Synthesis, crystal and molecular structure of [{C5Me5FeC5Me4CH2} + B{C6H3(CF3)2}- 4], the first example of a structurally characterized primary ferrocenylcarbocation

Article abstract of DOI:10.1016/S0022-328X(00)00566-0

The synthesis and the first X-ray structural study of a salt of the primary ferrocenylcarbocation [{C₅Me₅MC₅Me₄CH₂} ⁺ B{C₆H₃(CF₃)₂}^- ₄] (M = Fe, 1a) are reported. The C_Cp-C_α bond shows considerable inclination relative to the plane of the cyclopentadienyl ring so that the C_α atom becomes closer to the etal centre, the inclination angle α being equal to 23.6°. The Fe-C_α distance (2.567(12) A?) is still significantly longer than the covalent Fe-C σ-bond, which may be considered as an indication that the donor-acceptor interaction of the carbocationic centre with the metal electron pair is substantially weaker than in the earlier studied Ru- and Os-analogues (1b, 1c) wherein the positive charge was mostly localized on the metal centre (metallonium cations). Thus, complex 1a obviously preserves much more of the carbocationic state than its heavier analogues.

Full text of DOI:10.1016/S0022-328X(00)00566-0

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Journal of Organometallic Chemistry 616 (2000) 106–111
Synthesis, crystal and molecular structure of
[{C5Me5FeC5Me4CH2}+B{C6H3(CF3)2}−4 ], the first example of a
structurally characterized primary ferrocenylcarbocation
Arkadii Z. Kreindlin *, Fedor M. Dolgushin, Aleksander I. Yanovsky,
Zoya A. Kerzina, Pavel V. Petrovskii, Margarita I. Rybinskaya
A.N. Nesmeyano6 Institute of Organoelement Compounds, Russian Academy of Sciences, 28 Va6ilo6 St., Moscow 117813, Russia
Received 3 June 2000; accepted 3 August 2000
Abstract
The synthesis and the first X-ray structural study of a salt of the primary ferrocenylcarbocation [{C5Me5MC5Me4CH2}+
B{C6H3(CF3)2}−4 ] (M=Fe, 1a) are reported. The CCp–Ca bond shows considerable inclination relative to the plane of the
cyclopentadienyl ring so that the Ca atom becomes closer to the metal centre, the inclination angle h being equal to 23.6°. The
,
Fe–Ca distance (2.567(12) A) is still significantly longer than the covalent Fe–C s-bond, which may be considered as an
indication that the donor–acceptor interaction of the carbocationic centre with the metal electron pair is substantially weaker than
in the earlier studied Ru- and Os-analogues (1b, 1c) wherein the positive charge was mostly localized on the metal centre
(metallonium cations). Thus, complex 1a obviously preserves much more of the carbocationic state than its heavier analogues.
© 2000 Elsevier Science B.V. All rights reserved.
Keywords: Carbocations; Metallonium cations; Iron; Crystal struture; NMR spectra; X-ray study
also confirmed by the MO calculation carried out by
the extended Hu¨ckel method [6]. It is noteworthy that
this charge transfer process does not imply oxidation of
the metal, but rather results in the increase of its
coordination number; the C5Me4CH2-ligand coordina-
tion may be described as either h6 or s,h5. Thus, those
cations should in fact be regarded not as carbocations
but as true onium compounds, which we named metal-
lonium cations by analogy with corresponding onium
organic derivatives [7].
The structure of the Fe-containing cation 1a (M=
Fe) remained unknown for a long time because of the
difficulties associated with the preparation of X-ray
quality single crystals of its salts. It should be empha-
sized that the structure of permethylated Fe-containing
primary carbocation is of substantial interest as a basis
for theoretical treatment of the nature of chemical
bonding in these ions. All available structural data were
limited to systems with the substitution at the carbo-
cationic centre, e.g. C5H5FeC5H4CPh+2 BF4− [8],
(C5H5FeC5H4)2CH+BF4− [9], and (C5H5FeC5H4)C3Ph+2
BF−4 [10]. The substituents inevitably cause notable
1. Introduction
Earlier we reported the synthesis [1,2] and X-ray
structural studies of the salts of permethylated primary
cations [(C5Me5MC5Me4CH2)+ BPh4−] (1b, M=Ru [3];
1c, M=Os [2]). Structural results showed that Ru- and
Os-containing cations have a rather unusual geometry
with the CH2-group significantly displaced from the
Cp-ring plane towards the metal atom. The CCp–Ca
bond is inclined to the Cp-ring plane by 40.3 and 41.8°
in the Ru- and Os-complexes respectively, and the
,
M–Ca distances are equal to 2.270 (Ru) and 2.224 A
(Os) which are indeed quite close to the lengths of the
corresponding M–C s-bonds [4,5]. These results indi-
cated effective interaction between the carbocationic
centre and the lone electron pair (LEP) of the metal
atom, which leads to the formation of a donor–accep-
tor bond and, ultimately, to the complete charge trans-
fer from the carbon atom to the metal centre. This was
* Corresponding author. Tel.: +95-135-9308; fax: +95-135-5085.
