The ruthenocenylmethylium cation: Isolation and structures of η5-cyclopentadienyl-η6-fulvene-ruthenium(II) salts

Article abstract of DOI:10.1021/om010667+

Salts of the ruthenocenylmethylium cation, 1⁺, can be synthesized from the reaction of ruthenocenylmethanol with either Br?nsted or Lewis acids. The X-ray crystal structures of the tetrakis{3,5-bis(trifluoromethyl)phenyl}borate and trifluoromethanesulfonate salts of 1⁺ reveal that the methylium carbon is bound to the ruthenium with Ru-C bond lengths in the range 2.251(9)-2.40(1) A? and confirm the description of the cation structure as η⁵-cyclopentadienyl-η⁶-fulvene-ruthenium(II). The UV-vis spectrum of 1⁺ shows a d-d transition at an energy similar to those of ruthenocene and the η⁵-cyclopentadienyl-η⁶-benzeneruthenium(II) cation, but with increased absorptivity. Cyclic voltammetry indicates that 1⁺ is reduced at considerably less negative potential than its isomer, the η⁵-cyclopentadienyl-η⁶-benzene-ruthenium(II) cation. Chemical reduction with sodium amalgam in tetrahydrofuran leads to the formation of methylruthenocene, 1,2-bis(ruthenocenyl)ethane, and bis(ruthenocenylmethyl)ether. Reaction of 1⁺ with triphenylphosphine affords the (ruthenocenylmethyl)triphenylphosphonium cation; the crystal structure of the dichloromethane solvate of its tetrafluoroborate salt has been determined. Density functional calculations closely reproduce the crystallographically determined geometry of 1⁺ and allow rationalization of some characteristics of its structures, spectroscopy, and reactivity. The calculations suggest that the ferrocenylmethylium cation, 3⁺, has a geometry similar to 1⁺ with similar orbital structure, albeit with considerably more d-character to the occupied frontier orbitals.

Full text of DOI:10.1021/om010667+

Organometallics 2001, 20, 5351-5359
5351
Th e Ru th en ocen ylm eth yliu m Ca tion : Isola tion a n d
Str u ctu r es of
η5-Cyclop en ta d ien yl-η6-fu lven e-r u th en iu m (II) Sa lts
Stephen Barlow,*,† Andrew Cowley, J ennifer C. Green, Tim J . Brunker, and
Tony Hascall
Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford,
OX1 3QR, U.K.
Received J uly 25, 2001
Salts of the ruthenocenylmethylium cation, 1+, can be synthesized from the reaction of
ruthenocenylmethanol with either Brønsted or Lewis acids. The X-ray crystal structures of
the tetrakis{3,5-bis(trifluoromethyl)phenyl}borate and trifluoromethanesulfonate salts of
1+ reveal that the methylium carbon is bound to the ruthenium with Ru-C bond lengths in
the range 2.251(9)-2.40(1) Å and confirm the description of the cation structure as
η5-cyclopentadienyl-η6-fulvene-ruthenium(II). The UV-vis spectrum of 1+ shows a d-d
transition at an energy similar to those of ruthenocene and the η5-cyclopentadienyl-η6-
benzeneruthenium(II) cation, but with increased absorptivity. Cyclic voltammetry indicates
that 1+ is reduced at considerably less negative potential than its isomer, the η5-
cyclopentadienyl-η6-benzene-ruthenium(II) cation. Chemical reduction with sodium amalgam
in tetrahydrofuran leads to the formation of methylruthenocene, 1,2-bis(ruthenocenyl)ethane,
and bis(ruthenocenylmethyl)ether. Reaction of 1+ with triphenylphosphine affords the
(ruthenocenylmethyl)triphenylphosphonium cation; the crystal structure of the dichlo-
romethane solvate of its tetrafluoroborate salt has been determined. Density functional
calculations closely reproduce the crystallographically determined geometry of 1+ and allow
rationalization of some characteristics of its structure, spectroscopy, and reactivity. The
calculations suggest that the ferrocenylmethylium cation, 3+, has a geometry similar to 1+
with similar orbital structure, albeit with considerably more d-character to the occupied
frontier orbitals.
In tr od u ction
The group 8 metallocenes have long been known to
stabilize adjacent carbocations.1 This stabilization arises
through a direct orbital interaction between the metal
and the formally cationic carbon; the interaction can be
described as tending toward the structure η5-cyclopen-
tadienyl-η6-fulvene-metal(II) (Figure 1a), with the posi-
tive charge formally on the metal. Back-bonding from
the metal to the fulvene can be represented by contribu-
tions from a metal(IV) σ-CH2 extreme structure (Figure
1b). Recently a number of studies have involved the η5-
cyclopentadienyl-η6-fulvene-ruthenium(II) cation incor-
porated into various conjugated systems;2-6 these in-
F igu r e 1. Resonance structures for metallocenyl carboca-
tions and definition of the structural distortion angles, R
and â.
clude our own work on ruthenocene-terminated poly-
† Present address: Department of Chemistry, University of Arizona,
Tucson, AZ 85721.
(1) Watts, W. E. In Comprehensive Organometallic Chemistry;
Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: London,
1988; Vol. 8.
(2) Sato, M.; Kudo, A.; Kawata, Y.; Saitoh, H. Chem. Commun. 1996,
25-26.
methine cations,7-9 for which we were interested in
comparing spectroscopic, structural, and electrochemical
features of our compounds with those of the parent
ruthenocenylmethylium cation, [RcCH2]+, 1+. Although
there have been several studies of salts of the (nonam-
(3) Sato, M.; Kawata, Y.; Shintate, H.; Habata, Y.; Akabori, S.;
Unoura, K. Organometallics 1997, 16, 1693-1701.
(4) Sato, M.; Kawata, Y.; Kudo, A.; Iwai, A.; Saitoh, H.; Ochiai, S.
J . Chem. Soc., Dalton Trans. 1998, 2215-2224.
(5) Sato, M.; Iwai, A.; Watanabe, M. Organometallics 1999, 18,
3208-3219.
(7) Barlow, S.; Henling, L. M.; Day, M. W.; Marder, S. R. Chem.
Commun. 1999, 1567-1568.
(8) Barlow, S.; Day, M. W.; Marder, S. R. Acta Crystallogr. 2000,
C56, 303-304.
(6) Watanabe, M.; Sato, M.; Takayama, T. Organometallics 1999,
18, 5201-5203.
(9) Barlow, S.; Henling, L. M.; Day, M. W.; Schaefer, W. P.; Green,
J . C.; Hascall, T.; Marder, S. R. Manuscript in preparation.
10.1021/om010667+ CCC: $20.00 © 2001 American Chemical Society
Publication on Web 11/10/2001

5352 Organometallics, Vol. 20, No. 25, 2001
Barlow et al.
Sch em e 1
ethylruthenocenyl)methylium cation, 2+,10-13 there has
been little work published on its unsubstituted ana-
logue. Although 1+ has been recognized as an interme-
diate, for example in the solvolysis of RcCH2OAc,14 and
molecules when its salts are precipitated from various
ethers;20 in contrast, the salts of 1+ show no evidence
(elemental analysis, NMR, crystallography) for this type
of behavior.
Since trityl salts have been used to abstract hydride
from Mc(CHdCH)nCH2(CHdCH)nMc {Mc ) ferrocenyl,
n ) 1, 2, 3;21 Mc ) Rc, n ) 122}, we also attempted to
synthesize the (1′-methylruthenocenyl)methylium cation
from the analogous reaction with 1,1′-dimethylru-
thenocene. A mixture of products was formed, and the
target cation could not be isolated.
its pKR value has been determined,15 we are not aware
+
of any reports of the isolation of its salts. In this paper
we report on the synthesis, characterization, structures,
and reactivity of 1+ salts.
