Tetraethylammonium fluoride as a convenient source of hydroxide ions in acetonitrile solution. Its reaction with [Fe(η-C5H5)(CO)2(L)]+ salts and [Fe(η-C5H5)(CO)2X] complexes

Article abstract of DOI:10.1016/S0022-328X(01)00847-6

In acetonitrile solution, [Et₄N]F·2.5H₂O acts as a convenient source of hydroxide ions for use in organometallic chemistry. Within 20 min, at room temperature, it converts [Fe(η-C₅H₅)(CO)₂(L)]⁺ salts (molar ratio 1:1) to [Fe₂(η-C₅H₅)₂(CO) ₃(L)] (L=CO, CNMe and PPh₃) complexes in good yields with the evolution of CO₂ and, when L=CO, CO. Under the same conditions it converts [Fe(η-C₅H₅)(CO)₂Cl] (molar ratio 1:2 or, better, 1:3) to [Fe₂(η-C₅H₅)₂(CO) ₃(NCMe)]. Other [Fe(η-C₅H₅)(CO)₂X] (X=Br or I) react only slowly to give [Fe₂(η-C₅H₅)₂(CO)₄]. Other routes to [Fe₂(η-C₅H₅)₂(CO) ₃(PPh₃)] and [Fe₂(η-C₅H₅)₂(CO) ₃(NCMe)] involve prolonged photolysis and give impure or non-isolable products. This route gives them as analytically pure solids in high yields. It is proposed that in acetonitrile solutions, the F^- ions react with H₂O to give HF and OH^- in a reaction driven by the strength of the H-F bond and the lack of anion solvation in acetonitrile. The OH^- ions then attack the [Fe(η-C₅H₅)(CO)₂(L)]⁺ cations at CO with the evolution of CO₂ to give the [Fe(η-C₅H₅)(CO)(L)]^- which subsequently displaces L from the cations.

Full text of DOI:10.1016/S0022-328X(01)00847-6

Journal of Organometallic Chemistry 629 (2001) 182–186
www.elsevier.com/locate/jorganchem
Tetraethylammonium fluoride as a convenient source of hydroxide
ions in acetonitrile solution. Its reaction with
+
[
Fe(h-C H )(CO) (L)] salts and [Fe(h-C H )(CO) X] complexes
5
5
2
5
5
2
Stephen Byrne, M. Gary Cox, Anthony R. Manning *
Department of Chemistry, Uni6ersity College Dublin, Belfield, Dublin 4, Ireland
Received 31 October 2000; accepted 16 April 2001
Abstract
In acetonitrile solution, [Et N]F·2.5H O acts as a convenient source of hydroxide ions for use in organometallic chemistry.
4
2
+
Within 20 min, at room temperature, it converts [Fe(h-C H )(CO) (L)] salts (molar ratio 1:1) to [Fe (h-C H ) (CO) (L)]
L=CO, CNMe and PPh ) complexes in good yields with the evolution of CO2 and, when L=CO, CO. Under the same
5
5
2
2
5
5 2
3
(
3
conditions it converts [Fe(h-C H )(CO) Cl] (molar ratio 1:2 or, better, 1:3) to [Fe (h-C H ) (CO) (NCMe)]. Other [Fe(h-
5
5
2
2
5
5 2
3
C H )(CO) X] (X=Br or I) react only slowly to give [Fe (h-C H ) (CO) ]. Other routes to [Fe (h-C H ) (CO) (PPh )] and
5
5
2
2
5
5 2
4
2
5
5 2
3
3
[
Fe (h-C H ) (CO) (NCMe)] involve prolonged photolysis and give impure or non-isolable products. This route gives them as
2
5
5 2
3
−
analytically pure solids in high yields. It is proposed that in acetonitrile solutions, the F ions react with H O to give HF and
2
−
−
OH in a reaction driven by the strength of the HꢀF bond and the lack of anion solvation in acetonitrile. The OH ions then
+
−
attack the [Fe(h-C H )(CO) (L)] cations at CO with the evolution of CO to give the [Fe(h-C H )(CO)(L)] which subsequently
5
5
2
2
5
5
displaces L from the cations. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Iron; Carbonyl attack; Hydroxide; Fluoride; Reduction
1
. Introduction
and NMe ; and with R,R%/S,S%-[Fe {h,h-C H CH-
3
2
5
4
(
NMe )CH(NMe )C H }(CO) (m-CO) ][SO CF ]
it
2
3
5
4
2
2
3
3
In a previous publication from these laboratories [1],
gives R,R%/S,S%-[Fe {h,h-C H CH(NMe )CH(NMe )-
2
5
4
2
3
it was shown that commercial [Et N]F·nH O (n=2–3)
in tetrahydrofuran or dichloromethane solutions acted
as a source of F ions, but in acetonitrile it acted as a
C H }(CO) (m-CO) ][H F ] in dichloromethane, but in
4
2
5
4
2
2
5 6
acetonitrile [Fe {h,h-C H CH CH(NMe )C H }(CO) -
2
5
4
2
2
5
4
2
−
(m-CO) ] is formed in a Water–Gas-Shift reaction.
