Half-pseudoferrocene cations from nucleophilic addition of o-carboranyl anions to the [(η6-mesitylene)2Fe]2+ dication

Article abstract of DOI:10.1039/c2dt30181d

Reactions between the mesitylene (mes) dication [(η⁶-mes) ₂Fe]²⁺ (1a) [(PF₆^-)₂ salt] and lithium o-carboranes Li[1-R-1,2-C₂B₁₀H ₁₁] (2) (R = H, 2a; Me, 2b; Ph, 2c) at low temperature (-60 °C, 1 h, followed by stirring for 2 h at r.t.) in THF resulted in a clean addition of the corresponding carborane anions to one of the unsubstituted arene sites in 1a, forming a series of orange monocations of general structure [(η⁵-mes-exo-6-{2-R-1,2-C₂B₁₀H ₁₁})Fe(η⁶-mes)]⁺ (3) (R = H, 3a; Me, 3b; Ph, 3c) which were isolated as PF₆^- salts (3PF ₆) in yields ranging 50-75%. Individual complexes were obtained on purification by LC or preparative TLC on a silica gel substrate, using MeCN-CH₂Cl₂ mixtures as the mobile phase. Interestingly, the room-temperature reaction between 2a (threefold excess) and 1a(PF ₆)₂ with a reverse order of addition of the reaction components yielded an orange salt [(η⁵-mes-exo-6-{1,2-C ₂B₁₀H₁₁})Fe(η⁶-mes)] ⁺[closo-nido-H₁₁B₁₀C₂-C ₂B₁₀H₁₂]^- (3acCA) (cCA = conjucto-carborane anion = [closo-nido-H₁₁B₁₀C ₂-C₂B₁₀H₁₂]^-) as a sole product in 71% yield. The formation of this conjucto anion can be taken as a strong support for the participation of a radical-chain mechanism in the ostensible nucleophilic addition which we suppose to be initiated by the formation of the [(mes)₂Fe⁺] radical cation. The structures of both 3PF₆ and 3acCA have been established by X-ray diffraction and the constitution of all compounds isolated is in agreement with elemental analyses, multinuclear NMR data, and MS spectra.

Full text of DOI:10.1039/c2dt30181d

View Article Online / Journal Homepage / Table of Contents for this issue
Dynamic Article Links
Dalton
Transactions
Cite this: Dalton Trans., 2012, 41, 7151
www.rsc.org/dalton
PAPER
Half-pseudoferrocene cations from nucleophilic addition of o-carboranyl
anions to the [(η6-mesitylene)2Fe]2+ dication†
Mario Bakardjiev,a Bohumil Štíbr,*a Josef Holub,a Aleš Růžičkab and Zdeňka Padělkováb
Received 24th January 2012, Accepted 4th April 2012
DOI: 10.1039/c2dt30181d
Reactions between the mesitylene (mes) dication [(η6-mes)2Fe]2+ (1a) [(PF6−)2 salt] and lithium
o-carboranes Li[1-R-1,2-C2B10H11] (2) (R = H, 2a; Me, 2b; Ph, 2c) at low temperature (−60 °C, 1 h,
followed by stirring for 2 h at r.t.) in THF resulted in a clean addition of the corresponding carborane
anions to one of the unsubstituted arene sites in 1a, forming a series of orange monocations of general
structure [(η5-mes-exo-6-{2-R-1,2-C2B10H11})Fe(η6-mes)]+ (3) (R = H, 3a; Me, 3b; Ph, 3c) which were
isolated as PF6− salts (3PF6) in yields ranging 50–75%. Individual complexes were obtained on
purification by LC or preparative TLC on a silica gel substrate, using MeCN–CH2Cl2 mixtures as the
mobile phase. Interestingly, the room-temperature reaction between 2a (threefold excess) and 1a(PF6)2
with a reverse order of addition of the reaction components yielded an orange salt [(η5-mes-exo-6-{1,2-
C2B10H11})Fe(η6-mes)]+[closo–nido-H11B10C2-C2B10H12]− (3acCA) (cCA = conjucto-carborane anion =
[closo-nido-H11B10C2-C2B10H12]−) as a sole product in 71% yield. The formation of this conjucto anion
can be taken as a strong support for the participation of a radical-chain mechanism in the ostensible
nucleophilic addition which we suppose to be initiated by the formation of the [(mes)2Fe+]˙ radical cation.
