Chemical behavior of a pair of (COD)CpRh and - Ir complexes with pendant peripheral -B(C6F5)2 groups

Article abstract of DOI:10.1021/om800195d

Hydroboration of (COD)Rh(η⁵-C₅H ₄-allyl) (7) with the strongly electrophilic reagent HB(C ₆F₅)₂ yields (COD)Rh[η⁵-C ₅H₄-(CH₂)₃B(C₆F ₅)₂] (8). Nucleophilic N-heterocyclic reagents (1-methylimidazole or 1-methylbenzimidazole) add to the boron atom of the bifunctional complex to yield the respective adducts (9a, 9b). Both were characterized by X-ray diffraction. Addition of HB(C₆F ₅)₂ to the corresponding (COD)Ir(η⁵-C ₅H₄-allyl) complex (10) eventually results in the formation and isolation of the cycloborylated zwitterionic (COD) (η⁵-C₅H₃-cyclo-(CH₂) ₃B(C₆F₅)₂]IrH product (13) (also characterized by X-ray crystal structure analysis). However, 13 seems to thermally equilibrate in a reverse electrophilic aromatic substitution reaction with the thermodynamically disfavored open-chain (COD)Ir[η⁵- C₅H₄-(CH₂)₃B(C₆F ₅)₂] isomer (11). This follows from reactions of 13 with 1-methylimidazole or 1-methylbenzimidazole, which rapidly yield the corresponding open-chain adducts 14a and 14b at room temperature (both characterized by X-ray diffraction). In a slow reaction complex 13 even eventually reacts with pyrrole by ring opening to yield the open-chain product 15, which features the 2H-pyrrole isomer coordinated to the strong -B(C ₆F₅)₂ Lewis acid at the end of the trimethylene tether. Complex 15 was also characterized by an X-ray crystal structure analysis.

Full text of DOI:10.1021/om800195d

2328
Organometallics 2008, 27, 2328–2336
Chemical Behavior of a Pair of (COD)CpRh and -Ir Complexes
with Pendant Peripheral -B(C6F5)2 Groups†
Christoph Herrmann, Gerald Kehr, Roland Fröhlich, and Gerhard Erker*
Organisch-Chemisches Institut der UniVersität Münster, Corrensstrasse 40, 48149 Münster, Germany
ReceiVed March 2, 2008
Hydroboration of (COD)Rh(η5-C5H4-allyl) (7) with the strongly electrophilic reagent HB(C6F5)2 yields
(COD)Rh[η5-C5H4-(CH2)3B(C6F5)2] (8). Nucleophilic N-heterocyclic reagents (1-methylimidazole or
1-methylbenzimidazole) add to the boron atom of the bifunctional complex to yield the respective adducts
(9a, 9b). Both were characterized by X-ray diffraction. Addition of HB(C6F5)2 to the corresponding
(COD)Ir(η5-C5H4-allyl) complex (10) eventually results in the formation and isolation of the cycloborylated
zwitterionic (COD)(η5-C5H3-cyclo-(CH2)3B(C6F5)2]IrH product (13) (also characterized by X-ray crystal
structure analysis). However, 13 seems to thermally equilibrate in a reverse electrophilic aromatic
substitution reaction with the thermodynamically disfavored open-chain (COD)Ir[η5-C5H4-(CH2)3B(C6F5)2]
isomer (11). This follows from reactions of 13 with 1-methylimidazole or 1-methylbenzimidazole, which
rapidly yield the corresponding open-chain adducts 14a and 14b at room temperature (both characterized
by X-ray diffraction). In a slow reaction complex 13 even eventually reacts with pyrrole by ring opening
to yield the open-chain product 15, which features the 2H-pyrrole isomer coordinated to the strong
-B(C6F5)2 Lewis acid at the end of the trimethylene tether. Complex 15 was also characterized by an
X-ray crystal structure analysis.
(C6F5)2 substituent at the cyclopentadienyl ring. We have found
some remarkable differences in chemical behavior between the
rhodium and iridium examples. This will be described and
discussed in this article.
Introduction
Metal complexes with pendant very electrophilic boryl groups
attached to their periphery represent bifunctional transition
metal/main group element systems of considerable interest.1–3
The transition metal component can potentially act as a catalyst
precursor. The main group electrophile can bind nucleophilic
organic substrates and can potentially act as an intramolecular
catalyst activator. However, a limited number of these systems
have shown some unusual chemical behavior initiated by attack
of the boron electrophile at a π-ligand,4 most notably at the Cp
ligand to which it is bonded by a tether. The [Zr/B] system 1 is
a typical example.5 Within hours after being generated by
hydroboration of its respective alkenyl precursor, the complete
conversion to the “Cp-cycloborate” system (2) was observed.
We have recently reported a similar reaction in an iridium
system (3 f 4) (see Scheme 1).6
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We have now prepared a pair of group 9 (COD)MCp-X
complexes (M ) Rh, Ir) that each carry a pendant -(CH2)3B-
† Dedicated to Professor Ernst-Ulrich Würthwein on the occasion of his
60th birthday.
* Corresponding author. E-mail: erker@uni-muenster.de.
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10.1021/om800195d CCC: $40.75
2008 American Chemical Society
Publication on Web 04/15/2008

