Syntheses, properties, and X-ray crystal structures of iron and ruthenium compounds with the η5-C5Me4CF3 ligand. Compounds of the type [(η5-C5Me4CF 3)M(μ-CO)(CO)]2 (M = Fe, Ru)

Article abstract of DOI:10.1021/om961069b

(Trifluoromethyl)tetramethylcyclopentadiene, HC₅Me₄CF₃ (Cp?H), reacts with Ru₃(CO)₁₂ in refluxing n-decane to produce [(η⁵-C₅Me₄CF ₃)Ru(μ-CO)(CO)]₂ (1). In chlorinated hydrocarbon solutions, 1 reacts with the solvents in the presence of visible light to produce [(η⁵-C₅Me₄CF₃)Ru(CO) ₂(Cl)] (3a). Compound 1 reacts with iodine in refluxing CH₂Cl₂ to produce [(η⁵-C₅Me₄CF₃)Ru(CO) ₂(I)] (3b). The X-ray crystal structure of compound 3b is presented. Compound 3b reacts with triphenylphosphine in refluxing ethanol to produce [(η⁵-C₅Me₄-CF₃)Ru(CO)(PPh ₃)(I)] (4). The HC₅Me₄CF₃ ligand reacts with Fe(CO)₅ in refluxing heptane to produce [(η⁴-HC₅Me₄CF₃)Fe(CO) ₃] (5). Compound 5 represents a new mode of coordination (η⁴) for HC₅Me₄CF₃. The spectroscopic properties of compound 1 and its previously reported iron analog, [(η⁵-C₅Me₄CF ₃)Fe(μ-CO)(CO)]₂ (2), are compared with those of their η⁵-C₅H₅ and η⁵-C₅Me₅ parent analogs of the type [(η⁵-C₅R₅)M(μ-CO)(CO)]₂ (M = Fe, Ru). Compounds 1 and 2 were characterized by single-crystal X-ray crystallography and found to be in the trans configuration with respect to the η⁵-C₅Me₄CF₃ rings. Overall, the spectroscopic and X-ray structural data of 1 and 2 support the previous conclusions that the η⁵-C₅Me₄CF₃ ligand is electronically equivalent to η⁵-C₅H₅ and sterically equivalent to η⁵-C₅Me₅. Compounds 1 and 3b represent important synthons for subsequent ruthenium chemistry with the η⁵-C₅Me₄CF₃ ligand.

Full text of DOI:10.1021/om961069b

Organometallics 1997, 16, 1595-1603
1595
Syn th eses, P r op er ties, a n d X-r a y Cr ysta l Str u ctu r es of
Ir on a n d Ru th en iu m Com p ou n d s w ith th e η5-C5Me4CF 3
Liga n d . Com p ou n d s of th e Typ e
[(η5-C5Me4CF 3)M(µ-CO)(CO)]2 (M ) F e, Ru )
Luis P. Barthel-Rosa,† J ohn R. Sowa, J r.,*,‡ Paul G. Gassman,§ J ean Fischer,|
Bayrn M. McCarty, Seth L. Goldsmith, Michael T. Gibson, and
J ohn H. Nelson*,†
Department of Chemistry/ 216, University of NevadasReno, Reno, Nevada 89557-0020,
Department of Chemistry, Kolthoff Hall, University of Minnesota,
Minneapolis, Minnesota 55455, and Laboratoire de Cristallochimie (URA 424 du CNRS),
Universite´ Louis Pasteur, 4 rue Blaise Pascal, F-67070 Strasbourg Cedex, France
Received December 17, 1996X
(Trifluoromethyl)tetramethylcyclopentadiene, ΗC5Me4CF3 (CpqH), reacts with Ru3(CO)12
in refluxing n-decane to produce [(η5-C5Me4CF3)Ru(µ-CO)(CO)]2 (1). In chlorinated hydro-
carbon solutions, 1 reacts with the solvents in the presence of visible light to produce [(η5-
C5Me4CF3)Ru(CO)2(Cl)] (3a ). Compound 1 reacts with iodine in refluxing CH2Cl2 to produce
[(η5-C5Me4CF3)Ru(CO)2(I)] (3b). The X-ray crystal structure of compound 3b is presented.
Compound 3b reacts with triphenylphosphine in refluxing ethanol to produce [(η5-C5Me4-
CF3)Ru(CO)(PPh3)(I)] (4). The HC5Me4CF3 ligand reacts with Fe(CO)5 in refluxing heptane
to produce [(η4-HC5Me4CF3)Fe(CO)3] (5). Compound 5 represents a new mode of coordination
(η4) for HC5Me4CF3. The spectroscopic properties of compound 1 and its previously reported
iron analog, [(η5-C5Me4CF3)Fe(µ-CO)(CO)]2 (2), are compared with those of their η5-C5H5
and η5-C5Me5 “parent” analogs of the type [(η5-C5R5)M(µ-CO)(CO)]2 (M ) Fe, Ru). Compounds
1 and 2 were characterized by single-crystal X-ray crystallography and found to be in the
trans configuration with respect to the η5-C5Me4CF3 rings. Overall, the spectroscopic and
X-ray structural data of 1 and 2 support the previous conclusions that the η5-C5Me4CF3
ligand is electronically equivalent to η5-C5H5 and sterically equivalent to η5-C5Me5.
Compounds 1 and 3b represent important synthons for subsequent ruthenium chemistry
with the η5-C5Me4CF3 ligand.
In tr od u ction
discovered (trifluoromethyl)tetramethylcyclopentadienyl
ligand2ab (η5-C5Me4CF3) exhibits electronic properties
equivalent to those of η5-C5H5 but retains the steric
equivalence of η5-C5Me5.2 Besides being convenient
starting materials, compounds of the type [(η5-C5R5)M-
Cyclopentadienyl (η5-C5H5) and pentamethylcyclo-
pentadienyl (η5-C5Me5) ligands represent two of the
most widely used ancillary ligands for transition-metal
organometallic compounds. The substitution of η5-C5-
Me5 for η5-C5H5 in organometallic compounds usually
results in major changes in both the physical and
chemical properties of their respective derivatives.1
However, this substitution simultaneously alters both
the steric and electronic environment around the tran-
sition-metal center. Unfortunately, the dissection of
steric and electronic effects of the η5-C5Me5 ligand has
not been accomplished. Alternatively, the recently
(µ-CO)(CO)]2 (where M ) Fe,3ab Ru;3c,d R ) H,3a,c Me3b,d
)
and their derivatives represent some of the more widely
studied iron and ruthenium organometallic systems.
Therefore, entry of the η5-C5Me4CF3 ligand into orga-
nometallic iron and ruthenium chemistry is realized by
the syntheses of [(η5-C5Me4CF3)M(µ-CO)(CO)]2 (M )
Fe,2b,c Ru).
Herein we report the syntheses, properties, and X-ray
crystal structures of [(η5-C5Me4CF3)M(µ-CO)(CO)]2 (M
) Ru (1), Fe2b,c (2)) and compare these new compounds
with their parent iron and ruthenium compounds. In
† University of NevadasReno.
‡ Current address: Department of Chemistry, Seton Hall University,
South Orange, NJ 07079.
§ Deceased April 21, 1993.
| Universite´ Louis Pasteur.
NSF-REU Summer Undergraduate Participant.
(2) (a) Gassman, P. G.; Mickelson, J . W.; Sowa, J . R., J r. Inorg.
Synth. 1997, 31, 232. (b) Gassman, P. G.; Mickelson, J . W.; Sowa, J .
R., J r. J . Am. Chem. Soc. 1992, 114, 6942. (c) Gassman, P. G.; Sowa,
J . R., J r.; Hill, M. G.; Mann, K. R. Organometallics 1995, 14, 4879.
(3) (a) Fehlhammer, W. P.; Stolzenberg H. In Comprehensive Or-
ganometallic Chemistry; Wilkinson, G.; Stone, F. G. A.; Abel, E. W.,
Eds.; Pergamon: New York, 1982, Vol. 4; pp 514-585. (b) Fagan, P.
J . In Comprehensive Organometallic Chemistry II; Abel, E. W., Stone,
F. G. A., Wilkinson, G., Shriver, D. F., Bruce, M. I., Eds.; Pergamon:
New York, 1995; Vol. 7, pp 231-251. (c) Bennett, M. A.; Bruce, M. I.;
Matheson, T. W. In Comprehensive Organometallic Chemistry Wilkin-
son, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: New York, 1982;
Vol. 4; pp 823-839. (d) Haines, R. J . In Comprehensive Organometallic
Chemistry II; Abel, E. W., Stone, F. G. A., Wilkinson, G., Shriver, D.
F., Bruce, M. I., Eds.; Pergamon: New York, 1995; Vol. 7, pp 655-
674.
X Abstract published in Advance ACS Abstracts, March 15, 1997.
(1) For selected leading references see: (a) Cramer, R.; Seiwell, L.
P. J . Organomet. Chem. 1975, 92, 245. (b) King, R. B. Coord. Chem.
Rev. 1976, 20, 155. (c) Manriquez, J . M.; Fagan, P. J .; Marks, T. J . J .