The structures of both 3PF6 and 3acCA have been established by X-ray diffraction and the constitution of
all compounds isolated is in agreement with elemental analyses, multinuclear NMR data, and MS spectra.
Introduction
We have just recently entered the area of the [(MenC6H6−n)2-
Fe]2+ dications (1) by exploring their reactions with the
dicarbollide anion [7,8-C2B9H11]2− that generated a complete
series of polymethylated arene ferradicarbaboranes [1-(η6-
MenC6H6−n)-closo-1,2,3-FeC2B9H11] with the number of arene
methyls n = 1–6.1,2 These reactions resulted in the displacement
of one of the arene ligands2 in 1 by the π-donating dicarbollide
Scheme 1 General scheme of a single addition of a nucleophilic anion
to [(MenC6H6−n)2Fe]2+ dications.
dianion and not in nucleophilic addition to the arene ring.
Addition reactions of nucleophiles (Nu−) to iron dications gener-
ally proceed at the unsubstituted arene site (see Scheme 1) and
have never been observed with uncomplexed arenes. These types
of reactions have been reported mostly for carbanions and other
strong nucleophiles (for example, H−) and are known to be
strongly affected and restricted by the nature of the nucleophile,
arene, and solvent used.3 Although nucleophilic addition reac-
tions of the [2-Me-1,2-C2B10H10]− anion to the cyclopentadiene
ring in [RuCl(Cp)(PPh3)2] and to the arene ring in [(η6-arene)Cr-
(CO)3] have been reported4,5 no addition reactions of σ-bonding
carborane anions to iron-complexed arenes have surprisingly
been examined. Therefore we believe that this paper will rep-
resent the first successful attempt in the area of iron–arene
chemistry.
Results and discussion
Syntheses
In order to examine the scope of possible addition reactions, we
have started investigating reactions between the mesitylene (mes)
dication [(η6-mes)2Fe]2+ (1a) and Li+ salts of monofunctional σ-
bonding carboranyl anions, Li[1-R-1,2-C2B10H11] (2) (R = H,
2a; Me, 2b; Ph, 2c), in THF solvent. Scheme 2 shows that suc-
cessive addition of lithium carboranes 2 to 1a(PF6)2 at low temp-
erature (−60 °C, 1 h, followed by stirring for 2 h at r.t.) in THF
aInstitute of Inorganic Chemistry, Academy of Sciences of the Czech
Republic, 250 68 Řež, Czech Republic. E-mail: stibr@iic.cas.cz;
Fax: +420-2-2094-1502; Tel: +420-2-6617-3106
bDepartment of General and Inorganic Chemistry, Faculty of Chemical
Technology, University of Pardubice, Studentská 573, 532 10 Pardubice,
Czech Republic. E-mail: Ales.Ruzicka@upce.cz
†CCDC 789923 and 789924. For crystallographic data in CIF or other
electronic format see DOI: 10.1039/c2dt30181d
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 7151–7155 | 7151

View Article Online
½carb ꢀ carbꢁ2ꢀ þ H2O
!
½carb ꢀ carbHꢁꢀþOHꢀ
ð2Þ
ð3Þ
cCAꢀ
Possible alternations of a radical mechanism:
½ðmesÞ2Feꢁ2þ þ ½carbꢁꢀ ! ½ðmesÞ2Feþꢁ˙ þ ½carbꢁ˙
½ðmesÞ2Feþꢁ† þ ½carbꢁ†
!
½ðmesÞFe(mes-exo-6-carb)ꢁþ
3a
ð4Þ
ð5Þ
2 ½carbꢁ˙ ! carb–carb
Scheme 2 The main exo-mode of nucleophilic addition of lithium
o-carboranes (2) to the [(η6-mes)2Fe]2+ (1a) dication.
2 ½ðmesÞ2Feþꢁ† þ carb ꢀ carb !
