Reactions of alkyl-iron(II) and -ruthenium(II) complexes with B(C 6F5)3 and its water adducts. X-ray structure of a cyclometallated-iron(II) carbene

Article abstract of DOI:10.1016/S0020-1693(03)00327-X

The reactions of cis,trans-[M(CO)₂(PMe₃) ₂CH₃I] [M=Fe (1), Ru (2)] and cis,trans,cis-[Fe(CO) ₂(PMe₃)₂(CH₃)₂] (3) with B(C₆F₅)₃ involve Me-abstraction from the metal with formation of reactive species that undergo decomposition processes. In the presence of H₂O complex 2 reacts with B(C₆F ₅)₃ forming cis,trans-[Ru(CO)₂(PMe ₃)₂I(HOB(C₆F₅)₃)] (7) that slowly transforms in cis,trans-[Ru(CO)₂(PMe₃) ₂I(H₂O)]⁺[(HOB(C₆F₅) ₃)]^- (8), while complex 1 affords the cyclometallate complex trans-[Fe(CO)(PMe₃)₂I(=C(Me)-O-B(C ₆F₅)₂-OH-)] (9) whose molecular structure was investigated by X-ray diffraction studies.

Full text of DOI:10.1016/S0020-1693(03)00327-X

Inorganica Chimica Acta 353 (2003) 245Á252
/
www.elsevier.com/locate/ica
Reactions of alkylÁ
/
iron(II) and -ruthenium(II) complexes with
B(C6F5)3 and its water adducts. X-ray structure of a cyclometallated-
iron(II) carbene
Gianfranco Bellachioma a, Giuseppe Cardaci a,*, Elisabetta Foresti b, Alceo Macchioni a,
Piera Sabatino b,*, Cristiano Zuccaccia a
a Dipartimento di Chimica, Universita` di Perugia, Via Elce di Sotto 8, 06123 Perugia, Italy
b Dipartimento di Chimica ‘‘G. Ciamician’’, Universita` di Bologna, Via Selmi 2, 40126 Bologna, Italy
Received 16 December 2002; accepted 24 March 2003
Abstract
The reactions of cis,trans-[M(CO)2(PMe3)2CH3I] [MꢀFe (1), Ru (2)] and cis,trans,cis-[Fe(CO)2(PMe3)2(CH3)2] (3) with
/
B(C6F5)3 involve Me-abstraction from the metal with formation of reactive species that undergo decomposition processes. In the
presence of H2O complex 2 reacts with B(C6F5)3 forming cis,trans-[Ru(CO)2(PMe3)2I(HOB(C6F5)3)] (7) that slowly transforms in
cis,trans-[Ru(CO)2(PMe3)2I(H2O)]ꢁ[(HOB(C6F5)3)]ꢂ (8), while complex
[Fe(CO)(PMe3)2I(ÄC(Me)ÃOÃB(C6F5)2ÃOHÃ
# 2003 Elsevier B.V. All rights reserved.
1
affords the cyclometallate complex trans-
/
/
/
/
/
)] (9) whose molecular structure was investigated by X-ray diffraction studies.
Keywords: Cyclometallated-iron(II) carbene; B(C6F5)3 activation; B(C6F5)3×
/H2O reactivity
1. Introduction
[7d] was only recently described. In all the cases, the
activation of the alkyl complexes leads to the formation
of contact ion pairs in which the Lewis acid is bonded to
an alkyl group [6,8]. The presence of H2O affects the
reactivity of pentafluoroboranes [9] and this has been
attributed to the formation of water adducts, which act
as strong acids [10].
In this work we present the results of our studies on
the reactivity of B(C6F5)3 and its water adducts with the
isostructural and isoelectronic iron and ruthenium
There is great interest in the synthesis of electrophilic
transition metal complexes due to their strong catalytic
activity in the polymerization of olefins [1] and in the
activation of CÃ
/
H and CÃ/C bonds [2]. Pentafluorophe-
nyl boranes are important systems for increasing the
electrophilicity of transition metal alkyl complexes [3,4]
and they are commonly used as co-catalysts in metallo-
cene-based processes for the homogeneous polymeriza-
tion of olefins [5]. Many studies have been carried out
on the structure of the species responsible for the
catalytic activity [6] of the metallocene alkyl complexes
of the early transition metals. Fewer studies have been
carried out on the activation of the late transition metals
with pentafluorophenylboranes; the activation of mo-
lybdenum [7a], chromium [7b], nickel [7c] and platinum
complexes cis,trans-[M(CO)2(PMe3)2(Me)I] [MꢀFe
/
(1), Ru (2)] and cis,trans,cis-[Fe(CO)2(PMe3)2(Me)2]
(3).