Am. Chem. Soc. 1978, 100, 3939. (d) Maitlis, P. M. Acc. Chem. Res.
1978, 11, 301. (e) McLain, S. J .; Sancho, J .; Schrock, R. R. J . Am. Chem.
Soc. 1979, 101, 5451. (f) Freyberg, D. P.; Robbins, J . L.; Raymond, K.
N.; Smart, J . C. J . Am. Chem. Soc. 1979, 101, 892. (g) Wolczanski, P.
T.; Bercaw, J . E. Acc. Chem. Res. 1980, 13, 121. (h) Sikora, D. J .;
Rausch, M. D.; Rogers, R. D.; Atwood, J . L. J . Am. Chem. Soc. 1981,
103, 1265. (i) Rerek, M. E.; Basolo, F. J . Am. Chem. Soc. 1984, 106,
5908. (j) J eske, G.; Lauke, H.; Mauermann, H.; Swepston, P. N.;
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Davies, S. G.; McNally, J . P.; Smallridge, A. J . Adv. Organomet. Chem.
1990, 30, 1-73.
S0276-7333(96)01069-2 CCC: $14.00 © 1997 American Chemical Society

1596 Organometallics, Vol. 16, No. 8, 1997
Barthel-Rosa et al.
Ta ble 1. In fr a r ed Ca r bon yl Str etch in g
F r equ en cies of [(η5-Cp ′)M(µ-CO)(CO)]2 (η5-Cp ′ )
η5-C5H5, η5-C5Me4CF 3, η5-C5Me5; M ) F e, Ru )
Com p lexesa
Attempts to improve the yield of 1 using norbornene
as a hydrogen acceptor4,5 in the reaction of HC5Me4CF3
with Ru3(CO)12 were unsuccessful. In contrast, our
group5 and Paquette and co-workers4 have successfully
used this approach for the preparation of other Fe and
Ru dicarbonyl cyclopentadienyl complexes. In this case,
reaction of HC5Me4CF3 and Ru3(CO)12 resulted in the
formation of reasonable amounts of the triply bridging
alkene adduct [(µ-H)2Ru3(CO)9(µ3-η1:η2:η1-C7H8)] (A),
compd
ν(CO), cm-1
ref
trans-[(η5-C5H5)Ru(µ-CO)(CO)]2
1968, 1768b
7a,b
this work
8
2c
2c
2c
[(η5-C5Me4CF3)Ru(µ-CO)(CO)]2 (1) 1958, 1776
trans-[(η5-C5Me5)Ru(µ-CO)(CO)]2
trans-[(η5-C5H5)Fe(µ-CO)(CO)]2
[(η5-C5Me4CF3)Fe(µ-CO)(CO)]2 (2)
trans-[(η5-C5Me5)Fe(µ-CO)(CO)]2
1925, 1744
1955, 1773
1952, 1776
1922, 1747
1
which was characterized by H, 13C, and 13C{1H} NMR
spectroscopy and by X-ray crystallography. This com-
pound was also recently reported by J ohnson, Braga,
and co-workers;6 however we include the complete
characterization data for this compound in the Experi-
mental Section.
a
b
CH2Cl2 solvent. CHCl3 solvent.
addition, we report the syntheses of half-sandwich
derivatives [(η5-C5Me4CF3)Ru(CO)2(I)] (3b), [(η5-C5Me4-
CF3)Ru(CO)(PPh3)(I)] (4), and [(η4-HC5Me4CF3)Fe(CO)3]
(5). The crystal structure of 3b is also presented.
Compound 5 represents a new mode of coordination for
ΗC5Me4CF3.
Analysis of the data in Table 1 shows that the ν(CO)
stretching frequencies for 1 and 2 are similar to those
of their η5-C5H5 analogs. In contrast, the IR stretching
frequencies of the ruthenium and iron η5-C5Me5 analogs
are significantly different (>30 cm-1) compared to those
of 1 and 2. Other physical measurements, including
X-ray photoelectron spectroscopy (XPS)2b and elec-
trochemical2c data, reported for compound 2 reflect the
same trends. These comparisons indicate that the η5-
C5H5 and η5-C5Me4CF3 ligands are electronically simi-
lar.
Resu lts a n d Discu ssion
P r ep a r a tion a n d P r op er ties of [(η5-C5Me4CF 3)M-
(µ-CO)(CO)]2 (M ) F e, Ru ). Treatment of Ru3(CO)12
with 3 equiv of HC5Me4CF3 in refluxing n-decane
results in the formation of the ruthenium carbonyl
dimer [(η5-C5Me4CF3)Ru(µ-CO)(CO)]2 (1) in 84% yield
(eq 1). Compound 1 is readily soluble in halocarbon
2a
The IR spectral data for 1 and 2 (Table 1) show that
both compounds exist as the trans isomers, containing
bridging carbonyl ligands in solution. The sterically
similar compounds [(η5-C5Me5)Ru(µ-CO)(CO)]2,9 [(η5-C5-
11
Me5)Fe(µ-CO)(CO)]2,10 and (η5-C5Me4Et)Ru(µ-CO)(CO)]2
all exist in the thermodynamically preferred trans
configurations in the solid and solution states, and the
last species does not isomerize to the cis configuration
in solution, presumably due to unfavorable steric
interactions.3c,11 Moreover, compounds 1 and 2 crystal-
lize as the trans isomers (vide infra). This contrasts
with the behavior of [(η5-C5H5)M(µ-CO)(CO)]2 (M ) Fe,
Ru), which have been shown to exist as mixtures of all
four possible isomers in solution: cis and trans, with
bridging and nonbridging CO ligands.3a,c,4b Only two
ν(CO) bands are observed for both 1 and 2, whereas the
η5-C5H5 analogs have complex IR spectra in the carbonyl
regions with multiple bands. However, the room-
temperature 13C{1H} NMR spectra of both 1 and 2 each
show only one averaged CO resonance at 224 and 240
ppm, respectively. The 13C{1H} NMR data of 1 and 2
are similar to those of the reported iron and ruthenium
η5-C5H5 analogs.12 The ruthenium compound [(η5-
C5H5)Ru(µ-13CO)(13CO)]2 showed one average CO reso-
nance at ∼225 ppm12a (in carbon disulfide) while the
iron analog showed one CO resonance at ∼240 ppm (in
solvents, but such solutions must be protected from
visible light since a secondary reaction occurs (vide
infra). The 1H NMR spectrum of 1 in benzene-d6 shows
a quartet at 1.84 ppm (5J HF ) 0.97 Hz) for the methyl
hydrogens in the 2,5-position next to the CF3 group and
a singlet at 1.32 ppm for the methyl hydrogens in the
3,4-position (see Experimental Section for numbering
scheme). The most notable features of the 13C{1H}
NMR spectrum in benzene-d6 include the single “aver-
aged” resonance (vide infra) for the CO ligands at 224.46
ppm and the quartet at 125.69 ppm (1J CF ) 271.1 Hz)
1
for the CF3 carbon. The H NMR data for 1 compares
with those for the iron analog [(η5-C5Me4CF3)Fe(µ-CO)-
(4) Paquette, L. A.; McKinney, J . A.; McLaughlin, M. L.; Rheingold,
A. L. Tetrahedron. Lett. 1986, 27, 5599.
(CO)]2 (2),2c which shows a quartet at 1.84 ppm (5J HF
)
1.2 Hz) and a singlet at 1.59 ppm (in chloroform-d). The
13C{1H} NMR spectrum of 2 in chloroform-d shows a
similar broad, averaged resonance for the CO ligands
at 240.8 ppm, while the resonance for the CF3 group
appears as a quartet at 124.9 ppm (1J CF ) 272 Hz). The
IR spectrum of 1 in dichloromethane shows ν(CO) bands
at 1958 and 1776 cm-1 for the terminal and bridging
carbonyls, respectively, while in Nujol the ν(CO) bands
appear at 1955 and 1767 cm-1 with 13CO satellites at
1918 and 1738 cm-1. The IR data for both 1 and 2 are
summarized in Table 1 along with those of the η5-C5H5
and η5-C5Me5 parent analogs.
(5) Bhaduri, D.; Nelson, J . H.; Wang, T.; J acobson, R. A. Organo-
metallics 1994, 13, 2291.
(6) Brown, D. B.; Cripps, M.; J ohnson, B. F. G.; Martin, C. M.; Braga,
D.; Grepioni, F. J . Chem. Soc., Chem. Commun. 1996, 1425.
(7) (a) McArdle, P.; Manning, A. R. J . Chem. Soc. A 1970, 2128. (b)
For a thorough discussion on the properties of [(η5-C5H5)Ru(µ-CO)-
(CO)]2, see: Seddon, E. A.; Seddon, K. R. In The Chemistry of
Ruthenium; Clark, R. J . H., Ed.; Elsevier: New York, 1984; pp 909-
915.
(8) King, R. B.; Iqbal, M. Z.; King, A. D., J r. J . Organomet. Chem.
1979, 171, 53.
(9) Steiner, A.; Gornitzka, H.; Stalke, D.; Edelmann, F. T. J .
Organomet. Chem. 1992, 431, C21.