2þ
2ꢀ
2þ
resulting in a clean addition of the corresponding carborane
anions to one of the unsubstituted arene sites in 1a upon for-
mation of the exocyclic C–C bond. This entirely regioselective
reaction mode generated a series of three orange monocations of
general structure [(η5-mes-exo-6-{2-R-1,2-C2B10H11})Fe(η6-
mes)]+ (3) (R = H, 3a; Me, 3b; Ph, 3c) which were isolated as
½ðmesÞ2Feꢁ ½carb ꢀ carbꢁ þ ½ðmesÞ2Feꢁ
ð6Þ
that can either combine with [(mes)2Fe+]˙ to form cation 3a (eqn
(4)) or undergo C–C coupling to form the neutral carb–carb
dimer (eqn (5)). Its polyhedral expansion via addition of two
electrons onto one of the carborane subclusters (eqn (6)) would
then lead to the [carb–carb]2− dianion,7 from which the resulting
cCA− (or [carb–carbH]−) anion is formed on hydrolysis
(eqn (2)).
−
PF6 salts (3PF6) in good yields ranging from 50 to 75%. Indi-
vidual complexes were obtained on purification by LC or pre-
parative TLC on a silica gel substrate, using MeCN–CH2Cl2
mixtures as the mobile phase. No double addition, as reported,
e.g., for lithium alkyls LiR (R = tBu, Ph, CHvCH2),3a,d or
signs of addition to the Me-substituted site were observed. It
should be also noted, however, that similar reactions with [(η6-p-
xylene)2Fe]2+ and [(η6-durene)2Fe]2+ dications gave only intract-
able and rather complex product mixtures, which is in agreement
with the rules previously formulated by Astruc et al.3b
From the viewpoint of B-cluster chemistry, the cCA− anion
can be regarded as a derivative of a new [nido-C2B10H13]−
isomer, in which the skeletal CH2 vertex is exo-substituted by
the 1-o-carboranyl group. The isomerism of the nido subunit in
cCA− consists in m-positioning of the two cage carbon vertexes
in comparison to p-arrangement in the known isomer of the
[nido-C2B10H13]− anion.8
The room-temperature reaction between a threefold excess of
2a and the mesitylene dication 1a(PF6)2 using a reverse order of
addition of the reaction components (addition of 1a(PF6)2 to 2a).
The reaction yielded an orange species formulated as the mono-
cationic
[(η5-mes-exo-6-{2-R-1,2-C2B10H11})Fe(η6-mes)]+-
Structural studies
[closo-nido-H11B10C2-C2B10H12]− (3acCA) (cCA = conjucto-
carborane anion = [conjucto closo-nido-H11B10C2-C2B10H12]−)
as a sole product in 71% yield. The cationic part of this com-
NMR spectroscopy
The 11B NMR spectra of cations 3 (Table 1) consist of
1 : 1 : 2 : 2 : 2 : 2 patterns of doublets (with coincidental overlaps
of the B4,5/7,11 resonances) as expected for 1,2-disubstituted
o-carboranes with two different substituents at carbon sites.9
−
pound is the same as in 3aPF6, but the original PF6 counter-
anion has now been replaced by cCA−. The cCA− anion has
been isolated earlier by Xie et al.6 in the form of salts with two
lanthanide counter cations [LnCl2(THF)5]+ (Ln = Er and Y)
which were characterized structurally. However, this last report
formulates the species as [μ-CH-(closo-C2B10H11)-nido-
CB10H11]−.
1
Also the corresponding H NMR spectra (Table 2) are in agree-
ment with Cs symmetry, exhibiting two 3 : 9 resonances due to
mes-H and mes-Me, two 2 : 1 resonances assigned to cyclohexa-
diene (chd) H2,4 and endo-H6 hydrogens, and two 3 : 6 reson-
ances due to chd 3- and 1,5-methyls. The C–H, C–Me, and C–
Ph protons of the exo-carboranyl cage can be also clearly distin-
The formation of 3acCA from 1a seems to be in agreement
with the overall stoichiometry as in eqn (1) and (2) and the
double-cage nature of cCA− (see also Fig. 2) constitutes a direct
structural support for a radical-chain ET (electron transfer)
mechanism3b,c,h of the nucleophilic addition process. Some of
the possible steps of this radical mechanism are outlined in eqn
(3)–(6). The mechanism may be triggered by the formation of
the 19-electron radical cation [(mes)2Fe+]˙ (eqn (3)). This may
generate a carb˙ radical (carb = C2B10H11)
1
guished. In contrast to the previously reported H NMR spectra
of the neutral doubly substituted [(η5-6-R-mes)2Fe] (pseudo-
ferrocene) complexes (R = tBu and Ph),3a the corresponding
spectra of cations 3 are temperature independent. No significant
cross-peaks have been found in the [1H–1H]-COSY NMR
spectra of cations 3 because of non-adjacency of all C–H pos-
itions. The 13C–{1H} NMR spectrum of 3aPF6 (see
2ꢀ
½ðmesÞFe(mes-exo-6-carb)ꢁþ½carb ꢀ carbꢁ
ð1Þ
½ðmesÞ2Feꢁ2þþ3 ½carbꢁꢀ
!
