Ferra- and ruthenatricarbollides CpFeC3B8H 11 and Cp*RuC3B8H11

Article abstract of DOI:10.1021/om050139o

The room-temperature photochemical reaction of the tricarbollide anion [nido-7,8,9-C₃B₈H₁₁]^- (1a) with [CpFe(C₆H₆)]⁺ proceeds without cluster rearrangement to form the 12-vertex closo-ferratricarbollide 1-Cp-1,2,3,4-FeC₃B₈H₁₁ (2a, the metal atom is assigned number 1). 2a rearranges to the isomeric complex 1-Cp-1,2,3,5-FeC ₃B₈H₁₁ (2b) at 110°C and further to 1-Cp-1,2,4,10-FeC₃B₈H₁₁ (2c) at 165°C. The reaction of la with [Cp*RuCl]₄ is accompanied by polyhedral rearrangement giving 1-Cp*-1,2,3,5-RuC₃B₈H ₁₁ (3b). Its further isomerization occurs slowly at room temperature and rapidly at 65°C to give complex 1-Cp*-1,2,4,10-RuC ₃B₈H₁₁ (3c). Similar reactions of [nido-7,8,10-C₃B₈H₁₁]- (1b) with [CpFe(C ₆H₆)]⁺ and [Cp*RuCl]₄ afford 2b and 3b, respectively. A diamond-square-diamond mechanism for the 2a → 2b → 2c rearrangement sequence is proposed. The relative stability of isomers 2a-c was estimated by DFT calculations. The constitution of the compounds prepared was determined by multinuclear NMR spectroscopy and mass spectrometry. The structures of 2a, 2b, and 3c were established by X-ray diffraction.

Full text of DOI:10.1021/om050139o

Organometallics 2005, 24, 4387-4392
4387
Ferra- and Ruthenatricarbollides CpFeC3B8H11 and
Cp*RuC3B8H11
Dmitry S. Perekalin,† Josef Holub,‡ Denis G. Golovanov,†
Konstantin A. Lyssenko,† Pavel V. Petrovskii,† Bohumil Sˇt´ıbr,*,‡ and
Alexander R. Kudinov*,†
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
119991 Moscow, Russian Federation, and Institute of Inorganic Chemistry, Academy of
Sciences of the Czech Republic, 25068 Rˇ ezˇ, the Czech Republic
Received February 25, 2005
The room-temperature photochemical reaction of the tricarbollide anion [nido-7,8,9-
C3B8H11]- (1a) with [CpFe(C6H6)]+ proceeds without cluster rearrangement to form the 12-
vertex closo-ferratricarbollide 1-Cp-1,2,3,4-FeC3B8H11 (2a, the metal atom is assigned number
1). 2a rearranges to the isomeric complex 1-Cp-1,2,3,5-FeC3B8H11 (2b) at 110 °C and further
to 1-Cp-1,2,4,10-FeC3B8H11 (2c) at 165 °C. The reaction of 1a with [Cp*RuCl]4 is accompanied
by polyhedral rearrangement giving 1-Cp*-1,2,3,5-RuC3B8H11 (3b). Its further isomerization
occurs slowly at room temperature and rapidly at 65 °C to give complex 1-Cp*-1,2,4,10-
RuC3B8H11 (3c). Similar reactions of [nido-7,8,10-C3B8H11]- (1b) with [CpFe(C6H6)]+ and
[Cp*RuCl]4 afford 2b and 3b, respectively. A diamond-square-diamond mechanism for the
2a f 2b f 2c rearrangement sequence is proposed. The relative stability of isomers 2a-c
was estimated by DFT calculations. The constitution of the compounds prepared was
determined by multinuclear NMR spectroscopy and mass spectrometry. The structures of
2a, 2b, and 3c were established by X-ray diffraction.
Chart 1
Introduction
Due to the presence of the pentagonal open face and
single negative charge, the known 11-vertex nido-
tricarbaborane (tricarbollide) anions [nido-7,8,9-C3B8H11]-
(1a) and [nido-7,8,10-C3B8H11]- (1b) along with their
hypothetical congener [nido-2,8,10-C3B8H11]- (1c) can
be considered as close analogues of the Cp- anion, thus
making tricarbollide complexes similar to metallocenes.1,2
However, in contrast to the series of amino-substituted
tricarbollide complexes, e.g., 12-vertex closo-ferratricar-
3,4
bollides 1-Cp-12-NR2-1,2,4,12-FeC3B8H10 and 1-Cp-
10-NR2-1,2,4,10-FeC3B8H10,5 little is known about the
unsubstituted compounds of the CpFeC3B8H11 type. A
single preliminary note reports on the reaction between
1a and CpFe(CO)2I in refluxing toluene giving two
complexes formulated as 1-Cp-1,2,3,4-FeC3B8H11 (2a)
and 1-Cp-1,2,4,10-FeC3B8H11 (2c).6 However, the present
study revealed that the product previously assigned the
structure 2a (as a result of wrong interpretation of the
[11B-11B]-COSY NMR data) is in fact complex 1-Cp-
1,2,3,5-FeC3B8H11 (2b). Herein we describe syntheses
and rearrangements of three isomeric CpFeC3B8H11
compounds, 2a-c, which are derivatives of anions 1a-
c, respectively. The related ruthenium complexes
Cp*RuC3B8H11 are also reported. For these compounds
we use a numbering system in which the metal vertex
bears number 1. This system removes the disadvantages
of the original “C” numbering7 and has been already
used for the structurally related phosphadicarbollide
complexes closo-CpFePC2B8H10.8
* To whom correspondence should be addressed. E-mail: arkudinov@
ineos.ac.ru; stibr@iic.cas.cz.