(10) Teller, R. G.; Williams, J . M. Inorg. Chem. 1980, 19, 2770.
(11) Bailey, N. A.; Radford, S. L.; Sanderson, J . A.; Tabatabaian,
K.; White, C.; Worthington, J . M. J . Organomet. Chem. 1978, 154, 343.

Fe and Ru Complexes with the η5-C5Me4CF3 Ligand
Organometallics, Vol. 16, No. 8, 1997 1597
dichloromethane-d2).12c A similar phenomenon was also
observed for [PCpRu(µ-CO)(CO)]2,5 which also showed
one averaged CO resonance at 224.5 ppm. Therefore,
the 13C NMR data suggest that compounds 1 and 2 are
dynamic in solution and undergo a bridged-to-non-
bridged equilibrium12 that is rapid on the NMR time
scale.
Compound 1 is a red crystalline compound that is air-
stable indefinitely in the solid state. However, solutions
of 1 are photosensitive, even in room lighting, and must
be handled accordingly. If a solution of 1 in chloroform
is exposed to room lighting, it will completely convert
to the dicarbonyl chloride compound [(η5-C5Me4CF3)Ru-
(CO)2(Cl)] (3a ) in less than 24 h. The conversion of 1
into 3a can be monitored by IR spectroscopy (dichlo-
romethane), as the ν(CO) bands for 1 disappear and new
bands for 3a appear at 2063 and 2014 cm-1, which
indicates the presence of only terminal carbonyl ligands.
This reaction is slower in dichloromethane than in
chloroform and dramatically slower if the halocarbon
solutions are protected from light. Solutions of 1 in
benzene-d6 also show minimal decomposition if unpro-
tected from light, but the decomposition products re-
main unidentified. The ruthenium peralkylated cyclo-
pentadienyl carbonyl dimer [(η5-C5Me4Et)Ru(µ-CO)-
(CO)]2 displays the exact same behavior as observed for
1, gradually reacting in chlorocarbons to form [(η5-C5-
Me4Et)Ru(CO)2(Cl)].11 Similar to 1, the reactions of [(η5-
C5Me4Et)Ru(µ-CO)(CO)]2 in chloroform were accelerated
by visible light and were slower in dichloromethane
than in chloroform solutions.
pound 2 is stable in halocarbon solutions and does not
exhibit any sensitivity to visible light. It is noteworthy
that compound 2 was previously prepared using a rather
circuitous method as detailed in reference 13.
X-r a y Cr ysta l Str u ctu r es of 1 a n d 2. The molec-
ular structures of 1 and 2 are shown in Figures 1 and
2, respectively. Selected bond distances and angles are
listed in Tables 2 and 3, respectively. Crystallographic
data and details of structure determination and refine-
ment are given in Table 8. A comparative listing of bond
distances for 1, 2, and their η5-C5H5 and η5-C5Me5
analogs is given in Table 4. The analyses of both 1 and
2 reveal a distorted-octahedral geometry at each metal
with two mutually trans η5-C5Me4CF3 ligands and two
terminal and two symmetrically bridging carbonyl
ligands. There is a crystallographic center of symmetry
located midway between the metal atoms. The CF3
groups are oriented anti with respect to one another in
accordance with the center of symmetry. Compounds
1 and 2 are isostructural and isomorphic.
As shown in Table 4, the Ru-Ru bond distance in 1
of 2.7613(4) Å and the Ru-Cp′(centroid) distance of
1.924 Å are the longest distances in the ruthenium
series, although they are closer to those of the η5-C5-
Me5 analog than to those of the η5-C5H5 analog. The
Ru-Ru distance of 2.735(2) Å in the η5-C5H5 compound
is the shortest in the ruthenium series. Also for
compound 1, the terminal and bridging CO distances
of 1.865(3) and 2.044(3) Å are the same within experi-
mental error as those of the η5-C5Me5 compound:
1.866(3) and 2.041(3) Å, respectively. The Fe-Fe bond
distance in 2 of 2.563(1) Å and the Fe-Cp′(centroid)
distance of 1.766 Å are the longest in the iron series,
although they are nearly the same within experimental
error as those of the η5-C5Me5 analog: 2.560(1) and
1.764 Å, respectively. In the structure of 2, the terminal
CO has a slightly shortened Fe-C bond distance of
1.733(5) Å compared to both the η5-C5H5 and the η5-C5-
Me5 analogs, which have distances of 1.748(6) and 1.753
Å, respectively. This shortening of the Fe-C bond
distance is likely caused by the CF3 group on the η5-
C5Me4CF3 ring which is in close proximity to the
terminal CO ligand. However, it is noted that the
overall electron-withdrawing effect of the CF3 group in
1 and 2 is approximately balanced by the electron-
donating effect of the four methyl groups on the C5 ring,
The synthesis of [(η5-C5Me4CF3)Fe(µ-CO)(CO)]2 (2)
has been published;2b,c however, it is important to
highlight some subtle differences between the two
procedures. Initially it was found2b that treatment of
Fe(CO)5 with 3 equiv of HC5Me4CF3 in refluxing octane
produced 2 in 34% yield (eq 2). Unfortunately, this
procedure produced a trace impurity that was not easily
removed. During a subsequent study2c the trace impu-
rity was found to be problematic and electrochemically
active. The “impurity” was identified as [(η5-C5Me5)-
(CO)Fe(µ-CO)2Fe(CO)(η5-C5Me4CF3)] by mass spectrom-
etry. Pure samples of 2 were then prepared by oxidizing
“impure” 2 with I2 to make [(η5-C5Me4CF3)Fe(CO)2(I)]
followed by purification and reduction to 2 with cobal-
tocene (eq 3). Unlike the ruthenium analog 1, com-
(13) Bond, A.; Bottrill, M.; Green, M.; Welch, A. J . J . Chem. Soc.,
Dalton Trans. 1977, 2372.
(14) Mills, O. S.; Nice, J . P. J . Organomet. Chem. 1967, 9, 339.
(15) (a) Bryan, R. F.; Greene, P. T. J . Chem. Soc. A 1970, 3064. (b)
Also see: Mills, O. S. Acta Crystallogr. 1958, 11, 620.
(12) (a) Gansow, O. A.; Burke, A. R.; Vernon, W. D. J . Am. Chem.
Soc. 1976, 98, 5817. (b) Also see: Gansow, O. A.; Burke, A. R.; Vernon,
W. D. J . Am. Chem. Soc. 1972, 94, 2250. (c) Farrugia, L. J .; Mustoo,
L. Organometallics 1992, 11, 2941.

1598 Organometallics, Vol. 16, No. 8, 1997
Barthel-Rosa et al.
Ta ble 3. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for [(η5-C5Me4CF 3)F e(µ-CO)(CO)]2 (2)
Bond Distances (Å)
Fe(1)-Fe(1)′
Fe-C(14)
2.563(1)
1.925(4)
1.911(4)
1.733(5)
1.186(5)
1.164(5)
2.085(4)
2.119(4)
Fe-C(3)
2.170(4)
2.179(4)
2.167(4)
1.481(6)
1.348(6)
1.328(6)
1.331(5)
Fe-C(4)
Fe-C(14)′
Fe-C(13)
Fe-C(5)
C(1)-C(10)
F(1)-C(10)
F(2)-C(10)
F(3)-C(10)
C(14)-O(2)
C(13)-O(3)
Fe(1)-C(1)
Fe(1)-C(2)
Bond Angles (deg)
C(14)-Fe(1)-C(14)′ 96.2(2) Fe(1)′-Fe(1)-C(14)
C(14)-Fe(1)-C(13) 93.0(2) Fe(1)′-Fe(1)-C(14)′
C(14)′-Fe(1)-C(13) 94.4(2) Fe(1)-C(14)-O(2)
Fe(1)′-Fe(1)-C(13) 95.5(1) Fe(1)-C(13)-O(3)
Fe(1)′-C(14)-Fe(1) 83.8(2)
47.8(1)
48.3(1)
137.8(3)
177.0(4)
One notable feature common to both structures 1 and
2 is that the carbon atoms in the C5 rings bound to the
CF3 groups (metal-C-CF3) are closer to the metal
atoms than to the ring carbons bound to the CH3 groups
(metal-C-CH3). The Ru-C(CF3) bond distance of
2.230(2) Å is shorter than the four Ru-C(CH3) carbon
distances, which range from 2.238(2) to 2.311(3) Å. The
Fe-C(CF3) bond distance of 2.085(4) Å is also shorter
than the remaining Fe-C(CH3) distances of 2.119(4)-
2.167(4) Å. In each case, the largest observed distance
differential between the metal-C(CF3) carbon distance
and the longest metal-C(CH3) carbon distance is 0.08
Å. This shortening is attributed to the electron-
withdrawing effect of the CF3 group. A similar effect
is also observed in the recently reported2c crystal
structure of [(η5-C5Me4CF3)Fe(η5-C5H5)], where the Fe-
C(CF3) carbon distance of 2.007(6) Å is shorter than the
remaining Fe-C(CH3) distances, which range from
2.041(7) to 2.061(8) Å. Overall, however, the X-ray
crystallographic studies of 1 and 2 suggest that the
structural effects of the η5-C5Me4CF3 and η5-C5Me5
ligands are very similar.