1b
3a
7152 | Dalton Trans., 2012, 41, 7151–7155
This journal is © The Royal Society of Chemistry 2012

View Article Online
Table 1 Chem. shifts δ(11B) for cations of structure 3
Compd
B12
B9
B8,10
B4,5,7,11
B3,6
3aPF6
3bPF6
3cPF6
−4.9a
−7.7
−1.3
−3.3
−10.0
−2.7
−10.4
−10.0
−10.5
−12.9
−11.8
−12.9
−13.3
−13.9
−10.5
a δ(11B) in ppm relative to BF3·OEt2, assignments by [11B–11B]-COSY
experiments, measured at 128.3 MHz in CD3CN (296 K) with
broadband 1H decoupling; for o-carborane numbering system see ref. 9.
Table 2 Chem. shifts δ(1H) for cations of structure 3
Compd mes-H chd-H2,4 chd-H6 mes-Me chd-3-Me chd-1,5-Me2
a,b
3aPF6
5.63(3) 4.29(2) 3.45
2.38(9) 2.57(3)
2.34(9) 2.53(3)
2.27(9) 2.42(3)
2.21(9) 2.51(3)
1.78(6)
1.73(6)
1.38(6)
1.37(6)
3acCAa,c 5.54(3) 4.25(2) 3.41
Fig. 1 ORTEP representation of the crystallographically determined
molecular structure of [(η5-mes-exo-6-{2-R-1,2-C2B10H11})Fe(η6-mes)]+
(PF6−)·CH2Cl2 (3PF6) (crystallographic numbering) at 50% probability
level. The CH2Cl2 molecule was omitted for clarity. Selected bond
lengths (Å) and angles (°): arene ring: mean C–C 1.4115(12): mean
Fe–C 2.1124(13), Fe–arene (ring centroid) 1.572(3), mean C–C–C
119.99(10); chd ring: C1–C2 1.401(6), C1–C6 1.507(6), C2–C3 1.423(6),
C3–C4 1.416(7), C4–C5 1.411(7), Fe–chd (ring centroid) 1.571(3),
C6–C(carb) 1.560(6), C2–C1–C6 118.8(4), C2–C3–C4 116.1(4),
C1–C6–C(carb) 116.8(4), H6–C6–C19 107.2; carborane cluster:
C19–C20 1.676(7), mean C19–B 1.711(3), mean C20–B 1.712(3),
C6–C19–C20 114.5(4), C6–C19–B22 126.6(4).
a,d
3bPF6
5.43(3) 3.97(2) 2.83
5.44(3) 4.23(2) 2.17
a,e
3cPF6
a δ(1H) in ppm relative to TMS, measured at 400 MHz in CD3CN
(296 K), intensities other than 1 in parentheses. b δ(1H) (carb. cage):
3.67(CH). c δ(1H) (carb. cage): 3.62(CH), 3.54(CH), 2.85(2 H,CH).
d δ(1H) (carb. cage): 2.18(3 H,Me). e δ(1H) (carb. cage): 7.73–
7.75(5 H, Ph).
Experimental) exhibits all resonances for mes and chd ring
carbons and methyls expected from Cs symmetry.
The 11B NMR spectrum of 3acCA is very complex, consisting
of a severely overlapped area (29 B) between −3.2 and
−20.6 ppm, in which the 11B resonances due to the 3a cation
can be identified. The 1H NMR spectrum of the cCA− anion
contains four 1 : 1 : 2 resonances due to the three different cage-
CH environments. The ESI-MS spectrum of 3acCA exhibits the
molecular-ion envelope identical with the 3a cation (m/zmax
439.30).