2. Experimental
Complexes
cis,trans-[Fe(CO)2(PMe3)2CH3I]
(1)
[11,12], cis,trans-[Ru(CO)2(PMe3)2CH3I] (2) [13] and
cis,trans,cis-[Fe(CO)2(PMe3)2(CH3)2] (3) [14] were pre-
pared as described in the literature. Hydrated adducts of
B(C6F5)3 were obtained by adding H2O in n-hexane.
* Corresponding authors. Tel.: ꢁ
585 5598.
E-mail
piera@ciam.unibo.it (P. Sabatino).
/
39-075-585 5578; fax: ꢁ
/
39-075-
addresses:
cardchim@unipg.it (G. Cardaci),
0020-1693/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0020-1693(03)00327-X

246
G. Bellachioma et al. / Inorganica Chimica Acta 353 (2003) 245Á252
/
Benzene and n-hexane were dried by distillation over
sodium chips [15]. CH2Cl2, 1-pentene and cyclopentene
were dried by distillation over P2O5 [15]. The course of
the reactions was followed by IR and NMR spectro-
2.2. Reaction of cis,trans,cis-
[Fe(CO)2(PMe3)2(CH3)2] (3) and B(C6F5)3
100 mg of complex 3 were added at r.t. to a C6D6
solution containing equimolar amount of B(C6F5)3.
Precipitation of a brown oil was immediately observed.
scopies by using a 1725ꢃ
/
Perkin Elmer spectrophot-
Bruker DRX 400 spectrometer,
ometer and
a
1
respectively.
The H NMR spectrum of the solution showed broad
resonance at 1.34 ppm, assigned to PMe3, and at 0.56
One- and two-dimensional 1H, 31P, 13C and 19F NMR
spectra were measured on a Bruker DPX 200 or Bruker
DRX 400 spectrometer; referencing is relative to TMS
(1H and 13C), CCl3F (19F) and 85% H3PO4 (31P). NMR
samples were prepared by dissolving about 20 mg of the
compounds in 0.5 ml of deuterated solvent. Two-
ppm, assigned to the FeÃ
/
MeÃ
/
B group, with an intensity
ratio of 3/1. The 31P{1H} NMR spectrum shows a
singlet at 39.58 ppm. The solution was decanted and the
brown oil was dissolved in CD2Cl2. The formation of
complexes 4 and 5 was observed.
1
dimensional H NOESY and 19F,1H HOESY spectra
were recorded with a mixing time of 500Á800 ms.
Elemental analyses were carried out using a Carlo
Erba 1106 elemental microanalyzer.
/
2.3. Reaction of cis,trans-[Ru(CO)2(PMe3)2CH3I]
(2) and B(C6F5)3
100 mg of complex 2 were added to a C6D6 solution of
equimolar amount of B(C6F5)3. Immediate formation of
a brown oil was observed. The 1H NMR spectrum of the
2.1. Reaction of cis,trans-[Fe(CO)2(PMe3)2CH3I] (1)
and B(C6F5)3
solution shows
2
a
6.7 Hz) and a broad band at 0.40
Harris triplet at 1.59 ppm
100 mg of complex 1 were added to an equimolar
solution of B(C6F5)3 in C6D6 at room temperature (r.t.).
Immediate precipitation of a yellow solid was observed.
(j JHPꢁ4
/
JHPjꢀ
/
ppm. The brown oil was dissolved in CD2Cl2. The final
product was complex 6, which was characterized by
NMR [17].
The 1H NMR spectrum of the solution shows a triplet at
2
1.69 ppm (j JHPꢁ4
/
JHPjꢀ
/
7.5 Hz) and a broad band at
0.73 ppm; in IR two CO stretching frequencies are
observed at 2014 and 1964 cmꢂ1. After a few minutes
the precipitation was complete. The solution was
decanted and the solid was dried and dissolved in
CD2Cl2. In this solution complexes 4 and 5 are
recognized by their IR and NMR spectra, previously
described [11,16].
2.3.1. Complex 6
1H NMR (CD2Cl2, 298 K, J values in Hz): d 1.74 (t
2
Harris, j JHPꢁ4
/
JHPjꢀ
7.1, RuCH3); 19F NMR (CD2Cl2, 298
133.47 (s, oF), ꢂ165.62 (s, pF),
168.1 (s, mF); 31P{1H} NMR (CD2Cl2, 298 K, J
/7.9, PMe3), 0.53 (broad, BMe),
3
ꢂ
/
0.10 (t, JHP
ꢀ
/
K, J values in Hz): d ꢂ
/
/
ꢂ
/
values in Hz): d ꢂ
11.55 (s, PMe3); 13C{1H} NMR
/
(CD2Cl2, 298 K, J values in Hz): d 194.2 (t, 2JCP
ꢀ19.6,
/
2
2CO), 187.84 (t, JCP
2.1.1. Complex 4
1H NMR (CD2Cl2, 298 K, J values in Hz): d 1.72 (t
ꢀ/8.1, CO); IR (CD2Cl2): nCO
ꢀ
/
2115, 2045 cmꢂ1
.