† Russian Academy of Sciences.
‡ Academy of Sciences of the Czech Republic.
(1) Sˇt´ıbr, B. J. Organomet. Chem. 2005, 690, 2694.
(2) Holub, J.; Sˇt´ıbr, B.; Hhyk, D.; Fusek, J.; C´ısarˇova´, I.; Teixidor,
F.; Vin˜as, C.; Plza´k, Z.; Schleyer, P. v. R. J. Am. Chem. Soc. 1997,
119, 7750.
(3) Holub, J.; Gru¨ner, B.; C´ısarˇova´, I.; Fusek, J.; Plza´k, Z.; Teixidor,
F.; Vin˜as, C.; Sˇt´ıbr, B. Inorg. Chem. 1999, 38, 2775.
(4) Holub, J.; Gru¨ner, B.; Perekalin, D. S.; Golovanov, D. G.;
Lyssenko, K. A.; Petrovskii, P. V.; Kudinov, A. R.; Sˇt´ıbr, B. Inorg. Chem.
2005, 44, 1655.
(5) Gru¨ner, B.; Lehtonen, A.; Kiveka¨s, R.; Sillanpa¨a¨, R.; Holub, J.;
Teixidor, F.; Vin˜as, C.; Sˇt´ıbr, B. Inorg. Chem. 2000, 39, 2577.
(6) Sˇt´ıbr, B.; Holub, J.; Teixidor, F.; Vin˜as, C. Collect. Czech. Chem.
Commun. 1995, 60, 2023.
(7) Casey, J. B.; Evans, W. J.; Powell, W. H. Inorg. Chem. 1981, 20,
1333, and references therein. The main disadvantage of the “C”
numbering system for metallacarboranes consists of changing the
numbering order for the whole framework in the case of cluster
rearrangement.
10.1021/om050139o CCC: $30.25 © 2005 American Chemical Society
Publication on Web 07/28/2005

4388 Organometallics, Vol. 24, No. 18, 2005
Perekalin et al.
Scheme 1
Scheme 3
Scheme 4
Scheme 2
Results and Discussion
Synthesis. We have found earlier that the [CpFe-
(C6H6)]+ cation can be used for the incorporation of the
[CpFe]+ fragment into carborane cages.9 The photo-
chemical reaction of 1a with [CpFe(C6H6)]+ in CH2Cl2
at room temperature gives red complex 2a in 60% yield
(Scheme 1). 2a undergoes cluster rearrangement in
refluxing toluene to give the isomeric dark red com-
pound 2b in 71% yield (Scheme 2). Further rearrange-
ment is achieved by heating 2b in refluxing mesitylene,
resulting in almost quantitative formation of the orange
isomer 2c.
Scheme 5
Revision of the data reported previously6 allows us
to conclude that the reaction of 1a with CpFe(CO)2I in
refluxing toluene gives complexes 2b and 2c. We found
that the mixture of 2b (15%) and 2c (35%) is also formed
by reaction of the neutral tricarbaborane nido-7,8,9-
C3B8H12 (H[1a]) with [CpFe(CO)2]2 in refluxing diglyme.
Although compounds 2a-c are stable in the solid
state, 2a and 2b are less so in solution. Complex 2a
slowly disproportionates in polar solvents (MeNO2,
THF, CH2Cl2) to give ferrocene, H[1a] (both identified
by NMR spectroscopy), and an uncharacterized orange
Fe-containing precipitate. The disproportionation is
facilitated by increasing the temperature and polarity
of the solvent. Complex 2b, though stable in solution
in inert atmosphere, undergoes boron elimination upon
air oxidation in ethanol to produce the previously
reported6 11-vertex ferracarborane 1-Cp-1,2,3,4-closo-
FeC3B7H10 (4) in 45% yield (Scheme 3). Derivatives of
4 have been studied in detail by Sneddon and co-
workers.10
the 2b isomer via a cubooctahedral intermediate. Break-
age of the second C-C connectivity in the next step
leads to 2c, a framework with maximum separation of
the cage carbon atoms.
A different reaction scenario was observed for the an-
alogous ruthenatricarbollide compounds Cp*RuC3B8H11.
Thus, a room-temperature reaction between 1a and
[Cp*RuCl]4 in THF for 2 h affords the rearranged light
yellow complex 1-Cp*-1,2,3,5-RuC3B8H11 (3b) (58%)
instead of the expected 3a (Scheme 5). This indicates a
lower barrier for the isomerization of the ruthenium
compounds in comparison with that for the iron ana-
logues. It is further confirmed by the quantitative
conversion of 3b into the isomeric 1-Cp*-1,2,4,10-
RuC3B8H11 (3c) compound upon prolonged standing at
room temperature in solution. More surprisingly, this
rearrangement also proceeds in the solid state although
The formation of ferratricarbollides 2b,c via thermal
isomerization of 2a is associated with progressive space
separation of the CH vertexes that is consistent with a
diamond-square-diamond mechanism11 outlined in
Scheme 4. The rearrangement starts with the breaking
of the unfavorable C-C connectivity in 2a, leading to
(8) (a) Sˇt´ıbr, B.; Holub, J.; Bakardjiev, M.; Pavl´ık, I.; Tok, O. L.;
C´ısarˇova´, I.; Wrackmeyer, B.; Herberhold, M. Chem. Eur. J. 2003, 9,
2239. (b) Sˇt´ıbr, B.; Holub, J.; Bakardjiev, M.; Hnyk, D.; Tok, O. L.;
Milius, W.; Wrackmeyer, B. Eur. J. Inorg. Chem. 2002, 2320.