X-ray diffraction analyses
The structures of 3aPF6·CH2Cl2 and 3acCA were established by
an X-ray diffraction study and are shown in Fig. 1 and 2. It is
seen that the pseudoferrocene ligand in the cationic part adopts
configuration similar to that found for structurally established
pseudoferrocene compounds [Fe(η5-mes-exo-6-tBu)2]7 and [(η6-
(mes)Fe(η5-mes-exo-6-Y](PF6) (where Y = CH2Cl and CHCl2),3i
with the central Fe atom sandwiched between η6-mesitylene and
η5-trimethylcyclohexadienyl ligands. The carborane substituted
nido subcluster in the cCA− anion contains two m-positioned
open-face CH vertexes with two extra long C31–B33 (1.990(3)
Å) and C31–B36 (2.002(2) Å) distances (marked by dotted
lines) associated with the carbon interconnecting the closo and
nido subclusters.
Fig. 2 ORTEP representation of the crystallographically determined
molecular structure of [(η5-mes-exo-6-{2-R-1,2-C2B10H11})Fe(η6-
mes)]+(cCA)− (3acCA) (crystallographic numbering). Bond lengths (Å)
and angles (°) in the cationic part are very similar to those in 3aPF6
(Fig. 1). The cCA anion: nido-carborane subcluster, open face:
C31–C34 2.581(3), mean C31–B 2.075(4), mean C34–B 1.642(4),
mean B32–B 1.773(5), mean B–B (other) 1.756(5), C43–C31–H31
106.5(3), C31–B32–C34 64.6(4); bond lengths in the −1-closo-1,2-
C2B10H11 subcluster are similar to those in 3aPF6 (Fig. 1).
Conclusions
C2B10H11] carboranes should generate cations near structure 3
with a modified carborane functionality. Similar reactions, for
example with monocarbaborane Li2[closo-CBnHn] compounds,
may be expected to lead to neutral monocarbaborane analogs of
3. Moreover, boron-removal reactions on the carborane part of 3,
The isolation of the o-carboranyl-trimethylcyclohexadienyl
cations of type 3 surely opens a new, broader area of carboranyl-
substituted pseudoferrocene chemistry. For example, reactions of
the 1a dication with the isomeric Li[closo-1,7 and 1,10-
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 7151–7155 | 7153

View Article Online
Synthesis of [(η5-mes-exo-6-{1,2-C2B10H11})Fe(η6-mes)]+-
(B10H11C2-C2B10H12)− (3acCA)
followed by metal complexation, are expected to provide bi-
metallic sandwich assemblies of designed molecular shape, and
decomplexation procedures applied to structures of type 3 should
generate aryl or cyclohexadienyl carboranes with unusual substi-
tuents. Relevant experiments are currently underway in our
laboratories.
Solid [(η6-mes)2Fe](PF6)2 (1aPF6) (530 mg, 1 mmol) was added
in several portions to a solution of Li[1,2-C2B10H11] (2a)
(451 mg, 3 mmol) in THF (50 ml) at room temperature and the
mixture was stirred 3 h. Further work up as in the preceding
experiment gave 516 mg (71%) of orange 3acCA upon crystalli-
zation from a CH2Cl2 solution onto the surface of which a layer
of hexane was carefully added. Anal. (calcd/found): 39.64/
38.41%C, 8.04/8.12%H. ESI-MS: m/z (100%) (calcd/found):
439.31/439.28 [M+ corresponding to 3a].
Experimental
General
All reactions were carried out with the use of standard vacuum
or inert-atmosphere techniques as described by Shriver and
Drezdzon,10 although some operations, such as column LC, were
carried out in air. The starting dication 1a was prepared accord-
ing to the literature.11 Dichloromethane and hexane were dried
over CaH2 and freshly distilled before use, THF was dried with
sodium diphenyl ketyl and distilled. Other chemicals were of
reagent or analytical grade and were used as purchased. Analyti-
cal TLC was carried out on ®Silufol (silica gel on aluminum
foil; detection by I2 vapor, followed by 2% aqueous AgNO3
spray). Column chromatography was performed on silica gel
(Aldrich, 250–350 mesh). Mass spectra were recorded on a
X-ray crystallography
The X-ray data for orange crystals of compounds 3aPF6·CH2Cl2
and 3acCA were obtained at 150 K using an Oxford Cryostream
low-temperature device and a Nonius KappaCCD diffractometer
with MoKα radiation (λ = 0.71073 Å), a graphite monochroma-
tor, and the ϕ and χ scan mode. Data reductions were performed
with DENZO-SMN.13 The absorption was corrected by inte-
gration methods.14 Structures were solved by direct methods
(Sir92)15 and refined by full matrix least-squares based on F2
(SHELXL97).16 Hydrogen atoms could be mostly localized on a
difference Fourier map. However, to ensure uniformity of treat-
ment of crystal structures, they were recalculated into idealized
positions (riding model) and assigned temperature factors
1
Thermo Finnigan LCQ Fleet Ion Trap mass spectrometer. H,
11B and 13C NMR spectroscopy was performed on a Varian
Mercury 400 instrument. The 11B NMR spectra (referenced to
BF3·OEt2 standard) were assigned by [11B–11B]-COSY
measurements.12
U
iso(H) = 1.2 Ueq(pivot atom) or of 1.5 Ueq for the methyl moi-
eties with C–H = 0.96 Å, 0.97, and 0.93 Å for the methyl,
methylene, and aromatic hydrogen atoms, respectively, and
1.1 Å for B–H and C–H bonds in the carborane cage.