2
−
source of [OH] . Thus, with [Fe {h,h-C H CH CH-
These observations prompted us to investigate the
2
5
4
2
(
NMe )C H }(CO) (m-CO) ][SO CF ] in acetonitrile it
use of [Et N]F·nH O in acetonitrile solution as a conve-
3
5
4
2
2
3
3
4
2
−
gives
[Fe {h,h-C H CH CH(NMe )C H }(CO) (m-
nient and clean source of [OH] ions in organometallic
chemistry. We have looked at its reactions with various
metal–carbonyl complexes and report here on those
2
5
4
2
3
5
4
2
CO) ][OH]; with R,S%-[Fe {h,h-C H CH(NMe )CH-
2
2
5
4
2
(
NMe )C H }(CO) (m-CO) ][SO CF ] in tetrahydro-
3
5
4
2
2
3
3
+
furan it gives R,S%-[Fe {h,h-C H CH(NMe )CH-
with [Fe(h-C H )(CO) (L)] salts (L=CO, PPh and
2
5
4
2
5
5
2
3
(
NMe )C H }(CO) (m-CO) ][H F ], but in acetonitrile it
CNMe) and [Fe(h-C H )(CO) X] complexes (X=Cl,
3
5
4
2
2
4
5
5
5
2
brings about a Hoffman elimination to give the enam-
Br and I).
ine [Fe {h,h-C H CHCH(NMe )C H }(CO) (m-CO) ]
2
5
4
2
5
4
2
2
2
. Experimental
*
Corresponding author. Tel.: +353-1-7062311; fax: +353-1-
Published methods or extensions thereof were used to
prepare [Fe(h-C H )(CO) ][BF ] [2], [Fe(h-C H )(CO) -
7
0
062127.
E-mail address: anthony.manning@ucd.ie (A.R. Manning).
5
5
3
4
5
5
2
022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00847-6

S. Byrne et al. / Journal of Organometallic Chemistry 629 (2001) 182–186
183
(
PPh )]Cl·3H O
[3],
[Fe(h-C H )(CO) (CNMe)]-
Using the same procedure, [Fe(h-C H )(CO) -
3
2
5
5
2
5
5
2
[
(
SO CF ] [4], [Fe(h-C H )(CO) Cl] [5], [Fe(h-C H )-
(CNMe)][BF ] was completely converted to [Fe (h-
3
3
5
5
2
5
5
4
2
CO) Br] [5,6] and [Fe(h-C H )(CO) I] [7–9]. Other
C H ) (CO) (CNMe)] [13] as the sole product within 5
2
5
5
2
5 5 2 3
chemicals were purchased and used as received.
All reactions were carried out at room temperature
(
min and CO was evolved. The former was isolated and
2
purified in the same way as [Fe (h-C H ) (CO) ] and
2
5
5 2
4
r.t.) under an atmosphere of nitrogen and monitored
identified by analysis and spectroscopy (yield \95%).
