Syntheses and structures of vinyl and aryl derivatives of carbonyl halide iron complexes

Article abstract of DOI:10.1016/j.ica.2004.05.013

cis,trans-Fe(CO)₂(PMe₃)₂(p-Y-C ₆H₄)X [X=Br, Y=H (4a), MeO (4b), Cl (4c), F (4d), Me (4e); X=I, Y=H (5); X=Cl, Y=H (6)] and cis,trans-Fe(CO)₂(PMe ₃)₂(σ-CH=CH₂

Full text of DOI:10.1016/j.ica.2004.05.013

Inorganica Chimica Acta 357 (2004) 3712–3720
www.elsevier.com/locate/ica
Syntheses and structures of vinyl and aryl derivatives
of carbonyl halide iron complexes
*
Chiara Venturi, Gianfranco Bellachioma, Giuseppe Cardaci , Alceo Macchioni
Dipartimento di Chimica, Universitꢀa di Perugia, Via Elce di Sotto 8, I-06123 Perugia, Italy
Received 26 March 2004; accepted 1 May 2004
Available online 8 June 2004
Abstract
cis,trans-Fe(CO)2(PMe3)2(p-Y-C6H4)X [X ¼ Br, Y ¼ H (4a), MeO (4b), Cl (4c), F (4d), Me (4e); X ¼ I, Y ¼ H (5); X ¼ Cl, Y ¼ H
(6)] and cis,trans-Fe(CO)2(PMe3)2(r-CH@CH2)X [X ¼ Br (7); X ¼ I (8); X ¼ Cl (9)] are prepared by reacting dihalide complexes
cis,trans,cis- Fe(CO)2(PMe3)2X2 [X ¼ Br (1), X ¼ I (2), X ¼ Cl (3)] with Grignard reagents p-Y-C6H4-MgBr (Y ¼ H, OMe, Cl, F,
Me) or CH2@CH–MgBr and with lithium reagents PhLi, CH2@CH–Li. With both reagents, the reaction proceeds following two
parallel pathways: one is the metallation reaction which yields alkyl derivatives, the other affords 17 electron complexes
[Fe(CO)2(PMe3)2X] via monoelectron reductive elimination. The influence of the halides and organometallic reagents on the yield of
1
the metallation reaction is discussed. The solution structure of the complexes is assigned on the basis of IR and H, 13C, 19F, 31P
NMR spectra. The solid state structure of complexes 4a, 5 and 6 is determined by single crystal X-ray diffractometric methods.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Syntheses; Phenyl complexes of iron; Vinyl complexes of iron; Halide iron complexes
1. Introduction
tion [6,7]. In contrast, only the oxidative addition of
alkyl halides in tetracoordinated unsaturated d8 inter-
mediates [8] or pentacoordinated saturated d8 com-
pounds [9–11] was used to prepare the isoelectronic
alkyl complexes of iron. In these last complexes, only the
oxidative addition of the alkyl halides was effective, so it
was not possible to prepare vinyl and aryl complexes.
In this work, we explore the possibility of using the
metallation method with lithium and Grignard reagents
to obtain the vinyl and aryl derivatives of iron.
Alkyl and aryl complexes are very important in or-
ganometallic chemistry and in homogeneous catalysis
because they are intermediates in the formation of C–C
bonds [1]. They have been widely studied and various
preparative methods have been used: nucleophilic attack
on metal halides (organolithium or Grignard reagents),
electrophilic attack on the metal (organic halide re-
agents), oxidative addition of organic halides and in-
sertion of olefins in the M–H or M–C bond [2,3].
Comparing the methods reported in the literature to
prepare the alkyl derivatives of the VIII group metals,
almost all of the above-mentioned methods were used to
prepare ruthenium monoalkyl Ru(CO)2L2RX (X ¼ Cl,
Br, I) and dialkyl Ru(CO)2L2RR0 (R,R0 ¼ alkyl and
aryl) complexes, as shown by Mawby and coworkers
who used the transmetallation [4] and insertion [5] re-
actions and by our group that used the oxidative addi-
2. Experimental
cis,trans,cis-Fe(CO)2(PMe3)2X2 (X ¼ Br (1), I (2))
were prepared by reacting Fe(CO)4X2 [12] with PMe3 in
diethylether (DE), following the method described in
[8a]. cis,trans,cis-Fe(CO)2(PMe3)2Cl2 (3) was prepared
as described in [13]. Alkyl and aryl lithium, Grignard
reagents Y-C6H4MgBr (Y ¼ H, MeO, Cl, F, Me) and
PMe3 were commercial products. Vinyl lithium was
prepared as described in [14]. Diethylether, tetrahydro-
furan (THF) and dimethoxyethane (DME) were purified
* Corresponding author. Tel.: +39-075-5855578; fax:+39-075-5855
598.
E-mail address: cardchim@unipg.it (G. Cardaci).
0020-1693/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.05.013

C. Venturi et al. / Inorganica Chimica Acta 357 (2004) 3712–3720
3713
by refluxing with NaOH pellets, distilling, refluxing with
Na and benzophenone and then freshly distilling under
nitrogen before use; n-hexane was dehydrated with Na
and distilled under nitrogen. All operations were carried
out under nitrogen.
The 1H, 31P{1H}, 19F{1H} and 13C{1H} NMR
spectra were measured on a Bruker DRX 400 spec-
trometer; referencing was 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 solvents. Infrared spectra were
recorded on a Perkin–Elmer 1725X FTIR spectropho-
tometer. Elemental analyses were performed on a Carlo
Erba 1106 elemental microanalyzer.
2.1.3. Preparation of cis,trans-Fe(CO)2(PMe3)2(p-Cl-
C6H4)Br (4c)
Complex 4c was prepared by reacting complex 1 and
p-Cl-C6H4MgBr (1 M solution in DE) following the
method described for complex 4a. Yield: 40%. Anal.
Calc. for C14H22BrClFeO2P2: C, 36.92 H, 4.87. Found:
C, 36.75; H, 4.95%. mCO(cmꢀ1, DE): 2012, 1944.