General synthesis of [(η5-mes-exo-6-{2-R-1,2-C2B10H11})Fe(η6-
mes)]+(PF6)− (3PF6) (R = H, Me, and Ph) complexes
Acknowledgements
A solution of lithium carboranes Li[1-R-1,2-C2B10H10] (2) (R =
H, 2a; Me, 2b; Ph, 2c) (1.1 mmol reaction scale) in THF (50 ml)
was cooled to ca. −60 °C and treated with solid [(η6-mes)2Fe]-
(PF6)2 (1aPF6) (530 mg, 1 mmol). The mixture was stirred at
−40 to −60 °C for 1 h and then for an additional 2 h at ambient
temperature. Water (ca. 1 ml, dropwise) was carefully added and
the bulk of THF rotary evaporated. The residue was digested
with 30 ml-portions of CH2Cl2 and water and the orange-
coloured bottom layer was separated, dried over MgSO4, filtered,
and subjected to LC separation on a silica gel substrate. Elution
with a CH2Cl2–MeCN mixture (ca. 10 : 1) developed the main
orange bands (anal. RF ca. 0.30–0.35) which were evaporated to
The work was supported by The Grant Agency of the Czech
Republic (project no. P207/11/0705).
Notes and references
1 (a) B. Štíbr, M. Bakardjiev, J. Holub, A. Růžička and M. Kvíčalová,
Inorg. Chem., 2009, 48, 10904; (b) B. Štíbr, M. Bakardjiev, J. Holub,
A. Růžička, Z. Padělková and P. Štěpnička, Inorg. Chem., 2011, 50,
3097.
2 For some recent arene-displacement reactions see, for example:
(a) D. A. Loginov, M. M. Vinogradov, Z. A. Starikova, P. V. Petrovskii
and A. R. Kudinov, Izv. Akad. Nauk. SSSR, Ser. Khim., 2007, 2046;
(b) D. A. Loginov, M. M. Vinogradov, L. S. Shuĺpina, A. V. Vologzagina,
P. V. Petrovskii and A. R. Kudinov, Izv. Akad. Nauk. SSSR, Ser. Khim.,
2007, 2088; (c) A. R. Kudinov, D. A. Loginov and P. V. Petrovskii, Russ.
Chem. Bull., 2007, 56, 1930.
3 (a) J. F. Helling and D. M. Braitsch, J. Am. Chem. Soc., 1970, 92, 7207;
(b) M. Madonik, D. Mandon, P. Michaud, C. Lapinte and D. Astruc,
J. Am. Chem. Soc., 1984, 106, 3381; (c) D. Mandon, L. Toupet and
D. Astruc, J. Am. Chem. Soc., 1986, 108, 1320; (d) K. C. Sturge and
M. J. Zaworotko, J. Chem. Soc., Chem. Commun., 1990, 1244;
(e) T. S. Cameron, M. D. Clerk, A. Linden, K. C. Sturge and
M. J. Zaworotko, Organometallics, 1988, 7, 2571; (f) M. D. Clerk,
K. C. Sturge, P. S. White and M. J. Zaworotko, J. Organomet. Chem.,
1989, 362, 155; (g) M. V. Gaudet, A. W. Hanson, P. S. White and
M. J. Zaworotko, Organometallics, 1989, 8, 286; (h) D. Mandon and
D. Astruc, Organometallics, 1990, 9, 341; (i) J. L. Atwood,
S. D. Christie, M. D. Clerk, D. A. Osmond, K. C. Sturge and
M. J. Zaworotko, Organometallics, 1992, 11, 337.
−
dryness to isolate cations 3a, 3b and 3c as PF6 salts in unopti-
mized yields 70, 60, and 75%, respectively. Individual com-
plexes can be crystallized by adding carefully excess Et2O onto
the surface of acetone solutions. Anal. (calcd/found):
3aPF6·CH2Cl2: 37.01/36.40%C, 5.48/5.51%H. 3bPF6: 42.13/
43.53%C, 6.24/6.12%H. 3cPF6: 47.26/48.12%C, 5.96/6.02%H.
