The cyclo-C3 ligand: Trimetallic cyclopropenium complexes of Group 6-8 metals, including the X-ray crystal structure of [{Fe(CO)2(Cp)}3(μ3-C3)][SbF 6]

Article abstract of DOI:10.1016/S0022-328X(98)01115-2

Several trimetallic cyclopropenium cations have been prepared via reactions of three equivalents of a metallate anion with [C₃Cl₃][SbF₆]. The X-ray crystal structure of [{Fe(CO)₂(Cp)}₃(μ₃-C₃)][SbF ₆] (1) shows a nearly equilateral C₃ ring with an iron center bonded to each vertex. The cyclopropenium complexes [{Ru(CO)₂(Cp)}₃(μ₃-C₃)][SbF ₆] (2), [{Mo(CO)₃(Cp)}₃(μ₃-C₃)][SbF ₆] (3), [{W(CO)₃(Cp)}₃(μ₃-C₃)][SbF ₆] (4), and [{Re(CO)₅}₃(μ₃-C₃)][SbF ₆] (5) were spectroscopically characterized. Because of the 3-fold symmetrical nature of these complexes, their NMR spectra display a single cyclo-C₃ ring carbon resonance and a single set of resonances for the metal moiety. Compound 1 reacts with Li[BHEt₃] and LiMe to give complex reaction mixtures. We were not able to add a fourth metal center to the C₃ ring of 1. The spectroscopically characterized C₉ complex [{Fe(CO)₂(Cp)}₃{μ₃-C ₃(C≡C)₃}][SbF₆] (6), prepared by the reaction of three equivalents of [Fe(C≡CSiMe₃)(CO)₂(Cp)] with [C₃Cl₃][SbF₆], was not stable enough to isolate in analytically pure form.

Full text of DOI:10.1016/S0022-328X(98)01115-2

Journal of Organometallic Chemistry 578 (1999) 133–143
The cyclo-C3 ligand: trimetallic cyclopropenium complexes of Group
6–8 metals, including the X-ray crystal structure of
[{Fe(CO)2(Cp)}3(m3-C3)][SbF6]
Michael S. Morton, John P. Selegue *
Department of Chemistry, Uni6ersity of Kentucky, Lexington, KY 40506-0055, USA
Received 21 July 1998
Abstract
Several trimetallic cyclopropenium cations have been prepared via reactions of three equivalents of a metallate anion with
[C3Cl3][SbF6]. The X-ray crystal structure of [{Fe(CO)2(Cp)}3(m3-C3)][SbF6] (1) shows a nearly equilateral C3 ring with an iron
center bonded to each vertex. The cyclopropenium complexes [{Ru(CO)2(Cp)}3(m3-C3)][SbF6] (2), [{Mo(CO)3(Cp)}3(m3-C3)][SbF6]
(3), [{W(CO)3(Cp)}3(m3-C3)][SbF6] (4), and [{Re(CO)5}3(m3-C3)][SbF6] (5) were spectroscopically characterized. Because of the
3-fold symmetrical nature of these complexes, their NMR spectra display a single cyclo-C3 ring carbon resonance and a single set
of resonances for the metal moiety. Compound 1 reacts with Li[BHEt3] and LiMe to give complex reaction mixtures. We were
not able to add a fourth metal center to the C3 ring of 1. The spectroscopically characterized C9 complex [{Fe(CO)2(Cp)}3{m3-
C3(CꢀC)3}][SbF6] (6), prepared by the reaction of three equivalents of [Fe(CꢀCSiMe3)(CO)2(Cp)] with [C3Cl3][SbF6], was not
stable enough to isolate in analytically pure form. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Carbide; Cyclopropenium; Iron; Molybdenum; Rhenium; Ruthenium; Tungsten
1. Introduction
carbon fragments have been proposed as intermediates
in metal-catalyzed Fischer–Tropsch and hydrocarbon
conversion reactions [11–16]. In fact, Fischer and
Tropsch originally proposed the buildup of larger hy-
drocarbons via reactive surface carbides [17,18]. Small
carbon fragments such as C2 and C3 have been spectro-
scopically observed in interstellar space and in the tail
of a comet [3,4].
C3 is one of the most important and abundant spe-
cies in carbon vapor [3]. The ground state of C3 has
been calculated to be a linear, symmetrical singlet with
an excited singlet state and several metastable triplet
states [19]; cyclic C3 is much higher in energy [3]. Metal
complexes of linear C3 have recently been prepared by
Gladysz [20,21] and Templeton [22]. We report here
additional details on [{Fe(CO)2(Cp)}3(m3-C3)][SbF6] (1)
[23] and several new cyclo-C3 complexes.
Small, unsaturated carbon fragments are important
in fields ranging from organometallic chemistry [1] to
materials science [2] to astrophysics [3,4]. Small,
gaseous carbon fragments are the essential building
blocks in the formation of macroscopic carbonaceous
materials such as graphite, diamond and fullerenes.
Species such as C1, C2, C3, and C4 can be generated in
the laboratory by subjecting hydrocarbons or graphite
to an electrical arc, high temperatures or irradiation
[3,5]. The fullerenes (C60, C70, etc.) are formed by
resistive heating [6,7] or the arc-heating of graphite
under an inert atmosphere [8,9], probably via the coa-
lescence of small carbon fragments [10]. Surface-bound
* Corresponding author.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(98)01115-2

134
M.S. Morton, J.P. Selegue / Journal of Organometallic Chemistry 578 (1999) 133–143
2. Results
2.1. Synthesis
Reactions of nucleophilic metallates with [C3Cl3]-
[SbF6] resulted in cyclopropenium cations with three
organometallic substituents. For example, the reaction
of three equivalents of [Fe(CO)2(Cp)]− with [C3Cl3]-
[SbF6], generated by reacting C3Cl4 with AgSbF6, in
THF resulted in the formation of [{Fe(CO)2(Cp)}3(m3-
C3)][SbF6] (1) in about 65% yield (Scheme 1). Reduc-
tion of [Fe2(CO)4(Cp)2] with NaK2.8 [24] rather than
Na/Hg led to a simpler workup with superior yields.
Dark amber–brown crystals of 1 are stable in air
indefinitely, and in solution for several days. The reac-
tion of three equivalents of [Fe(CO)2(Cp)]− with tetra-
chlorocyclopropene resulted in the formation of
[{Fe(CO)2(Cp)}3(m3-C3)][Cl] which could be converted
to [{Fe(CO)2(Cp)}3(m3-C3)][PF6] by anion exchange
(Scheme 1). Attempts to prepare [Fe(h1-C3Cl2)(CO)2-
(Cp)]+ and [{Fe(CO)2(Cp)}2(m-C3Cl)]+ by reacting
[C3Cl3][SbF6] with less than three equivalents of [Fe-
(CO)2(Cp)]− simply resulted in lower yields (40–50%)
of 1. Reactions of [C3Cl3][SbF6] with more than three
equivalents of [Fe(CO)2(Cp)]−, or of Na[Fe(CO)2(Cp)]
with pre-formed 1, again resulted in 1, rather than
neutral [{Fe(CO)2(Cp)}4(C3)]. An attempt to prepare
[{Fe(CO)2(Cp)}2(m2-C3O)] by reacting K[Fe(CO)2(Cp)]
with dichlorocyclopropenone failed similarly.