(9) Earlier, using this cation we have prepared, 1-Cp-4-SMe2-1,2,3-
closo-FeC2B9H10: Kudinov, A. R.; Meshcheryakov, V. I.; Petrovskii, P.
V.; Rybinskaya, M. I. Izv. Akad. Nauk, Ser. Khim. 1999, 177; Russ.
Chem. Bull. 1999, 48, 176 (Engl. Transl.).
(10) (a) Plumb, C. A.; Carroll, P. J.; Sneddon, L. G. Organometallics
1992, 11, 1665. (b) Wasczcak, M. D.; Lee, C. C.; Hall, I. H.; Carroll, P.
J.; Sneddon, L. G. Angew. Chem., Int. Ed. Engl. 1997, 36, 2228. (c)
Barnum, B. A.; Carroll, P. J.; Sneddon, L. G. Inorg. Chem. 1997, 36,
1327. (d) Ramachandran, B. M.; Trupia, S. M.; Geiger, W. E.; Carroll,
P. J.; Sneddon, L. G. Organometallics 2002, 21, 5078.
(11) Lipscomb, W. N. Science 1966, 153, 373.

Ferra- and Ruthenatricarbollides
Organometallics, Vol. 24, No. 18, 2005 4389
Scheme 6
much slower. Complex 3c can also be obtained directly
from 1a and [Cp*RuCl]4 by extending the reaction time
to 4 days.
Nothing was known previously about the coordinating
ability of the tricarbollide anion 1b. We found that this
anion reacts easily with [CpFe(C6H6)]+ (hν, 20 °C, 5 h)
and [Cp*RuCl]4 (20 °C, 2 h) to give the corresponding
metallatricarbollides 2b and 3b (Scheme 6). No rear-
rangement was observed during these reactions.
NMR Study. The NMR spectra for all the compounds
isolated, except 2a,12 have been completely assigned
using [11B-11B]-COSY13 and 1H{11B(selective)}14 NMR
techniques. Simplified stick diagrams in Figure 1 show
graphical intercomparison of the 11B NMR shifts for all
four isomers of CpFeC3B8H11 thus far known (2a-c, and
the recently reported 1-Cp-1,2,8,10-FeC3B8H11 (2d)15)
and for two isomers of Cp*RuC3B8H11 (3b and 3c).
Generally, iron and ruthenium complexes with identical
positions of the cage carbon atoms display very similar
spectral patterns. The spectrum of the 1,2,3,4-isomer
2a shows a 2:1:1:2:2 pattern of doublets, while the
spectra of the 1,2,3,5-isomers 2b and 3b exhibit 1:2:2:
1:2 behavior. The spectra of the isostructural pair 2c
and 3c of the 1,2,4,10-constitution display 1:2:1:2:2
patterns, while the spectrum of isomer 2d shows a 2:2:
1:1:2 pattern.
Figure 1. Simplified stick representation of the 11B NMR
shifts of all known isomers of CpFeC3B8H11 (compounds
2a-d) and Cp*RuC3B8H11 (compounds 3b and 3c).
The most characteristic feature of the 1H NMR
spectra of the compounds isolated is the resonances of
the cage CH units. In this respect, the 1,2,3,5-isomers
2b and 3b exhibit 2:1 patterns, while the 1,2,4,10-
isomers display 1:2 behavior (reading upfield). Similarly,
the 13C NMR spectra of the 12-vertex ruthenatricarbol-
lides 3b and 3c show 2:1 and 1:2 patterns for the cage
C units, respectively.
X-ray Diffraction Study. The structures of com-
pounds 2a, 2b, and 3c were determined by a single-
crystal X-ray diffraction study. The structure of ferra-
tricarbollide 2a (Figure 2) represents the first 12-vertex
metallacarborane having three adjacent carbon atoms.
Despite such heteroatom crowding, C-C, C-B, and
B-B cage connectivities are within the usual length
range. The distance from the iron atom to the middle
cage carbon atom (2.003 Å) is significantly shorter than
to the outer ones (av 2.037 Å). Accordingly, the C3B2
face is slightly nonplanar (mean deviation 0.016 Å), with
Figure 2. Molecular structure of 2a with 50% thermal
ellipsoids. The second conformation of the disordered Cp-
ring and the hydrogen atoms are omitted for clarity.
Selected interatomic distances (Å): Fe1-C2 2.028(2), Fe1-
C3 2.003(2), Fe1-C4 2.045(2), Fe1-B5 2.092(4), Fe1-B6
2.077(4), Fe1-C13 2.030(4), Fe1-C14 2.057(4), Fe1-C15
2.082(4), Fe1-C16 2.075(4), Fe1-C17 2.047(4), C2-C3
1.619(3), C3-C4 1.613(3), C4-B5 1.691(4), B5-B6 1.779-
(4), B6-C2 1.700(4).
the C3 atom being deviated from the C2-C4-B5-B6
plane by 0.059 Å toward the iron atom. The Cp ring is
disordered over two positions. The Fe‚‚‚Cp distance (av
1.675 Å) is only slightly longer than that in ferrocene
(1.660 Å),16 indicating similar bonding strength.