[Fe(h-C H )(CO)(Ph PCH CH PPh )]Cl failed to re-
by IR spectroscopy.
5
5
2
2
2
2
act with [Et N]F·2.5H O in MeCN.
4
2
2
.1. The reactions of [Fe(p-C H )(CO) (L)]X salts and
5 5 2
[
Et N]F·2.5H O
2.2. The reaction of [Et N]F·2.5H O with
4 2
4
2
[
Fe(p-C H )(CO) X] (X=Cl, Br and I)
5 5 2
Solid [Et N]F·2.5H O, (0.33 g, 1.7 mmol) or its solu-
4
2
3
tion in MeCN (15 cm ) was added to a solution of
The addition of a solution of [Et N]F·2.5H O (1.09 g,
4 2
3
[
(
Fe(h-C H )(CO) ][BF ], (0.5 g, 1.7 mmol) in MeCN
4.70 mmol) in MeCN (15 cm ) to one of [Fe(h-
5
5
3
4
3
3
80 cm ). A rapid reaction took place with the evolution
C H )(CO) Cl] (0.5 g, 2.35 mmol) in MeCN (50 cm )
5
5
2
of CO and CO , which was detected by IR spec-
troscopy. The solution changed colour from yellow to
red. The reaction was complete within 5 min to give
(molar ratio 2:1) gave a mixture of [Fe (h-C H ) (CO) ]
2
2
5
5 2
4
and [Fe (h-C H ) (CO) (NCMe)]. The reaction was
2
5
5 2
3
complete within 10 min, but was nearly instantaneous
[
Fe (h-C H ) (CO) (m-CO) ] as the sole product. It was
when a three-fold excess of [Et N]F·2.5H O was used.
2
5
5 2
2
2
4
2
isolated in \95% yield from the filtered reaction mix-
ture by removal of the solvent at reduced pressure and
recrystallization of the residue from toluene–hexane
mixtures. If an excess of [Et N]F·2.5H O was used, the
reaction was faster, but the product remained the same.
No reaction took place if the reaction was carried out
[Fe (h-C H ) (CO)(NCMe)(m-CO) ] was then the sole
2
5
5 2
2
product and it could be isolated as an analytically pure
green solid in \60% yield by immediate removal of the
solvent at reduced pressure followed by washing of the
residue with cold EtOH. If the work-up was delayed,
large amounts of [Fe (h-C H ) (CO) ] were also formed
4
2
2
5
5 2
4
in dry THF or in the absence of H O, e.g. using
and the two were impossible to separate. When this
2
anhydrous KF/18-crown-6 in rigorously dried MeCN.
reaction was carried out in PhCN or PhCH CN solu-
2
[
Fe (h-C H ) (CO) (m-CO) ] was identified by elemental
tions, it was much slower even with a large excess of
2
5
5 2
2
2
analysis and spectroscopy [7,11]. When the final reac-
tion mixtures were washed with H O, the aqueous
layers were acidic to litmus paper.
[Et N]F·2.5H O. Consequently, the [Fe (h-C H ) (CO)-
4
2
2
5
5 2
(NCR)(m-CO)2] was contaminated with varying
amounts of [Fe (h-C H ) (CO) (m-CO) ] which could
2
2
5
5 2
2
2
A solution of [Et N]F·2.5H O (0.29 g, 1.24 mmol) in
not be separated from it. [Fe (h-C H ) (CO)(NCMe)(m-
4
2
2
5
5 2
MeCN was added to one of [Fe(h-C H )(CO) -
(
cm ). CO was evolved and the solution changed colour
from yellow to green. The reaction was complete within
CO) ] was identified by elemental analysis. Anal.
5
5
2
2
PPh )]Cl·3H O (0.657 g, 1.24 mmol) also in MeCN (80
Found: C, 49.0; H, 3.3; N, 3.2. Calc. for [Fe (h-
3
2
2
3
C H ) (CO)(NCMe)(m-CO) ]: C, 48.2; H, 3.5; N, 3.8%.