Scheme 2.
The reaction of three equivalents of [Fe(CꢀCSi-
Me3)(CO)2(Cp)] [25] with [C3Cl3][SbF6] in THF resulted
in [{Fe(CO)2(Cp)}3{m3-C3(CꢀC)3}][SbF6] (6, Scheme 3).
In this complex, each metal center is separated from the
cyclopropenium ring by an ethynediyl group. Like the
Ru complex 2, we were unable to obtain an analytically
pure sample of 6.
Samples of these metal-containing cyclopropenium
cations uniformly gave poor elemental analyses, analyz-
ing low by three or more carbon atoms per formula
unit, even with combustion aids. Presumably this was
caused by the formation of refractory metal carbide
phases leading to incomplete combustion. The forma-
tion of metal carbide phases was supported by the
thermogravimetric analysis of 1. Upon heating the sam-
ple to 1000°C, mass losses consistent with the loss of
SbF5, carbon monoxide and cyclopentadienyl frag-
ments occurred. The residue presumably consisted of
mixed iron carbides and fluorides.
2.2. Characterization
Several other metallate anions reacted with [C3Cl3]-
[SbF6] to give M3C3 complexes. [{Ru(CO)2(Cp)}3(m3-
C3)][SbF6] (2) was prepared via the reaction of
K[Ru(CO)2(Cp)] with [C3Cl3][SbF6] (Scheme 2). Cy-
clopentadienyl-containing impurities were present in all
samples. Three equivalents of K[Mo(CO)3(Cp)] or
K[W(CO)3(Cp)] reacted with [C3Cl3][SbF6] to give
[{M(CO)3(Cp)}3(m3-C3)][SbF6] (3, M=Mo, 4, M=W,
Scheme 2). The yield of Mo complex 3 (15%) was much
lower than that of W complex 4 (42%). The reaction of
Na[Re(CO)5] [24] with [C3Cl3][SbF6] resulted in
[{Re(CO)5}3(m3-C3)][SbF6] (5, Scheme 2), the first M3C3
complex with only carbonyl ancillary ligands. Re com-
plex 5 decomposes in a few hours in solution to a
mixture of rhenium-containing species. Similar reac-
tions of [C3Cl3][SbF6] with [Mn(CO)5]− or [Co(CO)4]−
did not lead to stable M3C3 products.
The structure of (1) was determined by X-ray crystal-
lographic methods. Crystal data and experimental con-
ditions for 1 are listed in Table 1. A plot of the
molecular structure is shown in Fig. 1. Selected bond
distances and angles are listed in Tables 2 and 3. The
structure shows a nearly equilateral C3 ring with a
[Fe(CO)2(Cp)] center bonded to each vertex, accompa-
nied by a well-separated [SbF6]− counterion. The spec-
1
troscopic characterization of compounds 1–6 by H-
and 13C-NMR, IR, MS and TGA is discussed below.
2.3. Attempted reactions of
[{Fe(CO)2(Cp)}3(v3-C3)][SbF6] (1)
Complex 1 is surprisingly unreactive. The reaction of
1 with Br2 gave a low yield of [FeBr(CO)2(Cp)] and an
intractable, black precipitate, whereas 1 did not react
with I2 or Me3NO. Reduction of [{Fe(CO)2(Cp)}3(m3-
C3)][Cl] with Na/Hg gave small amounts of
[Fe2(CO)4(Cp)2] and [FeCl(CO)2(Cp)], and some recov-
ered starting material. Reactions of 1 with the small
nucleophiles Li[BHEt3] and LiMe gave complex reac-
tion mixtures plus recovered starting material. Simi-
larly, we were unable to prepare tetrametallic C3
complexes from 1 and [Fe(CO)2(Cp)]−, [Co(CO)4]− or
[Pd(dba)2] (dba=PhCH=CHCOCH=CHPh).
Scheme 1.

M.S. Morton, J.P. Selegue / Journal of Organometallic Chemistry 578 (1999) 133–143
135
Scheme 3.
1
3. Discussion
multiple recrystallizations, the H-NMR spectrum of 2
showed one major and several minor Cp resonances.
The result was the same whether [Ru(CO)2(Cp)]− was
produced by reducing the dimer with NaK2.8, sodium
amalgam or potassium metal. The impurities may be
partially substituted [{Ru(CO)2(Cp)}x(C3Cl3−x)]+
(x=1,2) species. The relative kinetic inertness of ruthe-
nium may account for the observation of these partial
substitution products which are not seen for iron.
The Group 6 cyclopropenium complexes, [{Mo-
(CO)3(Cp)}3(m3-C3)][SbF6] (3) and [{W(CO)3(Cp)}3(m3-
C3)][SbF6] (4), were similar to their Group 8 analogs.
Yields of 3 and 4 were lower than that of 1, possibly
owing to less efficient metal-anion formation [24,37,38]
or lower nucleophilicity of the Group 6 anions [39–41].
We did not try to prepare the analogous Cr complex.
A trimetallic cyclopropenium complex with only car-
bonyl ancillary ligands, [{Re(CO)5}3(m3-C3)][SbF6] (5),
was prepared in 34% yield from Na[Re(CO)5] and
[C3Cl3][SbF6]. We were not able to prepare the man-
ganese analog. Compound 5 appears to be sensitive to
either heat or light, decomposing in solution over a few
hours. Insoluble 5 dissolves in ethyl ether over about 5
h to give an orange solution containing [Re2(CO)10],
[Re3H3(CO)12], and [Re(CO)6]+.
The cyclopropenium cation, with two p electrons
delocalized over three carbon atoms, is the smallest
Hu¨ckel-aromatic ring [26]. Substituted cyclopropenium
compounds have been known for about 40 years, start-
ing with the triphenylcyclopropenium cation in 1957
[27,28]. The preparation of substituted cyclopropenium
cations via nucleophilic additions to C3Cl3+ [29] is well
precedented [30,31]. For example, triferrocenylcyclo-
propenium tetrachloroaluminate was prepared in 1975
by the Friedel–Crafts reaction of ferrocene with
[C3Cl3][AlCl4] [32,33]. Cyclopropenium cations with one
directly-bonded metal substituent have been prepared
from halo- and amino-substituted cyclopropenium pre-
cursors. [Fe(C3Ph2)(CO)2(Cp)][BF4] was obtained by
reacting [Fe(SiMe3)(CO)2(Cp)] with 1-chloro-2,3-
diphenylcyclopropenium
[Fe{C3(NEt2)2}(CO)2(Cp)][ClO4] was prepared by re-
acting with tris(diethylamino)-
[Fe(CO)2(Cp)]−
tetrafluoroborate
and
cyclopropenium perchlorate [34]. The reaction of 1,1-
dichloro-2,3-diphenylcyclopropene with palladium
black gave [Pd2Cl2(m-Cl)2(C3Ph2)2] [35], and the same
method was used for analogous di-tert-butyl and bis(di-
isopropylamino) compounds [36]. No cyclopropenium
cation with more than one s-metal substituent had
been reported prior to our study [23].