E-mail address: krekis@ineos.ac.ru (A.Z. Kreindlin).
0022-328X/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00566-0

A.Z. Kreindlin et al. / Journal of Organometallic Chemistry 616 (2000) 106–111
107
distortions of the geometry of the cation (vide infra)
which made it so important to obtain the data for the
primary carbocation. The difficulties with the prepara-
tion of the crystals of the salts of the 1a cation were due
primarily to the peculiar chemical behaviour of ferro-
cenylmethyl cations [11], i.e. their involvement in the
redox tautomerism [12–14] of the monomer and subse-
quent dimerization both in solution and in the solid
state:
common organic solvents and higher stability even in
strong acidic solutions than their tetraphenylborate
analogues [15–19]. In the present work we prepared the
salts of 1a with both anions from C5Me5FeC5Me4-
CH2OH (3) according to the following reaction scheme:
C5Me5FeC5Me4CH2OH (3)+CF3CO2H“
[(C5Me5FeC5Me4CH+2 )CO2CF3−]
[(C5Me5FeC5Me4CH+2 )CO2CF3−]+NaAn“
[(C5Me5FeC5Me4CH2)+An−]
C5Me5Fe:C5Me4CH+2 An− (1a)U
C5Me5Fe+·C5Me4C·H2An− (1a%)
“12(C5Me5Fe+·C5Me4CH2)2An−2 (2)
An=BPh4, B{C6H3(CF3)2-3,5}4
The BPh4 salt was obtained by the treatment of the
alcohol 3 with the acetic acid doped by less than 5% of
CF3COOH and subsequent addition of the NaBPh4
solution in AcOH. The B{C6H3(CF3)2-3,5}4 salt was
synthesized by protonation of 3 with CF3COOH in
CH2Cl2 and subsequent treatment by the solution of
NaB{C6H3(CF3)2-3,5}4 in CH2Cl2. The structure and
composition of the 1a·BPh4 salt were confirmed by
In the kinetic studies of the two-stage dimerization
process we have shown that (a) the rate of the tau-
tomerism and dimerization depends on the nature of
the anion and decreases with the increasing bulk of the
anion in the BF−4 \PF6−\AlBr−4 series, and (b) the
limiting stage of the process is the migration of the
anion accompanied by the rearrangement of the crystal
lattice [14]. The nature of the anion was found to play
a significant role in the determination of the dimeriza-
tion rate even in the solution. These data suggested that
the stability of the salts 1a increases in going to the
bulkier anions characterized by lower migration rates.
1
elemental analysis and the H-NMR spectra (see Sec-
tion 4). It was impossible to grow single crystals of this
salt because of the dimerization process, even though
this process is indeed much slower than in case of the
salts with smaller anions like BF4, PF6, and AlBr4. At
the same time, we succeeded in growing the crystals of
1a·B{C6H3(CF3)2-3,5}4 suitable for the X-ray experi-
ment. The orange crystals were obtained from the
CH3NO2–Et2O mixture at −12° (in the freezer). It is
important to mention that upon prolonged storage
(more than 3 weeks at −12°) the dimerization process
does occur even in case of the 1a·B{C6H3(CF3)2-3,5}4
salt. This process causes both the crystals and the
mother liquor to change colour from orange to green,
which gives a clear indication of the above mentioned
redox process and eventual formation of dimerization
product 2. The structure of 2 was assigned unambigu-
ously on the basis of 1H, 13C, 11B and 19F-NMR spectra
(see Section 4). It is also noteworthy that even at −12°
after 6 days (the time and conditions of the X-ray
diffraction experiment) the crystals show definite signs
of formation of 2. It may be this dynamic process
which accounts for the limited accuracy of the final
X-ray structural results. The structure of cation 1a in
the crystals of its B{C6H3(CF3)2-3,5}4 salt is shown in
Fig. 1, bond lengths and main bond angles are listed in
Table 1.