1H NMR (CD2Cl2): d ¼ 8:15 (br, o-H), 7.50 (br, o-H),
4
7.06 (d, 3JHH ¼ 7.9, m-H), 1.37 (tHarris, 2JHP + JHP ¼ 8.6,
2
PMe3). 13C{1H} NMR d ¼ 217:5 (t, JCP ¼ 26.7, CO
trans Br), 209.3 (t, 2JCP ¼ 14.8, CO trans phenyl), 158.2 (t,
2JCP ¼ 30.9, C–Fe), 143.2 (s, o-C), 142.2 (s, o-C), 129.9 (s,
1
p-C), 127.1 (s, m-C), 16.5 (t, JCP + 3JCP ¼ 15.8, PMe3).
31P{1H} NMR: d ¼ 11:3 (s, PMe3).
2.1. Reactions with Grignard reagents
2.1.4. Preparation of cis,trans-Fe(CO)2(PMe3)2(p-F-
C6H4)Br (4d)
2.1.1. Preparation of cis,trans-Fe(CO)2(PMe3)2(C6H5)
Br (4a)
Complex 4d was prepared by reacting complex 1 with
p-F-C6H4MgBr (2 M solution in DE). Yield: 30%. Anal.
Calc. for C14H22BrFFeO2P2: C, 38.30; H, 5.05. Found:
C, 38.50; H, 4.96%. mCO(cmꢀ1, DE): 2013, 1944.
The 0.5 g of complex 1 was dissolved in DE (30 ml);
1.1 ml of C6H5MgBr 3 M in DE (molar ratio 2/1) was
added drop by drop to the stirred solution at room
temperature. The colour of the solution changed in-
stantaneously from red to green. The solution reacts
with air, changing the colour from green to red, and
Fe(CO)3(PMe3)2 precipitated as yellow crystals
(mCO ¼ 1873 cmꢀ1 in DE). The supernatant solution was
shaken with water and the ether phase separated and
dried with MgSO4. Complex 4a was crystallized as or-
ange crystals by n-hexane (yield 50%). Anal. Calc. for
C14H23BrFeO2P2: C, 39.54; H, 5.51. Found: C, 39.32; H,
5.60%. mCO(cmꢀ1, DE): 2009, 1941.
1H NMR (CD2Cl2): d ¼ 8:15 (br, o-H), 7.47 (br, o-H),
3
6.84 (dd, JHH ¼ 3JHF ¼ 8.0, m-H), 1.36 (tHarris
,
2JHP + 4JHP ¼ 8.2, PMe3). 13C{1H} NMR: d ¼ 217:6 (t,
2JCP ¼ 26.6, CO trans Br), 209.4 (t, 2JCP ¼ 14.8, CO trans
1
phenyl), 160.0 (d, JCF ¼ 240.1, C–F), 156.2 (t,
2JCP ¼ 31.2, C–Fe), 141.6 (s, o-C), 141.4 (s, o-C), 114.2 (s,
m-C), 16.5 (t, 1JCP + 3JCP ¼ 15.8, PMe3). 31P{1H} NMR:
d ¼ 11:7 (s, PMe3). 19F{1H} NMR: d ¼ ꢀ124:8 (m, p-F).
2.1.5. Preparation of cis,trans-Fe(CO)2(PMe3)2(p-Me-
C6H4)Br (4e)
1H NMR (CD2Cl2): d ¼ 8:20 (br, o-H), 7.59 (br, o-
3
H), 7.06 (t, 3JHH ¼ 7.00, m-H), 6.98 (t, JHH ¼ 6.6, p-H),
Complex 4e was prepared by reacting complex 1 with
p-Me-C6H4MgBr (1 M solution in DE). Yield: 25%.
Anal. Calc. for C15H25BrFeO2P2: C, 41.41; H, 5.79.
Found: C, 41.60; H, 5.90%. mCO(cmꢀ1, DE): 2008, 1940.
2
1.37 (tHarris, JHP + 4JHP ¼ 8.6, PMe3). 13C{1H} NMR:
2
d ¼ 217:7 (t, JCP ¼ 27.6, CO trans Br), 209.4 (t,
2
2JCP ¼ 14.3, CO trans phenyl), 159.4 (t, JCP ¼ 30.5; C–
1H NMR (CD2Cl2): d ¼ 8:00 (br, o-H), 7.40 (br, o-H),
Fe), 141.6 (s, o-C), 127.4 (s, m-C), 123.1 (s, p-C), 16.6 (t,
1JCP + 3JCP ¼ 15.7, PMe3). 31P{1H} NMR: d ¼ 11:7 (s,
PMe3).
3
6.90 (d, JHH ¼ 7.8, m-H), 2.3 (s, Me),1.37 (tHarris
,
2JHP + 4JHP ¼ 8.2, PMe3). 13C{1H} NMR: 217.8 (t,
2JCP ¼ 27.0, CO trans Br), 209.3 (t, 2JCP ¼ 14.3, CO trans
phenyl), 154.0 (t, 2JCP ¼ 29.4,C–Fe), 141.4(s, o-C), 132.3 (s,
p-C), 128.5 (s, m-C), 20.7 (s, Me), 16.6 (t, 1JCP + 3JCP ¼ 15.4,
PMe3). 31P{1H} NMR: d ¼ 11:6 (s, PMe3).
2.1.2. Preparation of cis,trans-Fe(CO)2(PMe3)2(p-
MeO-C6H4)Br (4b)
Complex 4b was prepared by reacting complex 1 and
p-MeO-C6H4MgBr (1 M solution in THF) following the
method described for complex 4a. Yield: 41%. Anal.
Calc. for C15H25BrFeO2P2: C, 39.94, H, 5.59. Found: C,
40.01; H, 5.51%. mCO(cmꢀ1, DE): 2008, 1941.
1H NMR (CD2Cl2): d ¼ 8:00 (br, o-H), 7.40 (br, o-
2.1.6. Preparation of cis,trans-Fe(CO)2(PMe3)2(m-Cl-
C6H4)Br (4f)
Complex 4f was prepared by reacting complex 1 with
m-Cl-C6H4MgBr (0.5 M solution in THF). Yield: 32%.
Anal. Calc. for C14H22BrClFeO2P2: C, 36.3; H, 4.80.