Resu lts a n d Discu ssion
Syn th esis. RcCH2OH (Rc ) ruthenocenyl) has previ-
ously been synthesized from [RcCH2NMe3]+[I]- 16 and
by NaBH4 reduction of RcCHO.17 We obtained the
alcohol from RcCHO18 using LiAl(OtBu)3H, by analogy
with the method described for RuCp*(η5-C5Me4CH2-
OH)10 (Scheme 1). Treatment of an ether solution of the
alcohol with ethereal HBF4 afforded a pale cream
precipitate, identified by NMR spectroscopy and ana-
lytical data as [RcCH2]+[BF4]-, 1a . [RcCH2]+[BAr′4]-
{Ar′ ) 3,5-bis(trifluoromethyl)phenyl}, 1b, was obtained
from 1a by using the method described by Manr´ıquez
and co-workers for the synthesis of [FeCp2]+[BAr′4]-.19
[RcCH2]+[PF6]-, 1c, can be synthesized from the alcohol
by treatment with either aqueous HPF6 in THF or
[Ph3C]+[PF6]- in dichloromethane, while [RcCH2]+[CF3-
SO3]-, 1d , was precipitated by the addition of CF3SO3-
SiMe3 to an ether solution of the alcohol. The analogous
ferrocenylmethylium cation, 3+, is complexed by ether
Salts of 1+ appear to be indefinitely stable under
nitrogen, both in the solid state and in dichloromethane
solution, in contrast to ferrocene analogues, which
rapidly dimerize to bis(ferroceniumyl)ethanes.23-26 When
exposed to air, solid cream-colored 1+ salts decompose
to black material on a time scale of weeks; solutions
decompose more rapidly. Solutions of 1+ in acetonitrile
or nitromethane slowly turn yellowish on standing, even
1
in the absence of air; H NMR spectroscopy reveals a
complex mixture of products.
Triphenylphosphine reacts with 1+ at the exo position
to afford [RcCH2PPh3]+; this is consistent with the large
LUMO coefficient on the exo carbon (vide infra, Figure
6). Accordingly, RcCH2OH can be converted to [RcCH2P-
Ph3]+[BF4]- using a method analogous to that described
for FcCH2OH27,28 and RcCHROH {R ) Me, Ph}.29 The
[RcCH2PPh3]+ cation has previously been obtained from
[RcCH2NMe3]+.30
(10) Kreindlin, A. Z.; Petrovskii, P. V.; Rybinskaya, M. I.; Yanovskii,
A. I.; Struchkov, Y. T. J . Organomet. Chem. 1987, 319, 229-237.
(11) Yanovsky, A. I.; Struchkov, Y. T.; Kreindlin, A. Z.; Rybinskaya,
M. I. J . Organomet. Chem. 1989, 369, 125-130.
(12) Kirchner, K.; Dasgupta, S.; Schmid, R. J . Chem. Res. S 1993,
340-1.
(13) Kamyshova, A. A.; Kreindlin, A. Z.; Rybinskaya, M. I.; Petro-
vskii, P. V. Russ. Chem. Bull. 1999, 48, 581-585.
(14) Hill, E. A.; Richards, J . H. J . Am. Chem. Soc. 1961, 83, 3840-
3846.
(15) Tang, J .; Top, S.; Vessie`res, A.; Sellier, N.; Vaissermann, J .;
J aouen, G. Appl. Organomet. Chem. 1997, 11, 771-781.
(16) Hofer, O.; Schlo¨gl, K. J . Organomet. Chem. 1968, 13, 443-456.
(17) Schneider, M.; Wenzel, M. J . Labeled Compd. Radiopharm.
1980, 17, 1-20.
(20) Ceccon, A.; Giacometti, G.; Venzo, A.; Paolucci, D.; Benozzi, D.
J . Organomet. Chem. 1980, 185, 231-239.
(21) Tolbert, L. M.; Zhao, X.; Ding, Y.; Bottomley, L. A. J . Am. Chem.
Soc. 1995, 117, 12891-12892.
(22) Barlow, S. Unpublished results.
(23) Rinehart, K. L.; Michejda, C. J .; Kittle, P. A. J . Am. Chem. Soc.
1959, 81, 3162-3163.
(24) Fedin, E. I.; Blumenfeld, A. L.; Petrovskii, P. V.; Kreindlin, A.
Z.; Fadeeva, S. S.; Rybinskaya, M. I. J . Organomet. Chem. 1985, 292,
257-268.
(25) Zou, C.; Wrighton, M. S. J . Am. Chem. Soc. 1990, 112, 7578-
7584.
(26) Bildstein, B.; Hradsky, A.; Kopacka, H.; Malleier, R.; Ongania,
K.-H. J . Organomet. Chem. 1997, 540, 127-145.
(27) Boev, V. I.; Dombrovskii, A. V. Zh. Obshch. Khim. 1984, 54,
1192-1197.
(28) Boev, V. I.; Dombrovskii, A. V. J . Gen. Chem. USSR 1984, 54,
1067-1071.
(29) Boev, V. I. Zh. Org. Khim. 1992, 28, 770-778.
(18) Sanders, R.; Mueller-Westerhoff, U. T. J . Organomet. Chem.
1996, 512, 219-224.
(19) Cha´vez, I.; Alvarez-Carena, A.; Molins, E.; Roig, A.; Maniuk-
iewicz, W.; Aranacibia, A.; Aranacibia, V.; Brand, H.; Manr´ıquez, J .
M. J . Organomet. Chem. 2000, 601, 126-132.

The Ruthenocenylmethylium Cation
Organometallics, Vol. 20, No. 25, 2001 5353
F igu r e 2. View of the 1+ cation of in the crystal structure
of 1b (non-hydrogen atoms are shown with 50% thermal
ellipsoids, hydrogen atoms as spheres of arbitrary radius).
The cation lies on a crystallographic 2-fold rotation axis
and so is required to be disordered; the cyclopentadienyl
rings are related by the 2-fold axis, with C6 modeled at
half-occupancy. The symmetry-generated C6′ is omitted
from this view.
F igu r e 5. UV-vis spectrum of 1a in dichloromethane.
F igu r e 3. View of the nondisordered 1+ cation in the
crystal structure of 1d (non-hydrogen atoms are shown
with 50% thermal ellipsoids, hydrogen atoms as spheres
of arbitrary radius).
F igu r e 4. View of the [RcCH2PPh3]+ cation in the crystal
structure of [RcCH2PPh3]+[BF4]-‚0.5CH2Cl2 (non-hydrogen
atoms are shown with 50% thermal ellipsoids, hydrogen
atoms as spheres of arbitrary radius). The atom labels are
omitted from one of the phenyl groups for clarity.
F igu r e 6. LUMO (top) and HOMO-3 (bottom) of 1+
according to density functional calculations. These orbitals
are broadly similar to the LUMO and HOMO-2 respectively
of 3+.
Cr ysta l Str u ctu r es. The crystal structures of 1b and
1d were determined by single-crystal X-ray diffraction.
In both cases the structures are complicated by disorder.
The cation in 1b (Figure 2) is disordered due to its
location on a crystallographic 2-fold axis, while the
asymmetric unit of 1d contains four distinct cations, two
of which are disordered over inversion centers, one of
which shows thermal parameters indicative of unre-
solved disorder, and one of which is fully ordered (Figure
3, Table 1). Nevertheless, in all these cations it is clear
that the CH2 group is coordinated to the metal. The
(30) Bunting, H. E.; Green, M. L. H.; Marder, S. R.; Thompson, M.
E.; Bloor, D.; Kolinsky, P. V.; J ones, R. J . Polyhedron 1992, 11, 1489-
1499.

5354 Organometallics, Vol. 20, No. 25, 2001
Barlow et al.