A series of large, raft-like polycarbon ligands can be
envisioned by placing CꢀC linkages between a C3 ring
and the appended metal centers. As an approach to a
C9 complex, we investigated the reaction of three equiv-
alents of [Fe(CꢀCSiMe3)(CO)2(Cp)] with [C3Cl3][SbF6].
Chlorotrimethylsilane elimination led to [{Fe(CO)2-
(Cp)}3{m3-C3(CꢀC)3}][SbF6] (6) in 34% yield. We were
not able to obtain analytically pure 6 even after re-
peated recrystallizations from CH2Cl2–ethyl ether.
3.1. Synthesis
The reaction of three equivalents of a metallate anion
with [C3Cl3][SbF6] is a rather general method for the
synthesis of trimetallic cyclopropenium ions such as
[{Fe(CO)2(Cp)}3(m3-C3)][SbF6]
(1).
Alternatively,
[{Fe(CO)2(Cp)}3(m3-C3)][Cl] was prepared by reacting
[Fe(CO)2(Cp)]− with tetrachlorocyclopropene in THF
without prior halide abstraction. The chloride counte-
rion was readily exchanged for hexafluorophosphate
(Scheme 1) Attempts to add fewer than three equiva-
lents of [Fe(CO)2(Cp)]− to [C3Cl3]+ did not lead to
[{Fe(CO)2(Cp)}x(C3Cl3-x)]+ (x=1, 2), but rather gave
reduced yields of 1 and unreacted trichlorocycloprope-
nium salt.
3.2. X-ray crystal structure of
[{Fe(CO)2(Cp)}3(v3-C3)][SbF6] (1)
The structure of 1 has a nearly equilateral C3 ring
with an iron center bonded to each vertex. The average
˚
Fe–Cring bond length, 1.92 A, falls near the middle of
the range of Fe–C bonds with some multiple character.
The Fe–C bonds in 1 are shorter than typical Fe–Csp
3
˚
Congeneric [{Ru(CO)2(Cp)}3(m3-C3)][SbF6] (2), pre-
pared by reacting [Ru(CO)2(Cp)]− with [C3Cl3][SbF6],
could not be obtained analytically pure. Even after
or Fe–Csp single bond lengths of 2.0–2.1 A in several
2
[Fe(R)(CO)2(Cp)] compounds [42], and shorter than the
˚
1.979(3) and 1.996(2) A Fe–C bonds in the cyclohepta-

136
M.S. Morton, J.P. Selegue / Journal of Organometallic Chemistry 578 (1999) 133–143
trienylidene complexes [Fe(h1-C7H6)(CO)2(Cp)][PF6] (7)
and [Fe(h1-C11H8)(CO)2(Cp)][PF6] (8) [43,44]. The Fe–
C bonds in 1 are about the same length as the Fe–Csp
bond in [Fe(CꢀCPh)(CO)2(Cp)] [45], the average 1.91(2)
˚
A Fe–Cring bond in the cyclobutenylidene complex
[{Fe(CO)2(Cp)}2(m2-C4HPh2)][ClO4] (9) [46,47], and the
˚
1.92(3) A Fe–C bond in the cyclobutenylidene complex
[{Fe(CO)2(Cp)}(m2-C4PhMe2){Cr(CO)5}] (10) [48], but
˚
longer than the 1.81(1) A Fe–C bond to the strong
p-acceptor CCl2 in [Fe(CCl2)(CO)2(Cp)][BCl4] [49].
Table 1
Crystallographic
[{Fe(CO)2(Cp)}3(m3-C3)][SbF6] (1)
data
and
experimental
details
for
Fig. 1. Perspective drawing of the molecular structure of
[{Fe(CO)2(Cp)}3(m3-C3)][SbF6] (1). The ellipsoids correspond to 50%
probability contours of atomic displacement.
Formula
C
24H15F6Fe3O6Sb
Formula weight
Temperature (K)
Color and form
Space group
802.66
297(1)
Thus, the Fe–C bond lengths in 1 exhibit some degree
of multiple bond character.
Dark amber–brown fragment
(
P1 (No. 2)
˚
a (A)
10.265(2)
10.833(2)
13.821(3)
101.04(3)
111.00(3)
100.80(3)
1352.2(5)
2
˚
b (A)
˚
c (A)
h (°)
i (°)
k (°)
3
˚
V (A )
Z
Imposed symmetry
None
1.971
2.645
780
Dcalc. (g cm−3
)
Absorption coefficent v (mm−1
F(000)
)
The C–C bond lengths in the cyclopropenium ring
Crystal size (mm3)
Theta range for data (°)
Index range
0.15×0.40×0.45
1.64–24.97
−12BhB12, 0BkB12,
−16BlB16
5027
˚
are about equal, averaging 1.39(1) A, nearly equal to
the mean C–C distance in a localized cyclopropenyli-
dene complex such as [Mn(cyclo-C3Ph2)(CO)2(Cp)]
˚
Reflections collected
Reflections observed [I\2|(I)]
Independent reflections
Diffractometer
(d(C–C)=1.349(6) and 1.424(6) A) [50,51]. In an 18-
2724
electron [M(CR2)(CO)2(Cp)] complex with significant
M–C p-donation, the carbene ligand is expected to be
‘vertical’, i.e. Cp(centroid)–M–C–R torsion angles are
0 and 9180°. In compound 1, two of the cyclopentadi-
enyl rings are above and the other is below the C3
plane, with scattered Cp(centroid)–Fe–Ca–Cb torsion
angles (about Fe1–C1: 99.7°, −65.5°; Fe2–C2: 105.5°,
−78.0°; Fe3–C3: 132.0°, −52.2°). This evidence sug-
gests that Fe to cyclopropenyl p-donation is of minor
importance in the structure of 1 [52].
4753 (Rint=0.0195)
Enraf–Nonius CAD-4
Mo–Ka (u=0.7107 A)
˚
Radiation
Monochromator
Scan type
Scan range (°)
Max counting time
X-ray exposure
No. of standard reflections
Max. variation standard
reflections
Absorption correction
Refinement method
Graphite
ꢀ–2q
0.70+0.35°tanU
100 s
90 h
3
12.6% (random)
Empirical (CAMEL)
Full-matrix least-squares on
F2
3.3. Spectroscopy
Data/restraints/parameters
Final R indices [I\2|(I)]a
R indices (all data)a
4753/0/361
R1=0.0480, wR2=0.1235
R1=0.1244, wR2=0.1393
0.950
Spectroscopic properties of the trimetallic complexes
1
Goodness-of-fit on F2b
(D/|)max and (D/|)mean
1-6 reflect their effective threefold symmetry. H- and
0.980 and 0.072
13C-NMR spectra show a single [Fe(CO)2(Cp)] environ-
ment in 1 from −80°C to room temperature, consis-
tent with free rotation about the Fe–C bonds in
solution. The cyclopropenyl carbon atoms display a
single 13C-NMR resonance at 256.6 ppm, downfield of
most organic cyclopropenium ions (118–175 ppm) [53].