Found: C, 36.92; H, 4.87%. mCO(cmꢀ1, DE): 2012, 1946.
H), 6.72 (d, 3JHH ¼ 8.2; m-H), 3.70 (s, OMe),1.36 (tHarris
,
2JHP + 4JHP ¼ 8.4, PMe3). 13C{1H} NMR d ¼ 217:8 (t,
2
2JCP ¼ 27.3, CO trans Br), 209.4 (t, JCP ¼ 14.5, CO
2
2.1.7. Preparation of cis,trans-Fe(CO)2(PMe3)2
(CaHc ¼ CbHaHb)Br (7) (Ha trans to Hc)
trans phenyl), 157.3 (s, p-C), 146.2 (t, JCP ¼ 33.0, C–
Fe), 141.4 (s, o-C), 114.0 (s, m-C), 55.2 (s, OMe),16.6 (t,
1JCP + 3JCP ¼ 15.5, PMe3). 31P{1H} NMR: d ¼ 11:7 (s,
PMe3).
Complex 7 was prepared by reacting complex 1 with
(CH2@CH)MgBr (1 M solution in THF) (molar ratio 1/

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C. Venturi et al. / Inorganica Chimica Acta 357 (2004) 3712–3720
1) following the method described for the previous
complexes. Yield: 56%. Anal. Calc. for C10H21
BrFeO2P2: C, 32.38; H, 5.71. Found: C, 32.95; H,
5.83%. mCO(cmꢀ1, DE):2010, 1947.
127.7 (s, m-C), 123.0 (s, p-C), 18.1 (t, 1JCP + 3JCP ¼ 16.1,
PMe3). 31P{1H} NMR: d ¼ 8:3 (s, PMe3).
2.2.3. Reaction of cis,trans-Fe(CO)2(PMe3)2Cl2 (3)
with PhLi
3
1H NMR (CD2Cl2): d ¼ 7:65 (ddt, JHcP ¼ 3.9;
3
4
3JHcHb ¼ 10.3; JHcHa ¼ 18.6, Hc), 5.96 (ddt, JHbP ¼ 6.2;
The 0.5 g of complex 3 was dissolved at room tem-
perature in DE (30 ml); 0.15 ml of PhLi (2 M solution in
cyclohexane–ether mixture 70:30) was added drop by
drop. The reaction was immediate and the red solution
changed to green. The IR spectrum shows the formation
of a complex with CO stretching bands at 1984 and 1935
cmꢀ1. Attempts to crystallize this complex were un-
fruitful owing to decomposition.
2
4
3JHbHc ¼ 10.3; JHbHa ¼ 1.8, Hb), 5.96 (ddt, JHaP ¼ 4.5;
3JHaHc ¼ 18.6; JHaHb ¼ 1.8, Ha), d ¼ 1:53 (tHarris
,
2
2JHP + 4JHP ¼ 8.3, PMe3). 13C{1H} NMR: 217.5 (t,
2JCP ¼ 27.3, CO trans Br), 208.9 (t, JCP ¼ 14.1, CO
2
2
trans vinyl), 170 (t, JCP ¼ 30.1, Ca), 123.9 (s, Cb), 16.11
(t, JCP + 3JCP ¼ 15.6, PMe3). 31P{1H} NMR: d ¼ 12:0
1
(s, PMe3).
2.1.8. Reaction of complex 1 with (o-Me-C6H4)MgBr
Complex 1 reacted with (o-Me-C6H4)MgBr giving
decomposition products.
2.2.4. Preparation of cis,trans-Fe(CO)2(PMe3)2
(C6H5)Cl (6)
The 0.1 g of complex 4a was dissolved at room tem-
perature in 15 ml of CH2Cl2, an excess of (n-Bu)4NCl
(0.13 g) (molar ratio 1/50) was added and the solution was
stirred for 1 h. The solution was dried and the residue was
dissolved in n-hexane. Complex 6 was crystallized by the
n-hexane solution at )20 °C as orange crystals. Anal.
Calc. for C14H23ClFeO2P2: C, 44.65; H, 6.16. Found: C,
44.30; H, 6.28%. mCO(cmꢀ1, CH2Cl2): 2012, 1943.
1H NMR (CD2Cl2): d ¼ 8:03 (br, o-H), 7.56 (br, o-
2.1.9. Reaction of complex 1 with RMgX (R ¼ Me, X ¼ I;
R ¼ C2H5, X ¼ Br)
Complex 1 reacts with alkyl Grignard reagents giving
decomposition products.
2.2. Reaction with lithium reagents
3
3
2.2.1. Preparation of complex 4a
H), 7.08 (t, JHH ¼ 7.0, m-H), 6.99 (t, JHH ¼ 6.9; p-H),
2
The 1 g of complex 1 was dissolved in DE (100 ml);
PhLi (1.9 M solution in cyclohexane–ether mixture
70:30) was added drop by drop. The colour changed
immediately from orange to green after reaction with air
as observed for the Grignard reagents. The solution was
shaken with H2O to decompose the excess PhLi. The
ether phase was separated and dried with MgSO4; the
solvent was evaporated and the residue was dissolved in
n-hexane: complex 4a was crystallized by this solvent as
orange crystals: yield 90%.
1.31 (tHarris, JHP + 4JHP ¼ 8.6, PMe3). 13C{1H} NMR:
2
d ¼ 216:2 (t, JCP ¼ 26.8, CO trans Br), 209.5 (t,
2JCP ¼ 14.4, CO trans phenyl), 161.3 (t, JCP ¼ 30.4, C–
2
Fe), 141.5 (s, o-C), 139.2 (s, o-C), 127.3 (s, m-C), 123.2
1
(s, p-C), 15.8 (t, JCP + 3JCP ¼ 15.3, PMe3). 31P{1H}
NMR: d ¼ 15:0 (s, PMe3).
2.2.5. Preparation of complex 7
The 100 mg of complex 1 (2.38 ꢁ 10ꢀ4 mol) was dis-
solved in DE (25 ml) at 0 °C. An equimolar quantity of
CH2@CHLi in DE was added drop by drop to the
stirred solution of complex 1. The reaction was complete
in 10 min. The solution was washed with water to de-
compose the excess of CH2@CHLi; the ether phase was
dehydrated by MgSO4, then dried and complex 7 was
crystallized as orange crystals by n-hexane at )20 °C.