Ta ble 1. Com p a r ison of Cr ysta llogr a p h ica lly
Deter m in ed P a r a m eter s for 1+ w ith DF -Ca lcu la ted
P a r a m eter s for 1+ a n d 3+
rings being nonparallel. In the nondisordered cation of
1d this ring tilt, R (Figure 1), is 7.1°. Disorder affects
the apparent value of R in the other cations; in the two
cations of 1d which lie on inversion centers this effect
is especially severe, the crystallographic symmetry
causing the rings to appear parallel (R ) 0). The ring
tilt for 2+[BPh4]-‚CH2Cl2 is 9.0°.11 The two five-
membered rings of the 1+ cations vary from almost
perfectly eclipsed conformation (in 1b) to perfectly
staggered (the disordered cations of 1d ), with interme-
diate cases (the ordered cation of 1d ). In summary,
crystallographic data show 1+ and 2+ have very similar
geometry.
crystal structureb calculated using LDA-DFT
bond lengths,
anglesa/Å, deg
1+
2.080(4)
1+
2.075
3+
1.924
M-C1
M-C2
2.177(4)
2.245(4)
2.235(4)
2.175(4)
2.272(4)c
2.185
2.254
2.254
2.183
2.263
2.026
2.081
2.079
2.024
2.161
M-C3
M-C4
M-C5
M-C6
M-CC5H5, range
M-CC5H5, av
C1-C2
2.187(4)-2.215(4) 2.185-2.212 2.024-2.058
2.194(13)
1.458(6)
1.459(6)
1.405(6)
1.413(7)
1.429(6)
1.412(6)
2.199(13)
1.455
1.452
1.403
1.408
2.040(16)
1.450
1.450
1.396
1.405
C1-C5
The crystal structure of [RcCH2PPh3]+[BF4]-‚xCH2Cl2
{x ) ca. 0.5} has also been determined and confirms
the molecular structure, as shown in Figure 4. In
contrast to the CH2 group of 1b and 1d , that of the
[RcCH2PPh3]+ cation does not interact with the ruthe-
nium center; the CCp-CCH2 bond is actually bent very
slightly away from the metal leading to a Ru-CCH2
distance of 3.290(6) Å. The ring tilt is only 1.5°, and the
Ru-CCp distances range from 2.158(5) to 2.190(5) Å
(average 2.173(10) Å), similar to those for other “normal”
ruthenocenes. Thus, [RcCH2PPh3]+ is a “normal” phos-
phonium salt. The two cyclopentadienyl rings are ap-
proximately eclipsed.
C1-C6
C2-C3
C3-C4
1.430
1.406
1.428
1.405
C4-C5
CC5H5-CC5H5, range 1.414(8)-1.425(7) 1.420-1.427 1.417-1.428
CC5H5-CC5H5, av
1.418(6)
7.1
42.6
1.424(3)
5.3
41.2
1.421(4)
10.5
44.0
R
â
a
Atom labeling is that shown in Figure 3; angles R (ring tilt)
and â (angle between CCp-Cexo and the attached ring) are defined
b
in Figure 1. Parameters for the ordered cation in the crystal
structure of 1d . c Range for all the cations in the structures of 1b
and 1d is 2.251(9)-2.40(1) Å.
R-CCH2 bond lengths in 1b and 1d , which should be
little affected by the disorder, fall in the range 2.251-
(9)-2.40(1) Å; the value for the nondisordered cation of
1d is 2.272(4) Å. The corresponding value for 2+ in the
dichloromethane solvate of its tetraphenylborate salt is
2.270(3) Å,11,31 and values in the range 2.281(9)-2.571-
(4) Å have been reported for other more complex
ruthenocenyl carbocations.4,5,7-9,32,33 The average Ru-
CCp and Ru-Cfulvene bond lengths in the nondisordered
cation of 1d are not significantly different from each
other, or from the corresponding distances in 2+, in [(η6-
arene)RuCp]+ derivatives,34-36 or in ruthenocene itself.37
The C-C bond lengths within the C5H4CH2 ligand of
the nondisordered cation of 1d show significant alterna-
tion similar to that seen for 2+11 and for some susbti-
tuted (η6-fulvene)Cr(CO)3 derivatives,38 consistent with
the description of the C5H4CH2 ligand as coordinated
fulvene. In each 1+ cation it is also evident that the
fulvene ligand is nonplanar; in the nondisordered cation
of 1d the angle, â (Figure 1), between the CCp-CCH2
bond and the attached five-membered ring is 42.6°,
while in the other cations of 1d and that of 1b the
apparent value of this angle is somewhat affected by
disorder. The corresponding angle in the structure of
2+[BPh4]-‚CH2Cl2 is 40.3°,11 and â falls in the range
29.9-40.4° for other systems.4,5,7-9,32,33 The coordination
of CH2 to the Ru also leads to the two five-membered
Sp ectr oscop y. In the 1H NMR spectrum, the CH2
resonance of 1a is observed at 5.07 ppm in CD2Cl2 and
at 5.25 ppm in acetone-d6, and that of 1c is at 5.02 ppm
in CD2Cl2; for 2+ a corresponding value of 4.75 ppm has
been reported, both for the tetrafluoroborate in acetone-
d6 and for the hexafluorophospate in CD2Cl2.39 The
10
CH2 13C resonance of 1a is seen at 72.7 ppm in CD2Cl2;
values of 77.810 and 74.739 ppm have been reported for
the corresponding shifts of the hexafluorophosphate of
1
2+ in CH2Cl2. The decrease in H shift and increase in
13C shift brought about by methylation perhaps reflect
the presence of opposing effects; presumably the induc-
tive effect of the methyl groups and the interaction with
the metal are both important factors. The CH2 reso-
nances for the ruthenium species, 1+ and 2+, are at
consistently lower frequency than those of their iron an-
alogues; values for the CH2 1H resonance of the ferro-
cenylmethylium cation, 3+, have been reported in the
range 5.75-6.00 ppm for a variety of solvents and coun-
terions,20,40-42 while for the (nonamethylferrocenyl)-
methylium ion, 4+, the CH2 1H and 13C resonances are
in the ranges 4.98-5.29 and 90.7-91.2 ppm, respec-
1
tively.24,43 The cyclopentadienyl H and 13C NMR reso-
nances of 1+ are at considerably higher frequency than
those of simple ruthenocenes. The C5H5 1H chemical
shifts allow one to compare the ligand properties of
fulvene with those of its isomer, benzene; in acetone-d6
these resonances are at 5.70 and 5.45 ppm for 1a and
η5-cyclopentadienyl-η6-benzene-ruthenium(II) hexafluo-
rophosphate,44 respectively (ruthenocene is at 4.60 ppm
(31) The structure of the hexafluorophosphate of 2+ has also been
reported (see ref 10), but the parameters reported are seriously affected
by disorder.
(32) Watanabe, M.; Moyoyama, I.; Takayama, T. J . Organomet.
Chem 1996, 524, 9-18.
(33) Watanabe, M.; Motoyama, I.; Takayama, T. Bull. Chem. Soc.
J pn. 1996, 69, 2877-2884.
(39) Kreindlin, A. Z.; Fedin, E. I.; Petrovskii, P. V.; Rybinskaya, M.
I.; Minyaev, R. M.; Hoffmann, R. Organometallics 1991, 10, 1206-
1209.
(34) Huckett, S. C.; Miller, L. L.; J acobson, R. A.; Angelici, R. J .
Organometallics 1988, 7, 686-691.
(35) Fagan, P. J .; Ward, M. D.; Calabrese, J . C. J . Am. Chem. Soc.
1989, 111, 1698-1719.
(40) Cais, M.; Dannenberg, J . J .; Eisenstadt, A.; Levenburg, M. I.;
Richards, J . H. Tetrahedron Lett. 1966, 1695-1701.