Largest difference peak and hole 0.825 and −1.154
−3
˚
(e A
)
a R=(SꢀꢀFoꢀ−ꢀFcꢀꢀ/SꢀFoꢀ); Rw=[Sw(ꢀFoꢀ–ꢀFcꢀ)2/SwFo2]1/2, where w=
4I/(|2(I)=0.02I2).
b GOF=[Sw(ꢀFoꢀ−ꢀFcꢀ)2/(No−Nv)]1/2
.

M.S. Morton, J.P. Selegue / Journal of Organometallic Chemistry 578 (1999) 133–143
137
Table 3
Table 2
˚
Selected bond angles (degrees) with Esd’s for the structure of
Selected bond distances (A) with Esd’s for the structure of
[{Fe(CO)2(Cp)}3(m3-C3)][SbF6] (1)
[{Fe(CO)2(Cp)}3(m3-C3)][SbF6] (1)
C(5)–Fe(1)–C(4)
C(5)–Fe(1)–C(1)
C(4)–Fe(1)–C(1)
Cp1a–Fe(1)–C(1)
Cp1a–Fe(1)–C(4)
Cp1a–Fe(1)–C(5)
C(7)–Fe(2)–C(6)
C(7)–Fe(2)–C(2)
C(6)–Fe(2)–C(2)
Cp2b–Fe(2)–C(2)
Cp2b–Fe(2)–C(6)
Cp2b–Fe(2)–C(7)
C(9)–Fe(3)–C(8)
C(9)–Fe(3)–C(3)
C(8)–Fe(3)–C(3)
Cp3c–Fe(3)–C(3)
Cp3c–Fe(3)–C(8)
Cp3c–Fe(3)–C(9)
C(2)–C(1)–C(3)
C(2)–C(1)–Fe(1)
C(3)–C(1)–Fe(1)
C(3)–C(2)–C(1)
C(3)–C(2)–Fe(2)
C(1)–C(2)–Fe(2)
C(2)–C(3)–C(1)
C(2)–C(3)–Fe(3)
C(1)–C(3)–Fe(3)
O(1)–C(4)–Fe(1)
O(2)–C(5)–Fe(1)
O(3)–C(6)–Fe(2)
O(4)–C(7)–Fe(2)
O(5)–C(8)–Fe(3)
O(6)–C(9)–Fe(3)
C(11)–C(10)–C(14)
C(12)–C(11)–C(10)
C(11)–C(12)–C(13)
C(14)–C(13)–C(12)
C(10)–C(14)–C(13)
C(19)–C(15)–C(16)
C(17)–C(16)–C(15)
C(16)–C(17)–C(18)
C(19)–C(18)–C(17)
C(15)–C(19)–C(18)
C(21)–C(20)–C(24)
C(20)–C(21)–C(22)
C(21)–C(22)–C(23)
C(22)–C(23)–C(24)
C(23)–C(24)–C(20)
F(5)–Sb–F(1)
94.5(4)
91.1(3)
92.7(3)
120.3(4)
124.0(4)
125.3(4)
93.8(4)
90.4(3)
89.9(3)
120.7(4)
125.9(4)
125.9(4)
94.5(4)
Fe(1)–C(5)
Fe(1)–C(4)
Fe(1)–Cp1a
Fe(1)–C(1)
Fe(1)–C(11)
Fe(1)–C(12)
Fe(1)–C(10)
Fe(1)–C(14)
Fe(1)–C(13)
Fe(2)–C(7)
Fe(2)–C(6)
Fe(2)–C(2)
Fe(2)–C(18)
Fe(2)–C(15)
Fe(2)–C(17)
Fe(2)–C(16)
Fe(2)–C(19)
Fe(2)–Cp2b
Fe(3)–C(9)
Fe(3)–C(8)
Fe(3)–C(3)
Fe(3)–C(23)
Fe(3)–C(24)
Fe(3)–C(20)
Fe(3)–C(21)
Fe(3)–C(22)
Fe(3)–Cp3c
O(1)–C(4)
O(2)–C(5)
O(3)–C(6)
O(4)–C(7)
O(5)–C(8)
O(6)–C(9)
C(1)–C(2)
C(1)–C(3)
C(2)–C(3)
C(10)–C(11)
C(10)–C(14)
C(11)–C(12)
C(12)–C(13)
C(13)–C(14)
C(15)–C(19)
C(15)–C(16)
C(16)–C(17)
C(17)–C(18)
C(18)–C(19)
C(20)–C(21)
C(20)–C(24)
C(21)–C(22)
C(22)–C(23)
C(23)–C(24)
Sb–F(5)
1.755(9)
1.762(8)
1.721(8)
1.913(6)
2.083(7)
2.091(8)
2.098(7)
2.101(8)
2.100(8)
1.776(8)
1.778(9)
1.917(6)
2.079(8)
2.081(8)
2.092(8)
2.094(8)
2.106(7)
1.725(8)
1.742(9)
1.752(10)
1.919(7)
2.039(10)
2.064(11)
2.064(12)
2.073(10)
2.074(11)
1.731(11)
1.125(9)
1.146(9)
1.123(9)
1.105(9)
1.145(10)
1.158(9)
1.388(9)
1.394(9)
1.375(9)
1.393(12)
1.403(12)
1.375(12)
1.426(12)
1.423(12)
1.362(12)
1.404(12)
1.389(13)
1.413(12)
1.371(11)
1.27(2)
89.9(3)
88.8(3)
122.2(4)
126.1(4)
124.8(4)
59.2(5)
149.6(5)
150.6(5)
60.6(4)
151.4(5)
148.0(5)
60.2(5)
151.5(5)
148.3(5)
179.3(9)
179.4(8)
177.1(7)
177.4(9)
177.5(9)
178.4(7)
107.3(8)
109.6(8)
108.5(8)
105.8(8)
108.7(8)
108.0(8)
107.9(8)
106.8(8)
108.0(8)
109.3(8)
106.8(14)
111(2)
108.6(13)
108.2(13)
105.4(13)
88.2(6)
95.5(6)
92.7(5)
88.9(6)
88.0(4)
175.6(5)
175.8(7)
93.3(7)
88.4(6)
87.3(6)
93.2(6)
178.3(5)
86.3(4)
F(5)–Sb–F(4)
F(1)–Sb–F(4)
F(5)–Sb–F(6)
F(1)–Sb–F(6)
F(4)–Sb–F(6)
F(5)–Sb–F(2)
F(1)–Sb–F(2)
F(4)–Sb–F(2)
F(6)–Sb–F(2)
F(5)–Sb–F(3)
F(1)–Sb–F(3)
F(4)–Sb–F(3)
F(6)–Sb–F(3)
F(2)–Sb–F(3)
1.39(2)
1.30(2)
1.30(2)
1.33(2)
1.728(8)
1.790(7)
1.793(7)
1.802(7)
1.812(9)
1.838(7)
Sb–F(1)
Sb–F(4)
Sb–F(6)
Sb–F(2)
92.9(4)
85.3(6)
Sb–F(3)
a Cp1 is the centroid of the C10–C14 cyclopentadienyl ring.
b Cp2 is the centroid of the C15–C19 cyclopentadienyl ring.
c Cp3 is the centroid of the C20–C24 cyclopentadienyl ring.
a Cp1 is the centroid of the C10–C14 cyclopentadienyl ring.
b Cp2 is the centroid of the C15–C19 cyclopentadienyl ring.
c Cp3 is the centroid of the C20–C24 cyclopentadienyl ring.