(12) Unfortunately, the decomposition of 2a in solution with the
formation of paramagnetic species does not allow performing the
1H{11B(selective)} NMR experiments.
(13) See, for example: (a) Kennedy, J. D. In Multinuclear N. M. R.;
Mason, J., Ed.; Plenum Press: New York, 1987; p 221. (b) Hutton, W.
C.; Venable, T. L.; Grimes, R. N. J. Am. Chem. Soc. 1984, 106, 29. (c)
Schraml, J.; Bellama, J. M. Two-Dimensional NMR Spectroscopy;
Wiley: New York, 1982, and references therein.
In the case of the isomeric compound 2b (Figure 3),
the Fe-C5 distance (2.067 Å) is longer than two other
Fe-C(cage) distances (av 2.022 Å). The C3B2 face is
more distorted than in 2a, the C5 atom being deviated
from the C2-C3-B4-B6 plane by 0.133 Å away from
(14) Fontaine, X. L. R.; Kennedy, J. D. J. Chem. Soc., Dalton Trans.
1987, 1573.
(15) Gru¨ner, B.; Mikula´×f0ek, L.; C´ısarˇova´, I.; Sˇt´ıbr, B. J. Orga-
nomet. Chem. 2005, submitted.
(16) Haaland, A.; Nilsson, J. E. Acta Chem. Scan. 1968, 23, 2653.

4390 Organometallics, Vol. 24, No. 18, 2005
Perekalin et al.
DFT Calculations. The geometries of three CpFeC3-
B8H11 isomers (2a-c) were optimized at the B3LYP/6-
31G* level. The calculated structures of 2a (disregarding
the conformation of the Cp ring) and 2b agree well with
experimental data (deviations for 2a: max 0.022, av
0.008 Å; for 2b: max 0.021, av 0.014 Å), providing
reliability of the calculation results. Isomer 2c was
found to be more stable than 2b (by 8.53 kcal/mol) and
2a (by 25.48 kcal/mol). Thus, the experimentally ob-
served 2a f 2b f 2c isomerization sequence shown in
Scheme 2 correlates well with the calculated order of
thermodynamic stabilities.
As shown in Table 1, the 11B NMR chemical shifts,
calculated using the GIAO method, are in a very good
agreement with experimental values. For example, in
the case of 2a the deviation of the calculated chemical
shifts from the experimental ones (max 1.9 ppm, av 0.9
ppm) is comparable to the difference between chemical
shifts measured in different solvents, CDCl3 and toluene-
d8 (max 1.5, av 1.2 ppm). This makes possible the
assignment of NMR signals even in the absence of [11B-
11B]-COSY correlations.
To estimate the strength of the Fe-tricarbollide bond,
we calculated the enthalpies of reactions of the [CpFe]+
fragment with 1a and Cp- anions leading to 2a and
ferrocene, respectively. The formation of ferrocene was
found to be 58.58 kcal/mol more favorable than the
formation of 2a. This result correlates with the observed
disproportionation of 2a in polar solvents (vide supra).
Figure 3. Molecular structure of 2b with 50% thermal
ellipsoids. The hydrogen atoms are omitted for clarity.
Selected interatomic distances (Å): Fe1-C2 2.018(2), Fe1-
C3 2.025(2), Fe1-B4 2.059(3), Fe1-C5 2.067(2), Fe1-B6
2.051(3), Fe1-C13 2.049(2), Fe1-C14 2.048(2), Fe1-C15
2.050(2), Fe1-C16 2.048(2), Fe1-C17 2.054(2), C2-C3
1.614(2), C3-B4 1.699(3), B4-C5 1.681(3), C5-B6 1.700-
(3), B6-C2 1.707(3).
Conclusion
We have developed simple and effective routes to the
isomeric CpFeC3B8H11 and Cp*RuC3B8H11 complexes
that can be considered as tricarbollide analogues of
ferrocene and ruthenocene. The compounds obtained are
the first representatives of the unsubstituted metalla-
tricarbollide series. The rearrangement of initially
formed 1,2,3,4-isomers (2a and 3a) is compatible with
the diamond-square-diamond mechanism successively
giving 1,2,3,5- (2b and 3b) and 1,2,4,10-isomers (2c and
3c) in accordance with progressive separation of the
carbon atoms. In contrast to aminosubstituted metal-
latricarbollides,3 the 1,2,4,12-isomer was neither iso-
lated nor detected in the unsubstituted series, indicating
that the complexation and rearrangement reactions are
strongly influenced by the electronic and steric effects
of a substituent.
Figure 4. Molecular structure of 3c with 50% thermal
ellipsoids. The second conformation of the disordered Cp*
ring and the hydrogen atoms are omitted for clarity.
Selected interatomic distances (Å): Ru1-C2 2.168(5),
Ru1-B3 2.118(7), Ru1-C4 2.156(7), Ru1-B5 2.109(7),
Ru1-B6 2.124(7), Ru1-C13 2.221(12), Ru1-C14 2.228(12),
Ru1-C15 2.194(15), Ru1-C16 2.196(12), Ru1-C17 2.178-
(12), C2-B3 1.665(10), B3-C4 1.693(10), C4-B5 1.690(10),
B5-B6 1.771(11), B6-C2 1.756(10).