(41) Histame, M.; Yamakawa, K. Tetrahedron 1971, 27, 2101-2110.
(42) Cerichelli, G.; Floris, B.; Ortaggi, G. J . Organomet. Chem. 1974,
78, 241-252.
(43) Kreindlin, A. Z.; Dolgushin, F. M.; Yanovsky, A. I.; Kerzina, Z.
A.; Petrovskii, P. V.; Rybinskaya, M. I. J . Organomet. Chem. 2000,
616, 106-111.
(36) Nolan, S. P.; Martin, K. L.; Stevens, E. D. Organometallics 1992,
11, 3947-3953.
(37) Seiler, P.; Dunitz, J . D. Acta Crystallogr. 1980, B36, 2946-
2950.
(38) Lubke, B.; Edelmann, F.; Behrens, U. Chem. Ber. 1983, 116,
11-26.

The Ruthenocenylmethylium Cation
Organometallics, Vol. 20, No. 25, 2001 5355
in this solvent), suggesting fulvene is a more “electron-
poor” ligand than benzene when coordinated to [Ru(η5-
C5H5)]+.45
These results may be compared to those for η5-
cyclopentadienyl-η6-benzene-ruthenium(II) cation; re-
duction with sodium amalgam under conditions similar
to ours has been reported to give varying ratios of η5-
cyclopentadienyl-η5-cyclohexadienylruthenium (presum-
ably resulting from the 19-electron Ru(I) species ab-
stracting H• from a solvent or other molecule, paralleling
our observation of RcMe) and ruthenocene (presumably
formed by ligand exchange) as the main isolable prod-
ucts.48,52 Products arising from dimerization of the
reduced species through the arene, paralleling our
observation of RcCH2CH2Rc, have been observed for
other η5-cyclopentadienyl-η6-areneruthenium(II) deriva-
tives; in these cases the dimerization leads to a µ-η:5η5-
1,1′-dihydrobiphenyl (or a similar derivative) ligand.48
The dimerization of 1• is also reminiscent of the reaction
of FcCHROH {where R can be various alkyl groups}
with Zn/HCl to give FcCHRCHRFc; it is thought that
the ferrocenyl carbocation is formed initially and then
reduced to [FcCHR]•.53 The reactivity of 1• and [FcCHR]•
through the exo-carbon presumably reflects the high
LUMO coefficient of 1+ and 3+, and thus high SOMO
coefficient for 1• and 3•, on this carbon (vide infra, Figure
6).
Den sity F u n ction a l Ca lcu la tion s. To rationalize
features of the structure, spectroscopy, and reactivity
of 1+, and to gain insight into the structure of its iron
analogue, 3+, for which crystallographic data are un-
available (due to its instability with respect to dimer-
ization to 1,2-bis(ferroceniumyl)ethane), we performed
density functional (DF) calculations. Minimization of the
geometry of 1+ using the local density approximation
(LDA) gave structural parameters in excellent agree-
ment with the corresponding values for the ordered
cation in the structure of 1d (Table 1). The correspond-
ing LDA-DF-derived parameters for 3+ are also given
in Table 1 and suggest geometry quite similar to that
for 1+. Other DF methods including gradient corrections
(such as the BLYP method, see Experimental Section)
gave somewhat longer M-C bond distances and lower
values for â, but the general pattern of bond lengths
and angles was the same.
The UV-vis spectrum of 1a is shown in Figure 5. The
feature at ca. 320 nm is similar in energy to the spin-
allowed d-d transitions of both ruthenocene46 and the
η5-cyclopentadienyl-η6-benzene-ruthenium(II) cation;47
the considerably increased absorptivity in the present
compound presumably indicates relaxation of the parity
selection rule due to the lower symmetry of the ligand
field. Calculations (vide infra) confirm that the HOMO
and particularly the LUMO of 1+ have far-from-ideal
inversion symmetry. The higher energy part of the
spectrum resembles the η5-cyclopentadienyl-η6-benzene-
ruthenium(II) spectrum more closely than that of ru-
thenocene; the onset of intense, presumably charge-
transfer, absorption appears at a similar energy in 1a
and the benzene complex.
Red ox Ch em istr y. Cyclic voltammetry of 1a in
acetonitrile reveals an irreversible reduction at -1450
mV vs ferrocenium/ferrocene, while η5-cyclopentadienyl-
η6-benzene-ruthenium(II) hexafluorophosphate is ir-
reversibly reduced at -2420 mV in the same solvent.48,49
The greater ease of reduction of 1+ is consistent with
the NMR evidence that fulvene acts as a more “electron-
poor” ligand than benzene (vide supra). In dichlo-
romethane, the reduction peak is observed at -1235
mV; the electron transfer appears to be a little more
reversible in this solvent, with a weak reverse wave
observed, and E1/2 may be estimated as ca. -1110 mV.
This may be compared to values of E1/2 of -730, -830,
-760, and -640 mV for [Rc(CH)3Fc]+, [Rc(CH)3Fc′′]+
{Fc′′ ) 2,3,4,5,1′,2′,3′,4′-octamethylferrocen-1-yl}, [Rc-
(CH)3Rc]+, and [Rc(CH)5Rc]+, respectively, in the same
solvent.9,22 The greater ease of reduction for these ter-
and pentamethine species relative to 1+ may be at-
tributed to the differences between the LUMOs (Figure
6 for 1+; Figure 9 of ref 50 for [Rc(CH)3Rc]+). Chemical
reduction with sodium amalgam in THF afforded a
mixture of products, which were separated by column
chromatography to give low yields of the new compound
RcCH2CH2Rc and of RcCH2OCH2Rc (which has previ-
ously been observed as a side product from the chro-
matography of RcCH2OH on alumina16,17 and presum-
ably arises from reaction of 1• with the solvent, or of 1+
with any traces of NaOH present), as well as a trace of
the known compound RcMe.16,51
A previous MNDO/AM1 study gave a geometry simi-
lar to our LDA-DF structure for 1+ with â ) 41.5°, but
gave a very different â of 5.0° for 3+,54 while an
extended-Hu¨ckel study of 3+ gave â ) 40°, although the
authors believed this was somewhat overestimated.55
Since the submission of our paper, BLYP-DF calcula-
tions have been reported for 2+ (M-CCH2, 2.410 Å; â,
32.4°) and 4+ (2.324 Å, 34.0°)56 and give geometries
similar to our calculations using the same method for
(44) Nesmeyanov, A. N.; Vol’kenau, N. A.; Bolesova, I. N.; Shul’pina,
L. S. J . Organomet. Chem. 1979, 182, C36-C38.
(45) For [Ru(η6-C5Me4CH2)Cp]+ NMR data in acetonitrile-d3 have
been reported in ref 3; the CH2 1H and 13C resonances were observed
at 5.05 and 69.4 ppm, respectively, and the Cp 1H and 13C resonances
were seen at 5.19 and 85.9 ppm, respectively. The different solvent
means these data are not directly comparable with the data discussed
here for 1+, 2+, and [Ru(η6-benzene)Cp]+.
1
+ (2.368 Å, 35.8°) and 3+ (2.278 Å, 37.8°), respectively.
The disparities between the crystallographic11,43 and
BLYP-DF56 values of M-CCH2 and â for 2+ and 4+ have
been attributed to crystal-packing effects. Further
evidence that these parameters are particularly sensi-
(46) Sohn, Y. S.; Hendrickson, D. N.; Gray, H. B. J . Am. Chem. Soc.
1971, 93, 3603-3612.
(47) Gill, T. P.; Mann, K. R. Organometallics 1982, 1, 485-488.
(48) Gusev, O. V.; Ievlev, M. A.; Peterleitner, M. G.; Peregudova, S.
