH2)[FeCl5(OH2)] (3) 1.98 Ϫ2.04 3.07ϫ10Ϫ6
Ϫ
Ϫ
Ϫ
4.30
4.45
4.28
Ϫ0.73
Ϫ6.92
Ϫ16.6
ported to be around 7 K [13] and the ordering temperatures
of the alkali metal salts also have been described as “un-
usually high” [14a], so it is possible that the more bulky
nature of the ethylenediammonium cation compared with
the Mϩ cations might be the dominant factor in this case.
For the recently reported diethylenetriammonium aquapen-
tachloroferrate(III), however, TN is 2.70 K [15], and it may
be that a combination of cation flexibility and its greater
ability for hydrogen bonding permits somewhat better ex-
change than in the (enH2)2ϩ case, but the factors remain
unclear.
The mechanism of superexchange pathways between the
electrons of iron(III) in the systems studied appears to be
that, in view of lack of bridging ligands between the Fe3ϩ
ions, the most probable interaction pathway is likely to oc-
cur through orbitals of neighboring chloride ligands, na-
mely Fe-Cl···Cl-Fe or additionally via the free chloride ions
[7, 16]. For complex 3, the interaction pathway could also
involve the water ligand. Since the Fe···Fe distances in the
The variation of the magnetization M versus the mag-
netic field H for the complexes 1, 2 and 3 at 2 K (Figure 5)
clearly supports the occurrence of weak antiferromagnetic
interactions. As the magnetic field increases, the M versus
H curve for 1 indicates a linear relation up to ϳ1 Tesla
and then shows a sinusoidal variation up to 5 Tesla, with
saturation at M ϭ 4.78 B.M. The M versus H curve for 2
is linear in the whole field range and indicates a value of
magnetization 2.94 B.M. at 5 T. Magnetization of the
sample even at 5 Tesla and 2 K is well below the saturation
5
value of 5 B.M. expected for an S ϭ /2 ground state with
g ϭ 2 in the absence of zero-field splitting or antiferromag-
netic coupling. The M versus H curve for 3 is linear in the
whole field range and indicates a value of magnetization
1.61 B.M. at 5 T, also well below the saturation value.
Z. Anorg. Allg. Chem. 2007, 2683Ϫ2688
 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
2687

B. D. James, J. Mrozinski, J. Klak, B. W. Skelton, A. H. White
[3] M. B. Millikan, B. D. James, J. Inorg. Nucl. Chem. 1981, 43,
1175.
[4] H. L. Friedman, J. Am. Chem. Soc. 1952, 74, 5.
[5] B. N. Figgis, C. L. Raston, R. P. Sharma, A. H. White, Aust.
J. Chem. 1978, 31, 2717.
examined compounds are all rather long (vide supra), it is
to be expected that the coupling between electrons of the
Fe3ϩ ions in the systems will be weak.
The EPR spectra of all the complexes at room tempera-
ture, 77 K and 4.5 K indicate a single isotropic line only,
[6] a) J. A. Zora, K. R. Seddon, P. B. Hitchcock, C. B. Lowe, D.
P. Shum, R. L.Carlin, Inorg. Chem. 1990, 29, 3302; b) R.
Shaviv, C. B. Lowe, J. A. Zora, C. B. Aakeröy, P. B. Hitchcock,
K. R. Seddon, R. L. Carlin, Inorg. Chim. Acta 1992, 198Ϫ200,
613; c) R. Shaviv, R. L. Carlin, Inorg. Chem. 1992, 31, 710; d)
R. Shaviv, K. E. Merabet, D. P. Shum, C. B. Lowe, D. Gonza-
lez, R. Burriel, R. L. Carlin, Inorg. Chem. 1992, 31, 1724.
[7] a) Z. Warnke, D. Wyrzykowski, G. Wawrzyniak, Pol. J. Chem.
2003, 77, 1121; b) D. Wyrzykowski, Z. Warnke, R. Kruszynski,
J. Klak, J. Mrozinski, Transition Met. Chem. 2006, 31, 765.
[8] H. Remy, H. J. Rothe, J. Prakt. Chem. 1926, 114, 137.
[9] B. D. James, M. Bakalova, J. Liesegang, W. M. Reiff, D. C. R.
Hockless, B. W. Skelton, A. H. White, Inorg. Chim. Acta 1996,
247, 169.
6
characteristic for an unresolved S1 state and a transition
1
ϩ
/
↔ Ϫ1/2 (Table 3). The EPR spectrum of the FeIII
2
atom in a tetrahedral crystal field is strongly dependent on
the character of the tetrahedral distortion and the compo-
sition of the coordination sphere (types of ligands). For
complexes containing the symmetric anionic form [FeCl4]Ϫ
good quality, intense signals of the EPR spectra are ob-
served, which are broadened with lowering temperature.
Those of 3 are not very different, and may reflect the quasi-
centrosymmetric nature of the ion in the structure.
Table 3 EPR data of complexes 1؊3.
[10] G. M. Sheldrick, SHELXL-97, ’A Program for Crystal Struc-
ture Refinement’, University of Göttingen, Göttingen, Ger-
many, 1997.
[11] E. König, Magnetic Properties of Coordination and Organome-
tallic Transition Metal Compounds, Springer-Verlag, Berlin,
1966.
[12] J. Samuel Smart, Effective Field Theories of Magnetism, W. B.
Saunders Co., Philadelphia and London 1966.
[13] S. R. Brown, I. Hall, J. Mag. Magnet. Mat. 1992, 104Ϫ107,
921.
Compound
293 K
77 K
4.5 K
*
*
*
giso δHpp /Gs giso δHpp /Gs giso
δHpp /Gs
(tmedH2)[FeCl4]Cl (1) 2.027
(ddmpH2)[FeCl4]Cl (2) 2.021
(enH2)[FeCl5(OH2)] (3) 2.002
370
350
160
2.048
2.023
2.002
650
390
150
2.111
2.090
2.078
760
440
690
* peak to peak linewidth
[14] a)A. J. Schultz, R. L. Carlin, Acta Crystallogr. 1995, B51, 43;
b) C. J. O’Connor, B. S. Deaver Jr., E. Sinn, J. Chem. Phys.
1979, 70, 5161.
References
[1] See, for example, S. M. Nelson in Comprehensive Coordination
Chemistry, G. Wilkinson, R. D. Gillard and J. A. McCleverty
(Eds), volume 4, chapter 44, Pergamon Press, Oxford, 1987.
[2] R. L. Carlin, Magnetochemistry, Springer-Verlag, Berlin, 1986.
[15] B. D. James, J. Mrozinski, J. Klak, B. W. Skelton, A. H. White,
Z. Anorg. Allg. Chem. 2007, 633, 974.
[16] C. B. Lowe, R. L. Carlin, A. J. Schulz, C.-K. Loong, Inorg.
Chem. 1990, 29, 3308.
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