Harris, j JHPꢁ4
11 2
/
JHPjꢀ
7.8, CH3); 19F NMR (CD2Cl2, 298
133.30 (s, oF), ꢂ165.35 (s, pF),
/
8.8, PMe3), 0.54 (broad band,
In another experiment, the reaction was carried out in
n-pentene as a solvent in order to stabilize the inter-
mediate. No difference was observed with respect to the
reaction carried in C6D6: both the intermediate and final
product were the same.
MeB), 0.14 (t, 3JHP
ꢀ
/
K, J values in Hz): d ꢂ
/
/
ꢂ
167.74 (s, mF); 31P{1H} NMR (CD2Cl2, 298 K, J
/
values in Hz): d 15.12 (s, PMe3); 13C{1H} NMR
2
(CD2Cl2, 298 K, J values in Hz): d 208.44 (t, JCP
ꢀ
/
2
24.8, CO), 203.6 (t, JCP
nCO
2085, 2021 cmꢂ1
ꢀ14.1, CO); IR (CD2Cl2):
/
2.4. Preparation of complexes 7 and 8
ꢀ
/
.
170 mg of complex 2 were dissolved in n-hexane. An
B(C6F5)3 in n-hexane solu-
2.1.2. Complex 5
1H NMR (CD2Cl2, 298 K, J values in Hz): d 1.60 (t
equimolar amount of H2O×
/
tion was added at r.t. to the stirred solution of the
ruthenium complex. An instantaneous reaction was
observed with the formation of a yellow precipitate.
The solution was left at r.t. for 1 h to allow complete
precipitation of the solid. The solid (complex 7) was
separated by filtration (150 mg of yellow crystals, yield:
32%). Anal. Found: C, 32.79; H, 2.05. Calc. for
C26H20BF15IO3P2Ru: C, 32.3; H, 2.09%.
2
Harris, j JHPꢁ4
/
JHÃPjꢀ
/
7.9, trans PMe3), 1.51 (d,
2JHP
3JHP
ꢀ
/
8.4, PMe3), 0.54 (broad, BMe), ꢂ
/0.14 (dt,
3
8.1, JHP
ꢀ
/
ꢀ
/
10.5, CH3); 19F NMR(CD2Cl2, 298
K, J values in Hz): d ꢂ
/
133.30 (s, oF), ꢂ
/
165.35 (s, pF),
ꢂ
167.74 (s, mF); 31P{1H} NMR (CD2Cl2, 298 K, J
/
2
values in Hz): d 15.91 (d, JPP
ꢀ
/
65.8, PMe3), 11.40 (t,
ꢀ .
2018, 1965 cmꢂ1
2JPP
ꢀ
/
62, PMe3); IR(CD2Cl2): nCO
/

G. Bellachioma et al. / Inorganica Chimica Acta 353 (2003) 245Á
/252
247
1
2.4.1. Complex 7
1H NMR (C6D6, 298 K, J values in Hz): d 2.74
j JCPꢁ3
/
JCPjꢀ
/
28.9, PMe3). IR (n-hexane): nCO
ꢀ
/
1950
cmꢂ1
.
5
(septet, JHF
2
ꢀ
/
3.4, OH), 1.14 (t Harris, j JHPꢁ4
/
JHPjꢀ
/
7.9, PMe3); 19F NMR (C6D6, 298 K, J values in Hz): d
ꢂ
/
131.46 (s, oF), ꢂ
/
158.24 (t, 3JFF
ꢀ
/
20.7, pF), ꢂ
20.7, mF); 31P{1H} NMR
(C6D6, 298 K, J values in Hz): d (ppm), ꢂ13.79 (s,
/
163.78
2.6. X-ray crystallography
3
3
(dd, JFF
ꢀ
/18.8, JFF
ꢀ
/
/
Crystals of 9 suitable for X-ray single crystal studies
were precipitated from cyclopentene at ꢂ18 8C. Crystal
PMe3); 13C{1H} NMR (C6D6, 298 K, J values in Hz): d
/
2
196.5 (t, JCP
2
13.6, CO), 188.41 (t, JCP
ꢀ
/
ꢀ10.9, CO),
/
1
148.23 (d, JCF
1
data and details of structure refinement are reported in
Table 1. Diffraction intensities were collected at 293 K
on a Bruker AXS SMART 2000 CCD diffractometer
using graphite monochromated Mo Ka radiation. The
data were collected using 0.38 wide v scans, crystal-to-
detector distance of 5.0 cm, and corrected for absorp-
tion empirically using the SADABS routine. Data
collections nominally covered a full sphere of reciprocal
space with 10 s exposure time per frame. The structure
was solved by direct methods and refined on F2 by full-
matrix least-squares calculations using the SHELXTL/PC
package [18]. Thermal vibrations were treated anisotro-
pically. Unambiguous location of the hydrogen atom
bound to O(2) has been made possible from both the
quality of the crystal data and redundancy of reflections
ꢀ
/
226.0, oC), 140.35 (d, JCF
ꢀ
/
248.9,
249.0, mC), 121.7 (s, Cipso),
33.6, PMe3).