138
M.S. Morton, J.P. Selegue / Journal of Organometallic Chemistry 578 (1999) 133–143
The carbonyls resonate at 212.6 ppm, in the typical
range of [FeL(CO)2(Cp)]+ compounds [54]. The 1H-
NMR shift of the Cp ligand (l 5.45) falls between
[FeL(CO)2(Cp)]+ cations with very strong p-acceptor
ligands such as L=CO (l 5.84) [55] and CS (l 6.05)
[56], and neutral [FeR(CO)2(Cp)] complexes with
poorly p-accepting ligands such as R=CꢀCMe (l 4.93)
carbonyls do not undergo cis/trans exchange on the
NMR time scale. Solution infrared spectra (CH2Cl2) of
3 and 4 each display two carbonyl stretching absorp-
tions, fewer than predicted for C1 or Cs symmetry [63].
The mass spectra (+FAB-MS) of 3 and 4 show molec-
ular ions at 771 and 1035 amu, respectively, each with
the correct isotope distribution. The fragmentation pat-
terns show the loss of all nine carbonyls.
[57] and R=Pri, Bu (l 4.68) [58,59]. The H-NMR Cp
shift of 1 is similar to [FeL(CO)2(Cp)]+ cations with
strongly delocalized carbene ligands such as [Fe(cyclo-
C3Ph2)(CO)2(Cp)]+ (l 5.55) [60], 7 (l 5.50) [43,44],
[Fe{C(SMe)Me}(CO)2(Cp)]+ (l 5.36) [61], or 9.(l 5.20)
[46,47,62]. Thus, the NMR data are consistent with
weak p-acceptor character of the cyclopropenium lig-
and in 1.
t
1
The 13C-NMR spectrum of [{Re(CO)5}3(m3-
C3)][SbF6] (5) displays a single 13C-NMR resonance at
237.8 ppm for the C3 ring, and a single (presumably cis)
carbonyl resonance at 179.8 ppm. Because of the insta-
bility of 5 in solution and quadrupolar broadening by
185Re and 187Re (both I=5/2), the trans-CO resonance
was not resolved. The spectrum is consistent with free
rotation about the Re–cyclopropenyl bonds, but we
cannot rule out the (unlikely) possibility of rapid cis/
trans carbonyl exchange on the NMR time scale. A
solution infrared spectrum (CH2Cl2) displays three car-
bonyl stretching absorptions, fewer than predicted for
C1 or Cs symmetry [63]. The mass spectrum (+FAB-
MS) shows a molecular ion at 1014 amu with an
isotope distribution consistent with 5. Fragments result-
ing from the loss of up to nine carbonyls are observed.
Spectroscopically, [{Fe(CO)2(Cp)}3{m3-C3(CꢀC)3}]-
A solution infrared spectrum of 1 (CH2Cl2) displays
three carbonyl stretching absorptions, fewer than the
maximum of six absorptions for C1 or Cs symmetry
predicted by group theory [63]. The simple solution
spectrum may be attributed to the generation of effec-
tive C36 symmetry by free rotation about Fe–C bonds
(unlikely on the infrared time scale), or to the overlap
of carbonyl absorptions from several rotamers. A solid-
state infrared spectrum (KBr) displays four carbonyl
stretching absorptions and two weak shoulders, consis-
tent with C1 symmetry.
1
[SbF6] (6) closely resembles 1. The H-NMR spectrum
The mass spectrum (+FAB-MS) shows a molecular
ion at 567 amu with an isotope distribution consistent
with 1. A fragmentation pattern consistent with the loss
of six carbonyls can also be seen in the mass spectrum.
The spectroscopic data for [{Ru(CO)2(Cp)}3(m3-
C3)][SbF6] (2) are incomplete because we were not able
of 6 shows a singlet corresponding to the cyclopentadi-
enyl hydrogens. A solution infrared spectrum (CH2Cl2)
of 6 displays two medium and two weak absorptions in
the w(CO) region. By comparison with 1, we suggest
that the weak absorption at 2071 cm−1 is due to
w(CꢀC). Because we were unable to remove all cy-
clopentadienyl-containing impurities from 6, neither a
satisfactory 13C-NMR spectrum nor an elemental anal-
ysis was obtained. The mass spectrum (+FAB-MS)
shows a molecular ion at 643 amu, 4 amu higher than
the calculated value. We attribute this to commonly
observed hydrogen addition taking place during the
FAB-MS experiment.
1
to completely purify it. The H-NMR spectrum of 2
shows a single [Ru(CO)2(Cp)] environment at room
temperature, consistent with free rotation about the
1
Ru–C bonds in solution on the H-NMR time scale. A
solution infrared spectrum (CH2Cl2) displays two car-
bonyl stretching absorptions, as predicted for C36 sym-
metry [63]. The mass spectrum (+FAB-MS) shows a
molecular ion at 704 amu with an isotope distribution
consistent with 2. A fragmentation pattern consistent
with the loss of six carbonyls can also be seen in the
mass spectrum.
3.4. Attempted reactions of
[{Fe(CO)2(Cp)}3(v3-C3)][SbF6] (1)
Spectroscopic
data
for
[{Mo(CO)3(Cp)}3(m3-
The structure of 1 seemed to indicate that the C3 ring
would be accessible to external reagents. We were dis-
appointed with the lack of reactivity of this molecule
and with our inability to isolate pure products when
reactions did occur.
Cyclopropenium compounds generally react with
small nucleophiles [64–68]. In an attempt to prepare
[{Fe(CO)2(Cp)}3(m3-C3H)], LiBHEt3 (‘super hydride’)
was reacted with 1 in THF. The IR spectrum of the
reaction mixture showed multiple carbonyl stretches
distinct from those of 1; thin-layer chromatography on
silica gel revealed an inseparable mixture of compo-
nents. Methyllithium was added to 1 in THF. Analysis
C3)][SbF6] (3) and [{W(CO)3(Cp)}3(m3-C3)][SbF6] (4) are
similar to those of 1. H- and 13C-NMR spectra show
1
single [M(CO)3(Cp)] (M=Mo or W) environments at
room temperature, consistent with free rotation about
the M–C bonds in solution over the time scale of the
1
NMR experiment. The H-NMR spectra of both 3 and
4 show singlets corresponding to the cyclopentadienyl
hydrogens. The 13C-NMR spectra of both 3 and 4 show
four resonances corresponding to the cyclopentadienyl
carbons, the two magnetically inequivalent carbonyl
carbons and the C3-ring carbons. The observation of
two distinct carbonyl carbon resonances shows that the

M.S. Morton, J.P. Selegue / Journal of Organometallic Chemistry 578 (1999) 133–143
139
of the ethyl-ether-soluble product showed it to contain
4. Conclusions
[FeBr(CO)2(Cp)], probably arising from the LiMe·LiBr
used. Analysis of the ethyl-ether-insoluble residue
showed a high recovery of unreacted 1.