F igu r e 1. Structural drawing of [(η5-C5Me4CF3)Ru(µ-CO)-
(CO)]2 (1) showing the atom-numbering scheme (50%
probability ellipsoids). Hydrogen atoms have been omitted
for clarity.
Because of the similarity of the η5-C5Me4CF3 and η5-
C5Me5 ligands, this study confirms previous arguments
that the trans geometry of [(η5-C5R5)M(µ-CO)(CO)]2
complexes3b,c,11 are favored over the cis geometry for
steric reasons. However, it is interesting to note that
flash photolysis studies of trans-[(η5-C5Me5)Fe(µ-CO)-
(CO)]2 produced equal amounts of the cis and trans
isomers.16 The energy of activation for the isomerization
of the cis to the trans isomer was measured to be 68 (
5 kcal mol-1, as compared to the value for cis-[(η5-C5H5)-
Fe(µ-CO)(CO)]2 of 54 ( 8 kcal mol-1. The authors state
that “it is not yet clear whether the higher activation
barrier {for [(η5-C5Me5)Fe(µ-CO)(CO)]2} is due to steric
or electronic factors”.16 It is possible that future studies
of 2 will help resolve some of these questions. In
addition, the reported complex [{η5-C5Me4(SiMe2NMe2)}-
Fe(µ-CO)(CO)]2 was shown by IR spectroscopy to occur
as the trans isomer and smaller amounts of the cis
isomer in polar solvents in spite of the bulky substituted
cyclopentadienyl ligand.17 Although steric factors ac-
count for the thermodynamic predominance of the trans
isomer of substituted η5-C5R5 iron dicarbonyl deriva-
tives, steric and electronic factors may both be impor-
tant in determining the kinetics of isomerization.
F igu r e 2. Structural drawing of [(η5-C5Me4CF3)Fe(µ-CO)-
(CO)]2 (2) showing the atom-numbering scheme (50%
probability ellipsoids). Hydrogen atoms have been omitted
for clarity.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for [(η5-C5Me4CF 3)Ru (µ-CO)(CO)]2 (1)
Bond Distances (Å)
Ru-Ru′
2.7613(4)
2.045(3)
2.042(3)
1.865(3)
1.170(4)
1.134(4)
2.230(2)
2.238(2)
Ru-C(5)
Ru-C(6)
Ru-C(7)
C(3)-C(8)
F(1)-C(8)
F(2)-C(8)
F(3)-C(8)
2.297(3)
2.311(3)
2.308(3)
1.488(4)
1.365(5)
1.282(5)
1.327(7)
Ru-C(1)
Ru-C(1)′
Ru-C(2)
C(1)-O(1)
C(2)-O(2)
Ru-C(3)
Ru-C(4)
Bond Angles (deg)
C(1)-Ru-C(1)′
C(1)-Ru-C(2)
C(1)′-Ru-C(2)
Ru′-Ru-C(2)
Ru′-C(1)-Ru
95.0(1)
92.1(1)
93.1(1)
93.90(9)
85.0(1)
Ru′-Ru-C(1)
Ru′-Ru-C(1)′
Ru-C(1)-O(1)
Ru-C(2)-O(2)
47.44(8)
47.54(8)
137.2(2)
176.5(3)
(16) Moore, B. D.; Poliakoff, M.; Turner, J . J . J . Am. Chem. Soc.
1986, 108, 1819.
(17) Mora´n, M.; Pascual, M. C.; Cuadrado, I.; Losada, J . Organo-
metallics 1993, 12, 811.
(18) Haines, R. J .; du Preez, A. L. J . Chem. Soc., Dalton Trans. 1972,
944.
(19) Nelson, G. O.; Sumner, C. E. Organometallics 1986, 5, 1983.
because the CO stretching frequencies of 1 (1958, 1776
cm-1) and 2 (1952, 1776 cm-1) are similar to those of
the C5H5 complexes (trans-[(η5-C5H5)Ru(µ-CO)(CO)]2
(1968, 1768 cm-1) and trans-[(η5-C5H5)Fe(µ-CO)(CO)]2
(1955, 1773 cm-1)).

Fe and Ru Complexes with the η5-C5Me4CF3 Ligand
Organometallics, Vol. 16, No. 8, 1997 1599
Ta ble 4. Com p a r ison of M-M, M-Cp ′, a n d M-CO Bon d Dista n ces (Å) in tr a n s-[(η5-Cp ′)M(µ-CO)(CO)]2
(η5-Cp ′ ) η5-C5H5 , η5-C5Me4CF 3, η5-C5Me5; M ) F e, Ru ) Com p lexes
M-CO
terminal
M-CO
compd
M-M
M-Cp′a
bridgingb
ref
[(η5-C5H5)Ru(µ-CO)(CO)]2
2.735(2)c
2.7613(4)
2.752(1)
2.534(2)
2.563(1)
2.560(1)
1.915
1.924
1.917
1.754
1.766
1.764
1.855(14)
1.865(3)
1.866(3)
1.748(6)
1.733(5)
1.753(3)
1.986(13)
2.044(3)
2.041(3)
1.914(5)
1.918(4)
1.929(3)
14
d
9
15a
d
10
[(η5-C5Me4CF3)Ru(µ-CO)(CO)]2 (1)
[(η5-C5Me5)Ru(µ-CO)(CO)]2
[(η5-C5H5)Fe(µ-CO)(CO)]2
[(η5-C5Me4CF3)Fe(µ-CO)(CO)]2 (2)
[(η5-C5Me5)Fe(µ-CO)(CO)]2
a
b
d
M-Cp′ ) metal-centroid of cyclopentadienyl ring distance. Average distances. c Standard deviations are given in parentheses. This
work.
Ta ble 5. In fr a r ed Ca r bon yl Str etch in g
F r equ en cies of [(η5-Cp ′)M(CO)2(I)] (η5-Cp ′ )
η5-C5H5, η5-C5Me4CF 3, η5-C5Me5; M ) F e, Ru )
Com p lexesa
compd
ν(CO), cm-1
ref
[(η5-C5H5)Ru(CO)2(I)]
2048, 1997
2060, 1998
2030, 1981
18
[(η5-C5Me4CF3)Ru(CO)2(I)] (3b)
[(η5-C5Me5)Ru(CO)2(I)]
this work
19
a
CH2Cl2 solvent.
P r ep a r a tion of [(η5-C5Me4CF 3)Ru (CO)2(I)] (3b).
Treatment of 1 with I2 in refluxing dichloromethane (in
the absence of light) leads to the formation of the
dicarbonyliodoruthenium complex 3b in 89% yield (eq
4). The 1H NMR spectrum of 3b shows a quartet at 2.23
F igu r e 3. Structural drawing of [(η5-C5Me4CF3)Ru(CO)2-
(I)] (3b) showing the atom-numbering scheme (50% prob-
ability ellipsoids).
ppm (5J HF ) 0.95 Hz) for the 2,5-methyl hydrogens and
a singlet at 2.14 ppm for the 3,4-methyl hydrogens. The
notable features of the 13C{1H} NMR spectrum of 3b in
chloroform-d include the resonance at 195.43 ppm for
the carbonyl ligands and a quartet for the unique CF3
carbon at 124.21 ppm (1J CF ) 271.5 Hz). The IR
spectral data for 3b are listed in Table 5 along with
those of the η5-C5H5 and η5-C5Me5 analogs for compari-
son.
Ta ble 6. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for [(η5-C5Me4CF 3)Ru (CO)2(I)] (3b)
Bond Distances (Å)
Ru(1)-I(1)
Ru(1)-C(1)
Ru(1)-C(2)
Ru(1)-C(3)
Ru(1)-C(4)
2.6989(8)
1.881(6)
2.264(4)
2.249(4)
2.152(6)
C(3)-C(4)
C(2)-C(3)
C(2)-C(2)*
C(4)-C(5)
F(1)-C(5)
F(2)-C(5)
1.439(6)
1.409(6)
1.442(9)
1.496(10)
1.312(5)
1.301(8)
Analysis of the data in Table 5 shows that the ν(CO)
stretching frequencies for 3b are similar to those of the
η5-C5H5 analog. Compound 3b was also characterized
by X-ray crystallography to extend the structural da-
tabase for the η5-C5Me4CF3 ligand.