2
5
5 2
2
−
1
IR (MeCN, cm ): (wCꢁO) 1941 (6.7), 1742 (10) with
relative peak heights in parentheses. Its low stability
prevented the measurement of its NMR spectrum. This
compound has been prepared previously but was not
isolated or characterized in any way [14].
2
0 min to give [Fe (h-C H ) (CO) (PPh )] as the major
2
5
5 2
3
3
product together with traces of [Fe (h-C H ) (CO) ].
Partial removal of the solvent at reduced pressure fol-
lowed by storage at −10°C gave [Fe (h-C H ) (CO) -
(
tallized from MeCN (yield 65%). The original filtrate
was concentrated at reduced pressure to give [Fe (h-
C H ) (CO) ] (yield 14%), much of which appeared to
be formed during the work-up. [Fe (h-C H ) -
(
by elemental analysis. Anal. Found: C, 62.8; H, 4.3; P,
5
6
2
5
5 2
4
2
5
5 2
3
PPh )] as a green solid that was filtered off and recrys-
If [Fe(h-C H )(CO) Cl] was replaced by [Fe(h-
3
5
5
2
C H )(CO) Br] or [Fe(h-C H )(CO) I], the reactions
5
5
2
5
5
2
2
were very much slower and the sole product was
5
5 2
4
[Fe (h-C H ) (CO) (m-CO) ] even when a large excess
2
5
5 2
2
2
2
5
5 2
of [Et N]F·2.5H O was used. The rate of reaction de-
4 2
CO)(PPh )(m-CO) ] (m.p. 186–189°C) was identified
clined along the series [Fe(h-C H )(CO) Cl]\[Fe(h-
3
2
5
5
2
C H )(CO) Br]\[Fe(h-C H )(CO) I].
5
5
2
5
5
2
.8. Calc. for [Fe (h-C H ) (CO)(PPh )(m-CO) ]: C,
2
5
5 2
3
2
−1
3.2; H, 4.2; P, 5.3%. IR (MeCN, cm ): w(CꢁO) 1948
8.7), 1727 (10) with relative peak heights in parenthe-
(
3. Results and discussion
1
ses. H-NMR(l ppm): cyclopentadienyl protons at 4.16
5), 4.19 (5) at 313 K, and 3.82 (1.6), 4.05 (3.4), 4.31 (5)
(
Commercial tetraalkylammonium fluorides are hy-
drates of somewhat indeterminate composition [15]. We
have used both [Me N]F·xH O and [Et N]F·yH O in
at 243 K with integrations in parentheses; coalescence
temperature 282 K (toluene-D solution). It has been
8
4
2
4
2
obtained previously in an impure state [12].
the course of this work, but the former is deliquescent

184
S. Byrne et al. / Journal of Organometallic Chemistry 629 (2001) 182–186
and so we preferred the latter. Its composition was
determined by elemental analysis and our sample was
shown to be [Et N]F·2.5H O.
The formation of CO suggests that the most plausi-
2
ble pathway for this reaction is that shown in Scheme 1.