1
pC), 137.88 (d, JCF
ꢀ
/
16.32 (t Harris, j JCPꢁ3
/
JCPjꢀ
/
1
Complex 7 was rather stable in benzene; in hydrated
CH2Cl2 it reacted slowly with H2O to form complex 8,
which was characterized by NMR.
2.4.2. Complex 8
1H NMR (CD2Cl2, 298 K, J values in Hz): d 5.14 (s,
H2O), 5.7 (s, OHꢁ
/
2H2O), 1.82 (t Harris,
7.9, PMe3); 19F NMR(CD2Cl2, 298 K,
2
j JHPꢁ4
/
JHPjꢀ
/
3
133.50 (d, JFF
J values in Hz): d ꢂ
/
ꢀ18.8, oF),
/
3
165.70 (t, JFF
3
168.2 (dd, JFF
ꢂ
/
ꢀ
/
20.33, pF), ꢂ
/
ꢀ
/
ꢀ
20.3, mF); 13C{1H} NMR (CD2Cl2, 298
/
3
18.6, JFF
K, J values in Hz): d 195.6 (t, 2JCP
ꢀ
/
12.3, CO), 189.4 (t,
225.0, oC), 139.7 (d,
254.0, mC), 121.26
JCPjꢀ34.4, PMe3).
1
10.6, CO), 148.2 (d, JCF
2JCP
1JCF
ꢀ
/
ꢀ
/
collected. The remaining H atoms were geometrically
˚
H 0.96 A] and refined ‘‘riding’’ on their
1
247.0, pC), 137.17 (d, JCF
positioned [CÃ
/
ꢀ
/
ꢀ
/
1
(s, Cipso), 16.53 (t Harris, j JCPꢁ3
/
/
corresponding carbon atoms. Refinement converged at
0.033, wR2ꢀ
a final Rꢀ 0.069, Sꢀ1.01. Molecular
/
/
/
graphics were prepared using ORTEP3 for WINDOWSNT
[19].
2.5. Preparation of complex 9
200 mg of complex 1 were dissolved in n-hexane at r.t.
A solution containing B(C6F5)3 and H2O (molar ratioꢀ
0.5) was added. A precipitate formed immediately. The
solution was left at ꢂ18 8C for 12 h to complete the
precipitation. The solid was separated and washed with
cold n-hexane. The solid was extracted with cyclopen-
tene. Orange crystals of complex 9 precipitated from the
/
Table 1
Crystal data and details of refinement for complex 9
/
Empirical formula
Fw
Temperature (K)
C21H22BF10FeIO3P2
767.89
293
˚
Wavelength (A)
0.71069
monoclinic
P21/n
Crystal system
Space group
Unit cell dimensions
solution in cyclopentene at ꢂ18 8C (yield 20%). The
/
molecular structure of complex 9 in the solid state was
determined by X-ray diffractometric methods (see
infra). Anal. Found: C, 33.01; H, 3.00; Calc. as
C21H22BF10IO3P2Fe: C, 32.85; H, 2.89%.