By reacting three equivalents of a metal anion with a
trichlorocyclopropenium salt, a new class of fully
metal-capped cyclopropenium cations can be prepared.
[{Fe(CO)2(Cp)}3(m3-C3)][SbF6] (1), [{Ru(CO)2(Cp)}3(m3-
C3)][SbF6] (2), [{Mo(CO)3(Cp)}3(m3-C3)][SbF6] (3),
[{W(CO)3(Cp)}3(m3-C3)][SbF6] (4), and [{Re(CO)5}3(m3-
C3)][SbF6] (5) have been prepared by this method. By
reacting three equivalents of [Fe(CꢀCSiMe3)(CO)2(Cp)]
with a trichlorocyclopropenium salt, [{Fe(CO)2(Cp)}3-
{m3-C3(CꢀC)3}][SbF6] (6) was also prepared. Spectro-
scopic evidence, and in the case of 1, X-ray crystal
structural determination, showed that these complexes
consist of three equivalent metal centers with ancillary
ligands bonded to a central C3-ring. Unfortunately,
reactivity studies on 1 as a representative of this new
class of compounds failed to lead to new derivatives.
The compound, 1 showed a lack of reactivity with
reductants and nucleophiles. and as a result, no deriva-
tives of the trimetallic cyclopropenium salts were pre-
pared. Similarly, all attempts to use the trimetallic
cyclopropenium salt, 1, to form p-complexes with a
fourth metal center failed.
Reactions of [C3Ph3]+ and other cyclopropenium
ions with transition metals to give h3-cyclopropenyl
complexes and derived species are well-precedented
[69–74]. For example, [Pt(PPh3)2(h2-C2H4)] reacts with
[C3Ph3][PF6] to form [Pt(h3-C3Ph3)(PPh3)2][PF6] [75].
Zerovalent palladium and platinum dba complexes re-
act with C3Ph3Br to give [Pd3(m2-C3Ph3)2Br2], in which
the cyclopropenyl rings have opened up [76].
[Co(CO)4]− reacts with [C3Ph3][BF4] to form the cy-
clobutenonyl complex [Co(CO)3(h3-C3Ph3CO)], which
loses CO upon photolysis to give [Co(CO)3(h3-C3Ph3)]
[73].
However, attempts to prepare M3M%C3 complexes by
adding a fourth metal center to [{Fe(CO)2(Cp)}3(m3-
C3)][SbF6] (1) failed. Reacting four or more equivalents
of K[Fe(CO)2(Cp)] with [C3Cl3][SbF6] gave only 1 and
the unreacted anion, which was converted to
[Fe2(CO)4(Cp)2] during the workup. Reacting
K[Fe(CO)2(Cp)] with pre-formed
1
also failed.
[Co(CO)4]− was reacted with 1 in CH3CN, but the
product was completely insoluble. Reactions of
[Pd(dba)2] with 1 in the presence of LiBr resulted in the
deposition of Pd metal and recovery of 1.
The failure of [{Fe(CO)2(Cp)}3(m3-C3)]+ to react
with larger nucleophiles may be caused by steric hin-
drance created by the rotation of the metal centers. The
C3 ligand is apparently sufficiently protected by the
metal centers so that external reagents cannot approach
the ring.
Iron-carbon bonds can usually be cleaved with halo-
gens [42]. Whereas 1 did not react with I2 in refluxing
CH2Cl2, reactions with Br2 produced an intractable
black precipitate along with traces of [FeBr(CO)2(Cp)].
5. Experimental
All reactions were carried out under a dry, nitrogen
atmosphere using standard Schlenk techniques or in a
Vacuum Atmospheres HE-493 glove box. Solvents were
dried using appropriate drying agents, freshly distilled,
and collected under nitrogen before use. (CD3)2CO,
CDCl3, C6D6, and CD2Cl2 were obtained in sealed
ampoules from Cambridge Isotope Laboratories and
were used without further purification. [Fe2(CO)4(Cp)2]
[80], [Ru2(CO)4(Cp)2] [81], [M2(CO)6(Cp)2] (M=W,
Mo) [82], [Fe(CꢀCSiMe3)(CO)2(Cp)] [25], dichloro-
cyclopropenone [77], [Pd(dba)2] [83] and NaK2.8 [24]
were prepared according to the cited procedures. Tetra-
chlorocyclopropene, bis(trimethylsilyl)acetylene and
Me3NO (Aldrich), AgSbF6 (Atochem), [Re2(CO)10] and
Neither
C3X)][SbF6] (X=Br or I).
reaction
produced
[{Fe(CO)2(Cp)}2(m2-
[{Fe(CO)2(Cp)}3(m3-C3)][SbF6] did not react with
Me3NO in refluxing CH2Cl2. IR analysis of the reaction
mixture showed only unreacted starting materials. The
reaction of K[Fe(CO)2(Cp)] with dichlorocyclo-
propenone [77] is an alternative approach to a possible
oxidative Fe–C cleavage product. Unfortunately, the
only characterizable product of that reaction was
[Fe2(CO)4(Cp)2].
Reduction of triphenylcyclopropenium cation gives
bis(triphenylcyclopropenyl), which thermally rearranges
into hexaphenylbenzene. A similar reduction of triferro-
cenylcyclopropenium cation gives less well character-
ized Fe6C6 species [78,79]. The reduction of
[{Fe(CO)2(Cp)}3(m3-C3)][Cl] with sodium amalgam was
studied as an approach to M6C6 complexes. Evidently a
stronger reducing agent is needed, because only the
unreacted starting material was recovered.
1
[Co2(CO)8] (Pressure) were used as received. H-NMR
spectra (200 MHz) were recorded on a Varian Gemini
200 NMR spectrometer, and 13C-NMR spectra (100
MHz) were recorded on a Varian VXR-400 NMR
spectrometer. 1H- and 13C-NMR spectra were refer-
enced to the solvent peak. IR data were recorded on a
Mattson Galaxy Series 5000 FT-IR spectrometer and
are reported in cm−1. Mass spectra were recorded on a
Kratos Concept 1H, double-focusing, EI/FAB Mass
Spectrometer. Thermal analysis was performed on a
TA 2950 high-resolution thermogravimetric analyzer.
Chemical analyses were performed by the Microanalyti-
cal Services Laboratory, University of Illinois, Urbana.

