Bi- and trinuclear σ-aryl complexes of iron and manganese

Article abstract of DOI:10.1070/MC2003v013n02ABEH001730

The binuclear and trinuclear aryl σ-complexes of iron and manganese have been prepared by the palladium-catalysed reactions of m-diiodobenzene, p-diiodobenzene or 1,3,5-triiodobenzene with cyclopentadienyldicarbonyliron and manganese pentacarbonyl anions.

Full text of DOI:10.1070/MC2003v013n02ABEH001730

,
2003, 13(2), 43–45
Bi- and trinuclear σ-aryl complexes of iron and manganese
Galina A. Artamkina and Irina P. Beletskaya*
Department of Chemistry, M. V. Lomonosov Moscow State University, 119992 Moscow, Russian Federation.
Fax: +7 095 939 3618; e-mail: beletska@org.chem.msu.ru
1
0.1070/MC2003v013n02ABEH001730
The binuclear and trinuclear aryl σ-complexes of iron and manganese have been prepared by the palladium-catalysed reactions of
m-diiodobenzene, p-diiodobenzene or 1,3,5-triiodobenzene with cyclopentadienyldicarbonyliron and manganese pentacarbonyl
anions.
2
The preparation of polynuclear arene complexes with sp -tran-
sition metal bonds is not only an interesting synthetic goal but
also a problem of practical importance because these complexes
exhibit valuable physico-chemical properties. These complexes
can be used in the development of new materials for non-linear
Evidently, the second step (the formation of the binuclear iron
carbonyl complex) is much slower than the first step because of
2
1–23
the strong donor effect of the CpFe(CO) group.
2
Surprisingly, in the case of p,p'-diiodobiphenyl, only mono-
substituted product 3 was formed even in the presence of 2 equiv.
of iron carbonylate.
1
–5
optics or as liquid crystals, catalysts, and sensors.
The interaction of aryl halides with transition metal carbonyl
anions (carbonylates) is the simplest method for the synthesis
of the σ-aryl derivatives of transition metals. However, carbo-
nylates do not enter nucleophilic substitution reactions with non-
I
I
6
–9
8
activated aryl halides. Thus, it was found that the yield of
2 ClZn[Fe(CO) Cp]
2
the σ-aryl complex of iron in the reaction of supernucleophilic
–
PdCl (PPh )
2 3 2
iron carbonylate [CpFe(CO) ] with iodobenzene was 2%,
2
1
.5 h
whereas only traces of a binuclear complex were obtained in
9
the reaction with diiodobenzene.
Previously, such polynuclear complexes were usually pre-
pared by the two-step synthesis including the preparation and
decarbonylation of acyl metal complexes.
I
Fe(CO) Cp
2
9
–17
3
66%
∆
or UV
–
L M + Ar(COCl)
Ar(COMLm)n
Ar(ML ) ,
m n
m
n
Cp(CO) Fe
Fe(CO) Cp
2
2
where n = 1–3.
A number of binuclear and trinuclear manganese, rhenium,
and iron complexes with aryl bridges were prepared using this
method. The total yields of the complexes varied within a range
of 26–62%. Note that not always the parent acyl metal com-
4
With the use of the Pd (dba) ·CHCl complex of zero-valent
2
3
3
palladium (dba is dibenzylideneacetone) in the presence of tri-
furylphosphine, the formation of binuclear complex 4 was also
not observed, whereas the yield of complex 3 significantly
decreased (36%). An increase in the reaction time to 5 h also
resulted in a decrease in the yield of complex 3 (18%). We
synthesised complex 4 in a low yield (20%) from isolated
mononuclear complex 3.
9,13,14
plexes can be prepared and successfully decarbonylated.
Previously,1
8,19
we found that the cross-coupling reaction of
aryl and vinyl halides with carbonylates in the presence of pal-
ladium or nickel complexes can be used for the synthesis of the
mononuclear σ-aryl and σ-vinyl complexes of transition metals.
In this work, we attempted to apply this reaction to the syn-
thesis of the binuclear and trinuclear arene complexes of iron
and manganese.