M.; Denisovich, L. I.; Petrovskii, P. V.; Ustynyuk, N. A. J . Organomet.
Chem. 1997, 534, 57-66.
(49) Using a correction of E1/2(ferrocenium/ferrocene) ) +400 mV
vs SCE (Connelly, N. G.; Geiger, W. E. Chem. Rev. 1996, 96, 877-
910).
(50) Barlow, S.; Marder, S. R. Chem. Commun. 2000, 1555-1562,
and references therein.
(51) Albers, M. O.; Liles, D. C.; Robinson, D. J .; Shaver, A.;
Singleton, E.; Wiege, M. B.; Boeyens, J . C. A.; Levendis, D. C.
Organometallics 1986, 5, 2321-2327.
(52) Vol’kenau, N. A.; Bolesova, I. N.; Shul’pina, L. S.; Kitaigorodskii,
A. N. J . Organomet. Chem. 1984, 313-321.
(53) Cais, M.; Eisenstadt, A. J . Org. Chem. 1965, 30, 1148-1154.
(54) Gal’pern, E. G.; Gambaryan, N. P.; Kreindlin, A. Z.; Rybinskaya,
M. I.; Stankevich, I. V.; Chistyakov, A. L. Metalloorg. Khim. 1992, 5,
831-838.
(55) Gleiter, R.; Seeger, R. Helv. Chim. Acta 1971, 54, 1217-1220.
(56) Rybinskaya, M. I.; Nekrasov, Y. S.; Borisov, Y. A.; Belokon′, A.
I.; Kreindlin, A. Z.; Kamyshova, A. A.; Kruglova, N. V. J . Organomet.
Chem. 2001, 631, 9-15.

5356 Organometallics, Vol. 20, No. 25, 2001
Barlow et al.
Ta ble 2. En er gies a n d d -Or bita l Con ten t of Som e
F r on tier Or bita ls of 1+ a n d 3+ Accor d in g to DF
Ca lcu la tion sa
symmetric sandwich species, i.e., to e1u in D5d), so it is
the HOMO-3. The occupancies of the fulvene fragment
LUMO resulting from this interaction are found to be
0.60 and 0.56 for 1+ and 3+, repectively, consistent with
the longer CCp-Cexo bond calculated in the ruthenium
compound and corresponding to more contribution from
the resonance structure (b) of Figure 1 in 1+ than in
3+.
The HOMO-LUMO gap for 1+ (3.27 eV) is of the
same order of magnitude as the observed lowest energy
transition in the UV-vis (vide supra). Moreover, the gap
for 3+ (2.39 eV) is considerably smaller, consistent with
the lower energy visible absorption reported for ferro-
cenyl carbocations (they are reported to be orange or
red) and with the smaller singlet-triplet separations
suggested to be responsible for their dimerization to bis-
(ferroceniumyl)ethanes.57
1+
3+
energy/eV
% d
energy/eV
% d
LUMO
HOMO
HOMO-1
HOMO-2
HOMO-3
-6.45
-9.72
-9.75
40
76
79
-7.02
-9.41
49
82
82
66
-9.53
-10.63
-10.95
47
a
The HOMO-3 of 1+ corresponds to the HOMO-2 of 3+ (see text).
tive to crystal packing comes from the range of M-CCH2
values (2.251(9) to 2.40(1) Å) found for the five crystal-
lographically distinct 1+ cations in the crystal structures
of 1b and 1d and from the variation in â and Ru-CCH2
observed between the tetrafluoroborate32 and hexafluo-
rophosphate33 of a mixed iron-ruthenium [1.1]metal-
locenophane carbocation, and between [Rc(CH)3-
Rc]+[PF6]-7 and [Rc(CH)3Rc]+[BAr′4]-.9 In addition,
while BLYP-DF calculations predict a shorter M-CCH2
distance for 4+ than 2+, and while we find shorter
M-CCH2 for 3+ than 1+ using a variety of DF methods,
the structure of 4+[BAr′4]- (the only crystallographically
characterized ferrocenyl carbocation free of additional
stabilizing substituents) exhibits an Fe-CCH2 bond
length of 2.57(1) Å,43 longer than the corresponding
distance in that of 2+[BPh4]-‚CH2Cl2 (2.270(3) Å),11 and
a â of 23.6°.43 Nevertheless, BLYP-DF calculations, both
in our present study of 1+ and 3+ and in the previous
study of 2+ and 4+,56 also consistently overestimate
other M-C and C-C bond lengths relative to crystal-
lographic data. Thus, it seems that the LDA-DF struc-
ture (i.e., that summarized in Table 1) is likely to be a
better approximation to the gas-phase structure of 3+,
although the degree of bending of the CH2 toward the
iron atom may be very different in condensed phases.
The DF-derived orbital schemes for 1+ and 3+ are
broadly similar. The frontier orbitals of both species
have considerable d-character (Table 2), although the
orbitals have far from ideal inversion symmetry, con-
sistent with the high absorptivity of the “d-d transition”
for 1+ (vide supra). There is less d-contribution to both
HOMO and LUMO for the ruthenium species, reflecting
stronger forward-bonding and back-bonding. The LU-
MOs (shown in Figure 6 for 1+; the corresponding orbital
for 3+ is broadly similar in appearance) are reminiscent
of those of axially symmetric d6 sandwich compounds,
such as ferrocene and bis(benzene)chromium, where the
LUMO is a d-ligand antibonding orbital having πg
symmetry (for ideal axial D∞h-symmetry, corresponding
to e1g in D5d) with respect to the M-ligand axis. However,
a notable feature of the LUMO of 1+ and 3+ is the large
coeffecient on the CH2 carbon, consistent with the sites
of reaction observed for 1+ and 1• (vide supra). The
HOMO and HOMO-1 of 1+ and 3+ are largely d in
character, as are those of axially symmetric d6 sandwich
compounds. The remaining filled d-based orbital inter-
acts strongly with the LUMO of the fulvene fragment
(Figure 6); it consequently has much reduced d-char-
acter relative to the HOMO and HOMO-1 and is
considerably lower in energy. For 3+ this orbital is the
HOMO-2, but for 1+ the d-fulvene interaction is suf-
ficiently strong to push this orbital below one of the
ligand-based orbitals (analogous to the πu level in axially
Su m m a r y
Salts of the simplest ruthenocenyl carbocation,
[RcCH2]+, have been isolated for the first time; their
structures, spectroscopy, electrochemistry, and reactiv-
ity have been investigated and compared with substi-
tuted derivatives and with the isoelectronic η5-cyclo-
pentadienyl-η6-arene-ruthenium(II) cations. Crystallogra-
phic data confirm that the formally cationic carbon is
coordinated to the ruthenium and that the structure is
best described as η5-cyclopentadienyl-η6-fulvene-ruthe-
nium(II). Density functional theory gave an optimized
geometry for [RcCH2]+ in good agreement with the
crystallographic data and suggested a similar structure
for the [FcCH2]+ cation.
Exp er im en ta l Deta ils
Electrochemistry was performed using deoxygenated solu-
tions, ca. 10-4 M in sample and 0.1 M in [nBu4N]+[PF6]-, in
freshly distilled dried solvents, Pt wire auxiliary and pseudo-
reference electrodes, and a glassy carbon working electrode.
Ferrocene was used as an internal reference. Solvents were
dried by distillation from sodium-benzophenone (diethyl
ether), sodium-potassium alloy (pentane), potassium (THF),
or calcium hydride (dichloromethane, acetonitrile).