Experimental Section
the iron atom. Similar to 2a, the Fe‚‚‚Cp distance (1.662
Å) is very close to that in ferrocene.
General Remarks. All reactions were carried out under
argon in anhydrous solvents, which were purified and dried
using standard procedures. The isolation of products was
conducted in air unless otherwise stated. The starting materi-
als [Cp*RuCl]4,19 [Cp*RuCl2]2,20 [CpFe(C6H6)]PF6,21 H[1a], Tl-
In the structure of ruthenatricarbollide 3c (Figure 4),
one of three cage carbon atoms is located in the
m-position with respect to the metal atom and to two
other carbon atoms lying on the C2B3 face. The overall
geometry is significantly distorted from the expected Cs
symmetry. The C2B3 face is twisted, so that the C4 and
B3 vertexes are deviated by 0.096 Å from the C2-B6-
B5 plane up and down, respectively. The Cp* ring is
disordered over two positions. The Ru‚‚‚Cp* distance in
3c (av 1.818 Å) is close to that found in the related
dicarbollide complex [1-Cp*-1,2,3-RuC2B9H11]- (1.819
Å),17 but is noticeably longer than in pentamethylru-
thenocene (1.793 Å).18
(17) Kudinov, A. R.; Perekalin, D. S.; Rynin, S. S.; Lyssenko, K. A.;
Grintselev-Knyazev, G. V.; Petrovskii, P. V. Angew. Chem., Int. Ed.
2002, 41, 4112.
(18) Zanin, I. E.; Antipin, M. Yu.; Struchkov, Yu. T. Kristallografiya
1991, 36, 420.
(19) Fagan, P. J.; Ward, M. D.; Calabrese, J. C. J. Am. Chem. Soc.
1989, 111, 1698.
(20) Tilley, T. D.; Grubbs, R. H.; Bercaw, J. E. Organometallics 1984,
3, 274.
(21) (a) Nesmeyanov, A. N.; Vol’kenau, N. A.; Bolesova, I. N.
Tetrahedron Lett. 1963, 4, 1725. (b) Nesmeyanov, A. N.; Vol’kenau, N.
A.; Bolesova, I. N.; Polkovnikova, L. S. Koord. Khim. 1975, 1, 1252.

Ferra- and Ruthenatricarbollides
Table 1. Calculated and Experimental 11B NMR Chemical Shifts for 2a-d
11B NMR shifts (assignment)
Organometallics, Vol. 24, No. 18, 2005 4391
compound
2a
in CDCl3
-9.8 (B5,6)
-8.6
-10.9 (B12)
-9.7
-12.3 (B10)
-10.8
-18.0 (B9,11)
-16.7
-28.9 (B7,8)
-28.0
in toluene-d8
calculated
in CDCl3
-9.4
-11.2
-13.3
-18.2
-30.8
2b
2c
2d
-11.0 (B12)
-13.3
-9.3 (B3)
-9.1
-7.0 (B2,6)
-4.9
-16.0 (B4,6)
-15.7
-17.2 (B9,10)
-17.3
-12.3 (B12)
-16.3
-15.4 (B9)
-17.4
-21.0 (B7)
-21.5
-25.0 (B8,11)
-26.2
calculated
in CDCl3
-10.2 (B5,6)
-10.4
-18.4 (B9,11)
-19.5
-23.7 (B7,8)
-25.0
calculated
15
in CDCl3
-9.1 (B4,5)
-7.8
-17.8 (B12)
-18.9
-24.3 (B7,11)
-25.2
calculated
[1a], Me4N[1a], and Ph4P[1b]2 were prepared as described in
the literature. Visible light irradiation was performed by a
high-pressure mercury vapor lamp with a phosphor-coated
bulb (400 W). The 1H, 11B, and 13C NMR spectra were recorded
with Bruker AMX-400, Varian XL-500, and Varian MERCURY
400 instruments. The [11B-11B]-COSY and 1H{11B(selective)}
NMR experiments were performed essentially as described
previously.22 Chemical shifts are given in ppm relative to
internal SiMe4 (1H, 13C) or external BF3‚OEt2 (11B); the J(11B-
1H) constants are given in Hz. Unless otherwise stated,
measurements were made at room temperature from CDCl3
solutions.
1-Cp-1,2,3,4-FeC3B8H11 (2a). A mixture of Me4N[1a] (83
mg, 0.4 mmol) and [CpFe(C6H6)]PF6 (138 mg, 0.4 mmol) in 15
mL of CH2Cl2 was irradiated with stirring at room tempera-
ture for 2 h, resulting in a color change from yellow to orange-
red. Since 2a is rather unstable in solution in air, the isolation
of the product was carried out under argon atmosphere. The
mixture was eluted through a short (3 cm) layer of silica gel
and evaporated to dryness. The resulting red crystals were
washed with petroleum ether to remove traces of ferrocene and
dried in a vacuum to give 41 mg (40%) of 2a. Alternatively, a
solution of Me4N[1a] (124 mg, 0.6 mmol) and [CpFe(C6H6)]-
PF6 (206 mg, 0.6 mmol) in acetone (ca. 10 mL) was stirred for
0.5 h in order to induce ion metathesis, and the solvent was
removed in a vacuum. The residue was dissolved in CH2Cl2
(20 mL) and irradiated as described above to give 2a (92 mg,
60%). 1H NMR (400 MHz, toluene-d8): δ 4.61 (s, 1H, H3), 4.31
(s, 5H, Cp), 2.69 (s, 2H, H2,4). [11B-11B]-COSY NMR (128
MHz): all cross-peaks were observed. MS (70 eV, EI), m/z
(%): 256 (42) [M]+, 255 (60) [M - H]+. Anal. Calcd for C8H16B8-
Fe: C, 37.75; H, 6.34; B, 33.98. Found: C, 37.40; H, 6.27; B,
33.81.