140
M.S. Morton, J.P. Selegue / Journal of Organometallic Chemistry 578 (1999) 133–143
5.1. Preparation of [{Fe(CO)2(Cp)}3(v3-C3)][SbF6] (1)
with H2O (10 ml) to remove NH4Cl and unreacted
NH4PF6. The CH2Cl2 layer was separated and evapo-
rated in vacuo. Repetitive washing with ethyl ether
followed by recrystallization from CH2Cl2–ethyl ether
led to a brown powder of [{Fe(CO)2(Cp)}3(m3-C3)][PF6]
(230 mg, 91%). M.p. (dec.\400°C). 1H-NMR (200
To Na/Hg (50 mg, 2.2 mmol in 20 g, 100 mmol Hg)
was added [Fe2(CO)4(Cp)2] (250 mg, 0.706 mmol) in
THF (20 ml). The mixture was stirred for 0.5 h at room
temperature. The resulting yellow solution was cooled
to −78°C. To AgSbF6 (144 mg, 0.419 mmol) was
added C3Cl4 (72 mg, 0.41 mmol) in THF (20 ml) cooled
to −78°C. The mixture was stirred for 0.5 h, resulting
in a milky-white suspension. The Na[Fe(CO)2(Cp)] so-
lution was slowly added to the [C3Cl3][SbF6] suspension
and allowed to stir for 15 h while warming to ambient
temperature. The resulting dark brown solution was
evaporated in vacuo and repeatedly washed with ethyl
ether to remove the [Fe2(CO)4(Cp)2]. The remaining
brown powder was dissolved in dichloromethane (30
ml) and filtered. After removal of the solvent in vacuo,
[{Fe(CO)2(Cp)}3(m3-C3)][SbF6] (1, 244 mg, 65%) was
collected. Recrystallization from CH2Cl2–ethyl ether
led to dark amber crystals. M.p. (dec\400°C). 1H-
NMR (200 MHz, CD2Cl2) lH 5.18 (s, Cp), (C3D6O) lH
5.45 (s, Cp). 13C-NMR (100 MHz, CD2Cl2) lC 86.7 (s,
MHz, CD2Cl2) lH 5.18 (s, Cp). MS (+FAB) 567 amu
12
(M+), Calc. 567 amu for
C
24
1H15 56Fe3 16O6. IR
(CH2Cl2) w(CO) 2052 m, 2040 m, 1997 m.
5.4. Preparation of [{Ru(CO)2(Cp)}3(v3-C3)][SbF6] (2)
To [Ru2(CO)4(Cp)2] (779 mg, 1.75 mmol) was added
NaK2.8 (0.21 ml, 0.50 mmol) in THF (20 ml). The
mixture was stirred for 1.5 h at room temperature,
resulting in a dark yellow–brown solution which was
slowly added at −78°C to a [C3Cl3][SbF6] suspension
prepared from AgSbF6 (403 mg, 1.20 mmol) and C3Cl4
(0.15 ml, 1.2 mmol) in THF (20 ml). The mixture was
allowed to stir for 15 h while warming to ambient
temperature. The resulting dark brown solution was
evaporated in vacuo and repeatedly washed with ethyl
ether to remove [Ru2(CO)4(Cp)2]. The remaining brown
powder was dissolved in dichloromethane (30 ml) and
filtered. After removal of the solvent in vacuo, the
brown powder was collected. Recrystallization from
Cp), 212.6 (s, CO), 256.6 (s, C3). MS (+FAB) 567 amu
12
(M+), Calc. 567 amu for
C
24
1H1556Fe316O6. IR
(CH2Cl2) w(CO) 2052 m, 2040 m, 1997 m. Anal. Calc.
(Found) for C24H15F6Fe3O6Sb: C, 35.91 (31.26), H,
1.88 (2.10).
CH2Cl2–ethyl ether led to
a brown powder of
[{Ru(CO)2(Cp)}3(m3-C3)][SbF6]
(2).
M.p.
(dec.
5.2. Preparation of [{Fe(CO)2(Cp)}3(v3-C3)][Cl]
\400°C). 1H-NMR (200 MHz, CD2Cl2) lH 5.32 (s,
Cp). MS (+FAB) 704 amu (M+), Calc. 702 amu for
12
To Na/Hg (120 mg, 5.22 mmol in 29.8 g, 0.148 mol
Hg) was added [Fe2(CO)4(Cp)2] (509 mg, 1.44 mmol) in
THF (20 ml). The mixture was stirred for 0.5 h at room
temperature. The resulting yellow solution was slowly
added at −78°C to tetrachlorocyclopropene (0.090 ml,
0.74 mmol) in THF (5 ml). The mixture was stirred for
16 h while warming to room temperature, resulting in a
dark brown suspension. Evaporation of the solvent in
vacuo followed by repetitive washing with ethyl ether to
remove [Fe2(CO)4(Cp)2] and other neutral impurities
gave a dark brown powder which was dissolved in
CH2Cl2 (30 ml), filtered and evaporated to dryness.
Recrystallization from CH2Cl2–ethyl ether led to a
brown powder of [{Fe(CO)2(Cp)}3(m3-C3)][Cl] (214 mg,
C
24
1H1516O6101Ru3. IR (CH2Cl2) w(CO), 2055 m, 2004
m.
5.5. Preparation of [{Mo(CO)3(Cp)}3(v3-C3)][SbF6] (3)
To [Mo2(CO)6(Cp)2] (860 mg, 1.7 mmol) was added
NaK2.8 (0.30 ml, 0.50 mmol) in THF (20 ml). The
mixture was stirred for 15 h, resulting in a dark rose
solution which was slowly added at −78°C to a
[C3Cl3][SbF6] suspension prepared from AgSbF6 (406
mg, 1.18 mmol) and C3Cl4 (0.15 ml, 1.2 mmol) in THF
(10 ml). The mixture was allowed to stir for 15 h while
warming to ambient temperature. The resulting brown
solution was evaporated in vacuo and repeatedly
washed with ethyl ether to remove [Mo2(CO)6(Cp)2]
and other neutral impurities. The remaining brown
powder was dissolved in dichloromethane (30 ml) and
filtered. Recrystallization from CH2Cl2–ethyl ether led
to a brown powder of [{Mo(CO)3(Cp)}3(m3-C3)][SbF6]
1
48%). H-NMR (200 MHz, C3D6O) lH 5.45 (s, Cp). IR
(CH2Cl2) w(CO) 2052 m, 2040 m, 1997 m.
5.3. Preparation of [{Fe(CO)2(Cp)}3(v3-C3)][PF6]
1
To [{Fe(CO)2(Cp)}3(m3-C3)][Cl] (214 mg, 0.355
mmol) in MeOH (25 ml) was added NH4PF6 (134 mg,
0.822 mmol) in H2O (0.50 ml). The suspension was
stirred for 0.5 h at room temperature, resulting in a
dark yellow–orange suspension. Evaporation of the
solvent in vacuo led to a dark brown powder. The
powder was dissolved in CH2Cl2 (40 ml) and extracted
(3, 180 mg, 15%). M.p. (dec.)\ 400°C. H-NMR (200
MHz, C3D6O) lH 6.12 (s, Cp). 13C-NMR (400 MHz,
C3D6O) lC 95.1 (s, Cp), 224.8 (s, CO), 231.1 (s, CO),
251.3 (s, C3). MS (+FAB) 771 amu (M+), Calc. 771
12
amu for
C
27
1H1596Mo316O9. IR (CH2Cl2) w(CO) 2046
m, 1977 m. Anal. Calc. (Found) for C27H15F6Mo3O9Sb:
C, 32.31 (31.32), H, 1.50 (1.61).