RcCH2OH. A solution of tert-butyl alcohol (distilled from
CaH2; 4.25 mL, 45 mmol) in diethyl ether (15 mL) was added
dropwise to a suspension of LiAlH4 (purified by dissolution in
diethyl ether and filtration, 600 mg, 15 mmol) in diethyl ether
(15 mL). When the addition was complete, a solution of
RcCHO18 (544 mg, 2.10 mmol) in diethyl ether (50 mL) was
added dropwise. After stirring for 2 h at room temperature,
water (50 mL) was added cautiously. The layers were sepa-
rated, and the aqueous layer was extracted with 3 × 50 mL of
diethyl ether. The combined organics were dried over K2CO3,
filtered, and evaporated under reduced pressure to afford
RcCH2OH as a white powder (440 mg, 1.68 mmol, 80%). 1H
NMR (300 MHz, benzene-d6): δ 4.54 (apparent t, 2H, J ) 1.7
Hz, C5H4), 4.37 (s, 5H, C5H5), 4.35 (apparent t, 2H, J ) 1.7
Hz, C5H4), 4.00 (d, 2H, J ) 5.9 Hz, CH2), 1.11 (t, 1H, J ) 5.9
Hz, OH). 13C{1H} NMR (75 MHz, benzene-d6): δ 95.7 (C5H4
quat.), 70.9 (C5H4 CH), 70.6 (C5H5), 70.5 (C5H4 CH), 58.9 (CH2).
[RcCH2]+[BF 4]- (1a ). HBF4 (ca. 2 mL of a 48% solution in
diethyl ether) was added dropwise to a stirred solution of
RcCH2OH (150 mg, 0.57 mmol) in diethyl ether (20 mL),
resulting in an instant white precipitate. After 5 min, the
(57) Rybinskaya, M. I.; Kreindlin, A. Z.; Fadeeva, S. S. J . Organomet.
Chem. 1988, 358, 363-374.

The Ruthenocenylmethylium Cation
Organometallics, Vol. 20, No. 25, 2001 5357
supernatant was removed from the precipitate by filter can-
nula; the precipitate was washed with diethyl ether (3 × 20
mL) and dried in vacuo. The solids were then extracted into
dichloromethane (20 mL) and precipitated by dropwise addi-
tion of diethyl ether (80 mL). The supernatant was removed
by filter cannula, and the solids were washed with diethyl
ether (2 × 20 mL) before drying in vacuo to afford a pale cream
powder (178 mg, 0.54 mmol, 92%). 1H NMR (300 MHz,
dichloromethane-d2): δ 6.26 (apparent t, 2H, J ) 1.8 Hz, C5H4),
5.56 (s, 5H, C5H5), 5.25 (apparent t, 2H, J ) 1.8 Hz, C5H4),
NMR (282 MHz, dichloromethane-d2): δ -79.3. Anal. Calcd
for C12H11F3O3RuS: C, 36.64; H, 2.82; Found: C, 36.79; H,
3.15.
R ea ct ion of 1,1′-Dim et h ylr u t h en ocen e w it h [P h 3-
C]+[BF 4]-. A solution of [Ph3C]+[BF4]- (265 mg, 0.80 mmol)
in dichloromethane (15 mL) was added dropwise to a solution
of a 1,1′-dimethylruthenocene59 (225 mg, 0.87 mmol) in dichlo-
romethane (15 mL). The mixture slowly darkened. After 15 h
the solvent was removed under reduced pressure to leave a
1
mixture of dark oil and solid. H NMR spectroscopy revealed
1
5.07 (s, 2H, CH2). H NMR (300 MHz, acetone-d6): δ 6.44 (m,
a complex mixture of products. Repeating the reaction at -78
°C, or using [Ph3C]+[PF6]- in place of [Ph3C]+[BF4]-, led to no
significantly different result.
2H, C5H4), 5.70 (s, 5H, C5H5), 5.47 (s, 2H, C5H4), 5.25 (s, 2H,
CH2). 13C NMR (75 MHz, dichloromethane-d2): δ 108.4 (C5H4
quat.), 93.0 (C5H4 CH), 86.7 (C5H4 CH), 84.5 (C5H5), 72.7 (CH2).
Anal. Calcd for C11H11BF4Ru: C, 39.91; H, 3.35; Found: C,
39.96; H, 3.44. UV (dichloromethane): λmax 323 (ꢀ323 540) nm
(M-1cm-1). UV (acetonitrile): λmax 319 nm. IR (KBr): 3105,
3084, 1409, 1336, 1306, 1259, 1237, 1099 (s, br), 1032 (s, br),
876, 845, 826, 806, 745, 534, 522, 502, 456, 429, 419 cm-1. ES-
MS (MeOH): m/z 245 (100%, RcCH2+).
[RcCH2P P h 3]+[BF 4]-. HBF4 (ca. 0.4 mL of a 40% aqueous
solution) was added to a solution of RcCH2OH (400 mg, 1.53
mmol) and PPh3 (400 mg, 1.53 mmol) in dichloromethane (2
mL). The resulting mixture was stirred for 1 h, after which
diethyl ether (100 mL) was added. The white precipitate was
collected on a frit, washed with diethyl ether (3 × 30 mL), and
1
dried in vacuo at 100 °C (850 mg, 1.43 mmol, 94%). H NMR
[RcCH2]+[BAr ′4]- (1b). Dichloromethane (6 mL) was added
(300 MHz, chloroform-d): δ 7.78 (br apparent t, 3H, J ) ca. 7
Hz, Hp), 7.68-7.54 (overlapping multiplets, 12H, Ho and Hm),
58
to 1a (52 mg, 0.16 mmol) and [Na]+[BAr′4]- (127 mg, 0.14
mmol); the resulting mixture was heated under reflux for 30
min. The solvent was then removed under reduced pressure,
and the remaining solids were extracted with diethyl ether
(15 mL). The ether extracts were concentrated (to 3 mL) under
reduced pressure, and pentane (25 mL) was added to afford a
pale cream precipitate, which was washed with pentane (2 ×
10 mL) and dried in vacuo (110 mg, 0.099 mmol, 69%). 1H
NMR (300 MHz, dichloromethane-d2): δ 7.72 (br s, 8H), 7.57
(s, 4H), 6.11 (apparent t, 2H, J ) 1.8 Hz), 5.46 (s, 5H), 5.14
(apparent t, 2H, J ) 1.8 Hz), 5.02 (s, 2H). 19F NMR (282 MHz,
dichloromethane-d2): δ -63.2. 13C{1H} NMR (75 MHz, dichlo-
romethane-d2): δ 162.1 (q, J BC ) 50 Hz, Cipso), 135.1 (Co), 129.2
(qq, J CF ) 32, ca. 3 Hz, Cm), 124.9 (q, J CF ) 272 Hz, CF3), 117.8
(septet, J CF ) ca. 4 Hz, Cp), 108.0 (C5H4 quat.), 92.4 (C5H4 CH),
86.4 (C5H4 CH), 84.1 (C5H5), 72.1 (CH2). 11B NMR (160 MHz):
δ -6.25. Anal. Calcd for C43H23BF24Ru: C, 46.63; H, 2.09.
Found: C, 46.33; H, 2.66. IR (KBr): 3134, 1611, 1417, 1357
(s), 1278 (s), 1118 (s, br), 935, 899, 890, 841, 714, 683, 672
4.60 (s, 5H, C5H5), 4.39 (apparent s, 2H, C5H4), 4.29 (d, J PH
)
11.5 Hz, CH2), 4.25 (apparent s, 2H, C5H4). 13C{1H} NMR (75
MHz, chloroform-d): δ 135.1 (Cp), 133.9 (d, J CP ) 9 Hz, Co or
Cm), 130.2 (d, J CP ) 12 Hz, Co or Cm), 117.5 (d, J CP ) 85 Hz,
C
ipso), 76.1 (C5H4 quat.), 72.5 (C5H4 CH), 71.9 (C5H5), 71.0 (C5H4
CH), 26.5 (d, J CP ) 45 Hz, CH2). 31P{1H} NMR (122 MHz): δ
20.2. Anal. Calcd for 29H26BF4PRu: C, 58.70; H, 4.08.
C
Found: C, 58.15; H, 4.42. ES-MS (MeCN): m/z 507 (30%,
RcCH2PPh3+), 245 (100%, RcCH2+).