1-Cp-1,2,4,10-FeC3B8H11 (2c). A solution of compound 2b
(154 mg, 0.6 mmol) in mesitylene (8 mL) was refluxed for 12
h and then evaporated to dryness in a vacuum. The residue
was dissolved in petroleum ether and eluted through a short
(3 cm) layer of silica gel. The filtrate was evaporated to
dryness, and the crude product was recrystallized from pen-
tane at -78 °C to give pure 2c (128 mg, 80%) identified by
NMR spectroscopy.6 Alternatively, compound 2b (50 mg, 0.2
mmol) was sealed in a glass ampule under argon and heated
at ca. 200 °C for 12 h. The ampule was opened at -78 °C, the
contents were removed quantitatively by CH2Cl2, and the
solvent was evaporated. Sublimation of the residue at ca. 120
°C in oil-pump vacuum gave 48 mg (96%) of pure 2c.
Reaction of H[1a] with [CpFe(CO)2]2. A solution of H[1a]
(100 mg, 0.74 mmol) and [CpFe(CO)2]2 (177 mg, 0.5 mmol) in
diglyme (10 mL) was refluxed for 12 h. The solvent was
removed in a vacuum, the residue was dissolved in CH2Cl2 (5
mL), and the solution was placed onto the top of a silica gel
column (30 × 1.5 cm). Elution with 5% CH2Cl2/hexane under
argon gave red-orange and yellow bands, from which com-
pounds 2b (28 mg, 15%) and 2c (65 mg, 35%) were respectively
isolated and identified by NMR spectroscopy.
1-Cp*-1,2,3,5-RuC3B8H11 (3b). Method A (by reaction of
anion 1a with [Cp*RuCl]4). A mixture of [Cp*RuCl]4 (41 mg,
0.038 mmol) and Me4N[1a] (33 mg, 0.16 mmol) in THF (3 mL)
was stirred for 2 h. The resulting red solution was filtered and
evaporated to dryness in a vacuum at room temperature. The
residue was extracted by CH2Cl2/petroleum ether (1:1) and
eluted through a short (3 cm) layer of silica gel. Evaporation
of the solvent and recrystallization from petroleum ether gave
1
32 mg (58%) of 3b. H NMR (400 MHz): δ 2.92 (s, 1H, H5),
2.63 (s, 2H, H4,6), 2.20 (s, 1H, H12), 1.94 (s, 15H, Cp*), 1.69
(s, 1H, H7), 1.59 (s, 4H, H2,3/H9,10), 1.34 (s, 2H, H8,11). 11B
NMR (128 MHz): δ -8.0 (d (147), 1B, B12), -14.8 (d (165),
2B, B4,6), -19.4 (d (159), 2B, B9,10), -21.8 (d (160), 1B, B7),
-26.9 (d (159), 2B, B8,11); all [11B-11B]-COSY cross-peaks
were observed except for B7-B12. 13C{1H} NMR (100.6
MHz): 90.1 (s, 5C, C5Me5), 43.1 (br s, 1C, C5), 41.1 (br s, 2C,
C2,3), 10.5 (s, 5C, C5Me5). MS (70 eV, EI), m/z (%): 371 (40)
[M]+, 370 (100) [M - H]+. Anal. Calcd for C13H26B8Ru: C,
42.21; H, 7.08; B, 23.38. Found: C, 42.44; H, 7.30; B, 23.21.
Method B (by reaction of anion 1b with [Cp*RuCl]4).
A mixture of [Cp*RuCl]4 (54 mg, 0.05 mmol) and Ph4P[1b] (94
mg, 0.2 mmol) in THF (5 mL) was stirred for 2 h, and the
solvent was removed in a vacuum at room temperature. The
residue was dissolved in CH2Cl2, eluted through a short (3 cm)
layer of silica gel, and evaporated to give 56 mg (76%) of 3b.
1-Cp*-1,2,4,10-RuC3B8H11 (3c). Method A (by rear-
rangement of 3b). A solution of 3b (55 mg, 0.15 mmol) in
THF (4 mL) was left for 4 days or refluxed for 2 h. The solvent
was evaporated in a vacuum, and the residue was dissolved
in a mixture of petroleum ether and CH2Cl2 (2:1) and eluted
through a short (3 cm) layer of silica gel. The evaporation of
1-Cp-1,2,3,5-FeC3B8H11 (2b). Method A (by rearrange-
ment of 2a). A solution of 2a (40 mg, 0.16 mmol) in toluene
(4 mL) was refluxed for 5 h. The solvent was evaporated in a
vacuum, and the residue was dissolved in a CH2Cl2/petroleum
ether mixture (2:1) and filtered. The evaporation of the
resulting solution gave 28 mg (71%) of 2b. Analytically pure
sample was obtained by recrystallization from a concentrated
1
hexane solution at 0 °C. H NMR (500 MHz): δ 4.79 (s, 5H,
Cp), 3.70 (s, 2H, H4,6), 3,49 (s, 1H, H5), 2.45 (s, 1H, H12),
1.38 (s, 4H, H2,3/H9,10), 1.35 (s, 1H, H7), 1.18 (s, 2H, H8,11).