Yield: 95%.
The preparation of complex 4a was carried out using
the same procedure in n-hexane and THF. The yield
varied greatly in function of the nature of the solvent: n-
hexane, 18%; THF, 95%.
2.2.2. Preparation of cis,trans-Fe(CO)2(PMe3)2
(C6H5)I (5)
The 0.5 g of complex 2 was dissolved in DE (30 ml);
PhLi was added following the procedure described for
the reaction with complex 1. The reaction was immedi-
ate. Excess reagent was eliminated by shaking with
H2O. After separation of the ether phase, complex 5 was
crystallized by n-hexane as red crystals: yield 80%.
Anal. Calc. for C14H23FeIO2P2: C, 35.93; H, 4.95.
Found: C, 36.02; H, 5.01%. mCO(cmꢀ1, DE): 2003, 1939.
1H NMR (CD2Cl2): d ¼ 8:38 (br, o-H), 7.64 (br, o-
2.2.6. Reaction of complex 2 with CH2@CHLi
Complex 2 reacts with CH2@CHLi at room temper-
ature. The formation of cis,trans-Fe(CO)2(PMe3)2
(CH@CH2)I (8) was observed by IR (mCO(cmꢀ1, DE):
2005, 1946). Complex 8 decomposed during the reaction
with the formation of Fe(CO)3(PMe3)2.
2.2.7. Preparation of complex cis,trans-Fe(CO)2
(PMe3)2(CaHc@CbHaHb)Cl(Ha trans to Hc) (9)
The 100 mg of complex 3 (2.98 ꢂ 10ꢀ4 mol) was dis-
solved in DE (30 ml) at 0 °C. An equimolar quantity of
CH2@CHLi was added drop by drop to the stirred
2
H), 7.00 (m, m-H ep-H), 1.47 (tHarris, JHP + 4JHP ¼ 8.3,
2
PMe3). 13C{1H} NMR: d ¼ 219:1 (t, JCP ¼ 26.4, CO
2
trans Br), 209.8 (t, JCP ¼ 14.4, CO trans phenyl), 157.8
2
(t, JCP ¼ 31.3, C–Fe), 146.5 (s, o-C), 141.6 (s, o-C),

C. Venturi et al. / Inorganica Chimica Acta 357 (2004) 3712–3720
3715
solution of complex 3. The reaction was instantaneous
and the IR spectrum showed CO stretching bands at
2010 and 1945 cmꢀ1. The solution was washed with
H2O, the ether phase was dehydrated by MgSO4 and
dried. Complex 9 was crystallized by n-hexane as yellow
crystals at )20 °C. Yield: 90%.
correspond to those of cis,trans,cis-Fe(CO)2(PMe3)2Me2
previously characterized by us [15]. The reaction was
also carried out in DME, THF and n-hexane and the
yield of the dimethyl complex was strongly dependent
on the nature of the solvent: n-hexane, 29%; DME, 83%;
THF, 95%.
3
1H NMR (CD2Cl2): d ¼ 7:44 (ddt, JHcP ¼ 3.8;
3
4
3JHcHb ¼ 10.4; JHcHa ¼ 18.7, Hc), 5.95 (ddt, JHbP ¼ 6.2;
2.3. X-ray crystallography
2
4
3JHbHc ¼ 10.3; JHbHa ¼ 1.8, Hb), 5.37 (ddt, JHaP ¼ 4.0;
3JHaHc ¼ 18.7; JHaHb ¼ 1.8, Ha), d ¼ 1:48 (t
,
Monocrystals of complex 4a, 5 and 6 were obtained
by crystallization in n-hexane at )20 °C. Crystal data
and details of structure refinement for complexes 4a, 5
and 6 are reported in Table 1. Diffraction intensities
were collected at 293 K on a XCALIBUR (Kuma
4CCD) diffractometer, using graphite monochromated
2
Harris
2JHP + 4JHP ¼ 8.6, PMe3). 13C{1H} NMR: 216.6 (t,
2JCP ¼ 27.0, CO trans Br), 209.0 (t, JCP ¼ 14.1, CO
2
2
trans vinyl), 172.7 (t, JCP ¼ 30.0, Ca), 123.5 (t,
3JCP ¼ 5.8, Cb), 15.3 (t, JCP + 3JCP ¼ 16.4, PMe3).
1
31P{1H} NMR: d ¼ 15:0 (s, PMe3).
ꢁ
Mo Ka (k ¼ 0:70930 A). The scans and the frame data
2.2.8. Reaction with methyl lithium: preparation of
cis,trans,cis-Fe(CO)2(PMe3)2(CH3)2
were acquired with CRYSALIS (CCD169) software.
The crystal to detector distance was 65.77 mm. The
frames were processed using CRYSALIS (RED 169)
software to give the hkl file corrected for scan speed,
background and Lorentz and polarization effects.
Standard reflections, measured periodically, showed no
apparent variation in intensity during data collection, so
no correction for crystal decomposition was necessary.
The data were corrected for absorption by using the
SADABS [16] program. The structure was solved by di-
rect methods using the SIR97 [17] program and refined
on F2 by the full-matrix least squares method using
SHELXL-97 [18] WINGX [19] version. All non-hydrogen
The 1 g of complex 1 was dissolved in DE (100 ml);
MeLi (1.6 M solution in DE) was added drop by drop.