It is similar to that proposed to account for the forma-
4
2
6
6
tion of [Mn (h -C Me ) (CO) (m-CO) ] from [Mn(h -
The reaction of [Fe(h-C H )(CO) ][BF ] with an
2
6
6 2
2
2
5
5
3
4
+
−
C Me )(CO) ] and [BH ] in the presence of water
equimolar amount of [Et N]F·2.5H O in acetonitrile,
6
6
3
4
4
2
5
5
[
18], and of [Fe (h -C H ) (CO) (m-CO) ] from [Fe(h -
but not tetrahydrofuran gives [Fe (h-C H ) (CO) (m-
2
6
7 2
2
2
2
5
5 2
2
+
C H )(CO) ] and a large excess of [Me N]OH·5H O
CO) ] as the sole product in \95% isolated yields
6
7
3
4
2
2
[
18]. In all three reactions, the reactive species are
whilst IR studies suggest that the reaction is quantita-
hydroxide ions. In the present case, they are formed in
tive and that CO and CO are evolved in comparable
2
−
acetonitrile by the reaction of F ions with H O. This
2
amounts. [Fe(h-C H )(CO) (CNMe)][SO CF ] gives
5
5
2
3
3
reaction is driven by the formation of the very strong
HꢀF bond coupled with limited anion solvation in
acetonitrile. Alternatively, it may be more accurate to
represent this step as a polarization of the water
[
Fe (h-C H ) (CO) (CNMe)] quantitatively, and [Fe(h-
2
5
5 2
3
C H )(CO) (PPh )]Cl·3H O gives [Fe (h-C H ) (CO)-
(
evolved. The rate of the reaction decreases along the
5
5
2
3
2
2
5
5 2
PPh )(m-CO) ]. In both cases, CO but not CO is
3
2
2
−
molecule by F rather than complete ionization. It is
series L=CO\CNMeꢀPPh3 whilst [Fe(h-C H )-
5
5
consistent with the proposed scheme that the reactions
do not take place in solvents such as tetrahydrofuran
(
CO)(Ph PCH CH PPh )]Cl fails to react.
2 2 2 2
Scheme 1.

S. Byrne et al. / Journal of Organometallic Chemistry 629 (2001) 182–186
185
−
1
which solvate anions more effectively or in the absence
of water, e.g. with anhydrous KF/18-crown-6 in dry
acetonitrile. HF is also formed and is responsible for
the acidity observed in the aqueous layer when the
reaction mixtures are washed with water.
2015/2054 cm
;
[Fe(h-C H )(CO) Br] 2010/2052
5
5
2
−
1
−1
cm ; [Fe(h-C H )(CO) I] 2009/2047 cm }suggest
5
5
2
that the electrophilicities of the CO ligands are all quite
low and do not differ greatly. Consequently, a second
pathway must operate when X=Cl, though not when
X=Br or I, and we suggest that in it the reactive
−
The attack by [OH] ions on coordinated CO is well
+
+
documented. [Fe(h-C H )(CO) L] salts (L=CO or
species is [Fe(h-C H )(CO) (NCMe)] (Scheme 1, L=
5
5
2
5
5
2
−
PPh ) have been reported to react with KOH to give
NCMe). It is well-known that the Cl ligand in [Fe(h-
C H )(CO) Cl] is labile, e.g. unlike [Fe(h-C H )(CO) X]
3
isolable [Fe(h-C H )(CO)(L)(CO H)] and K[Fe(h-
5
5
2
5
5
2
5
5
2
C H )(CO)(PPh )(CO )] [16,17]. The subsequent decar-
(X=Br or I) it dissolves in water with the formation of
5
5
3
2
+
−
boxylation may proceed via [Fe(h-C H )(CO)(L)-
[Fe(h-C H )(CO) (OH )] Cl , so it is not unreason-
5
−
5
5
5
2
2
(
CO H)] or [Fe(h-C H )(CO)(L)(CO )]
to [Fe(h-
able to suggest that a similar solvolysis takes place in
2
5
5
2
−
C H )(CO)(L)H] or [Fe(h-C H )(CO)(L)] , respec-
acetonitrile even if only to a very limited extent. [Fe(h-
C H )(CO) (NCMe)]
5
5
5
5
+
tively.
would be expected to react
5
5
2
The formation of CO in comparable amounts to CO2
when L=CO and its absence when L=CNMe or PPh3
is the evidence for nucleophilic attack by [Fe(h-
much more rapidly than the covalent halo-complexes
due to its more electrophilic CO groups as reflected in
−
1
its higher w(CꢁO) frequencies (2029/2074 cm ). How-
ever, this does not explain why two moles of
[Et N]F·2.5H O are required to bring about a complete
−
+
C H )(CO)(L)] on [Fe(h-C H )(CO) (L)] with dis-
5
5
5
5
2
placement of the weakest p-acceptor ligand, L, from the
cation. [Fe (h-C H ) (CO) ] may be a primary product
4
2
reaction of [Fe(h-C H )(CO) Cl].