2. Results and discussion
In contrast to tetraphenylborate (BPh4), the te-
trakis(3,5-bis(trifluromethyl)phenyl)borate anion which
has eight trifluoromethyl substitutents ([B{C6H3(CF3)2-
3,5}4]), has only recently become an anion of choice for
the preparation of a wide range of cationic complexes
[15–19]. Its salts normally show better solubility in
Earlier, in [7] we predicted the approximate Fe–Ca
distance and the CCp–Ca-bond/Cp-plane inclination an-
gle in the primary ferrocenylcarbocation and came up
,
with the values of 2.5 A and 25–30° respectively. The
,
X-ray structural study gave the results of 2.567(12) A
Fig. 1. Molecular structure of cation [C5Me5FeC5Me4CH2]+ (1a).
Methyl H atoms are omitted for clarity.
for the Fe–C(11) distance and 23.6° for the inclination
angle which thus shows a fairly good agreement with

108
A.Z. Kreindlin et al. / Journal of Organometallic Chemistry 616 (2000) 106–111
Table 1
gles than corresponding salts of primary cations (2.482
,
Bond lengths (A) and selected bond angles (°) in 1a
,
and 2.387 A, 34.0 and 38.4° for 4b and 4c respectively
[20,21]). Geometrical parameters of cations 1a and 4a
may be compared with those found in [22,23] for
neutral chromium complexes (CO)3CrC5H4CH2 and
(CO)3CrC5H4CPh2. The Cr–CH2 and Cr–CPh2 dis-
tances in these complexes are equal to 2.352 and 2.548
Fe(1)–C(1)
Fe(1)–C(2)
Fe(1)–C(3)
Fe(1)–C(4)
Fe(1)–C(5)
Fe(1)–C(6)
Fe(1)–C(7)
Fe(1)–C(8)
Fe(1)–C(9)
Fe(1)–C(10)
Fe(1)–C(11)
C(1)–C(2)
C(1)–C(5)
C(1)–C(11)
C(2)–C(3)
C(2)–C(12)
1.97(1)
2.05(1)
2.12(1)
2.14(1)
2.05(1)
2.09(1)
2.10(1)
2.06(1)
2.01(2)
2.12(1)
2.57(1)
1.45(1)
1.42(1)
1.37(2)
1.38(1)
1.51(1)
C(3)–C(4)
C(3)–C(13)
C(4)–C(5)
C(4)–C(14)
C(5)–C(15)
C(6)–C(7)
C(6)–C(10)
C(6)–C(16)
C(7)–C(8)
C(7)–C(17)
C(8)–C(9)
C(8)–C(18)
C(9)–C(10)
C(9)–C(19)
C(10)–C(20)
1.46(1)
1.53(1)
1.42(1)
1.47(1)
1.51(1)
1.43(1)
1.43(2)
1.51(1)
1.37(2)
1.51(2)
1.40(2)
1.54(2)
1.41(2)
1.49(2)
1.47(2)
,
A, the inclination angles h are equal to 35 and 31°
respectively.
It seems worthwhile to consider also some other
details of the structure and geometry of cation 1a and
its analogues 1b, 1c. In particular, the C(1)–C(11) bond
,
length in 1a is equal to 1.37(2) A, whereas in 1b [3] and
1c [2] the corresponding bond length is equal to 1.401
,
and 1.426 A, i.e. the certain lengthening of this bond
accompanies the shortnening of the M–C(11) distance
in the Fe“Ru“Os series. This observation is in agree-
ment with the calculated decrease in Mulliken bond
orders for C(1)–C(11) bonds (1.14, 1.11 and 1.09) and
the increase in bond orders for M–C(11) bonds (0.01,
0.16 and 0.22) from 1a to 1b and 1c respectively (see
[6]).