ClZn[Fe(CO)2Cp]
I
Fe(CO) Cp
2
The dicarbonylcyclopentadienyliron anion is most reactive
among transition metal carbonylates. According to Dessy et al.,20
its nucleophilicity in reactions with alkyl halides is higher than
that of manganese carbonylate by six orders of magnitude:
PdCl (PPh )
2 3 2
3
Cp(CO) Fe
Fe(CO) Cp
2
CpFe(CO) 2– (7.0×10 ) > Mn(CO) (77) > Co(CO) (1). At the
7
–
2
5
4
same time, this anion is a good reducing agent. We found that
side reactions associated with reduction can be eliminated with
the use of zinc salts, which were prepared in situ.
4
20%
1
8
The reaction of p-diiodobenzene with [CpFe(CO) ]ZnCl in
† General procedure of cross-coupling reactions.
2
THF in the presence of bis(triphenylphosphine)palladium di-
chloride at room temperature gave monosubstituted or disubsti-
tuted σ-aryl complexes of iron depending on the ratio between
reactants and the exposure time.
All operations with the solutions of carbonylate salts and reaction pro-
ducts were performed using standard vacuum-line / argon atmosphere
techniques. The solvent (THF) was vacuum transferred to the reaction
vessel. The reaction was performed in an apparatus that consisted of two
vessels joined with a tube with a sealed glass filter. The corresponding
†
3
dimer was reduced in a reaction vessel with intense stirring {0.07–0.08 cm
I
I
of an NaK2.8 alloy were taken per 0.5 mmol of the dimer [CpFe(CO)2]2
or Mn (CO) ; the reaction time was 1 h to 1 h 10 min}. The resulting
2
10
solution was filtered into the other vessel in which the reaction was
performed. A portion of ZnCl2 was loaded into this vessel and sublimed
onto the walls; thin-walled glass beads with sealed portions of the sub-
strate and the catalyst were also placed in the reaction vessel; these
beads were broken using a ground-glass hook. The reactant concentra-
tion in solution was 0.1–0.2 mol dm . The course of the reaction was
monitored by TLC (Silufol UV-254) with sampling at regular intervals
in a flow of argon. After completion of the reaction, the reaction mixture
was evaporated with a small amount of silica gel and chromatographed
PdCl (PPh )
2
3 2
20 °C
ClZn[Fe(CO) Cp]
2 ClZn[Fe(CO) Cp]
2
2
1.5 h
2.5–3.5 h
–
3
I
Fe(CO) Cp
Cp(CO) Fe
Fe(CO) Cp
2
2
2
1
70–75%
2 70–80%
on a column with SiO (L = 40/100 or 60/200).
2
–
43 –

,
2003, 13(2), 43–45
In contrast, the reaction of iron carbonylate with m-diiodo-
benzene [in the absence of conjugation with the CpFe(CO)2
group] gave only binuclear complex 5 regardless of the ratio
between reactants.
However, these products were formed in the course of chromato-
graphing the reaction mixture rather than in the course of the
reaction.‡
Our attempts to change the ratio between mono- and disub-
stitution products by varying the nature of the catalyst [Pd dba /
2
3
THF, PdCl (PPh )
(Fur) P, Ph As], solvent (diethyl ether), and temperature (–30 °C)
2
3 2
3 3
I
+ [CpFe(CO) ]ZnCl
2
1.5 h
were unsuccessful. A decrease in the carbonylate concentration,
namely, the reaction in THF at equimolar ratios between reac-
tants had also insignificant effect on the ratio between products
7 and 8. Monoarylated complex 7 was obtained in a reasonably
high yield (60%) by adding the potassium salt of manganese
carbonylate at equimolar ratios between the reactants. As men-
tioned above, with the use of the zinc salt, the product yield in
the cross-coupling reaction of iron carbonylate with iodobenzene
I
Fe(CO) Cp
2
Cp(CO) Fe
2
5
75%
1
18
According to H NMR-spectroscopic data, the reaction of
was much higher than that with the use of the potassium salt.
1
,3,5-triiodobenzene with 3 equiv. of [CpFe(CO) ]ZnCl resulted
Because manganese carbonylate is a weaker nucleophile and
reductant than iron carbonylate, it is better to use the potassium
salt in reactions with its participation.
2
in the formation of trinuclear complex 6 in a quantitative yield.