[11B-11B]-COSY NMR (128 MHz): all cross-peaks were ob-
served. MS (70 eV, EI), m/z (%): 256 (35) [M]+, 255 (70) [M -
H]+. Anal. Calcd for C8H16B8Fe: C, 37.75; H, 6.34; B, 33.98.
Found: C, 38.01; H, 6.87; B, 34.02.
Method B (by reaction of anion 1b with [CpFe-
(C6H6)]+). A mixture of Ph4P[1b] (142 mg, 0.3 mmol) and
[CpFe(C6H6)]PF6 (103 mg, 0.3 mmol) in 15 mL of CH2Cl2 was
irradiated under stirring at room temperature for 5 h, result-
ing in a color change from yellow to dark red. The resulting
mixture was evaporated to dryness, and the residue was
dissolved in a CH2Cl2/petroleum ether mixture (2:1). The
solution was eluted through a short (3 cm) layer of silica gel,
and the solvent was removed in a vacuum to give 47 mg (62%)
of 2b.
1
the resulting solution gave 53 mg (97%) of 3c. H NMR (400
MHz): δ 3.14 (s, 1H, H12), 2.87 (s, 1H, H3), 2.72 (bs, 2H, H2,4),
2.16 (s, 2H, H5,6), 2.08 (s, 2H, H9,11), 2.05 (bs, 1H, H10), 1.94
(s, 15H, Cp*), 1.47 (s, 2H, H4.8). 11B NMR (128 MHz): δ -8.7
(d (∼165), 1B, B3), -10.1 (d (180), 2B, B5,6), -13.7 (d (156),
1B, B12), -21.1 (d (171), 2B, B9,11), -26.9 (d (156), 2B, B7,8);
all [11B-11B]-COSY cross-peaks were observed except for B3-
(22) Plesˇek, J.; Sˇt´ıbr, B.; Fontaine, X. L. R.; Kennedy, J. D.;
Herˇma´nek, S.; Jel´ınek, T. Collect. Czech. Chem. Commun. 1991, 56,
1618.

4392 Organometallics, Vol. 24, No. 18, 2005
Perekalin et al.
B7,8. 13C{1H} NMR (100.6 MHz): 93.3 (s, 5C, C5Me5), 39.8 (br
s, 2C, C2,4), 31.9 (br s, 1C, C10), 10.5 (s, 5C, C5Me5). MS (70
eV, EI), m/z (%): 371 (41) [M]+, 370 (100) [M - H]+. Anal.
Calcd. for C13H26B8Ru: C, 42.21; H, 7.08; B, 23.38. Found: C,
42.26; H, 7.41; B, 23.13.
Table 2. Crystal Data and Structure Refinement
Parameters for 2a, 2b, and 3c
property
2a
2b
3c
molecular formula C8H16B8Fe
C8H16B8Fe
254.54
C13H26B8Ru
369.89
yellow prism
orthorhombic
Pbca
fw
254.54
Method B (by direct reaction of anion 1a with
[Cp*RuCl]4). A mixture of [Cp*RuCl]4 (82 mg, 0.075 mmol)
and Tl[1a] (101 mg, 0.3 mmol) or Me4N[1a] (62 mg, 0.3 mmol)
in THF (5 mL) was stirred at room temperature for 4 days or
refluxed for 5 h. Alternatively, [Cp*RuCl]4 was generated by
stirring [Cp*RuCl2]2 (92 mg, 0.15 mmol) and Zn dust (100 mg,
excess) in THF for 1 h followed by addition of Tl[1a]. The
resulting light yellow solution was filtered and evaporated to
dryness at room temperature. The residue was extracted by a
CH2Cl2/petroleum ether (1:1) mixture and eluted through a
thin layer (3 cm) of silica gel. The filtrate was evaporated to
give small light yellow crystals of 3c (88 mg, 80%). In the case
where the product was oily, the elution through silica gel was
repeated.
cryst color, habit
cryst syst
space group
temperature (K)
a (Å)
red prism
red prism
orthorhombic monoclinic
P212121
120(2)
6.472(1)
10.300(2)
17.749(4)
P21/c
120(2)
120(2)
6.797(1)
9.929(2)
17.569(3)
91.420(4)
1185.4(4)
4 (1)
10.141(4)
14.429(4)
24.061(7)
b (Å)
c (Å)
â (deg)
V (Å3)
1183.3(5)
4(1)
3520.7(19)
8 (1)
Z(Z′)
F(000)
520
520
1504
F
calc (g cm-1
)
1.429
1.426
1.396
µ (cm-1
Tmin/Tmax
)
13.22
12.30
8.77
0.730/0.781
2.29-29.09
0.742/0.780
2.20-28.42
0.811/0.839
2.20-26.23
θ range (deg)
measd reflns (Rint
unique reflns
obsd reflns (I >
2σ(I))
)
5495 (0.0378) 10 892 (0.0563) 9069 (0.0704)
2991
2661
1-Cp-1,2,3,4-FeC3B7H10 (4). A solution of 2b (40 mg, 0.16
mmol) in ethanol (10 mL) was stirred in air for 12 h at room
temperature. The solvent was evaporated and the residue was
purified by preparative TLC chromatography on silica gel,
using hexane as a mobile phase. The violet band with Rf 0.30
was extracted by CH2Cl2, evaporated, and sublimated at ca.