Bond Angles (deg)
C(1)-Ru(1)-C(1)*
I(1)-Ru(1)-C(1)
Ru(1)-C(1)-O(1)
I(1)-Ru(1)-C(4)
91.5(3)
C(3)-C(4)-C(3)*
C(2)-C(3)-C(4)
C(2)*-C(2)-C(3)
C(3)-C(4)-C(5)
108.7(6)
107.0(4)
108.5(3)
125.1(3)
89.0(2)
177.4(5)
155.7(2)
A view of the molecular structure of 3b is shown in
Figure 3. Selected bond distances and angles are given
in Table 6. The analysis reveals a distorted octahedral
geometry about ruthenium with one η5-C5Me4CF3, two
cis-CO ligands, and one iodide completing the ruthe-
nium coordination sphere. The average Ru-C(carbonyl)
bond distance is 1.881(6) Å, and the Ru-I bond distance
is 2.6989(8) Å. The distance from the ruthenium to the
centroid of the η5-C5Me4CF3 ligand is 1.878 Å, which is
shorter than the Ru-η5-C5Me4CF3 centroid distance in
1 (1.917 Å). Similar to what was observed in the
structures of 1 and 2, the metal-C(CF3) carbon distance
in 3b is shorter than the remaining metal-C(CH3)
carbon distances. The Ru-C(CF3) bond distance of
2.152(6) Å is significantly shorter than the Ru-C(CH3)
and Ru-C(CH3) bond distances of 2.249(4) and 2.264(4)
Å, respectively. In comparison, the largest metal to
ring-carbon distance differential in 3b (0.11 Å) is greater
than the largest differential (0.08 Å) observed for 1 or
2. The CF3 group is anti or “staggered” with respect to
the iodo ligand and lies on the crystallographically
imposed mirror plane. To the best of our knowledge,
the crystal structures of the η5-C5H5 and η5-C5Me5 iodo
analogs of 3b are not known; however, the structures
of [PCpRu(CO)2(I)]5 and [(η5-C5Me4Et)Ru(CO)2(Br)]20
are suitable for comparison. The average Ru-C(CO)
bond distance in the [PCpRu(CO)2(I)] compound of
1.91(1) Å is longer than the Ru-C(CO) distance in 3b
of 1.881(6) Å, while the Ru-C(CO) distance in the η5-
C5Me4Et compound of 1.892(14) Å is the same within
experimental error. The Ru-I bond distance in 3b of
2.6989(8) Å is very similar to the Ru-I bond distance of
(20) Adams, H.; Bailey, N. A.; White, C. Inorg. Chem. 1983, 22, 1155.

1600 Organometallics, Vol. 16, No. 8, 1997
Barthel-Rosa et al.
2.708(1) Å in the [PCpRu(CO)2(I)] compound. In the η5-
C5Me4Et compound, the ethyl group is anti to the
bromide and lies on the mirror plane of the molecule,
which is similar to what is observed for the CF3 group
in 3b.
Ta ble 7. In fr a r ed Ca r bon yl Str etch in g
F r equ en cies of [(η4-HCp ′)F e(CO)3] (η4-Cp ′ )
η4-HC5H5, η4-HC5Me4CF 3, η4-HC5Me5) Com p lexesa
compd
ν(CO), cm-1
ref
[(η4-HC5H5)Fe(CO)3]
2048, 1981, 1974
2040, 1975, 1969
2031, 1964, 1955b
27b
this work
28b
[(η4-HC5Me4CF3)Fe(CO)3] (5)
[(η4-HC5Me5)Fe(CO)3]
Compound 3b may represent a convenient starting
point for other derivatives of the type [(η5-C5Me4CF3)-
Ru(CO)(L)(I)], where L is a neutral, two-electron-donor
ligand. The utility of [(η5-C5H5)Ru(CO)2(I)],3c,21,22 [(η5-
C5Me5)Ru(CO)2(I)],3d and [(η5-C5Me4Et)Ru(CO)2(I)]23 as
starting materials for such derivatives has been estab-
lished.
a
b
Hexane solution. Methylcyclohexane solution.
Ru; X ) Cl, Br, I).23,25 However, at least one example
has been reported where compounds of the type [(η5-
C5H5)Ru(L)2(H)] (L ) chelating phosphine) were pre-
pared from [(η5-C5H5)Ru(CO)2(H)].25 Therefore, the
range of possible derivatives from 1 and 2 may be
somewhat limited, especially if ancillary carbonyl ligands
are not desirable. Regardless, compounds 1 and 3b
represent important synthons for subsequent ruthenium
chemistry, since the η5-C5Me4CF3 analog of [(η5-C5Me5)-
RuCl2]226 is not known. We have previously shown that
treatment of RuCl3‚xH2O with HC5Me4CF3 affords the
ruthenocene [(η5-C5Me4CF3)2Ru] as the sole product.2b
P r epar ation of [(η4-HC5Me4CF3)Fe(CO)3] (5). Dur-
ing the course of preparing 2 in refluxing octane (eq 3),
a trace byproduct was isolated and subsequently identi-
fied as the iron tricarbonyl diene compound [(η4-HC5-
Me4CF3)Fe(CO)3] (5). Treatment of iron pentacarbonyl
with HC5Me4CF3 in refluxing heptane results in the
formation of 5 in 13% yield (eq 6). The most notable
P r ep a r a tion of [(η5-C5Me4CF 3)Ru (CO)(P P h 3)(I)]
(4). Treatment of 3b with 1.5 equiv of PPh3 in refluxing
ethanol displaces one carbonyl ligand and affords com-
pound 4 in 70% yield (eq 5). In an attempt to displace
both carbonyl ligands, the reaction was carried out with
a large excess of PPh3 in the presence of 2 equiv of
(CH3)3NO; however, compound 4 was the only tractable
product. Compound 4 is chiral at ruthenium, and the
1H NMR spectrum in chloroform-d shows four reso-
nances for the inequivalent methyl groups. The methyl
hydrogens in the 2,5-positions appear as broad reso-
nances at 2.15 and 1.56 ppm with unresolved fluorine
and phosphorus coupling. The methyl hydrogens in the
3,4-positions appear as doublets at 1.74 (4J HP ) 1.5 Hz)
and 1.51 ppm (4J HP ) 1.0 Hz). The 31P{1H} NMR
spectrum of 4 shows a quartet at 46.7 ppm (4J PF ) 2.3
Hz). The IR spectrum of 4 in dichloromethane shows a
ν(CO) stretching frequency at 1953 cm-1 that is broad-
ened, which is similar to the ν(CO) stretching frequency
of 1962 cm-1 that is observed for [(η5-C5H5)Ru(CO)-
(PPh3)(I)] in CS2.22 One noteworthy fact about the
preparation of compound 4 is that the CF3 group was
not esterified to the ethyl ester (CO2Et) by the action of
refluxing ethanol. This contrasts with the reported
example of η5-C5Me4CF3 esterification observed when
[(η5-C5Me4CF3)RhCl2]2 was reacted with diphenylvi-
nylphosphine in refluxing ethanol.24
1
feature in the H NMR spectrum of 5 in chloroform-d
is a quartet at 3.19 ppm (3J HF ) 6.5 Hz) for the proton
geminal to the CF3 group. This proton is probably endo
with respect to the metal due to steric reasons. How-
ever, a crystal structure of an iron substituted η4-
cyclopentadiene tricarbonyl complex, [η4-C5(1-H)(1-
CF3)(2-CF3)(3-OCH3)(4-H)(5-OCH2CH3)]Fe(CO)3, with a
CF3 group in the endo position was recently reported.27a
1
Only one isomer of 5 is observed by H NMR spectros-
copy at room temperature and at temperatures up to
80 °C (in toluene-d8). The IR spectral data for 5 are
listed in Table 7 along with those of the η4-HC5H5 and
η4-HC5Me5 analogs for comparison. The infrared spec-
trum for 5 in hexanes (Table 7) shows three ν(CO) bands
at 2040, 1975, and 1969 cm-1, as expected for iron η4-
diene tricarbonyl complexes.27b The carbonyl stretching
frequencies of 5 are lower in value than those of the
[(η4-HC5H5)Fe(CO)3] analog.27b This indicates that the
η4-HC5Me4CF3 ligand in 5 is slightly more electron
donating than the η4-HC5H5 ligand in its analogous iron
complex. In contrast, the ν(CO) values for all of the η5-
C5Me4CF3 metal complexes discussed above are more
similar to those of their η5-C5H5 metal analogs, because
Failure to displace both CO ligands from 3b is not
surprising, since this is usually difficult for complexes
of the type [(η5-C5R5)M(CO)2(X)] (R ) H, Me4Et; M )
(21) Bennett, M. A.; Khan, K.; Wenger, E. In Comprehensive
Organometallic Chemistry II; Abel, E. W., Stone, F. G. A., Wilkinson,
G., Shriver, D. F., Bruce, M. I., Eds.; Pergamon: New York, 1995; Vol.
7, pp 478-480.
(22) Brown, D. A.; Lyons, H. J .; Sane, R. T. Inorg. Chim. Acta 1970,
4, 621.
(23) Tabatabaeian, K.; White, C. J . Organomet. Chem. 1996, 510,
135.
(24) Barthel-Rosa, L. P.; Catalano, V. J .; Maitra, K.; Nelson, J . H.
Organometallics 1996, 15, 3924.
(25) White, C.; Cesarotti, E. J . Organomet. Chem. 1985, 287, 123.
(26) Koelle, U.; Kossakowski, J . Inorg. Synth. 1992, 29, 225-228.
(27) (a) Mitsudo, T.; Fujita, K.; Nagano, S.; Suzuki, T.; Watanabe,
Y.; Masuda, H. Organometallics 1995, 14, 4228. (b) Kochhar, R. K.;
Pettit, R. J . Organomet. Chem. 1966, 6, 272. (c) Whitesides, T. H.;
Shelly, J . J . Organomet. Chem. 1975, 92, 215.