C(11)–C(1)–C(5)
C(11)–C(1)–C(2)
C(5)–C(1)–C(2)
C(11)–C(1)–Fe(1)
C(3)–C(2)–C(1)
C(3)–C(2)–C(12)
C(1)–C(2)–C(12)
122.3(10)
122.6(11)
108.9(9)
98.9(11)
107.1(9)
127.9(10)
124.9(10)
C(10)–C(6)–C(16)
C(7)–C(6)–C(16)
C(16)–C(6)–Fe(1)
C(8)–C(7)–C(6)
C(8)–C(7)–C(17)
C(6)–C(7)–C(17)
C(17)–C(7)–Fe(1)
C(7)–C(8)–C(9)
C(7)–C(8)–C(18)
C(9)–C(8)–C(18)
C(18)–C(8)–Fe(1)
C(8)–C(9)–C(10)
C(8)–C(9)–C(19)
C(10)–C(9)–C(19)
C(19)–C(9)–Fe(1)
C(9)–C(10)–C(6)
C(9)–C(10)–C(20)
C(6)–C(10)–C(20)
125.4(10)
124.8(10)
130.7(8)
108.2(10)
122.8(12)
129.0(12)
129.1(9)
107.1(10)
127.3(14)
125.5(14)
125.9(10)
112.2(11)
126.9(13)
120.6(13)
126.1(11)
103.1(10)
131.7(12)
125.1(11)
Complex 1a is characterized by the small dihedral
angle between the Cp-ring planes (4.7°); the corre-
sponding dihedral angles in 1b and 1c are equal to 6.8
and 6.9° respectively. The C5Me4 moiety of the
C5Me4CH2 ligand is essentially planar, the displacement
of the C(1) atom from the C(2)C(3)C(4)C(5) plane (0.02
C(12)–C(2)–Fe(1) 128.7(8)
C(2)–C(3)–C(4)
C(2)–C(3)–C(13)
C(4)–C(3)–C(13)
109.4(9)
126.3(9)
124.1(10)
C(13)–C(3)–Fe(1) 130.8(8)
C(5)–C(4)–C(3)
C(5)–C(4)–C(14)
C(3)–C(4)–C(14)
106.9(9)
127.9(10)
125.2(10)
,
A) is within experimental error, the folding angle along
the C(2)–C(5) line is equal to 1.4°.
C(14)–C(4)–Fe(1) 129.9(9)
C(4)–C(5)–C(1)
C(4)–C(5)–C(15)
C(1)–C(5)–C(15)
C(15)–C(5)–Fe(1) 129.7(8)
C(10)–C(6)–C(7) 109.3(10)
107.6(9)
125.2(10)
127.0(10)
A common structural feature for all cations 1a–1c is
a non-symmetrical position of the metal atom relative
to the carbon atoms of the Cp-ring of the C5Me4CH2
ligand. Thus, the Fe atom in 1a is shifted from the
C(20)–C(10)–Fe(1) 127.3(9)
C(1)–C(11)–Fe(1) 49.2(10)
,
centre of the Cp-ring of the C5Me4 ligand by 0.14 A
(this shift is measured as a distance between the projec-
tion of the metal atom onto the Cp-ring plane and the
geometrical centre of the ring); the corresponding shifts
the values predicted in [7]. It turns out that the M–Ca
distance in the Fe-containing cation 1a is considerably
longer and the inclination angle h substantially smaller
than in its Ru- (1b) and Os-analogues (1c). The Fe–
C(11) distance in 1a is also much longer than all other
distances between the Fe atom and the carbon atoms of
,
for Ru (in 1b) and Os (in 1c) are equal to 0.20 A. The
shift of the Fe atom towards the C(1)–C(11) bond and
the displacement of C(11) from the Cp-ring plane in the
direction of the metal atom show correlation with the
noticeable variations in the Fe–CCp distances. Thus, the
,
both Cp-rings (1.97(1)–2.14(1) A), whereas the bond
,
Fe–C(1) distance (1.97(1) A) is considerably shorter,
lengths M–C(11) in 1b and 1c are quite close to the
range of distances found for M–C(i ) (M=Ru, Os;
i=2–5). This leads to the conclusion that the M–Ca+
interaction in 1a is substantially weaker than that in its
Ru- and Os-analogues (1b, 1c). At the same time the
donor–acceptor M–C+a interaction in 1a is undoubt-
edly stronger than in the tertiary cation salt
C5H5FeC5H4CPh+2 BF4−. The M–C(11) distance in the
,
the Fe–C(2) and Fe–C(5) distances (both 2.05(1) A)
are approximately equal, and the Fe–C(3) and Fe–C(4)
bonds are longer than the average bond length for the
Fe–C bonds involving the carbon atoms of the C5Me5
ligand.