M.S. Morton, J.P. Selegue / Journal of Organometallic Chemistry 578 (1999) 133–143
141
5.6. Preparation of [{W(CO)3(Cp)}3(v3-C3)][SbF6] (4)
AgSbF6 (56 mg, 0.16 mmol) and C3Cl4 (0.017 ml, 0.14
mmol) in THF (20 ml). The mixture was allowed to stir
for 20 h while warming to ambient temperature. The
resulting dark brown solution was evaporated in vacuo
and repeatedly washed with ethyl ether to remove unre-
acted [Fe(CꢀCSiMe3)(CO)2(Cp)]. The remaining brown
powder was dissolved in dichloromethane (30 ml) and
filtered. After removal of the solvent in vacuo, the
brown powder was collected. Recrystallization from
To [W2(CO)6(Cp)2] (590 mg, 0.88 mmol) was added
NaK2.8 (0.20 ml, 0.33 mmol) in THF (40 ml). The
mixture was stirred for 15 h, resulting in a brown
solution which was slowly added at −78°C to a
[C3Cl3][SbF6] suspension prepared from AgSbF6 (203
mg, 0.59 mmol) and C3Cl4 (0.070 ml, 0.6 mmol) in
THF (20 ml). The mixture was allowed to stir for 15 h
while warming to ambient temperature. The resulting
dark brown solution was evaporated in vacuo and
repeatedly washed with ethyl ether to remove
[W2(CO)6(Cp)2] and other neutral impurities. The re-
maining brown powder was dissolved in 30 ml
dichloromethane and filtered. Recrystallization from
CH2Cl2–ethyl ether led to brown powder of
[{W(CO)3(Cp)}3(m3-C3)][SbF6] (4, 0.30 g, 40%). M.p.
CH2Cl2–ethyl ether led to
a brown powder of
[{Fe(CO)2(Cp)}3{m3-C3(CꢀC)3}][SbF6] (6, 59 mg, 53%).
1
M.p. (dec.)\400°C. H-NMR (200 MHz, CD2Cl2) lH
5.22 (s, Cp). MS (+FAB): 643 amu (M+ +4), Calc.
12
639 for
C
30
1H1556Fe316O6. IR (CH2Cl2) w(CO, CꢀC)
2071 w, 2053 m, 2007 m, 1976 w.
5.9. Thermogra6imetric analysis of
[{Fe(CO)2(Cp)}3(v3-C3)][SbF6] (1)
1
(dec.)\400°C. H-NMR (200 MHz, CD2Cl2) lH 6.01
(s, Cp). 13C-NMR (400 MHz, CD2Cl2) lC 93.1 (s, Cp),
212.8 (s, CO), 217.7 (s, CO), 224.4 (s, C3). MS (+FAB)
A sample of 1 (6.9 mg, 0.0086 mmol) on a platinum
pan was heated from 50 to 1000°C using a high-resolu-
tion temperature ramp. The sample lost 27.01% mass at
220°C, corresponding to loss of SbF5 (Calc. 27.02%);
19.44% between 220 and 800°C, corresponding to the
loss of nine COs (Calc. 20.92%); and 18.33% between
800 and 1000°C corresponding to the loss of cyclopen-
tadienyl fragments (calc. 24.28%). The residual mass
was 35.22% (Calc. for Fe3C3F 27.78%)
1035
amu
(M+),
Calc.
1035
amu
for
12
C
27
1H1516O9184W3. IR (CH2Cl2) w(CO) 2041 m, 1996
m; Anal. Calc. (Found) for C27H15F6O9SbW3: C, 25.52
(21.85), H, 1.19 (0.58).
5.7. Preparation of [{Re(CO)5}3(v3-C3)][SbF6] (5)
To Na/Hg (96 mg, 4.17 mmol in 5 ml, 0.3 mol Hg)
was added [Re2(CO)10] (502 mg, 0.770 mmol) in THF
(20 ml). The mixture was stirred for 1 h at room
temperature. The resulting orange solution was slowly
added at −78°C to a [C3Cl3][SbF6] suspension pre-
pared from AgSbF6 (179 mg, 0.520 mmol) and C3Cl4
(0.065 ml, 0.54 mmol) in THF (10 ml). The mixture was
allowed to stir for 15 h while warming to ambient
temperature. The resulting orange solution was evapo-
rated in vacuo and repeatedly washed with ethyl ether
to remove neutral rhenium-containing species. The re-
maining grayish–brown power was dissolved in 30 ml
dichloromethane and filtered. After removal of the
solvent in vacuo, a brown powder was recovered. Re-
crystallization from CH2Cl2–ethyl ether led to a dark
brown powder of [{Re(CO)5}3(m3-C3)][SbF6] (5, 0.218 g,
34%). In solution, the compound decomposes into in-
tractable materials in about 5 h. M.p. (dec.)\400°C.
13C-NMR (400 MHz, CD2Cl2) lC 179.81 (s, Re-CO),
237.83 (s, C3). MS (+FAB) 1014 amu (M+), Calc.
5.10. Crystal structure determination of
[{Fe(CO)2(Cp)}3(v3-C3)][SbF6] (1)
Crystals of 1 suitable for X-ray diffraction were
obtained by slow diffusion of a layer of Et2O onto a
concentrated CH2Cl2 solution of 1 at room tempera-
ture. The crystal was coated with epoxy and mounted
on a glass fiber, nearly aligned along the long axis of
the crystal. The structure was solved by using SHELXL-
PC [84] and refined with SHELXL93 [85]. Crystal proper-
ties and details of X-ray data collection, solution and
refinement for 1 are listed in Table 1.
6. Supplementary material
12
16
18
1014 amu for
C
O
186Re3. IR (CH2Cl2) w(CO)
15
Crystallographic data for the structural analysis has
been deposited with the Cambridge Crystallographic
Data Centre, CCDC-No. ZAJRAD for [{Fe(CO)2-
(Cp)}3(m3-C3)][SbF6] (1).
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (Fax: +44-1223-336-033;
e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
2040 m, 1982 m, 1914 m.
5.8. Preparation of [{Fe(CO)2(Cp)}3{v3-C3(CꢀC)3}]-
[SbF6] (6)
A solution of [Fe(CꢀCSiMe3)(CO)2(Cp)] (104 mg,
0.38 mmol) in THF (10 ml) was slowly added at
−78°C to a [C3Cl3][SbF6] suspension prepared from

142
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We thank the Kentucky National Science Founda-
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Department of Energy (DE-FG05-85ER13432 and EP-
SCOR Traineeship DE-FG02-91ER75657) for financial
support, the University of Kentucky Major Research
Instrumentation Bond Program (IDc 7E-8E48-25) for
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8
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