Fe and Ru Complexes with the η5-C5Me4CF3 Ligand
Organometallics, Vol. 16, No. 8, 1997 1601
commercial sources (Aldrich or Fisher Scientific) or synthe-
sized as described below. Solvents were dried by standard
procedures and stored over Linde type 4 Å molecular sieves.
All syntheses were conducted in Schlenk glassware under a
the effects of the methyl and trifluoromethyl groups are
more evenly distributed through resonance in the planar
η5-C5Me4CF3 coordinated ligand than in 5.
Compound 5 is an air-stable, sublimable solid, whereas
the related derivatives [(η4-HC5H5)Fe(CO)3]27b and [(η4-
HC5Me5)Fe(CO)3]28 are air-sensitive, oily liquids. In the
case of 5, the electron-withdrawing nature and steric
bulk of the η4-HC5Me4CF3 ligand protects the metal
center from oxidation. Complex 5 cannot be deproto-
nated with excess 1,8-diazobicyclo[5.4.0]undec-7-ene
(DBU); however, deprotonation is observed with lithium
diisopropylamide in THF. Reprotonation with excess
methanol gives an unstable compound that has the
same CO stretching frequencies as the original complex.
It is likely that this compound is the isomer where the
CF3 group is endo with respect to the metal center;
however, no further attempts were made at character-
ization.
The previously reported [(η4-HC5H5)Fe(CO)3] and [(η4-
HC5Me5)Fe(CO)3] complexes are believed to be inter-
mediates in the preparation of [(η5-C5H5)Fe(µ-CO)(CO)]2
and [(η5-C5Me5)Fe(µ-CO)(CO)]2, respectively.27b,c,28 Thus,
it is likely that complex 5 is also an intermediate in the
preparation of 2. Purified samples of 5 were heated
under an argon atmosphere in refluxing octane solvent,
but only trace quantities of 2 were observed. Stronger
thermolysis27c or photolysis28b conditions may be re-
quired to affect this conversion.
2a
nitrogen atmosphere. HC5Me4CF3 and 22c were synthesized
by literature procedures. Elemental analyses were performed
by Galbraith Laboratories, Knoxville, TN. Melting points were
obtained using a Mel-Temp melting point apparatus and are
uncorrected. Solution infrared spectra were obtained on
Perkin-Elmer 599 or Paragon 1000 PC-FT spectrometers in
sealed CaF2 cells, and solid-state spectra were conducted on
NaCl windows. 1H, 13C{1H}, 31P{1H}, and 19F NMR spectra
were recorded at 499.8, 125.7, 202.4, and 470.3 MHz, respec-
tively, on a Varian Unity Plus 500 FT-NMR spectrometer.
Proton and carbon chemical shifts are relative to internal Me4-
Si, while phosphorus chemical shifts are relative to external
85% H3PO4 (aq) with positive values downfield of the respec-
tive reference. Fluorine chemical shifts are relative to external
CFCl3 with negative values upfield of the reference. NMR data
for A were obtained on General Electric GN and QE 300 MHz
spectrometers. NMR data for 2 were obtained on Varian VXR-
300 or Bruker NR 300 MHz spectrometers, IR data were
obtained on a Mattson Sirius 100 FTIR spectrophotometer, and
mass spectra were obtained with a Finnigan 4000 mass
spectrometer as described in the Experimental Section of ref
2c.
B. Syn th eses. P r ep a r a tion of [(η5-C5Me4CF 3)Ru (µ-
CO)(CO)]2 (1). A 50-mL Schlenk flask was charged with Ru3-
(CO)12 (0.57 g, 0.89 mmol) and 25 mL of freshly distilled
n-decane. This mixture was degassed, flushed with nitrogen,
and subsequently charged with 98% HC5Me4CF3 (0.52 g, 2.73
mmol). The clear red solution was refluxed for 6 h and
gradually turned dark brown. The reaction solution was then
stored at -25 °C for 24 h. The solution was filtered, and the
resulting orange-brown solid was washed with 3 × 5 mL
portions of cold hexanes. The crude product was dried in vacuo
(0.1 mmHg) to give 0.78 g of 1 in 84% yield based on Ru3(CO)12.
The product was then purified by chromatography. The crude
product was dissolved in a minimal amount of CH2Cl2 (about
75 mL), and enough Florisil was added to make a slurry and
adsorb the product (∼10 g). The CH2Cl2 was removed in vacuo,
and the adsorbed crude product was added to a dry-packed 2
× 35 cm column of Florisil. The column was eluted with
hexanes, which gave a yellow band containing unreacted Ru3-
(CO)12. Typically, 125-300 mL of hexanes was required to
obtain colorless fractions. The column was then eluted with
CH2Cl2 which gave a red-orange band that contained 1,
followed by a black band that was discarded. Typically about
400-600 mL of CH2Cl2 was required to completely remove 1
from the column. Solutions of 1 in CH2Cl2 were protected from
light. The solvent was removed in vacuo resulting in an
orange-brown solid which contained 0.39 g (42%) of pure 1.
Compound 1 was recrystallized by dissolving the orange-brown
residue in a minimal amount of CH2Cl2 and filtering the
solution into hexanes that was twice the volume of CH2Cl2.
The vessel was sealed, wrapped in aluminum foil, and stored
at -25 °C for 24 h. The resulting clear red-orange crystals
were collected on a medium-porosity glass frit and washed with
2 × 5 mL portions of cold hexanes. Compound 1 is air-stable
indefinitely in the solid state, but in aerated halocarbon
solutions 1 is sensitive to visible light. The reactions are slow
in CH2Cl2, faster in CHCl3, and in all cases greatly accelerated
if unprotected from visible light. Mp: 218 °C dec. Anal. Calcd
for C24H24F6O4Ru2: C, 41.62; H, 3.49. Found: C, 41.39; H,
3.51.
Su m m a r y
The chemistry of iron and ruthenium carbonyl dimers
of the type [(η5-C5R5)M(µ-CO)(CO)]2 (M ) Fe, Ru; R )
H, Me) is vast.3 The compounds [(η5-C5Me4CF3)Ru(µ-
CO)(CO)]2 (1) and [(η5-C5Me4CF3)Fe(µ-CO)(CO)]2 (2)
represent suitable precursors to other iron and ruthe-
nium compounds containing the sterically demanding,
electron-withdrawing η5-C5Me4CF3 ligand. Compounds
1 and 2 both crystallize as the trans isomers with
bridging carbonyl ligands. The crystal structures of 1
and 2 compare favorably with those of the η5-C5Me5
analogs, providing strong evidence that the steric bulk
of the ligand controls the overall trans geometry of these
complexes. Compound 1 is sensitive to visible light in
aerated solvents and reacts with chloroform or dichlo-
romethane to form [(η5-C5Me4CF3)Ru(CO)2(Cl)] (3a ).
Compound 1 reacts with I2 to produce [(η5-C5Me4CF3)-
Ru(CO)2(I)] (3b), which in turn reacts with PPh3 to form
[(η5-C5Me4CF3)Ru(CO)(PPh3)(I)] (4) in reasonable yield.
The compound [(η4-HC5Me4CF3)-Fe(CO)3] (5) is pre-
pared from Fe(CO)5 and represents a new mode of
coordination for the ΗC5Me4CF3 ligand. Overall, the
IR spectroscopic data for 1 and 2 and their η5-C5H5
analogs are very similar, and the X-ray crystallographic
data for 1 and 2 suggest that the structural effects of
η5-C5Me4CF3 and η5-C5Me5 are very similar. These
comparisons support the general conclusion2a,b that the
η5-C5Me4CF3 ligand is electronically equivalent to η5-
C5H5 and sterically equivalent to the η5-C5Me5 ligand.
Exp er im en ta l Section
A. Rea gen ts a n d P h ysica l Mea su r em en ts. All chemi-
cals were reagent grade and were used as received from
(28) (a) Balakrishnan, P. V.; Maitlis, P. M. J . Chem. Soc. A 1971,
1715. (b) Zou, C.; Wrighton, M. S.; Blaha, J . P. Organometallics 1987,
6, 1452.
5
1H NMR (C6D6): δ 1.84 (q, J HF ) 0.97 Hz, 6H, 2,5-CH3), 1.32
(s, 6H, 3,4-CH3). 13C{1H} NMR (C6D6): δ 224.46 (br s, CO),

1602 Organometallics, Vol. 16, No. 8, 1997
Barthel-Rosa et al.
1
4
125.69 (q, J CF ) 271.14 Hz, CF3), 105.28 (q, J CF ) 0.75 Hz,
3,4-CCH3), 104.48 (q, 3J CF ) 1.42 Hz, 2,5-CCH3), 89.36 (q, 2J CF
) 35.87 Hz, CCF3), 10.30 (q, 4J CF ) 2.10 Hz, 2,5-CH3), 8.70 (s,
203.82 (dq, 2J PC ) 21.3 Hz, 4J CF ) 1.3 Hz, CO), 134.24 (d, 2J PC
) 10.6 Hz, Co), 130.10 (d, 4J CP ) 2.4 Hz, Cp), 127.94 (d, 3J CP
)
10.2 Hz, Cm), Ci not observed, 125.35 (q, 1J CF ) 271.9 Hz, CF3),
5
2
3
3,4-CH3). 19F NMR (C6D6): δ -52.59 (sep, J HF ) 0.97 Hz).