The Cp-rings in cation 1a are in the staggered confor-
mation, the torsion angle C(1)X(1)X(2)C(9) (X(1) and
X(2) refer to the centroids of the C(1)–C(5) and C(6)–
C(10) rings respectively) is equal to 180°. Similar con-
formation was observed in 1b and 1c [2,3]. However,
the tertiary cation C5H5FeC5H4CPh+2 (4a) with non-
methylated Cp-rings has an almost eclipsed conforma-
tion (the corresponding torsion angle is equal to 153°).
,
latter is equal to 2.715 A [8]. Analogous relationships
were also observed within the groups of Ru- and Os-
containing compounds where the tertiary cation salts
C5H5MC5H4CPh+2 PF6− (4b, 4c) (b M=Ru, c M=Os)
show longer M–Ca bonds and smaller inclination an-

A.Z. Kreindlin et al. / Journal of Organometallic Chemistry 616 (2000) 106–111
109
The crystal structure of 1a·B{C6H3(CF3)2-3,5}4 is
built of alternating cationic and anionic layers which
are parallel to the crystalographic plane (010) (Fig. 2).
All interionic distances in both layers correspond to the
normal van der Waals contacts.
C5Me5FeC5Me4C+H2 (A%)lC5Me5Fe+C5Me4CH2 (A¦)
A
4. Experimental
The 1H, 13C and 11B-NMR spectra were recorded
with the Bruker AMX-400 instrument at 400.13 MHz,
with BF3·Et2O as an external standard. The 19F-NMR
spectra were recorded using Bruker WP-200SY (188.31
MHz) with CF3COOH as an external standard. The
NaB[C6H3(CF3)2]4 salt was obtained from the corre-
sponding arylbromide according to [18]. The synthesis
of 3 was reported earlier [14].
3. Conclusion
Summing up the obtained data one may conclude
that the geometry of the Fe-containing cation differs
considerably from the geometry of the Ru- and Os-ana-
logues. In particular, in going from Ru and Os deriva-
tives to the Fe complex the inclination angle of the
C–CH2 bond relative to the Cp-ring becomes smaller
and the M–CH2 bond becomes longer, so that the
4.1. Salt 1a·B{C6H3(CF3)2-3,5}4
,
observed Fe–CH2 distance in 1a is almost 0.5 A longer
The solution of 266 mg (0.3 mmol) of
NaB{C6H3(CF3)2-3,5}4 in 30 ml of CH2Cl2 was added
on stirring to the solution of 85 mg (0.25 mmol) of
alcohol 3 in 30 ml of CH2Cl2 containing 0.3 ml of
CF3COOH. The mixture was stirred for 15 min and
then evaporated to the minimum volume (approxi-
mately 5 ml). The addition of approximately 30 ml of
pentane precipitated 230 mg (0.2 mmol) of the product
(yield 86%). The orange–pink salt was dissolved in
CH3NO2, treated with Et2O and placed in the freezer.
The crystals precipitated after about 24 h proved to be
of sufficiently good quality for X-ray diffraction experi-
ment. In about 3 weeks the crystals stored at −12°
turned green which indicated the formation of dimer 2.
than the typical Fe–C s-bond length (for example,
,
2.131 A in Fe–CH2R, where R=Csp2 [24]). This means
that the Fe atom is involved in a relatively weak
interaction with the carbocationic centre; according to
the extended Huckel MO calculations the charge trans-
fer from the carbocation to the metal centre does not
exceed 10% [6]. Therefore, one may assume that this
cation preserves its carbocationic nature to a far greater
extent than its Ru and Os analogues. This is also
confirmed in the chemical behaviour of the ferrocenyl-
methyl cation which, in contrast to the Ru- and Os-
analogues, shows the ability for electron transfer from
the metal atom to the carbocationic centre (redox pro-
cess) with the formation of a cation-biradical species
capable of dimerization (vide supra). Thus, results ob-
tained show that the structure of primary Fe-containing
cation may be interpreted in terms of the resonance
hybrid A with greater contribution of carbocation form
A%, than that of metallonium structure A¦, which is
caracteristic for Ru- and Os-containing cations:
1
The dimer was characterized by H, 13C, 11B and 19F-
NMR spectra (vide supra) and elemental analysis.
Found:
C 50.87; H, 3.54; F, 38.57. Calc. for
C
104H82B2F48Fe2(CF3COOH): C, 51.11; H, 3.36; F,
1
38.86%. H-NMR spectra of this paramagnetic species
show both cation (−39.05 ppm (Dw1/2=32 Hz, C5Me5,
Fig. 2. Fragment of crystal packing of 1a·B{C6H3(CF3)2-3,5}4 projection onto the (010) crystallographic plane.