Pair of (COD)CpRh and –Ir Complexes
Organometallics, Vol. 27, No. 10, 2008 2329
Scheme 1
Scheme 2
Results and Discussion
We started this study with the synthesis of the respective
rhodium systems. For this purpose we reacted the η4-cyclooc-
tadienyl rhodium chloride dimer [(COD)RhCl]2 (5a) with the
(allyl-Cp)lithium reagent (6)7 to yield the corresponding allyl-
functionalized CpRh(I) complex (7) (see Scheme 2). The
pendant alkenyl functionality was then subjected to the hy-
droboration reaction8 using the HB(C6F5)2 reagent9,10 to yield
the anticipated bifunctional [Rh/B] system 8.
The hydroboration product 8 in our hands proved to be too
sensitive for isolation as a clean neat substance. Therefore, it
was generated in situ for spectroscopic characterization (see
below) and for carrying out subsequent reactions. Analysis of
the typical spectra of compound 8 in situ generated in d2-
dichloromethane (alternatively in d6-benzene) showed that a
regioselective H-B(C6F5)2 addition to the pendant -CH2-CHd
CH2 vinylic moiety had taken place with the usual “anti-
Markovnikov” orientation. The 19F NMR features are very
typical for the presence of tricoordinated boron11 in 8 [δ -129.8
(o), -147.4 (p), -160.9 (m)], as is the characteristic 11B NMR
resonance at δ 72.6. The B(C6F5)2 unit is connected to the
adjacent η5-C5H4 ring [13C NMR: δ 106.3 (ipso), and 86.9 (C2,
1
C5), 85.7 (C3, C4) all three as doublets with JRhC ) 3.8 Hz]
by a saturated trimethylene tether [13C NMR: δ 32.5 (br, CH2-
[B]), 27.4, 30.9]. The η4-1,5-COD ligand at Rh features a very
characteristic set of three 1H NMR resonances at δ 3.72 (br m,
4H, -CHdCH-) and δ 2.12, 1.89 (m, total of 8H,
-CH2-CH2-) with a pair of corresponding 13C NMR reso-
nances at δ 64.3 (1JRhC ) 14.2 Hz, -CHd) and δ 32.7
(-CH2-).
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2330 Organometallics, Vol. 27, No. 10, 2008
Herrmann et al.
Table 1. Selected NMR Data of the Complexes 9 and 14a
cmpd
M
lig
13C9
13C10
13C/1H11
1H2/5
1H3/4
19F: o,p,m-B(C6F5)2
11B
9ab
Rh
Rh
Ir
im
bim
im
63.7
64.4
47.3
47.4
32.4
32.9
34.5
34.4
136.0/7.69
141.3/7.53
135.7/7.00
141.2/7.55
5.09
5.13
5.00
5.00
4.91
4.77
4.72
4.71
-133.3
-133.1
-133.4
-132.9
-159.9
-158.8
-159.0
-158.3
-164.3
-6.1
-6.4
-5.5
-5.9
9bc
-164.1
-164.1
-163.8
14ac
14bc
Ir
bim
a im ) 1-methylimidazole, bim ) 1-methylbenzimidazole, atom numbering see Scheme 2. b NMR spectra recorded in CDCl3. c NMR spectra