101.23 (dq, J PC ) 3.3 Hz, J CF ) 1.6 Hz, 2- or 5-CCH3), 99.73
2 4
IR (CH2Cl2): ν(CO) 1958, 1776 cm-1. IR (Nujol): ν(CO) 1955,
1767 cm-1 (13CO satellites 1918, 1738). 1H NMR (CDCl3): δ
(br s, 3- or 4-CCH3), 99.09 (dq, J PC ) 3.5 Hz, J CF ) 0.75 Hz,
2 3
3- or 4-CCH3), 98.44 (dq, J PC ) 3.1 Hz, J CF ) 1.45 Hz, 2- or
5-CCH3), 81.48 (qd, 2J CF ) 35.5 Hz, 2J PC ) 2.9 Hz, CCF3), 11.43
5
2.05 (q, J HF ) 1.2 Hz, 6H, 2,5-CH3), 1.72 (s, 6H, 3,4-CH3).
1
4
3
13C{1H} NMR (CDCl3): δ 224.15 (br s, CO), 124.51 (q, J CF
)
(q, J CF ) 1.0 Hz, 2- or 5-CH3), 10.45 (d, J CP ) 0.88 Hz, 3- or
4
4
271.15 Hz, CF3), 104.76 (q, J CF ) 0.75 Hz, 3,4-CCH3), 103.92
4-CH3), 10.10 (q, J CF ) 2.0 Hz, 2- or 5-CH3), 9.55 (s, 3- or
(q, 3J CF ) 1.51 Hz, 2,5-CCH3), 88.83 (q, 2J CF ) 35.95 Hz, CCF3),
4-CH3). 19F NMR (CDCl3): δ -53.38 (m). IR (CH2Cl2): ν(CO)
10.02 (q, J CF ) 2.10 Hz, 2,5-CH3), 8.60 (s, 3,4-CH3).
1953 cm-1. IR (Nujol): ν(CO) 1936 (sh 1949 w, 1966 m) cm-1
.
4
P r ep a r a tion of [(η4-HC5Me4CF 3)F e(CO)3] (5). Under an
argon atmosphere, 40 mL of predistilled heptane was charged
with Fe(CO)5 (2.0 g, 10 mmol, filtered through glass wool) and
HC5Me4CF3 (2.0 g, 10.5 mmol). The solution was purged with
argon and heated to reflux for 48 h. After it was cooled to
room temperature, the heptane solution was filtered and the
solvent was removed under high vacuum. The resulting yellow
oil was sublimed onto a water-cooled sublimation probe (25
°C, 0.01 mmHg). The yellow oil was resublimed, and the
sublimate was recrystallized from hexanes at -78 °C to give
0.42 g of 5 in 13% yield as a yellow waxy solid. Mp: 128-129
Rea ction of 1 in CDCl3: F or m a tion of [(η5-C5Me4CF 3)-
Ru (CO)2(Cl)] (3a ). In an NMR tube, a CDCl3 solution of 1
was allowed to stand in visible light for 48 h. The red solution
darkened, and some brown solid precipitated. The solution
was filtered, and the solvent was removed in vacuo. The
residue was dissolved in CDCl3 for spectroscopic characteriza-
tion. No further attempts were made to purify the product
5
3a . 1H NMR (CDCl3): δ 2.12 (q, J HF ) 1.2 Hz, 6H, 2,5-CH3),
1.92 (s, 6H, 3,4-CH3). 13C{1H} NMR (CDCl3): 195.67 (s, CO),
1
3
124.33 (q, J CF ) 271.53 Hz, CF3), 105.74 (q, J CF ) 1.38 Hz,
2,5-CCH3), 103.06 (q, 4J CF ) 0.50 Hz, 3,4-CCH3), 80.55 (q, 2J CF
) 36.83 Hz, CCF3), 10.55 (q, 4J CF ) 2.26 Hz, 2,5-CH3), 9.24 (s,
°C. Anal. Calcd for
C
13H13F3FeO3: C, 47.30; H, 3.97.
3,4-CH3). IR (CDCl3): ν(CO) 2063, 2014 cm-1
.
Found: C, 47.15; H, 4.00.
P r ep a r a tion of [(η5-C5Me4CF 3)Ru (CO)2(I)] (3b). Under
a nitrogen atmosphere a Schlenk flask was charged with 30
mL of CH2Cl2, I2 (1.28 g, 5.0 mmol), and 1 (0.25 g, 0.36 mmol).
The deep red solution was purged with nitrogen and refluxed
for 1.5 h. The reaction solution was transferred to a separatory
funnel and washed with three 80 mL portions of 1.61 M
aqueous sodium thiosulfate to remove excess iodine. The
orange CH2Cl2 layer was separated and dried with magnesium
sulfate. The solution was filtered, and the solvent was
removed in vacuo to produce an orange solid which was dried
in vacuo (0.1 mmHg) to give 0.25 g of 3b in 74% yield.
Compound 3b was recrystallized from boiling ethanol to give
orange needles. It is air-stable in solution and the solid state.
Mp: 154-157 °C. Anal. Calcd for C12H12F3IO2Ru: C, 30.46;
H, 2.56. Found: C, 30.35; H, 2.42. 1H NMR (CDCl3): δ 2.23
3
1H NMR (CDCl3): δ 3.19 (q, J HF ) 6.5 Hz, 1H, H), 2.13 (s,
6H, CH3R), 1.52 (s, 6H, CH3â). 13C{1H} NMR (CDCl3): δ 211.98
(s, CO), 122.49 (q, 1J CF ) 291.0 Hz, CF3), 102.10 (q, 4J CF ) 0.9
2
3
Hz, CâdC), 65.41 (q, J CF ) 24.2 Hz, CCF3), 60.80 (q, J CF
)
4
1.7 Hz, CdCR), 15.27 (q, J CF ) 0.8 Hz, CH3R), 11.57 (s, CH3â).
19F NMR (CDCl3): δ -72.96 (d, J HF ) 6.5 Hz). IR (cyclohex-
3
ane): ν(CO) 2039, 1973, 1967 cm-1. MS: m/ e calcd for C13H13
-
FeO3 330.016 62, found 330.014 13.
5
(q, J HF ) 0.95 Hz, 6H, 2,5-CH3), 2.14 (s, 6H, 3,4-CH3). 13C-
Sp ect r oscop ic Da t a for [(µ-H )2R u 3(CO)9(µ3-η1:η2:η1-
C7H8)] (A). See ref 6 for synthesis and X-ray crystal structure
of A. The authors did not report complete details of 1H or 13C
NMR data.
4
{1H} NMR (CDCl3): δ 195.43 (q, J CF ) 1.09 Hz, CO), 124.21
1
3
(q, J CF ) 271.51 Hz, CF3), 104.79 (q, J CF ) 1.42 Hz,
2,5-CCH3), 102.04 (q, 4J CF ) 0.75 Hz, 3,4-CCH3), 82.66 (q, 2J CF
4
) 36.77 Hz, CCF3), 11.08 (q, J CF ) 2.14 Hz, 2,5-CH3), 10.59
(s, 3,4-CH3). 19F NMR (CDCl3): δ -54.34 (sep, J HF ) 0.95
5
Hz). IR (CH2Cl2): ν(CO) cm-1 2060, 1998. IR (Nujol): ν(CO)
2040, 1984 cm-1
.
P r ep a r a tion of [(η5-C5Me4CF 3)Ru (CO)(P P h 3)(I)] (4).
Under a nitrogen atmosphere, to a suspension of 3b (0.4 g,
0.84 mmol) in 45 mL of absolute ethanol was added tri-
phenylphosphine (0.47 g, 1.8 mmol). The reaction mixture was
refluxed for 48 h and the solution gradually turned from
orange to red. The reaction mixture was then cooled to room
temperature, and the solvent was removed in vacuo. A 60 mL
glass frit funnel was used as a column and attached to a 1000
mL Erlenmeyer flask equipped with a side arm. A 2.5 cm layer
of silica gel (grade 12, 28-300 mesh, Aldrich) was covered with
a 0.5 cm layer of Celite and firmly packed with a spatula and
3
1H NMR (300.16 MHz, CDCl3): δ 3.19 (apparent tt, J (H1H7)
) 3J (H1H8) ) 2.0 Hz, 3J (H1H5) ) 3J (H1H6) ) 1.35 Hz, 2H, H1,2),
1.90 (m, 2H, H3,5), 1.35 (apparent dt, 2J (H7H8) ) 9.3 Hz,
suction. The crude reaction product was dissolved in
a
4
minimal amount of CH2Cl2 and loaded onto the column, and
the residual solvent was removed with suction. All subsequent
solvents were eluted with suction. The column was eluted
with (1) 250 mL of hexanes and (2) 350 mL of CH2Cl2, and all
solvents were removed in vacuo. By 31P{1H} NMR spectro-
scopy, fractions 1 and 2 both contained the product and were
combined and dried to give 0.41 g of 4 in 69% yield. Compound
4 was recrystallized from boiling ethanol to give deep red
crystals which are air-stable in solution and the solid state.