˚
a (A)
8.796(2)
17.631(3)
18.335(3)
97.68(2)
2817.6
4
˚
b (A)
˚
c (A)
b (8)
Volume (A )
3
˚
2.5.1. Complex 9
1H NMR (CD2Cl2, 298 K, J values in Hz): d 3.03 (t,
Z
Density (Mg mꢂ3
F(000)
)
1.810
1504
2
4JHP
ꢀ
/
0.8, CH3), 1.46 (t Harris, j JHPꢁ4
/
JHÃPjꢀ
/
8.2,
Crystal size (mm)
0.2ꢃ
34
135
285l 5
Number of reflections collected 39 551
/0.3ꢃ/0.3
PMe3), 1.30 (broad, OH); 19F NMR (CD2Cl2, 298 K, J
u Range for data collection (8) 2Á
/
3
135.14 (d, JFF
values in Hz): d ꢂ
/
ꢀ
/
14.8, oF), ꢂ157.49
/
Index range
ꢂ/
/
h 5
/
13, ꢂ
/
215
/
k 5
/
27, ꢂ
/
3
(t, JFF
3
163.46 (dd, JFF
3
14.8, JFF
ꢀ
/
19.9, pF), ꢂ
/
ꢀ
/
ꢀ
/
/
/28
19.9, mF); 31P{1H} NMR (CD2Cl2, 298 K, J values in
Hz): d 5.84 (s, PMe3); 13C{1H} NMR (CD2Cl2, 298 K, J
Number of data/restraints/para- 10 605/0/333
meters
2
values in Hz): d 340.6 (t, JCP
ꢀ
ꢀ
/
21.2, FeÄ
241.3, oC), 140.4 (d,
215.5, mC), 101.28
22.1, Cipso), 44.4 (s, Me), 17.01 (t Harris,
/C), 219.3 (t,
Goodness-of-fit on F2
Final R indices [I ꢀ2s(I)]
Largest difference peak and hole 0.53Á
1.013
Rꢀ
0.0332, wR2ꢀ
0.50
2JCP
ꢀ
/
33.2, CO), 147.2 (d, JCF
/
1
/
/
/
0.0695
1JCF
ꢀ
/
290.6, pC), 137.7 (d, JCF
ꢀ
/
1
/
ꢂ3
2
(t, JCF
˚
(e A
)
ꢀ
/

248
G. Bellachioma et al. / Inorganica Chimica Acta 353 (2003) 245Á252
/
3. Results and discussion
With the suspicion that the decomposition processes
could be due to the presence of adventitious water, we
decided to carry out the reactions of complexes 1, 2, and
By the reactions of complex 1, 2 or 3 with B(C6F5)3 in
C6D6 at room temperature a brown solid or liquid
1
immediately precipitated. The H NMR spectra of the
supernatant C6D6 solutions indicated the formation of
3 with H2O×
/
B(C6F5)3, prepared as reported in the
literature [23]. The 1H NMR spectrum of the water
adduct in CD2Cl2 shows a resonance at 6.7 ppm,
assigned to H2O coordinated to B(C6F5)3; the 19F
BÃ
as supported by the presence of a broad resonance at
approximately 0.5Á
0.6 ppm typical of MeB(C6F5)3ꢂ
/
Me bond by attack of B(C6F5)3 to the methyl ligand
NMR spectrum shows resonances at ꢂ
/
133.8 ppm
/
(oF), ꢂ152.6 ppm (pF) and ꢂ163.0 ppm (mF), which
/
/
anion [20]. Attempts to trap the intermediates [21]
carrying out the reactions in n-pentene were unsuccess-
ful; other more nucleophilic ligands, such as carbon
monoxide and phosphine could not be used to stabilize
the intermediates because they react quickly with the
starting methyl-complexes affording acetyl complexes
[22].
The precipitates from C6D6 solutions dissolved in
CD2Cl2 showed the presence of complexes 4 and 5 in a
3/1 ratio in the case of reagents 1 and 3 and complex 6 in
the case of reagent 2 (Chart 1) as indicated by IR and
1H, 31P, 13C and 19F NMR spectroscopies and by the
comparison with the previously described [11,16,17]
complexes containing BPh4ꢂ as counteranion. The
formation of complexes 4, 5, and 6 in low yield can
only be explained by assuming that the intermediates
are very near to those assigned to this compounds in the
literature [10,23]. The 19F,1H HOESY spectrum shows a
strong contact between the ortho fluorine atoms and the
water protons, confirming the structure.
While the reactions of iron(II) alkyl complexes did not
afford clear results, the reaction of H2O×/B(C6F5)3 with
complex 2 in n-hexane gave a yellow precipitate which
was tentatively characterized as 7 (Chart 1), in which a
coordination position of ruthenium is occupied by the
oxygen of the [HOB(C6F5)3]ꢂ anion. Structure 7 was
deduced on the basis of an elemental analysis and of IR
and NMR spectra in C6D6. The 1H NMR spectrum
shows a septet at 2.74 ppm assigned to the OH proton,
which couples with 6 equiv. ortho fluorines of C6F5 [24]
(5JHÃF
ꢀ3.4 Hz) and a deceptive triplet at 1.14 ppm due
/
to two phosphine ligands [25]. The IR spectrum shows
two CO stretching bands of equal intensity at 2051 and
1991 cmꢂ1, indicating two cis CO ligands. This is
confirmed by the 13C{1H} NMR spectrum which shows
coming from B(C6F5)3 attack on metalÃ
/
Me group
undergo decomposition processes with a redistribution
of PMe3 and CO ligands.
Chart 1.

G. Bellachioma et al. / Inorganica Chimica Acta 353 (2003) 245Á
/252
249
Fig. 1. 19F,1H HOESY NMR spectrum (302 K, methylene chloride-
d2) of the mixture of complexes 7 and 8.