2
5
5 2
4
5
5
2
from the reaction when L=PPh , but we think that it
3
arises from the decomposition of [Fe (h-C H ) -
3.1. NMR spectra of [Fe (p-C H ) (CO) (L)]
2 5 5 2 3
2
5
5 2
(
CO)(PPh )(m-CO) ] as its concentration in the reaction
3
2
mixture increases with time.
The proposed scheme rationalizes satisfactorily the
The NMR spectra of [Fe (h-C H ) (CO) (L)] {L=
2
5
5 2
3
−
CO [18], CNMe [11,19], P(OPh) [20] and CN [12]}
3
ligand dependence of the reaction rate which, for the
have been reported and discussed in detail, and have
been instrumental in revealing the mechanism of flux-
ionality in metal–carbonyl compounds. However, com-
parable studies have not been carried out on
[Fe (h-C H ) (CO) (PPh )], perhaps because it was re-
+
[
Fe(h-C H )(CO) (L)] cations, decreases in the order
5
5
2
L=CO\CNMe and PPh . This dependency may be
3
linked to the frequencies of the w(CꢁO) vibrations of
−
1
the cations which decrease 2074/2124 cm
(L=CO),
2
5
5 2
3
3
−
1
−1
2019/2064 cm
(L=CNMe), and 2014/2057 cm
ported to be unstable [10]. However, we have found
(
L=PPh ). This is not surprising as the w(CꢁO) fre-
that when [Fe (h-C H ) (CO) (PPh )] is pure, it is suffi-
3
2
5
5 2
3
3
1
quencies and the electrophilicities of the CO groups
decrease with increasing back-bonding into the CO
ciently stable in toluene-d solution to allow its H-
8
NMR spectrum to be obtained at various temperatures.
Unfortunately, only the cyclopentadienyl resonances
could be studied. These are slightly broadened so that
p*-orbitals as L changes from CO to CNMe or PPh . It
3
also explains why there is no reaction between [Fe(h-
31
1
13
C H )(CO)(Ph PCH CH PPh )]Cl and [Et N]F·2.5H O
P– H coupling was not detected, and a C-NMR
5
5
2
2
2
2
4
2
as the metal centre is electron rich, which discourages
nucleophilic attack at the carbonyl C atom.
spectrum could not be obtained.
Spectroscopic data suggests that [Fe (h-C H ) -
2
5
5 2
Titration experiments have shown that the stoi-
chiometry of these reactions is 1:1. However, all are
faster if a three-fold excess of [Et N]F·2.5H O is used.
(CO)(PPh )(m-CO) ] has the same structure as that
3
2
found for [Fe (h-C H ) (CO){P(OPh) }(m-CO) ] [21].
2
5
5 2
3
2
There are two species present in its toluene-d solutions.
4
2
8
−
This is to be expected as the concentration of [OH]
At low temperatures, they are present in the ratio of
2.2:1 and each gives rise to a pair of singlet cyclopenta-
dienyl resonances which are due to the C H ligands
ions would be much higher and would facilitate rele-
vant steps in the scheme, particularly when L is the
5
5
stronger donor, PPh , and towards the end of the
bound to Fe(CO) and Fe(PPh ), respectively. The two
resonances at higher are coincident so that three peaks
3
3
’
reaction.
−
The same scheme with L=X may be used to
are observed. The two species are probably cis- and
trans-isomers, but it is not possible to establish which is
the major and which is the minor one. On warming,
isomer exchange becomes faster, the cyclopentadienyl
resonances broaden and coalesce so that when the fast
exchange limit is reached at ca. 40°C, these protons give
rise to two equal resonances, which are due to the two
account for the products from the reactions of [Fe(h-
−
C H )(CO) X] provided that [Fe (h-C H ) (CO) (X)] ,
5
5
2
2
5
5 2
3
solvolyses to [Fe (h-C H ) (CO) (NCMe)] (X=Cl) or
2
5
5 2
3
decomposes to [Fe (h-C H ) (CO) ] (X=Br or I).