Mp: 186-188 °C. Anal. Calcd for C29H27F3IOPRu: C, 49.23;
H, 3.85. Found: C, 49.18; H, 3.73. 1H NMR (CDCl3): δ 7.56-
4J (H4H8) ) J (H6H8) ) 3.9 Hz, 1H, H8), 1.20 (m, 2J (H3H4) )
4.50 Hz, 4J (H4H8) ) 3.9 Hz, 3J (H4H5) ) 2.4 Hz, 2H, H4,6), 0.68
(m, 2J (H7H8) ) 9.3 Hz, 3J (H1H7) ) 3J (H2H7) ) 2.0 Hz, 4J (H3H7)
) 4J (H5H7) ) 2.1 Hz, 1H, H7), -16.8 (broad, 1H, RuH), -20.2
(broad, 1H, RuH). 13C NMR (75.58 MHz, CDCl3): δ 192.44
(s, 3COax), 189.95 (s, 6COeq), 157.54 (s, C2,3), 53.52 (dd, 1J CH
)
149.3 Hz, 2J CH ) 7.3 Hz, C1,4), 50.97 (tt, 1J CH ) 133.8 Hz, 2J CH
) 6.3 Hz, C7), 27.12 (t of apparent tq, 1J CH ) 129.0 Hz, 2J CH
)
2
3
5.2 Hz, J CH ) J CH ) 2.6 Hz, C5,6). IR (CDCl3): ν(CO) 2120
m, 2100 s, 2070 vs, 2030 s, 2010 sh, 1990 sh cm-1
.
C. X-r a y Da ta Collection a n d P r ocessin g for 1, 2, a n d
3b. Crystal data and details of data collection and refinement
are given in Table 8. Other crystallographic data are included
in the Supporting Information.
4
7.35 (m, 15H, Ph), 2.15 (br m, 3H, 2- or 5-CH3), 1.74 (d, J PH
) 1.5 Hz, 3H, 3- or 4-CH3), 1.56 (br m, 3H, 2- or 5-CH3), 1.51
4
(d, J PH ) 1.0 Hz, 3- or 4-CH3). 13C{1H} NMR (CDCl3): δ

Fe and Ru Complexes with the η5-C5Me4CF3 Ligand
Organometallics, Vol. 16, No. 8, 1997 1603
Ta ble 8. Cr ysta llogr a p h ic Da ta for Com p ou n d s 1, 2, a n d 3b
1
2
3b
empirical formula
fw
cryst dimens (mm)
cryst syst
space group
a (Å)
C
692.6
24H24O4F6Ru2
C24H24O4F6Fe2
602.14
0.35 × 0.35 × 0.30
monoclinic
P21/n
8.451(3)
9.900(6)
14.437(8)
94.76(3)
1204(2)
2
C12H12F3O2RuI
473.20
0.88 × 0.08 × 0.08
monoclinic
P21/m
7.2526(4)
12.1952(6)
8.647(1)
99.020(9)
755.3(1)
2
0.40 × 0.40 × 0.40
monoclinic
P21/n
8.541(2)
9.804(2)
15.103(4)
97.37(2)
1254.2(9)
2
b (Å)
c (Å)
â (deg)
V (Å3)
Z
Dcalc (g/cm-3
)
1.834
1.661
12.78
Mo KR
24
2.080
31.08
Mo KR
20
µ(Mo KR) (cm-1
)
12.526
Mo KR
20
radiation (λ ) 0.710 69 Å)
temp (°C)
scan type
θ/2θ
ω-2θ
ω-2θ
scan rate (deg/min in ω)
scan width (deg)
2θmax (deg)
variable
1.06 + 0.34 tan Θ
54
16.5
16.0
0.60 + 0.35 tan Θ
51.9
2621
1.47 + 0.35 tan Θ
45.0
1143
1050
950
119
7.98
0.024, 0.026
3.42
no. of rflns collcd
no. of unique rflns
no. of observns (I > 3σ(I)) (No)
no. of variables (Nv)
No/Nv
3393
3191
2805
163
17.63
0.028, 0.061
1.45
0.56
-0.87
0.04
2515
1870a
163
11.47
0.045, 0.056
1.42
0.34
-0.36
0.00
Rb, Rw
c
goodness of fit
max peak final diff map (e Å-3
)
)
0.68
-0.74
0.64
min peak final diff map (e Å-3
max shift/error final cycle
a
b
I > 2σ(I). R ) ∑||Fo| - |Fc||/∑|Fo|. c Rw ) [(∑w(|Fo| - |Fc|)2/∑wFo2)]0.5
.
[(η5-C5Me4CF 3)Ru (µ-CO)(CO)]2 (1). Red-orange crystals
of 1 were grown by slow diffusion of hexanes into a saturated
CH2Cl2 solution that was protected from visible light at -25
°C. Data were collected using an Enraf-Nonius CAD4-F
automatic diffractometer at room temperature. Three stan-
dard reflections measured every 1 h during the entire data
collection period showed no significant trend. The raw data
were converted to intensities and corrected for Lorentz and
polarization factors. All calculations were performed on a VAX
computer using the Enraf-Nonius VAX/Molen package.29 The
structure was solved by the heavy-atom method. After refine-
ment of the non-hydrogen atoms, difference Fourier maps
revealed maxima of residual electron density close to positions
expected for hydrogen atoms. Hydrogen atoms were refined
at calculated positions with a riding model in which the C-H
vector was fixed at 0.95 Å with isotropic temperature factors
such as B(H) ) 1.3Beqv(C) Å. Fourier difference maps revealed
no significant maxima. Neutral atom scattering factor coef-
ficients and anomalous dispersion coefficients were taken from
a standard source.30
[(η5-C5Me4CF 3)Ru (CO)2(I)] (3b). Orange needles of 3b
were grown from hot ethanol. Data were collected on a Rigaku
AFC7R diffractometer with a 12 kW rotating-anode generator.
An empirical absorption correction based on azimuthal scans
of several different reflections was applied. The data were
corrected for Lorentz and polarization effects. A correction for
secondary extinction was applied (coefficient 5.41429 × 10-6).
The structure was solved by direct methods, and the non-
hydrogen atoms were refined anisotropically. Hydrogen atoms
were refined isotropically with a riding model. Neutral atom
scattering factors and anomalous dispersion coefficients were
taken from a standard source.30 All calculations were per-
formed using the TEXSAN crystallographic software package.32c
Ack n ow led gm en t. We are grateful to the donors
of the Petroleum Research Fund, administered by the
American Chemical Society, for financial support, to the
National Science Foundation (Grant Nos. UNRCHE-
9214294 and UMNCHE-9317570) for funds to purchase
the 500 MHz NMR spectrometers, and to J ohnson
Mathey Aesar/Alfa for a generous loan of Ru3(CO)12. We
thank Dr. Paul N. Swepston of Molecular Structure
Corp.33 for determining the crystal structure of 3b.
L.P.B.R. thanks Professor Tom Bitterwolf of The Uni-
versity of Idaho for his helpful discussions concerning
the photochemistry of 1. J .R.S. thanks Professor Doyle
Britton (UMN) for determining the crystal structure of
2.
[(η5-C5Me4CF 3)F e(µ-CO)(CO)]2 (2). Dark purple prismatic
crystals of 2 were grown from a mixture of CH2Cl2 and hexanes
overnight at -15 °C. Data were collected on an Enraf-Nonius
CAD-4 diffractometer and were corrected for Lorentz, polariza-
tion, and absorption using the DIFABS program.31 The
structure was solved by direct methods, and the non-hydrogen
atoms were refined anisotropically.32 Neutral atom scattering
factors and anomalous dispersion coefficients were taken from
a standard source.30 All calculations were performed using
the TEXSAN crystallographic software package.32c
Su p p or tin g In for m a tion Ava ila ble: For the compounds
1, 2, and 3b, listings of crystal and refinement data, atomic
coordinates and U values, bond lengths and angles, anisotropic
displacement parameters, and H atom coordinates and iso-
tropic displacement parameters (20 pages). Ordering informa-
tion is given on any current masthead page.
(29) Molen, An Interactive Structure Solution Procedure; Enraf-
Nonius, Delft, The Netherlands, 1990.
(30) Cromer, D. T.; Waber, J . T. International Tables for X-ray
Crystallography; Kynoch Press: Birmingham, England, 1974; Vol. IV,
Table 2.2b, Table 2.2A, Table 2.3.1.
(31) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39, 158.
(32) (a) Gilmore, C. J . Appl. Crystallogr. 1984, 17, 42. (b) Beurskens,
P. T. DIRDIF; Technical Report 1984/1; Crystallographic Laboratory,
Toernooiveld, 6525 Ed Nijmegen, The Netherlands. (c) TEXSAN:
Crystal Structure Analysis Package; Molecular Structure Corp., The
Woodlands, TX, 1985, 1992.
OM961069B
(33) Molecular Structure Corp., 3200 Research Forest Drive, The
Woodlands, TX 77381.