Fig. 2. ORTEP diagram of complex 9.
two triplets at 196.5 and 188.41 ppm coupled to 2 equiv.
trans phosphine ligands. The 19F,1H HOESY spectrum
in CD2Cl2 shows strong contacts between the ortho
fluorine atoms and the OH and PMe3 protons, indicat-
ing an intramolecular structure for these interacting
Table 2
˚
Selected bond distances (A) and angles (8) for complex 9
groups. The presence of the RuÃ
/
I bond was verified by
the precipitation of AgI after the decomposition of
complex 7 with HNO3 in H2O and the addition of
AgNO3.
Bond distances
FeÃ
FeÃ
FeÃ
FeÃ
FeÃ
FeÃ
BÃ
BÃ
BÃ
BÃ
/
I
2.6720(4)
1.718(3)
1.840(2)
2.012(2)
2.276(1)
2.280(1)
1.472(3)
1.498(3)
1.659(3)
1.663(3)
/
C(7)
C(8)
O(2)
P(2)
P(1)
/
The formation of complex 7 by reaction with H2O×
/
/
B(C6F5)3 is attributed to the strong Bronsted acid
character of the coordinated H2O [26] which is able to
protonate the methyl group bonded to the metal center
as previously observed by Puddephatt et al. in square
planar dimethyl platinum complexes [27].
/
/
/
O(2)
/O(3)
/C(10)
/C(16)
Complex 7 is rather stable in benzene, but in wet
CH2Cl2 it reacts slowly with H2O to give complex 8, in
which the OH bond to ruthenium is replaced by H2O
(Chart 1). The 1H NMR spectrum of 8 in CD2Cl2 shows
a band at 5.14 ppm (integrating for two protons)
assigned to coordinated H2O, a band at 5.7 ppm
(integrating for five protons) assigned to the OH of
the anion [HOB(C6F5)3]ꢂ, bonded by hydrogen bond to
two H2O (see Fig. 1) and a deceptive triplet (integrating
for 18 protons) assigned to two trans PMe3 ligands. The
19F,1H HOESY spectrum shows strong contacts be-
tween the ortho and meta fluorine atoms and the OH
proton and very weak contacts between the ortho and
meta fluorine atoms and the PMe3 protons; this
behavior is explained by the formation of contact ion
pairs [28]. A comparison of the intensity of the contacts
in complexes 7 and 8 clearly shows that in complex 7 all
the contacts are intramolecular, while in complex 8 the
OH gives intramolecular contacts and PMe3 gives
intermolecular contacts with the fluorine atoms (Fig.
Bond angles
C(7)Ã
C(7)Ã
C(8)Ã
C(7)Ã
C(8)Ã
O(2)Ã
C(7)Ã
C(8)Ã
O(2)Ã
P(2)ÃFeÃ
C(7)ÃFeÃ
C(8)ÃFeÃ
O(2)ÃFeÃ
P(2)ÃFeÃ
P(1)ÃFeÃ
O(2)Ã
O(2)Ã
O(3)Ã
O(2)Ã
O(3)Ã
C(10)Ã
/
FeÃ
FeÃ
FeÃ
FeÃ
FeÃ
FeÃ
FeÃ
FeÃ
FeÃ
/
C(8)
O(2)
O(2)
P(2)
P(2)
95.4(1)
175.9(1)
80.5(1)
/
/
/
/
/
/
88.9(1)
/
/
93.7(1)
/
/
P(2)
P(1)
P(1)
91.2(1)
88.9(1)
92.3(1)
/
/
/
/
/
/
P(1)
91.3(1)
/
/
P(1)
173.84(3)
93.3(1)
/
/
I
I
/
/
171.2(1)
90.72(5)
86.81(2)
87.52(2)
102.4(2)
113.3(2)
109.5(2)
113.9(2)
109.1(2)
108.4(2)
/
/
I
/
/
I
/
/
I
/
BÃ
BÃ
BÃ
BÃ
BÃ
BÃ
/
O(3)
/
/
C(10)
C(10)
C(16)
C(16)
/
/
/
/
/
/
/
/
C(16)

250
G. Bellachioma et al. / Inorganica Chimica Acta 353 (2003) 245Á252
/
1). The contact between the ortho fluorine and H2O
coordinated to the metal is very intense because it is
exchanging with the H2O bonded to OH by hydrogen
bond (Fig. 1).
OÃ
and FeÃ
longer than in 9, while the C(carbene)Ã
1.484(8), and C (carbene)ÃO(methoxy), 1.299(7) A,
values are strictly comparable with the C(carbene)Ã
C(methyl) and C(carbene)ÃO(ring) [1.499(3) and
1.297(3) A] distances in our complex.
Concerning the other bond distances in the five-
membered ring, the short OÃC(carbene) distance
[1.297(3) A] shows neat multiple bond character, while
the OÃB interactions are non-equivalent single bonds
[1.472(3) and 1.498(3) A]. Short intramolecular H-
bonding interactions occur between O(2)ÃH(2) and
both F(1) and F(10) atoms [Oꢀ ꢀ ꢀF distances 2.822 and
2.774, OÃHꢀ ꢀ ꢀF angles 113.9 and 115.68, respectively].
