X-rayStructureAnalysisOnline2014,VOL.30
2014©TheJapanSocietyforAnalyticalChemistry
49
X-ray Structure Analysis Online
Crystal Structure of PPh4[Fe(NO)2Cl2]
Hiroki AKUTSU,*† Jun-ichi YAMADA,* Shin’ichi NAKATSUJI,* and Scott S. TURNER**
*Graduate School of Material Science, University of Hyogo, 3-2-1 Kouto, Kamigori-cho, Ako-gun, Hyogo
678-1297, Japan
**Department of Chemistry, University of Surrey, Guildford, Surrey GU2 7XH, UK
The title compound, (C24H20P)(FeN2O2Cl2), was prepared by adapting of literature methods. It crystallizes in the
tetragonalspacegroupP4.ThestructureconsistsofoneP(C6H5)4cationandoneFe(NO)2Cl2anion.Theanionhasone
orderedNOgroupandoneorderedClligand.Theothertwoligandsaredisordered,suchthatonehalfofNOandahalf
ofClarelocatedateachposition.
(Received July 10, 2014; Accepted August 28, 2014; Published on web October 10, 2014)
The [FeCl4]– anion has attracted much attention due to its
paramagneticnature(d5),leadingtoitsuseasamagneticsource
inmagneticionicliquids,1organicmagneticconductors,2andso
on.Asimilarmagneticmonoanionhavingadifferentnumberof
valenceelectrons,[Fe(NO)2Cl2]–,isalreadyknown.3,4However,
thus far nobody has used this monoanion as a source of
magnetism. Here, we reported on the crystal structure,
magnetic properties, and attempt to prepare a charge-transfer
complexofthesalt,PPh4[Fe(NO)2Cl2].
PPh4[Fe(NO)2Cl2] was prepared by adapting a literature
method3,5 from (NH4)2[Fe4S3(NO)7].6 The anion [Fe(NO)2Cl2]–
was assigned by mass spectrometry (FAB–, m/z = 186). X-ray
analysis indicates that the crystal is isostructural with
AsPh4[Fe(NO)Cl3].5 Figure 1 shows the molecular units and
Fig.2showsthemolecularstructureofPPh4[Fe(NO)2Cl2]along
with the atom numbering scheme. Figure 3 shows the crystal
structureofthesaltasviewedalongthecrystallographiccaxis.
Thestructureconsistsofonehalf(locatedona2-foldaxis)and
two quarters (located on a 4 axis) of the PPh4 cation and one
anion that are crystallographically independent. For the four
tetrahedral sites of the anion, one NO (–N1–O1) and one Cl
(Cl4)ligandsareordered,andtheothertwositesaredisordered,
namely a half of NO and a half of Cl are located at each
position. Because bond length and bond angle restrictions
P
Cl
Cl
Fig. 1
Fe
NO
NO
StructureofPPh4[Fe(NO)2Cl2].
Towhomcorrespondenceshouldbeaddressed.
Present Address: Department of Chemistry, Graduate School of
Science, Osaka University, 1-1 Machikaneyama, Toyonaka,
Osaka 560-0043, Japan.
E-mail:[email protected]
†
(usingDIFXandDANGcommandsinSHELX-97)areapplied
to the disordered NO ligands (Fe–N–O = 180˚, Fe–N = 1.69 Å
andN–O=1.12Å),wecanonlydiscussdetailsconcerningthe
non-disordered –Fe1–N1–O1, which is almost linear.7 Table 1
givesthecrystallographicdataandTable2givesselectedbond
lengthsfortheanion.
Thetemperature-dependentmagneticsusceptibilityshowsthe
Curie-Weiss behavior with a Curie constant of C = 1.633
emu·K/molandaWeissconstantofq=–2.3K.TheCvalueis
closer to 1.875 (indicative of S = 3/2) than 3.000 (S = 2) or
1.000(S=1),indicatingthattheformalelectronconfiguration
of Fe in [Fe(NO)2Cl2]– is high-spin d7, namely, the oxidation
numberofFeisunusual,+1.
Table 1
Crystal and experimental data
Chemical formula: C24H20Cl2FeN2O2P
Formula weight = 526.16
T = 298 K
Crystal system: tetragonal
Space group: P4
a = 18.181(4)Å
c = 7.4559(14)Å
V = 2464.6(8)Å3
Z=4
DX = 1.418 g/cm3
Radiation: Mo Ka (l = 0.71075 Å)
m(Mo Ka) = 0.916 mm–1
F(0 0 0) = 1076.0
Crystal size = 0.30 ¥ 0.08 ¥ 0.07 mm3
No. of reflections collected = 18350
No. of independent reflections = 5673
q range for data collection: 2.24 to 30.81˚
Data/Restrains/Parameters = 5673/6/316
Goodness-of-fit on F2 = 1.030
R indices [I > 2s(I)]: R1 = 0.0590
R indices [all data]: R1 = 0.1122, wR2 = 0.1313
(D/s)max = 0.000
(Dr)max = 0.180 eÅ–3
(Dr)min = –0.210 eÅ–3
Measurement: Rigaku Mercury2/MicroMax-007HF/VariMax
system
Program system: CrystalStructure 4.1
Structure determination: Shelx 97
CCDC number: 991292
50
X-rayStructureAnalysisOnline2014,VOL.30
C10
C9
C8
C11
C12
C7
P1
C2
C23
P3
C24
N3
C20 C22
C19
C21
C5
C4
C3
N1
O1
o
C6
C1
O3 Cl3
b
C18
Cl2
Fe1 N2
O2
P2
C17
C16
C15
C14
C13
Cl4
Fig. 2 Molecular structure of PPh4[Fe(NO)2Cl2]. The labeled
atomsarecrystallographicallyindependent.