Red u ction of 1a w ith Sod iu m Am a lga m . A slurry of 1a
(120 mg, 0.36 mmol) in THF (30 mL) was added to an
amalgam, made from 400 mg (17 mmol) of sodium and 40 g of
mercury. The reaction mixture was stirred for 2 h and the
organic layer decanted from the amalgam by cannula and
filtered through Celite. The amalgam and Celite were washed
with additional THF (3 × 20 mL), and the combined THF
portions were evaporated under reduced pressure to give a
white solid (90 mg). The solid was chromatographed on silica
gel, initially eluting with 1:1 dichloromethane/hexane; the first
fraction (ca. 1 mg, 0.004 mmol, 1%) was identified as RcMe
by comparison of its 1H NMR spectrum with the literature.51
A second fraction was found to be RcCH2CH2Rc (ca. 10 mg,
cm-1
.
[RcCH2]+[P F 6]- (1c). Meth od A. Aqueous HPF6 (2 mL of
a 60% solution) was added dropwise to a stirred solution of
RcCH2OH (130 mg, 0.50 mmol) in THF (2 mL). After 5 min,
water (40 mL) was added; the resulting creamy precipitate was
washed was water (2 × 20 mL) and dried in vacuo (103 mg,
0.26 mmol, 52%). Meth od B. A solution of [Ph3C]+[PF6]- (155
mg, 0.40 mmol) in dichloromethane (10 mL) was added
dropwise to a stirred solution of RcCH2OH (107 mg, 0.41 mmol)
in dichloromethane (10 mL). The yellow color of the trityl
cation was instantly dissipated. After 5 min, the solution was
filtered; diethyl ether (100 mL) was then added dropwise to
precipitate a pale cream powder, which was washed with ether
1
0.020 mmol, 11%). H NMR (300 MHz, chloroform-d): δ 4.53
(s, 10H, C5H4), 4.51 (apparent t, 4H, J ) 1.6 Hz, C5H4), 4.45
(apparent t, 4H, J ) 1.6 Hz, C5H4), 2.35 (s, 4H, CH2). 13C{1H}
NMR (75 MHz, chloroform-d): δ 92.9 (C5H4 quat.), 79.6 (C5H4
CH), 70.4 (C5H5), 69.3 (C5H4 CH), 31.2 (CH2). EI-MS: m/z 490
(23%, M+), 245 (100%, RcCH2+), 167 (15%, RuCp+). A third
fraction was eluted with neat dichloromethane and found to
be RcCH2OCH2Rc (ca. 18 mg, 0.035 mmol, 20%). 1H NMR (300
MHz, chloroform-d): δ 4.61 (apparent t, 4H, J ) 1.6 Hz, C5H4),
1
1
(2 × 20 mL) and dried in vacuo (75 mg, 0.20 mmol, 50%). H
4.49 (apparent s, 14H, C5H5 and C5H4), 4.07 (s, 4H, CH2). H
NMR (300 MHz, dichloromethane-d2): δ 6.22 (apparent t, 2H,
J ) 1.8 Hz), 5.54 (s, 5H), 5.24 (apparent t, 2H, J ) 1.8 Hz),
5.02 (s, 2H). Anal. Calcd for C11H11F6PRu: C, 33.94; H, 2.85.
Found: C, 34.25; H, 3.35. IR (KBr): 3129, 1484, 1429, 1294,
NMR (300 MHz, benzene-d6): δ 4.66 (apparent t, 4H, J ) 1.6
Hz, C5H4), 4.43 (s, 10H, C5H5), 4.42 (apparent t, 4H, J ) 1.6
Hz, C5H4), 4.19 (s, 4H, CH2). 13C NMR (75 MHz, chloroform-
d): δ 87.2 (C5H4 quat.), 71.8 (C5H4 CH), 70.6 (overlapping C5H4
CH and C5H5 CH), 67.6 (CH2). 13C NMR (75 MHz, benzene-
d6): δ 88.2 (C5H4 quat.), 72.0 (C5H4 CH), 70.9 (C5H5 CH), 70.8
(C5H4 CH), 67.8 (CH2). EI-MS: m/z 506 (24%, M+), 262 (10%,
RcCH2O+ and RcCH2OH+), 245 (100%, RcCH2+), 167 (20%,
RuCp+).
Cr yst a l St r u ct u r es. Single crystals were mounted on a
glass fiber using perfluoropolyether oil and cooled rapidly to
150 K in a stream of cold nitrogen using an Oxford Cryosys-
tems CRYOSTREAM unit. Diffraction data were measured
using Enraf-Nonius DIP2000 image-plate (1b) or Enraf-Nonius
1050, 1015, 829 (s, br), 558, 492, 236, 420 cm-1
.
[RcCH2]+[CF 3SO3]- (1d ). CF3SO3SiMe3 (ca. 0.5 mL) was
added dropwise to a stirred solution of RcCH2OH (110 mg, 0.42
mmol) in diethyl ether (25 mL) at 0 °C, resulting in an instant
off-white precipitate. After 20 min, the precipitate was allowed
to settle; the supernatant was decanted by cannula, and the
solids were washed with diethyl ether (4 × 25 mL) and dried
in vacuo (130 mg, 0.33 mmol, 79%). 1H NMR (300 MHz,
dichloromethane-d2): δ 6.29 (apparent s, 2H, C5H4), 5.62 (s,
5H, C5H5), 5.29 (apparent s, 2H, C5H4), 5.09 (s, 2H, CH2). 19F
(58) Brookhart, M.; Grant, B.; Volpe, A. F. Organometallics 1992,
11, 3920-3922.
(59) Lemay, G.; Kaliaguine, S.; Adnot, A.; Nahar, S.; Cozak, D.;
Monnier, J . Can. J . Chem. 1986, 64, 1943-1948.

5358 Organometallics, Vol. 20, No. 25, 2001
Ta ble 3. Su m m a r y of Cr ysta llogr a p h ic Da ta
Barlow et al.
1b
1d
[RcCH2PPh3]+[BF4]-‚0.5CH2Cl2
formula
fw
C43H23BF24Ru
1108.5
C12H11F3O3RuS
345.34
C29.5H27BClF4PRu
635.81
cryst growth
cryst appearance
cryst size/mm
space group
CH2Cl2/pentane layering
pale green prism
0.2 × 0.2 × 0.8
C2
CH2Cl2/Et2O layering
pale yellow fragment
0.1 × 0.1 × 0.3
P21/c
evaporation of CH2Cl2/hexane solution
colorless plate
0.1 × 0.2 × 0.3
C2/c
a/Å
b/Å
c/Å
15.703(1)
12.742(1)
10.787(1)
97.974(4)
2137.5
16.2555(3)
13.2704(3)
18.7369(5)
104.543(2)
3912.4
33.0591(7)
12.5182(3)
13.7757(3)
101.591(1)
â/deg
cell vol/Å3
5584.7
Z
2
1.72
0.50
1094
12
1.76
1.37
2328
8
1.51
0.76
2568
Dc/g mL-1
µ/mm-1
F(000)
max θ/deg
26.6
6875
4149
0.028
27.5
28 639
9253
0.039
27.5
10 107
6308
0.047
total no. data measd
total no. of unique data
Rint
no. of observns and criterion
no. params refined
S
4122 (I > 3σ(I))
5483 (I > 3σ(I))
4083 (I > 2σ(I))
339
553
350
1.056
1.025
1.054
final R-indices
R ) 0.0328
Rw ) 0.0398
-0.70, 1.48
R ) 0.0371
Rw ) 0.0494
-0.76, 1.23
R1 ) 0.0632 (I > 2σ(I))
wR2 ) 0.1607 (I > 2σ(I))
-1.069, 1.689
min and max residuals/e Å-3
Kappa CCD diffractometers (1d and [RcCH2PPh3]+[BF4]-‚
0.5CH2Cl2), in each case with graphite-monochromated Mo KR
radiation, λ ) 0.71069 Å. Intensity data were processed using
the programs DENZO and SCALEPACK.60 Structures were
solved by direct methods using SIR92,61 which located all non-
hydrogen atoms. Subsequent full-matrix least-squares refine-
ment was carried out against observed F using the CRYSTALS
program suite62 (for 1b and 1d ) or against all F2 using
SHELXS-9763 within WinGX64 (for [RcCH2PPh3]+[BF4]‚0.5CH2-
Cl2). Coordinates and anisotropic thermal parameters of all
non-hydrogen atoms were refined. Further details of the
crystal structure determinations are given in Table 3 and in
the Supporting Information.