Also CÃHꢀ ꢀ ꢀF interactions occur both of intra-molecu-
lar, C(1) with F(10) [Cꢀ ꢀ ꢀF distance 3.32 A, CÃ
angle 161.98], and inter-molecular kind, C(2) with
/
Me}][OTf] [32]. Here the FeÃ
/
C(carbene), 1.859(6),
O, 2.045(5) A, distances are again slightly
C(ring),
˚
/
/
˚
/
When the H2O content is less than equimolar with
/
respect to H2O×/B(C6F5)3, the course of the reaction is
/
˚
different. The clearest results are obtained with complex
1. Complex 1 reacts instantaneously in n-hexane with
the formation of trans-[Fe(CO)(PMe3)2I(Ä
B(C6F5)2ÃOHÃ)] (9) (Chart 1) which in IR shows a
carbonyl stretching at 1950 cmꢂ1
/
C(Me)Ã
/
OÃ
/
/
˚
/
/
.
/
˚
The molecular structure of 9, obtained by a single
crystal X-ray diffraction study, is given in Fig. 2,
together with its crystallographic numbering. Table 2
reports selected bond distances and angles. The iron
/
/
atom is in the oxidation state ꢁ
/
2 and the negative
/
˚
charges are formally localized on the iodide ligand and
tetracoordinate boron. The iron atom exhibits the
expected octahedral geometry with the trimethylpho-
sphine ligands occupying trans positions. The equatorial
sites contain the carbene and oxygen donors included in
/
Hꢀ ꢀ ꢀF
˚
symmetry-related F(2) [Cꢀ ꢀ ꢀF distance 3.45 A, CÃ
/
Hꢀ ꢀ ꢀF angle 170.38].
The solution structure of complex 9 was determined
by NMR spectroscopy. The 1H NMR spectrum shows a
a five-membered Ã
/
C(Me)Ã
/
OÃ
/
BÃ
/
O(H)Ã
/
chelate ring.
The iodide and carbonyl ligands occupy the sites trans
to the carbene and oxygen, respectively. The idealized
molecular symmetry is Cs and also the groups appended
to the coordinated atoms conform to this symmetry.
The five-membered chelate ring represents one of the
few examples of cyclometallate iron carbenes and the
only one containing the B(C6F5)2 fragment [29]. The
triplet at 3.03 ppm assigned to the FeÄ
/
C(Me)Ã
/
group,
which couples to 2 equiv. phosphorus atoms; the
4
carbene structure is supported by the JHÃP coupling,
which is not observed in the acetyl complexes [17]. A
deceptive triplet, typical of 2 equiv. PMe3 ligands, is
observed at 1.46 ppm. The band at 1.30 ppm is assigned
to the OH coordinated to iron, broadened by the
coupling to quadrupolar boron. The 19F,1H HOESY
spectrum shows strong contacts between the ortho
fluorine atoms and the OH and PMe3 protons and
weak contacts between the ortho fluorine atoms and the
methyl carbene and between the meta fluorine atoms
and the PMe3 protons in agreement with the interatomic
distances in complex 9. The most interesting aspect of
the 13C{1H} NMR spectrum is a triplet at 340.4 ppm,
which is unusual and can be assigned to the carbene
carbon [33].
ring is strictly planar [rms deviation of all five atoms
˚
0.01 A] with the O(2)Ã
/
FeÃ
/
C(8) and O(2)Ã
/
BÃ
/
O(3)
angles of 80.5(1) and 102.4(2)8, respectively. The FeÃ
/
˚
C(carbene) bond [1.840(2) A] is comparable with the
C(O)R interac-
numerous values reported for other FeÃ
/
˚
tions in Fe(II) complexes [average 1.895 A] [29]. The
double bond character of this interaction is well
appreciated from a comparison of the FeÃ
/
C(carbonyl)
bond in our complex [1.718(3) A] and the FeÃC(methyl)
bond in Fe(II) complexes [29] [average value 2.083 A,
˚
/
˚
˚
cfr. 2.093 and 2.083 A in cis,trans- and trans,trans-
The formation of complex 9 can be explained on the
basis of Scheme 1. The first step of the reaction is the
interaction of free B(C6F5)3 with the oxygen of the
carbon monoxide (a), which catalyses the methyl
migration [34] and stabilizes the carbene structure (b)
[20]; H2O then binds to the free coordination site (c)
and, finally, the elimination of C6HF5 gives the cyclic
structure 9 [35].
In conclusion, the first step of the reaction of
complexes 1, 2 and 3 with B(C6F5)3 is the abstraction
of methyl to form cation like complexes, which are very
reactive and were not characterized. They continue to
decompose forming the stable complexes 4, 5 and 6. In
the presence of water, free H2O, B(C6F5)3, H2O.