The reaction was monitored by IR. An immediate col-
our change from orange to red was observed. The IR
controls showed that the reaction occurred in two steps:
the first gave cis,trans-Fe(CO)2(PMe3)2MeBr (mCO
¼
1999, 1938 cmꢀ1), the second gave the dimethyl complex
cis,trans,cis- Fe(CO)2(PMe3)2Me2 (mCO ¼ 1973, 1928
cmꢀ1). The solution was shaken with H2O; the ether
solution was evaporated and the dimethyl complex was
crystallized by n-hexane: yield 86%. The NMR bands
Table 1
Crystal data and details for complexes 4a, 5 and 6
Complex 4a
Complex 5
Complex 6
Crystal habit
Crystal colour
Formula weight
Crystal system
Space group
irregular prism
orange
421.02
irregular prism
red
468.01
irregular prism
orange
376.56
monoclinic
P21=c
monoclinic
P21=c
monoclinic
P21=c
Cell parameters
ꢁ
a (A)
9.759(2)
15.252(2)
12.442(2)
92.09(5)
9.818(10)
15.215(2)
12.663(2)
91,31(1)
9.763(2)
15.354(2)
12.203(2)
92.86(1)
ꢁ
b (A)
ꢁ
c (A)
b (°)
V (A )
ꢁ3
1850.7(13)
4
1.511
1891.1(4)
4
1827.0(5)
4
1.369
Z
Dcalc (Mg mꢀ3
)
1.644
2.597
5639
Absorption coefficient (mmꢀ1
Total data collected
)
3.145
16016
3376
1.145
12399
5103
Unique observed data
Criterion for observed
Unique data in the refinement (NO)
2131
Fc > 4rðFoÞ
2740
185
Fc > 4rðFoÞ
1504
185
Fc > 4rðFoÞ
3287
184
Number of refined parameters (NV)
Overdetermination ratio (NO/NV)
14.8
8.1
17.8
R
0.0490
0.1158
1.077
0.0605
0.1675
1.130
928
0.0522
0.0988
1.039
Rw
GOF
F ð000Þ
856
3.39–26.36
784
5.16–31.02
h Range for data collection (°)
5.17–29.94

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C. Venturi et al. / Inorganica Chimica Acta 357 (2004) 3712–3720
atoms were refined anisotropically. The hydrogen atoms
were added at the calculated positions and refined using
a riding model. Refinement converged at a final
R ¼ 0:040, Rw ¼ 0:1158 and GOF ¼ 1.077 for complex
4a; R ¼ 0:0605, Rw ¼ 0:1675 and GOF ¼ 1.130 for
complex 5 and R ¼ 0:0502, Rw ¼ 0:0988 and GOF ¼
3.2. Reactions with lithium reagents
The behaviour of the lithium reagents follows the
same scheme as the Grignard reagents; again, the reac-
tion of RLi with complexes 1–3 follows two reaction
pathways: one gives 17 electrons species via the radical
mechanism:
P
9
P
1.039 for complex 6 (R ¼
kFoj ꢀ jFck= jFcj):
h
i
8
<
1=2
ꢀ
ꢁ
P
2
w Fo2 ꢀ Fc2
PRLi þ FeðCOÞ ðPMe3Þ X2 !FeðCOÞ ðPMe3Þ X
=
;
i
2
2
2
2
ꢀ
ꢁ
þ LiX þ Rꢀ
h
i
Rw ¼
;
P
P
2
:
w Fo2
The second pathway yields the alkyl derivatives ac-
cording to the following scheme:
h
8
9
1=2
ꢀ
ꢁ
2
w Fo2 ꢀ Fc2
ðNO ꢀ NVÞ
<
=
;
GOF ¼
:
RLi þ FeðCOÞ ðPMe3Þ X2 ! FeðCOÞ ðPMe3Þ RX þ LiX
2
2
2
2
where NO is the number of observed reflections and NV
is the total number of parameters refined.
The reaction with MeLi proceeds up to the formation of
cis,trans,cis- Fe(CO)2(PMe3)2Me2 and it is not possible
to isolate the mono alkyl derivative. Other alkyl lithium
reagents (n-butyl, isopropyl, n-hexyl) react as MeLi, but
the reaction products are unstable and decomposed
during the purification. Vinyl lithium reacts at 0 °C with
complex 1 in 10 min and with complex 3 instanta-
neously; on the contrary, the reaction with complex 2
occurs slowly at room temperature. Phenyl lithium re-
acts fast with Fe(CO)2(PMe3)2X2 (X ¼ Br, I) giving
complexes 4a and 5; on the contrary the reaction with
the chloride derivative gives a very reactive paramag-
netic complex, which was tentatively assigned to the 17
electron complex [Fe(CO)2(PMe3)2Cl], similar to the
complexes characterized by Berke [20]; then complex 6
was prepared by exchange of bromide with chloride in
complex 4a.
The yield of the metallation reaction in DE follows
the order:
Vinyl(95%) > Ph(90%) > Me(80%).
The reaction between methyl lithium and complex 1
was carried out in various solvents: DE, DME, THF
and n-hexane. The yield of the reaction increased with
the polarity of the solvent following the order:
THF(95%) > DME(83%) ꢅ DE(86%) > n-hexane(29%).
3. Results
3.1. Reactions with Grignard reagents
The reactions of complexes 1–3 with Grignard re-
agents RMgBr (R ¼ CH3, C2H5) yield decomposition
products via the formation of 17 electron species
[Fe(CO)2(PMe3)2X], previously characterized by Berke
[20]. This radical species react with oxygen giving
Fe(CO)3(PMe3)2. In contrast, the reaction with vinyl-
MgBr and p-X-C6H4-MgBr (X ¼ H, F, Cl, Me, OMe,
Cl) follows two parallel pathways: one giving the 17
electron species [20], while the other yields cis,trans-
Fe(CO)2(PMe3)2RX complexes, which were isolated and
characterized.
The first reaction pathways proceed via a reductive
elimination mechanism which gives the 17 electron
species, according to the following scheme [21]:
RMgX þ FeðCOÞ ðPMe3Þ X2
2
2
! FeðCOÞ ðPMe3Þ X þ Rꢀ þ MgX2
2
2
The fate of Rꢀ species was not determined.