I
Fe(CO) Cp
Thus, under the tested conditions, binuclear complex 8 was
formed in a low yield. Moreover, it gave rearrangement pro-
ducts upon chromatographing. Our attempt to improve the yield
of the disubstitution product by using Pd (dba) ·CHCl /L as a
2
3
ClZn[Fe(CO) Cp]
2
3
h
2
3
3
I
I
Cp(CO) Fe
Fe(CO) Cp
2
2
catalyst, where L = Fur P, BINAP, were unsuccessful. A binuclear
3
6
80%
complex was prepared with the use of Xantphos as a ligand; the
reaction occurred almost quantitatively and resulted in the forma-
tion of complex 8 in 82% yield. p-Diiodobenzene can also serve
as the initial substrate in the reaction, although the yield of
complex 8 was lower in this case. The resulting product was
prevented from decomposition in the course of chromatographing
by the filtration of the reaction mixture, which was twofold
diluted with light petroleum, through a thin bed of SiO2.
Standard
chromatographic
workup
Fe(CO)2Cp
(
silica gel)
Fe(CO) Cp
2
5
1
The H NMR spectrum exhibited two singlets at 6.99 (3H)
Pd (dba) ·CHCl /Xantphos
2
3
3
and 4.85 ppm (5H); in this case, the signal of parent triiodo-
benzene was absent. However, only 1,3-binuclear complex 5
40–60%) was obtained with the use of a standard chromato-
(OC)5Mn
I
KMn(CO) 5
1.5 h
(
7
graphic procedure on silica gel, which was used previously for
(
CO) Mn
Mn(CO)5
5
†
separating σ-aryl complexes. Complex 5 was identical to that
obtained from m-diiodobenzene, that is, one CpFe(CO) group
2
8
82%
was eliminated. This by-process was removed by passing the
reaction mixture through a thin bed of Al O before chromato-
2
3
graphing (on a column with SiO ). In this case, complex 6 was
2
‡
p-(Pentacarbonylmanganese)benzaldehyde 9 and p-iodobenzaldehyde
0 were detected in the reaction products after chromatographing on a
obtained in 80% yield. It is interesting to note that the complex
thus purified underwent no degradation on passing it through
SiO . The degradation of the complex on SiO is possibly
1
column with SiO . Evidently, they are formed from complexes 7 and 8,
2
2
2
respectively, by an aryl–acyl rearrangement.
catalysed by some Pd species, which are removed by filtration
through Al O .
O
2
3
As would be expected, the reactivity of the zinc salt of
manganese carbonylate was found to be much lower than that
I
Mn(CO)5
I
C
H
Mn(CO)4L
of [CpFe(CO) ]ZnCl. Nevertheless, the conversion of the reac-
7
2
O
C
tion with p-diiodobenzene in the presence of PdCl (PPh ) as a
2
3 2
H+
catalyst (at a 1:2 ratio between the reactants) was 60% for 3.5 h.
However, as distinct from reactions with iron carbonylate, the
formation of a mixture of products (7–10) was observed.
I
10
O
PdCl (PPh )
2
3 2
I
I + 2 [(CO) Mn]ZnCl
(CO) Mn
Mn(CO)5
(CO) Mn
5
C
Mn(CO)4L
5
5
3
.5 h
8
O
H+
(
CO) Mn
I
(CO) Mn
Mn(CO)5
O
5
5
(
CO) Mn
C
H
5
7
34%
8 11–13%
9
These rearrangements are known for almost all transition metals;24
they readily occur with alkyl complexes and much more difficult with
aryl complexes.
O
C
(
CO) Mn
H
I
C
H
5
The IR spectrum of the reaction mixture before chromatographing
9
13%
10 traces
exhibited no characteristic bands of aldehyde (1720 cm–1) and acyl groups
(
–
1 9
~1587 cm ). Carbonyl bands were also absent from the reaction per-
Although the total yield of products was reasonably high
60%, 7–10) in the catalysis with PdCl (PPh ) , the yield of
binary complex 8 was much lower (11–13%) than that of mono-
nuclear complex 7 (34%). Note that the formation of two alde-
hydes 9 and 10 was observed along with substitution products.
formed in a CO atmosphere. This fact allowed us to conclude that
aldehydes 9 and 10 were formed on the column in the course of
chromatographing the reaction mixture. However, our attempts to per-
form an aryl–acyl rearrangement by stirring the reaction mixture with
silica gel before chromatographing was unsuccessful.