a
Fig. 3 AviewofPPh4[Fe(NO)2Cl2]alongthec-axis.
provide any charge-transfer salts. In addition, the mixing of a
dark-brown acetonitrile solution of (TTF)3(BF4)2 (TTF =
Table 2 Selected bond distances (Å)
tetrathiafulvalene) with a dark-red acetonitrile solution of
PPh4[Fe(NO)2Cl2] immediately gave a yellow solution,
Fe1-Cl2
2.234(8)
Fe1-Cl3
2.254(5)
suggesting the reduction of TTF+ to TTF0, in which
Fe1-Cl4
2.231(2)
Fe1-N1
1.681(4)
N1-O1
1.120(6)
PPh4[Fe(NO)2Cl2]actedasthereducingagent.
Inconclusions,thesaltPPh4[Fe(NO)2Cl2]hasbeenpreparedand
itscrystalstructureandspinstate(d7)havebeendetermined.It
was also found that traditional methods of preparing chargeWe have attempted to use this anion as a magnetic source in transfer salts do not work due to the reactive nature of the Fe
organic magnetic conductors. One of the most interesting anion.
compounds in the area of organic magnetic conductors is
l-(BETS)2FeCl4,3 where BETS = Bis(ethylenedithio)
tetraselenafulvalene. The isomorphous non-magnetic References
l-(BETS)2GaCl4(S=0)showsasuperconductingtransitionat6
K,whereasl-(BETS)2FeCl4(S=5/2)showsaverysharpmetal- 1. S. Hayashi, and H. Hamaguchi, Chem. Lett., 2004, 33,
insulator (MI) transition with a concomitant antiferromagnetic
1590.
transition at 8 K. Circumstantially, the MI transition could be 2. H.Kobayashi,H.Cui,andA.Kobayashi,Chem. Rev.,2004,
caused by a similar effect that leads to colossal
104,5265.
magnetoresistance (CMR),8,9 where the periodic magnetic 3. W. Beck, R. Grenz, F. Götzfried, and E.Vilsmaier, Chem.
Ber.,1981,114,3184.
potential of the antiferromagnetically ordered d-electrons
induces the insulating state. However, in 2009 Nishio et al. 4. D. Ballivet-Tkatchenko, M. Riveccie, and N. E. Murr, J.
Am. Chem. Soc.,1979,101,2763.
reported a contradictory result.10 Heat capacity measurements
indicated that the d-electrons are not antiferromagnetically 5. M. Steimann, U. Nagel, R. Grenz, and W. Beck, J.
Organomet. Chem.,1983,247,171.
ordered,butbehaveparamagnetically.Thisresultsuggeststhat
theoriginoftheMItransitionisnotfromasimilarmechanism 6. L.L.Martin,G.D.Fallon,andB.Wu,Acta Crystallogra.
Sect. E,2004,60,i37.
to that which gives CMR, and it is not fully explained.
Therefore, it is appropriate to research new magnetic BETS- 7. J.A.Kaduk,andJ.A.Ibers,Inorg. Chem.,1975,14,3070.
basedl-typesaltswithadifferentelectronconfigurationofFe 8. S. Jin, T. H. Tiefel, M. McCormack, R. A. Fastnacht, R.
Ramesh,andL.H.Chen,Science,1994,264,413.
in order to potentially lend clarity to the origin of the MI
transition in l-(BETS)2FeCl4. Therefore, we prepared the 9. Y.Shimakawa,Y.Kubo,andT.Manako,Nature,1996,379,
53.
[Fe(NO)2Cl2]–anioninordertoobtainl-(BETS)2[Fe(NO)2Cl2].
However, PPh4[Fe(NO)2Cl2] is so unstable that metathesis 10. H. Akiba, S. Nakano, Y. Nishio, K. Kajita, B. Zhou, A.
Kobayashi,andH.Kobayashi,J. Phys. Soc. Jpn.,2009,78,
occurs in organic solvents to give PPh4[FeCl4]. Therefore, the
033601.
electrocrystallisation of BETS with PPh4[Fe(NO)2Cl2] does not