In the second pathway, the Grignard reagent acts as a
carbanion:
3.3. Characterization in solution of cis,trans-Fe(CO)2
(PMe3)2RX
Cis,trans-Fe(CO)2(PMe3)2RX complexes (4a–4e, 5–9)
were characterized in solution by infrared spectroscopy
RMgX þ FeðCOÞ ðPMe3Þ X2
2
2
! Fe ðCOÞ ðPMe3Þ RX þ MgX2
1
and by H, 13C, 19F and 31P NMR spectroscopies. All
2
2
m-C6H4-MgBr Grignard reagent reacts similarly to the
para reagent, while the ortho reagent yield decomposi-
tion products. The yield of the aryl and vinyl complexes
with respect to the reactant complex was determined by
the spectroscopic absorbance of the CO stretching bands
and follows the order:
Vinyl(56%) > Ph (50%) > p-OMe-C6H4 (41%) ꢃ p-Cl-
C6H4(40%) > p-F-C6H4(30%) ꢃ m-Cl-C6H4(32%) > p-Me-
C6H4(25%)ꢄo-X-C6H4(0%) ꢃ CH3(0%) ꢃ C2H5(0%).
cis,trans-Fe(CO)2(PMe3)2RX complexes show two CO
stretching bands of equal intensity in IR, in agreement
with the cis-position of the two CO ligands. The nature
of R does not significantly influence the CO stretching
frequencies. The CO stretching frequencies increased
with the halides according to the trend Cl > Br > I, as
observed in the isoelectronic series cis,trans,cis-
Fe(CO)2(PMe3)2X2
CH3X.
and
cis,trans-Fe(CO)2(PMe3)2

C. Venturi et al. / Inorganica Chimica Acta 357 (2004) 3712–3720
3717
The proton and carbon resonances of the phenyl
group were assigned by using 1H-COSY, 1H, 13C-
HMQC and H, 13C-HMBC spectra. The H and 13C
NMR spectra show a Harris triplet [22] assigned to the
two PMe3 ligands, indicating an octahedral structure
with two PMe3 in the trans-position.
All the phenyl complexes showed hindered rotation
of the phenyl around the Fe–C bond. In fact at room
temperature, complexes 4a–4d, 5 and 6 showed two
broad bands in the range 7–8.7 ppm, which were as-
signed to the ortho protons of the phenyl group. At 247
K, the ortho proton signals of complex 4a became more
structured, but maintained some fluxional character.
The substituted phenyl derivatives 4c and 4d and the
unsubstituted complexes 5 and 6 showed two o-C signals
in the 13C NMR spectra.
observed for the 13C shift of the CO trans to halide
suggests that, in this case, the dative p bonding effect,
which follows the order Cl > Br > I [25], can be
important.
The halides influence the chemical shifts of the PMe3
protons: Cl(1,31) < Br(1.37) < I(1.47) and of the PMe3
carbons: Cl(15.8) < Br(16.6) < I(18.1); the reason for
this behaviour is not clear.
The effect of the substituents in the phenyl group on
the proton and carbon shifts of the ring in the complexes
cis,trans-Fe(CO)2(PMe3)2(p-X-C6H4)Br will be dis-
cussed assuming that the para position is that of X
substituent; the ortho and meta positions of the ring are
so defined, while the carbon bonded to the organome-
tallic moiety will be indicated as C–Fe.
The effect of the X substituents on the proton
chemical shifts cannot be evaluated for the ortho posi-
tions due to the fluxional behaviour of the protons. The
effect of the substituents on the chemical shifts of the
meta protons is very small. This could be due to the
contrasting effect of the para substituents and the or-
ganometallic moiety Fe(CO)2(PMe3)2Br [26].
The effects of the X substituents on the 13C chemical
shifts are stronger than the proton shifts. They are
similar to those observed in p-X-C6H4-COCH3, as in-
dicated by the linear trend of the chemical shift of cis,-
trans-Fe(CO)2(PMe3)2(p- X-C6H4)Br with respect to the
para-substituted benzoylacetones [27] reported in Fig. 1.
The effect on the para carbon is the strongest. The effect
of the substituents on the meta carbon shows the same
trend as the para carbon, even if it is weaker. The effect
of the substituents on the C–Fe group shows an inverted
effect with respect to the para carbon; this effect is the
same as that observed in benzoylacetone compounds
and indicates that the COCH3 and Fe(CO)2(PMe3)2Br
groups exert the same withdrawing effect on the phenyl.
By comparing the 13C chemical shifts of the iron
complexes with the Ru(CO)2(PMe2Ph)2(p-X-C6H4)2
complexes [4b], a similar trend is observed with parallel
effects on the different carbon atoms of the phenyl group.
1
1
The 31P{1H} NMRspectra of all the complexes
showed a singlet, confirming the trans structure of the
PMe3 ligands.
The chemical shifts of all the complexes were in-
fluenced by the halide and phenyl substituents. Se-
lected NMR chemical shift data of the complexes
synthesized in this work and of other isoelectronic
halide complexes are given in Table 2. The chemical
shifts of phosphorus and Fe–C carbon follow the
trend Cl > Br > I, while those of the CO carbon trans
to halide follow the inverse trend I > Br > Cl; the
chemical shift of the CO cis to halide was hardly in-
fluenced. The trend observed for phosphorus was also
observed in the series cis,trans,cis- Fe(CO)2(PMe3)2X2
and cis,trans-Fe(CO)2(PMe3)2 CH3X. This suggests
that halides deshield iron following the trend
Cl > Br > I in agreement with the electronegativity of
halide; so, the electron density on the iron increases as
the atomic number of the halide increases. This ob-
servation is contrary to that reported by Tilset et al.