(
2
3 2
–
44 –

,
2003, 13(2), 43–45
1
0 A. N. Nesmeyanov, K. N. Anisimov and N. E. Kolobova, Izv. Akad.
Nauk SSSR, Ser. Khim., 1963, 1348 (Bull. Acad. Sci. USSR, Div. Chem.
Sci., 1963, 12, 1225).
Pd (dba) ·CHCl /Xantphos
2
3
3
I
I
KMn(CO)5
1.5 h
1
1 A. N. Nesmeyanov, K. N. Anisimov, N. E. Kolobova and L. A. Ioganson,
Dokl. Akad. Nauk SSSR, 1967, 175, 358 [Dokl. Chem. (Engl. Transl.),
1967, 175, 627].
(
CO) Mn
Mn(CO)5
5
1
1
1
2 A. D. Hunter, Organometallics, 1989, 8, 1118.
3 S. F. Mapolie and J. R. Moss, Polyhedron, 1991, 10, 717.
4 A. D. Hunter, D. Ristic-Petrovic and J. L. McLernon, Organometallics,
8
63%
1992, 11, 864.
1
1
5 A. D. Hunter and J. L. McLernon, Organometallics, 1989, 8, 2679.
6 J. Li, A. D. Hunter, R. McDonald and B. D. Santarsiero, Organometallics,
PPh2
O
PPh2
PPh2
PPh2
1992, 11, 3050.
17 R. Chukwu, A. D. Hunter, B. D. Santarsiero, S. G. Bott, J. L. Atwood
and J. Chassaignac, Organometallics, 1992, 11, 589.
8 G. A. Artamkina, A. Yu. Mil’chenko, I. P. Beletskaya and O. A. Reutov,
Metalloorg. Khim., 1988, 1, 34 (in Russian).
1
1
BINAP
Xantphos
9 G. A. Artamkina, L. S. Sim and I. P. Beletskaya, Zh. Org. Khim., 1995,
3
1, 689 (Russ. J. Org. Chem., 1995, 31, 635).
The use of Xantphos as a ligand allowed us to obtain tri-
nuclear manganese complex 11 in good yield in the reaction
with 1,3,5-triiodobenzene, although the binuclear complex 12 was
detected along with the target product.
20 R. E. Dessy, R. L. Pohl and R. B. King, J. Am. Chem. Soc., 1966, 88, 5121.
21 R. P. Stewart and P. M. Treichel, J. Am. Chem. Soc., 1970, 92, 2710.
2 A. N. Nesmeyanov, J. F. Lescheva, J. V. Polovyanyuk and Y. A. Ustynyuk,
J. Organomet. Chem., 1972, 37, 159.
3 A. D. Hunter and J. L. McLernon, Organometallics, 1989, 8, 2679.
4 J. P. Collman, L. S. Hegedus, J. R. Norton and R. G. Finke, Principles
and Applications of Organotransition Metal Chemistry, University
Science Books, Mill Valley, California, 1987, vol. 1, ch. 6.
2
2
2
I
Pd (dba) /Xantphos
2
3
I
+ 3 KMn(CO)5
3
h
I
Mn(CO)5
Mn(CO)5
Mn(CO)5
(
CO) Mn
I
5
Mn(CO)5
11 50%
12 25%
Under the same conditions, only one bromine atom was
replaced in 1,3,5-tribromobenzene, and 1,3,5-dibromo(penta-
carbonylmanganese)benzene 13 was formed. Complex 13 was
also formed in the same yield in the reaction of 1,3,5-tri-
bromobenzene with the zinc salt of manganese carbonylate.
Br
Br
Pd (dba) /Xantphos
2
3
Br + 3 MMn(CO)5
M = K, ZnCl
Mn(CO)5
1.5 h
Br
Br
13 60%
All the binuclear and trinuclear complexes were characterised
1
by H NMR spectroscopy and mass spectrometry; their charac-
9
teristics were consistent with published data. In conclusion,
note that a number of new mononuclear iron and manganese
complexes and a binuclear manganese complex containing halo-
gens at the benzene ring were prepared in the course of this
study. All these complexes were characterised by elemental
1
13
analysis, IR spectroscopy and H NMR (and, in some cases,
C
NMR) spectroscopy.
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Received: 25th February 2003; Com. 03/2056
–
45 –