110
A.Z. Kreindlin et al. / Journal of Organometallic Chemistry 616 (2000) 106–111
15H), −33.90 ppm (Dw1/2=51 Hz, C5Me4, 12H), −
26.10 ppm (Dw1/2=32 Hz, CH2CH2, 1H), and −4.8
ppm (Dw1/2=21 Hz, CH2CH2, 1H)) and anion (+7.62
ppm (Dw1/2=13 Hz, o-H, 8H), +7.67 ppm (Dw1/2=13
Hz, p-H, 4H)) signals. The non-equivalence of
diastereotopic protons of the CH2CH2 link is obviously
due to the specific rotation of two C5Me5FeC5Me4-sub-
stituents about the CCH2–CCH2 bond. The 13C-NMR
spectra feature the cation (at −27.51 ppm (Dw1/2=37
Hz), −14.71 ppm (Dw1/2=53 Hz), +29.25 ppm
(Dw1/2=27 Hz), +161.32 ppm (Dw1/2=20 Hz),
tion of these positions with carbon atoms with s.o.f.s
equal to 0.5 produced significant improvement both in
the R-factor value and the overall accuracy of the
structure. The final refinement of 568 parameters con-
verged to R1=0.1132 (on F for 3304 observed reflec-
tions with I\2|(I)) and wR2=0.3067 (on F2 for all
independent reflections), the weight scheme used was
w
−1=|2(F2o)+(aP)2+bP, where P=(Fo2 +F2c)/3, a=
0.060, b=5.000. All calculations were performed on an
IBM PC using the SHELXTL PLUS 5 program package
[25].
+252.19 ppm (Dw1/2=33 Hz), +277.08 ppm (Dw1/2
=
53 Hz)) and anion (117.40 ppm (s, p-C), 124.42 ppm (q,
CF3, J19F–13C 271.8 Hz), 128.83 ppm (q, CCF3, J19F–13C
30.5 Hz), 134.57 ppm (s, o-C), 161.51 ppm (q, CCF3,
J11,10B–13C 49.9 Hz)) signals. In the 11B and 19F-NMR
spectra singlets at −6.727 (Dw1/2=1.7 Hz) and
+14.862 ppm (Dw1/2=22 Hz) respectively are observed.
5. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC no. 144753. Copies of this infor-
mation may be obtained free of charge from The
Director, CCDC, 12, Union Road, Cambridge CB2
1EZ, UK (Fax: +44-1223-336033; e-mail: deposit@
ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).
4.2. Salt 1a·BPh4
The solution of 0.206 g (0.6 mmol) of NaBPh4 in 30
ml of AcOH was added on stirring to the solution of
0.17 g (0.5 mmol) of alcohol 3 in 30 ml of AcOH
containing 0.5 ml of CF3COOH. The precipitate was
filtered, washed first with 5 ml of AcOH, and then three
times with 10 ml of dry Et2O and purified by precipitat-
ing with ether from CH2Cl2. 0.138 g (0.43 mmol) was
obtained (yield 86%). Found: C, 81.39; H, 7.65. Calc.
Acknowledgements
This work was supported by the Russian Foundation
for Basic Research (project nos. 00-03-32894, 00-03-
32807). The authors are grateful to Dr Erkke Koleh-
mainen, Yuvyaskyulya University, Finland for the gift
of BrC6H3(CF3)2-3,5.
1
for C44H49BFe: C, 81.99; H, 7.66%. H-NMR spectrum
(l): 1.28 (s, 6H, a-Me), 1.55 (s, 15H, Me), 1.92 (s, 6H,
b-Me), 5.29 (s, 2H, CH+2 ), 7.2–7.5 (m, 20H, C6H5).
4.3. X-ray diffraction study
References
Crystals of 1a·B{C6H3(CF3)2-3,5}4 (C20H29Fe(C32-
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(
H12BF24) are triclinic, space group P1, at 153 K. a=
,
11.929(7), b=13.049(5), c=17.756(10) A, h=86.47(4),
3
,
i=78.97(5), k=80.08(4)°, V=2671(3) A , Z=2,
D
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atom were located in the difference Fourier synthesis
and were included in the refinement with fixed posi-
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model approximation. Six peaks located in the differ-
ence Fourier synthesis most probably correspond to a
disordered solvent molecule. We were not able to deter-
mine the exact formula of this solvent, however popula-
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