ESI-MS: m/z (100%) (calcd/found): 3a: 439.31/439.28 [M+];
3b: 452.32/452.30 [M+]; 3c: 515.40/515.40. δ(13C)–{1H}
(100.6 MHz, CD3CN) for 3aPF6: 104.9 (1C, chd-3-ring), 94.9
(3C, mes-C1,3,5-ring), 84.8 (2C, chd-C1,5-ring), 66.1 (3C, mes-
C2,4,6-ring), 60.4 and 57.2 (2C, carb C), 49.7 (1C, chd-C6),
24.7 (1C, chd-3-Me), 19.0 (2C, chd-1,5-Me)15.4 (3C, mes-
1,3,5-Me).
7154 | Dalton Trans., 2012, 41, 7151–7155
This journal is © The Royal Society of Chemistry 2012

View Article Online
4 M. Basato, A. Biffis, C. Tubaro, C. Graiffa and A. Tiripicchio, Dalton
Trans., 2004, 4092.
5 T. J. Henly, C. B. Knobler and M. F. Hawthorne, Organometallics, 1992,
11, 2313.
6 S. Wang, Q. Yang, T. C. W. Mak and Z. Xie, Organometallics, 1999, 18,
4478.
S. Heřmánek and T. Jelínek, Collect. Czech. Chem. Commun., 1991,
56, 1618; (g) C. Viñas, G. Barbera and F. Teixidor, J. Organomet.
Chem., 2002, 642, 16.
9 V. I. Bregadze, Chem. Rev., 1992, 92, 209, and references therein.
10 D. F. Shriver and M. A. Drezdzon, Manipulation of Air Sensitive Com-
pounds, Wiley, New York, 2nd edn, 1986.
7 (a) T. D. Getman, C. B. Knobler and M. F. Hawthorne, Inorg. Chem.,
1992, 31, 101; (b) T. D. Getman, C. B. Knobler and M. F. Hawthorne,
11 B. Štíbr, M. Bakardjiev, Z. Hájková, J. Holub, Z. Padělková, A. Růžička
and J. D. Kennedy, Dalton Trans., 2011, 40, 5916.
J. Am. Chem. Soc., 1990, 112, 4593.
12 W. C. Hutton, T. L. Venable and R. N. Grimes, J. Am. Chem. Soc., 1984,
106, 29.
−
8 For works on [nido-C2B10H13
]
anions see: (a) G. B. Dunks,
R. J. Wiersema and M. F. Hawthorne, J. Chem. Soc., Chem. Commun.,
1972, 899; (b) G. B. Dunks, R. J. Wiersema and M. F. Hawthorne,
J. Am. Chem. Soc., 1973, 95, 3174; (c) M. R. Churchill and G. B. de
Boer, Inorg. Chem., 1973, 12, 2674; (d) E. I. Tolpin and
W. N. Lipscomb, Inorg. Chem., 1973, 12, 2257; (e) J. Plešek,
T. Jelínek, B. Štíbr and S. Heřmánek, J. Chem. Soc., Chem. Commun.,
1988, 348; (f) J. Plešek, B. Štíbr, X. L. R. Fontaine, J. D. Kennedy,
13 Z. Otwinowski and W. Minor, Methods Enzymol., 1997, 276, 307.
14 P. Coppens, in Crystallographic Computing, ed F. R. Ahmed, S. R. Hall
and C. P. Huber, Munksgaard, Copenhagen, 1970, pp. 255–270.
15 A. Altomare, G. Cascarano, C. Giacovazzo and A. Guagliardi, J. Appl.
Crystallogr., 1993, 26, 343.
16 G. M. Sheldrick, SHELXL-97, Program for the Refinement of Crystal
Structures, University of Göttingen, Göttingen (Germany), 1997.
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 7151–7155 | 7155