for Cp*Fe(dppe)X complexes [X ¼ F, Cl, Br, I;
dppe ¼ diphenylphosphineethane; Cp* ¼ C5Me5] [23],
but is the same of that reported by Gladysz et al. for
the CpRe(PPh3)(NO)X series [24]. The inverse trend
Table 2
Selected NMR chemical shift data of isoelectronic alkylmonohalides and dihalides complexes of iron
Complexes
31P NMR (ppm)
13C NMR (ppm)
dFeꢀC
dCO(trans to halide)
dCO(trans to alkyl)
cis,trans-Fe(CO)2(PMe3)2Br2 (1)
cis,trans-Fe(CO)2(PMe3)2I2 (2)
7.4
)0.1
13.6
11.7
8.3
cis,trans-Fe(CO)2(PMe3)2Cl2 (3)
cis,trans-Fe(CO)2(PMe3)2C6H5Br (4a)
cis,trans-Fe(CO)2(PMe3)2C6H5I (5)
cis,trans-Fe(CO)2(PMe3)2C6H5Cl (6)
cis,trans-Fe(CO)2(PMe3)2(CH@CH2)Br (7)
cis,trans-Fe(CO)2(PMe3)2(CH@CH2)Cl (9)
cis,trans-Fe(CO)2(PMe3)2CH3Br
cis,trans-Fe(CO)2(PMe3)2CH3I
159.4
157.8
161.3
170.0
172.7
217.7
219.1
216.2
219.1
216.6
209.4
209.8
209.5
209.8
209.0
15.0
12.0
15.0
15.3
11.4
18.6
)3.82
220.1
208.6
cis,trans-Fe(CO)2(PMe3)2CH3Cl

3718
C. Venturi et al. / Inorganica Chimica Acta 357 (2004) 3712–3720
170
160
150
140
130
120
110
F
Cl
H
CH3
OMe
F
OMe
p
CH3
Cl
Cl
H
CH3
H
OMe
F
110
120
130
140
150
160
170
(δ p-X-C6H4COMe) (ppm)
Fig. 1. 13C chemical shifts of phenyl carbons in cis,trans-Fe(CO)2(PMe3)2Br(p-X- C6H4) vs 13C chemical shifts of phenyl carbons in p-X-C6H4-
COCH3: d para-carbon; N C-Fe; j meta-carbon.
C12
The phenyl substituents do not appreciably influence
the chemical shifts of the PMe3 and CO ligands.
The NMR signals of complexes 7 and 9 were assigned
on the basis of the vinyl proton couplings and by com-
paring the chemical shifts of the isoelectronic vinyl
complexes of ruthenium [28,29].
C13
C14
P2
O1
C4
As previously observed for isoelectronic complexes of
iron and ruthenium, the coupling constants in the iron
C5
C1
C2
O2
Fe
C3
C6
C8
I
C7
C12
P1
C13
C10
C11
C14
P2
C9
Fig. 3. ORTEP diagram of complex 5.
O1
C4
C5
C3
O2
C2
C1
Fe
complexes were higher than those in the ruthenium
complexes [30].
C6
C8
C7
3.4. Solid structures
Br
P1
C10
The molecular structures of complexes 4a, 5 and 6 in
the solid state, obtained by single crystal X-ray diffrac-
tion methods, are given in Figs. 2–4, in which the same
crystallographic numbering was used. Table 3 reports
selected bond distances and angles for the three com-
plexes. The three structures are very similar. The iron
C11
C9
Fig. 2. ORTEP diagram of complex 4a.

C. Venturi et al. / Inorganica Chimica Acta 357 (2004) 3712–3720
3719
phosphine ligands are bent toward the phenyl sub-
stituent (P(2)–Fe–P(1) ¼ 170.99° for 4a, 170.81° for 5
and 171.06° for 6). The C(3)-Fe-halide angles are more
than 90° (96° for 4a, 96.7° for 5 and 94.74° for 6): this
supports an interaction of the halides and the meta hy-
drogen of the phenyl group as confirmed by the torsion
of the phenyl plane with respect to the mean equatorial
plane of the octahedral structure (# ¼ 9:9° for 4a, 8.7°
for 5 and 10.6 for 6) and by the contact distances be-
C12
C13
C14
P2
O1
C2
C5
C4
C1
O2
C3
Fe
C6
ꢁ
tween the protons and the halide atom (2.688 A for 4a,
ꢁ
ꢁ
2.785 A for 5 and 2.587 A for 6 ). Contact distances can
Cl
also be observed between the phosphine hydrogens and
C7
C8
ꢁ
ꢁ
ꢁ
the halides (2.921 A for 4a, 3.004 A for 5 and 2.8388 A
for 6). The torsion angle increases in the series Cl>Br>I
and can be explained on the basis of a balance of the
halide radius and of the Fe-halide bond distance.
P1
C10
C11
C9
Fig. 4. ORTEP diagram of complex 6.
4. Discussion
The values of 31P and 13C chemical shifts of the ligands
in organometallic complexes are used in the literature [23]
to obtain information about the electronic density on the
iron atom: the greater the chemical shifts of 31P and 13C,
the greater the electron density on the iron.
In Table 2 the chemical shifts of 31P and, in some
cases, of 13C of the complexes cis,trans,cis-Fe(CO)2
(PMe3)2X2, cis,trans-Fe(CO)2(PMe3)2 (C6H5)X, cis,-
atom exhibits the expected octahedral geometry with the
trimethylphosphine ligands occupying the trans position
and the other ligands occupying the four coordination
positions in the perpendicular plane with the CO ligands
in the cis position.
Besides Fe–Br, Fe–I and Fe–Cl, only Fe–C(3) is
notably different in complexes 4a,
5
and
6
ꢁ
ꢁ
ꢁ
trans-Fe(CO)2(PMe3)2(CH@CH2)X
and
cis,trans-
(Fe–C(3) ¼ 2.093 A for 4a, 2.058 A for 5 and 2.057 A for
6). All the other distances and angles are very similar
and will be discussed at the same time. The trimethyl-
Fe(CO)2(PMe3)2(CH3)X (X ¼ Cl, Br, I) are given. On
the basis of these chemical shifts, the electron density on
the iron follows the trend I > Br > Cl in agreement with
the r-electron withdrawing power of the halides [25].
Studies of the halide exchange in the series cis,trans-
Fe(CO)2(PMe3)2 (CH3)X (X ¼ Cl, Br, I) [31] and the
halide exchange results obtained in this work indicate
that the exchange equilibrium follows the trend
Cl > Br > I; therefore, in the previous series the behav-
iour of the iron atom was hard.
So both the monoelectron radical reduction and the
nucleophilic attack of carbanion with Grignard and
lithium reagents should be easier with the decreasing
electron density on the iron and the reaction rate should
follow the trend Cl > Br > I, as observed for the reac-
tions for which a difference in the reaction rates has been
observed as in the reactions of cis,trans-Fe(CO)2
(PMe3)2X2 (X ¼ Cl, Br, I) with vinyl lithium.