For 1b, both the Ru and B atoms lie on a crystallographic
2-fold rotation axis. The tetraarylborate anion is positioned
on the axis such that the crystallographic symmetry coincides
with the local symmetry of the molecule. However, the
symmetry requires the cation to be disordered. The cation has
been modeled as positioned with the Ru atom lying directly
on the axis with the cyclopentadienyl and fulvene ligands
disordered in such a way that their five-membered rings
overlap. The acceptable geometry and thermal ellipsoids shown
in Figure 2 indicate that this is a good approximation. The
large thermal parameters of some of the peripheral F atoms
of the anion suggest that the CF3 groups may be disordered,
but attempts to model this did not result in any improvement
of the fit to the data.
vene rings of each cation superimposed by the crystallographic
disorder. One of the other cationssthat containing Ru(2)shas
no crystallographic symmetry, but also appears to be disor-
dered as some C atoms have large anisotropic thermal
parameters and there is significant residual electron density
nearby; this disorder could not be successfully modeled. The
remaining cation (that containing Ru(1)) appears to be com-
pletely ordered, as do all three crystallographically distinct
triflate anions; these four moieties also have no crystal-
lographic symmetry.
The asymmetric unit of [RcCH2PPh3]+[BF4]-‚xCH2Cl2 con-
tains one cation and one anion, with no crystallographic
symmetry, and a dichloromethane molecule which was mod-
eled with one Cl atom on a 2-fold rotation axis, with the rest
of the molecule disordered as a result of the crystallographic
symmetry. There is therefore half (or less) of a dichlo-
romethane molecule in the asymmetric unit. 1H NMR spec-
troscopy of some of the crystals dissolved in CDCl3 confirmed
that x ) ca. 0.5. The thermal parameters of the tetrafluorobo-
rate ion are suggestive of some disorder around a noncrystal-
lographic 3-fold axis, and one of the phenyl rings also appears
slightly disordered. Attempts to model the disorder in these
groups did not lead to any improvement in the refinement.
Com p u ta tion a l Meth od s. Calculations were performed
using the density functional methods of the Amsterdam
Density Functional Package (ADF 2000.2).65-67 Type IV basis
sets were used with triple-ú accuracy sets of Slater-type
orbitals, with a single polarization function added to the main
group atoms. The cores of the atoms were frozen up to 2p for
Fe, 3p for Ru, and 1s for C. First-order relativistic corrections
were made to the cores of the atoms. Relativistic corrections
were included using the ZORA formalism. Three different
The unit cell of 1d contains three crystallographically
distinct triflate anions, which have no crystallographic sym-
metry, and four distinct 1+ cations. Two of thesesthose
containing Ru(3) and Ru(4)slie on crystallographic centers of
inversion, with the five-membered cyclopentadienyl and ful-
(60) Otwinowski, Z., Minor, W., Carter, C. W., Sweet, R. M., Eds.;
DENZO and SCALEPACK; Academic Press: New York, 1997; Vol. 276.
(61) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.;
Polidori, G.; Burla, M. C.; Camalli, M. J . Appl. Crystallogr. 1994, 27,
435.
(62) Watkin, D. J .; Prout, C. K.; Carruthers, J . R.; Betteridge, P.
W.; CRYSTALS issue 10; Chemical Crystallography Laboratory:
Oxford, UK, 1996.
(63) Sheldrick, G. M. SHELXS 97, Program for Crystallography;
University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(64) Ferrugia, L. J . WinGX: An Integrated System of Publically
Available Windows Programs for the Solution, Refinement, and
Analysis of Single-Crystal X-ray Diffraction Data; University of Glas-
gow: Glasgow, UK, 1998.
(65) te Velde, G.; Baerends, E. J . J . Comput Phys. 1992, 99, 84-98.
(66) Baerends, E. J .; Berces, A.; Bo, C.; Boerringter, P. M.; Cavallo,
L.; Deng, L.; Dickson, R. M.; Ellis, D. E.; Fan, L.; Fischer, T. H.; Fonseca
Guerra, C.; van Gisbergen, S. J .; Groeneveld, J . A.; Gritsenko, O. V.;
Harris, F. E.; van den Hoek, P.; J acobsen, H.; van Kessel, G.; Kootstra,
F.; van Lenthe, E.; Osinga, V. P.; Philipsen, P. H. T.; Post, D.; Pye, C.
C.; Ravenek, W.; Ros, P.; Schipper, P. R. T.; Schreckenbach, G.;
Snijiders, J . G.; Sola, M.; Swerhone, D.; te Velde, G.; Vernooijis, P.;
Versluis, L.; Visser, O.; van Wezenbeek, E.; Wiesenekker, G.; Wolff,
S. K.; Woo, T. K.; Ziegler, T. ADF Program System Release 1999;
Department of Theoretical Chemistry, Vrije Universiteit: Amsterdam,
1999.
(67) Guerra, C. F.; Snijders, J . G.; te Velde, G.; Baerends, E. J . Theor.
Chem. Acc. 1998, 99, 391-403.

The Ruthenocenylmethylium Cation
Organometallics, Vol. 20, No. 25, 2001 5359
procedures were used for optimization. The local density
approximation of Vosko, Wilk, and Nusair68 was used through-
out. First, no gradient correction was used. Second, the
nonlocal exchange corrections by Becke69 and nonlocal cor-
relation corrections by Perdew were used.70 Third, Becke
exchange69 and Lee, Wang, and Parr correlation71 corrections
were made (BLYP method).
EPSRC for a studentship (T.J .B.), J uan Manr´ıquez for
drawing our attention to his metathesis method of
obtaining [BAr′4]- salts, a referee for drawing our
attention to ref 56, and Colin Sparrow for acquiring
electrospray mass spectra.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
structure solution and refinement details, atomic coordinates
and equivalent isotropic displacement parameters, bond lengths
and angles, anisotropic displacement parameters, hydrogen
coordinates, and isotropic displacement parameters for 1b, 1d ,
and [RcCH2PPh3]+[BF4]-‚0.5CH2Cl2. This material is available
free of charge via the Internet at http://pubs.acs.org.
Ack n ow led gm en t. The authors thank J ohnson-
Matthey PLC for a generous loan of RuCl3‚xH2O, the
(68) Vosko, S. H.; Wilk, L.; Nusair, M. Can. J . Phys. 1990, 58, 1200.
(69) Becke, A. D. Phys. Rev. 1988, A38, 3098-3100.
(70) Perdew, J . P. Phys. Rev. 1986, B34, 8822-8824.
(71) Lee, C. T.; Yang, W. T.; Parr, R. G. Phys. Rev. 1988, B37, 785-
789.
OM010667+