100 °C (oil-pump vacuum) to give 18 mg (45%) of 4 (identified
3423
2301
4057
2113
parameters
R1 (on F for obsd
reflns)
219
0.0415
194
0.0425
210
0.0608
wR2 (on F2 for all 0.0922
0.0750
0.935
0.1251
1
by H and 11B NMR spectroscopy6).
reflns)
GOF
1.069
1.020
1.239/-0.635
Computational Details. All calculations were performed
using Gaussian 98 (Revision A.7) software23 at the B3LYP/6-
31G* level. The structures of 2a-d, Cp2Fe, [CpFe]+, [1,2,3,4-
FeC3B8H11]+, Cp-, and [7,8,9-C3B8H11]- were optimized using
tightened convergence criteria (options Opt ) Tight, SCF )
Tight). The frequency calculations were performed to confirm
the global minimum and include ZPE corrections to the energy.
The 11B NMR shifts were calculated using the GIAO method
by subtraction of calculated isotropic shielding values from
those of B2H6 (93.50 at B3LYP/6-31G*). The experimental
chemical shift of B2H6 was assigned 16.6 ppm.24
X-ray Crystallography. Crystals of 2a, 2b, and 3c suitable
for X-ray diffraction were grown by slow evaporation of CH2-
Cl2 solutions of the complexes. X-ray diffraction experiments
were carried out with a Bruker SMART 1000 CCD area
detector, using graphite-monochromated Mo KR radiation (λ
) 0.71073 Å, ω-scans with a 0.3° step in ω and 10 s per frame
exposure) at 120 K. Low temperature of the crystals was
maintained with a Cryostream (Oxford Cryosystems) open-
flow N2 gas cryostat. Reflection intensities were integrated
using SAINT software,25 and absorption correction was applied
semiempirically using the SADABS program.26 The structures
were solved by direct methods and refined by full-matrix least-
squares against F2 in anisotropic approximation for non-
F
max/Fmin (e Å-3
)
0.972/-0.603 0.849/-0.530
hydrogen atoms. The analyses of the Fourier density synthesis
have revealed that the Cp and Cp* ligands in 2a and 3c are
disordered by two positions with equal populations. All
polyhedron hydrogen atoms were located from the Fourier
density synthesis and refined in isotropic approximation. All
calculations were performed using the SHELXTL software.27
Crystal data and structure refinement parameters for 2a, 2b,
and 3c are given in Table 2.
The crystallographic data have been deposited with the
Cambridge Crystallographic Data Center, CCDC 264297 for
2a, CCDC 264298 for 2b, and CCDC 264299 for 3c. Copies of
this information may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK
(fax: +44-1223-336-033; e-mail: deposit@ccdc.cam.ac.uk or
http://www.ccdc.cam.ac.uk).
Acknowledgment. This work was supported by the
Grant Agency of the Czech Republic (Project No. 203/
05/2646) and by the Division of General Chemistry and
Material Sciences of Russian Academy of Sciences
(Grant No. 05-07). D.S.P. gratefully acknowledges IN-
TAS for Young Scientist Fellowship (Grant No. 04-83-
3848).
(23) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Zakrzewski, V. G.; Montgomery, J. A.,
Jr.; Stratmann, R. E.; Burant, J. C.; Dapprich, S.; Millam, J. M.;
Daniels, A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J.;
Barone, V.; Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo,
C.; Clifford, S.; Ochterski, J.; Petersson, G. A.; Ayala, P. Y.; Cui, Q.;
Morokuma, K.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.;
Foresman, J. B.; Cioslowski, J.; Ortiz, J. V.; Stefanov, B. B.; Liu, G.;
Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts, R.; Martin, R. L.;
Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.;
Gonzalez, C.; Challacombe, M.; Gill, P. M. W.; Johnson, B. G.; Chen,
W.; Wong, M. W.; Andres, J. L.; Head-Gordon, M.; Replogle, E. S.;
Pople, J. A. Gaussian 98 (Revision A.7); Gaussian, Inc.: Pittsburgh,
PA, 1998.
(24) Do¨rfler, U.; Ormsby, D. L.; Greatrex, R.; Kennedy, J. D. Inorg.
Chim. Acta 2000, 304, 268.
(25) SMART V5.051 and SAINT V5.00, Area Detector Control and
Integration Software; Bruker AXS, Inc.: Madison, WI, 1998.
(26) Sheldrick, G. M. SADABS; Bruker AXS, Inc.: Madison, WI,
1997.
Supporting Information Available: Details of crystal-
lographic experiments for compounds 2a, 2b, and 3c (tables
of crystal data collection, refinement parameters, atomic
coordinates, anisotropic displacement parameters, bond dis-
tances, and bond angles) and calculation details for compounds
2a-d, Cp2Fe, and fragments [CpFe]+, [1,2,3,4-FeC3B8H11]+,
Cp-, and [C3B8H11]- (atomic coordinates for optimized geom-
etry, energy data, summary of natural population analysis,
and GIAO NMR shielding parameters). This material is
available free of charge via the Internet at http://pubs.acs.org.
OM050139O
(27) Sheldrick, G. M. SHELXTL V5.10; Bruker AXS Inc.: Madison,
WI, 1997.