Table 3
ꢁ
Relevant bond lengths (A) and angles (°) for complexes 4a, 5 and 6
Complex 4a
Complex 5
Complex 6
Fe–C(1)
Fe–C(2)
Fe–C(3)
Fe–P(2)
Fe–P(1)
Fe–Hal
1.767(6)
1.800(5)
2.093(4)
1.762(18)
1.778(15)
2.058(13)
2.251(4)
2.260(4)
2.61(3)
1.758(3)
1.796(3)
2.057(3)
2.2534(9)
2.2587(9)
2.3717(10)
1.088(4)
1.140(4)
2.2540(14)
2.2585(15)
2.5128(12)
1.047(6)
O(1)–C(1)
O(2)–C(2)
1.063(19)
1.151(18)
1.133(6)
C(1)–Fe–C(2)
C(1)–Fe–C(3)
C(2)–Fe–C(3)
C(1)–Fe–P(2)
C(2)–Fe–P(2)
C(3)–Fe–P(2)
C(1)–Fe–P(1)
C(2)–Fe–P(1)
C(3)–Fe–P(1)
P(2)–Fe–P(1)
C(1)–Fe–Hal
C(2)–Fe–Hal
C(3)–Fe–Hal
P(2)–Fe–Hal
P(1)–Fe–Hal
90.2(2)
93.0(2)
90.6(8)
92.7(7)
176.4(7)
92.2(5)
95.4(5)
86.1(4)
89.9(5)
93.5(5)
84.9(4)
170.83(16)
170.4(10)
80.0(9)
96.7(9)
86.7(5)
92.7(5)
90.73(13)
92.15(12)
176.99(11)
92.68(9)
95.35(9)
85.39(7)
88.87(9)
93.43(9)
85.75(7)
171.06(3)
172.99(10)
82.40(9)
94.74(8)
86.63(3)
92.89(3)
176.6(2)
92.46(16)
95.56(17)
85.53(13)
89.34(16)
93.27(17)
85.56(13)
170.99(5)
170.85(17)
80.83(16)
96.02(13)
86.59(5)
93.02(5)
The yield of the radical reaction with respect to the
metallation reaction depends prevalently on the prop-
erties of the organometallic reagents: with the lithium
reagents the metallation reaction is prevailing (yield
ꢅ80–95%), while with the Grignard reagents the radical
reaction is prevailing (yield ꢅ45–100%). This is in
agreement with the general behaviour of the Grignard
reagents, which show a greater disposition to radical
reaction [21] than the lithium reagents.

3720
C. Venturi et al. / Inorganica Chimica Acta 357 (2004) 3712–3720
[6] G. Cardaci, J. Organometal. Chem. 323 (1987) C10.
The yield of the metallation reaction with both
[7] G. Bellachioma, G. Cardaci, A. Macchioni, A. Madami, Inorg.
Chem. 32 (1993) 554.
Grignard and lithium regents is higher with vinyl and
phenyl than with alkyl derivatives. This behaviour can
be explained on the basis of the higher stability of the
vinyl and phenyl carbanions, which is measured by the
PKa of the corresponding hydrocarbons [32,33] or by
the oxidation potential of Grignard [34] and lithium
reagents [35].
Polar solvents increase the yield of the metallation
reaction: this effect can also be explained by the solva-
tation of the carbanions, which increases their stability
according to the Born model [36].
[8] (a) G. Cardaci, G. Bellachioma, P.F. Zanazzi, Organometallics 7
(1988) 172;
(b) R. Birk, H. Berke, G. Huttner, L. Zsolnai, Chem. Ber. 121
(1988) 1557.
[9] M. Pankowski, M. Bigorgne, J. Organometal. Chem. 30 (1971)
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[10] G. Reichenbach, G. Cardaci, G. Bellachioma, J. Chem. Soc.,
Dalton Trans. (1982) 847.
[11] C.R. Jablonski, Inorg. Chem. 20 (1981) 3940.
[12] I.A. Cohen, F. Basolo, J. Inorg. Nucl. Chem. 28 (1966) 511.
[13] F. Mercier, F. Mathey, J. Augenault, J. Couturier, Y. Marey, J.
Organometal. Chem. 231 (1982) 237.
[14] G. Frenkel, H. Hyer, B.W. Su, in: R.O. Bach (Ed.), Lithium:
Current Applications in Sciece Technology and Medicine, Wiley-
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5. Supplementary material
[15] G. Bellachioma, G. Cardaci, A. Macchioni, C. Zuccaccia,
Organometal. Chem. 628 (2001) 255.
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Center, CCDC No. 225543 for complex 4a, CCDC
No. 225544 for complex 5 and CCDC No. 225545 for
complex 6. Copies of this information 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 www.ccdc.
cam.ac.uk).
[16] G.M. Sheldrick, SADABS:Program for the empirical correction
of area detector data, University of Gottingen, germany, 1996.
[17] A. Altomare, M.C. Burla, M. Camalli, G. Cascarano, C.
Giacovazzo, A. Gagliardi, A.G.G. Moliterni, G. Polidori, R.
Spagna, J. Appl. Cryst. 32 (1999) 115.
[18] G.M. Sheldrick, SHELXL-97, University of Gottingen, Germany,
1997.
[19] L.J. Farrugia, J. Appl. Cryst. 32 (1999) 837.
[20] H. Kandler, C. Gauss, W. Bidell, S. Rosenberger, T. Burgi, I.L.
Eremenko, D. Veghini, O. Orama, P. Burger, H. Berke, Chem.
Eur. J. 1 (1995) 541.
[21] W.E. Lindsell, in: G. Wilkinson (Ed.), Comprehensive Organo-
metallic Chemistry, vol. 1, Pergamon Press, Oxford, 1982, pp.
181–187.
Acknowledgements
[22] R.K. Harris, Can. J. Chem. 39 (1961) 216.
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Saillard, K. Costuas, A. Haynes, J. Am. Chem. Soc. 123 (2001)
9984.
The authors thank Dr. Cristiano Zuccaccia for useful
discussion. This work was supported by grant from the
ꢀ
Ministero dell’Istruzione, dell’Universita e della Ricerca
[24] S.K. Agbossou, C. Roger, A. Igau, J.A. Gladysz, Inorg. Chem. 31
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(MIUR, Rome, Italy), Programma di Rilevante Inter-
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