B(C6F5)3 and other hydrated species are in equilibrium
[10]. Under these conditions the behavior of complexes 1
and 2 is similar: all the reactions are possible with either
[Fe(CO)2(PMe3)2(CH3)I] [30]. A stereochemically and
electronically comparable situation has been found in
Fe(CO)(PEt3)2(Cl)[C(OSiMe3)CHCOOMe] [31]. An
analysis of the ironÁ
equivalent values for the FeÃ
against 2.276(1) and 2.272(1) A] and FeÃ
/
ligands distances shows strictly
˚
/
P [2.276(1) and 2.280(1) A
˚
/
C(carbonyl)
interactions [1.718(3) vs. 1.728(4) A] and slightly shorter
O values in our compound
˚
FeÃ
/
C(carbene) and FeÃ
/
˚
[1.840(2) and 2.012(2) A against 1.899(4) and 2.040(3)
˚
A]. Very probably the more localized nature of the p
bonds in the ring including a tetracoordinate boron
increases the FeÃ
/
C(carbene) and FeÃ/O bond orders
with respect to what found in the completely delocalized
system in Fe(CO)(PEt3)2(Cl)[C(OSiMe3)CHCOOMe]
[31]. A very similar carbene grouping has been recently
reported in [Fe(C5H5)(CO){k2(C, O)Ã
/C(OMe)C6H4-o-

G. Bellachioma et al. / Inorganica Chimica Acta 353 (2003) 245Á
/252
251
Scheme 1.
[2] (a) R.H. Crabtree, Chem. Rev. 85 (1985) 245;
the formation of the ionic complexes 4, 5, 6 or the
(b) R.E. Shilov, Activation of Saturated Hydrocarbon by Transi-
tion Metal Complexes, D. Reidel, Dordrecht, 1984.
[3] W.E. Piers, T. Chiver, Chem. Soc. Rev. 26 (1997) 345.
[4] H. Jacobsen, H. Berke, S. Doring, G. Kehr, G. Erker, R.
Frohlich, O. Meyer, Organometallics 18 (1999) 1724.
[5] X. Yang, C.L. Stern, T.J. Marks, J. Am. Chem. Soc. 119 (1991)
3623.
formation of complexes 7 and 9. The quantities of the
complexes depend on the relative rates of the reactions
and on the metal. In the case of complex 1, the
formation of 9 is prevailing, while in the case of complex
2, the main product is complex 7.
[6] (a) L. Jia, X. Yang, C.L. Stern, T.J. Marks, Organometallics 16
(1997) 842;
4. Supplementary material
(b) M.A. Giardello, M.S. Disen, C.L. Stern, T.J. Marks, J. Am.
Chem. Soc. 117 (1995) 12114;
(c) M.J. Snofield, S.W. Ewast, T.L. Tremblay, M.C. Baird, J.
Chem. Soc., Dalton Trans. (1997) 3097.
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Center, CCDC No. 196048 for compound 9.
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
[7a] E. Le Grognec, R. Poli, P. Richard, R. Llusar, S. Uriel, J.
Organomet. Chem. 640 (2001) 113.
[7b] G.C. Bazan, J.S. Rogers, C.C. Fang, Organometallics 20 (2001)
2059.
[7c] B.Y. Lee, G.C. Bazan, J. Vela, Z.J.A. Komon, X. Bu, J. Am.
Chem. Soc. 123 (2001) 5352.
Cambridge, CB2 1EZ, UK (fax: ꢁ44-1223-336-033;
/
e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
[7d] G.S. Hill, L.M. Rendina, R.J. Puddephatt, J. Chem. Soc., Dalton
Trans. (1996) 1809.
[8] (a) Y.-X. Chen, C.L. Stern, T.J. Marks, J. Am. Chem. Soc. 119
(1997) 2582;
(b) Y.-X. Chen, C.L. Stern, T.J. Marks, J. Am. Chem. Soc. 118
(1996) 12451;
Acknowledgements
(c) I. Tritto, R. Bonetti, M.C. Sacchi, P. Locatelli, G. Zannoni,
Macromolecules 32 (1999) 264;
Authors thank Professor Tobin J. Marks (North-
western University, IL) for a gift of B(C6F5)3 and
Professor Vincenzo G. Albano for useful discussion.
This work was supported by grant from the Ministero
dell’Istruzione, dell’Universita` e della Ricerca (MIUR,
Rome, Italy), Programma di Rilevante Interesse Nazio-
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/
[10] T. Beringhelli, D. Maggioni, G. D’Alfonso, Organometallics 20
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[11] G. Reichenbach, G. Cardaci, G. Bellachioma, J. Chem. Soc.,
Dalton Trans. (1982) 847.
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