2
5
5 2
4
However, this does not account for the markedly differ-
ent reaction rates for [Fe(h-C H )(CO) Cl] as compared
5
5
2
with its bromo or iodo counterparts. The w(CꢁO) fre-
quencies of the three compounds {[Fe(h-C H )(CO) Cl]
types of C H5 groups. The coalescence temperature
5
(9°C, 282 K) can be used to obtain the DG* values for
5
5
2

186
S. Byrne et al. / Journal of Organometallic Chemistry 629 (2001) 182–186
[
5] T.S. Piper, F.A. Cotton, G. Wilkinson, J. Inorg. Nucl. Chem. 1
the fluxional cis–trans isomerism [22]. These are 15.7
−
1
−1
(1955) 165.
kcal mol
the minor isomer. Although they are larger than the
corresponding values for [Fe (h-C H ) (CO) ], (ca. 10.4
from the major and 15.0 kcal mol
from
[
[
6] B.F. Hallam, P. Pauson, J. Chem. Soc. (1956) 3030.
7] T.S. Piper, G. Wilkinson, J. Inorg. Nucl. Chem. 2 (1956) 38.
2
5
5 2
4
[8] R.B. King, Organomet. Synth. 1 (1961) 175.
[9] R.B. King, Organomet. Synth. 1 (1961) 114.
[10] R.J. Haines, A.L. du Preez, Inorg. Chem. 8 (1969) 1459.
11] M. Ennis, R. Kumar, A.R. Manning, J.A.S. Howell, P. Mathur,
A.J. Rowan, F.S. Stephens, J. Chem. Soc. Dalton Trans. (1981)
−
1
kcal mol
of ca. 13.7 kcal mol
P(OPh) }] [20], and it is probale that the mechanism of
[18c]), these values are comparable to that
−
1
for [Fe (h-C H ) (CO) -
2
5
5 2
3
[
{
3
the fluxional process which brings about the inter-
change of cis- and trans-isomers of [Fe (h-C H ) -
1
251.
2
5
5 2
[
12] W.P. Fehlhammer, A. Schr o¨ der, F. Schoder, J. Fuchs, A. V o¨ lkl,
B. Boyadjiev, S. Schr o¨ lkamp, J. Organomet. Chem. 411 (1991)
405.
[13] J.H. Clark, Chem. Rev. 80 (1980) 429.
14] A.M. Morken, D.P. Eyman, M.A. Wolff, S.J. Schauer,
Organometallics 12 (1993) 725.
(
CO) (PPh )] is identical with that proposed for [Fe (h-
3
3
2
C H ) (CO) {P(OPh) }] [20].
5
5 2
3
3
1
We were unable to obtain the H-NMR spectrum of
[
[
Fe (h-C H ) (CO) (NCMe)].
2
5
5 2
3
[
[
15] J. Powell, M.J. Horvath, Organometallics 12 (1993) 4073.
16] N. Grice, S.C. Koa, R. Pettit, J. Am. Chem. Soc. 101 (1979)
1
627.
4
. Conclusions
[
[
17] D.H. Gibson, Tek-Sing Ong, J. Am. Chem. Soc. 109 (1987) 7191.
18] (a) J.G. Bullitt, F.A. Cotton, T.J. Marks, Inorg. Chem. 11 (1972)
In acetonitrile solution, [Et N]F·2.5H O is a conve-
4
2
6
71;
−
nient source of OH ions, and is a useful reagent
provided that the HF, which is also formed, does not
affect the reaction.
(
b) O.A. Gansow, A.R. Burke, W.D. Vernon, J. Am. Chem. Soc.
98 (1976) 5817;
(c) D.C. Harris, E. Rosenberg, J.D. Roberts, J. Chem. Soc.
Dalton Trans. (1974) 2398;
(
d) L.J. Farrugia, L. Mustoo, Organometallics 11 (1992) 2941.
[
19] (a) R.D. Adams, F.A. Cotton, J. Am. Chem. Soc. 95 (1973) 6589;
(b) R.D. Adams, F.A. Cotton, J.M. Troup, Inorg. Chem. 13
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