recorded in d6-benzene.
Figure 2. Molecular geometry of the 1-methylbenzimidazole [Rh/
B] complex 9b.
Scheme 3
Figure 1. Molecular geometry of the [Rh/B]-1-methylimidazole
adduct 9a.
Table 2. Selected Structural Parameters of the Complexes 9 and 14a
9a
9b
14a
14b
M
Rh
im
Rh
bim
Ir
im
Ir
bim
ligb
M-C1
2.211(3)
2.247(3)
2.239(3)
2.274(4)
2.266(3)
2.105(3)
2.106(3)
2.121(3)
2.132(3)
1.400(5)
1.398(5)
1.616(5)
1.623(4)
106.6(3)
125.5(3)
177.1(3)
167.4(3)
169.1(3)
84.9(4)
2.224(4)
2.256(4)
2.224(5)
2.271(5)
2.273(5)
2.116(4)
2.110(4)
2.128(4)
2.117(4)
1.417(7)
1.409(6)
1.622(6)
1.604(5)
109.3(3)
125.9(3)
-72.8(5)
160.4(3)
-70.2(4)
90.3(5)
2.208(3)
2.235(4)
2.236(4)
2.279(4)
2.253(3)
2.114(3)
2.118(4)
2.110(3)
2.114(3)
1.430(5)
1.431(6)
1.614(5)
1.614(4)
107.7(3)
125.0(3)
177.1(3)
167.2(3)
168.9(3)
85.9(4)
2.211(4)
2.260(5)
2.263(5)
2.210(5)
2.229(5)
2.108(4)
2.104(4)
2.111(4)
2.108(4)
1.415(7)
1.416(6)
1.625(5)
1.603(5)
108.7(3)
126.6(3)
73.3(5)
M-C2
M-C3
M-C4
M-C5
M-C11
M-C12
M-C15
M-C16
C11-C12
C15-C16
C8-B
1.647(5) Å), and the 1-methylimidazole nitrogen center [bond
angles at B: C8-B-N21: 106.6(3)°, C31-B-C41: 113.5(3)°,
C31-B-C8: 108.4(3)°, C31-B-N21: 107.4(3)°, C41-B-N21:
104.3(2)°, C41-B-C8: 115.9(3)°]. The ligand nitrogen center
(N21) bonded to boron is planar-tricoordinate (angles B-N21-
C25: 127.7(3)°, B-N21-C22: 125.5(3)°, C22-N21-C25:
106.9(3)°). Complex 9a adopts a conformation in the crystal
that has the C1-C6 substituent vector at Cp oriented above
the COD C11-C12 double bond.
B-N21
C8-B-N21
B-N21-C22
C1-C6-C7-C8
C6-C7-C8-B
C7-C8-B-N21
C2-C1-C6-C7
-160.6(3)
69.7(4)
84.1(5)
a Bond lengths in Å, angles and dihedral angles in deg. b im ) 1-methyl
imidazole, bim ) 1-methylbenzimidazole.
The 1-methylbenzimidazole [Rh/B] complex 9b (see Figure
2 and Table 2) shows similar structural features. However, it
adopts a different conformation of the trimethylene tether in
the crystal as compared to 9a.
Single crystals of 9a were obtained from a d2-dichloromethane
solution. Complex 9a features the structural parameters of a
typical CpRh(COD) moiety. The monosubstituted C5H4 ring is
uniformly η5-coordinated to rhodium with Rh-C(Cp) bond
lengths ranging from 2.211(3) to 2.274(4) Å (see Figure 1 and
Table 2).14 The bonds of the Rh center to the COD C(sp2)
carbons are shorter, ranging from 2.105(3) to 2.132(3) Å. The
trimethylene tether at the Cp ring is found in a fully extended
all-antiperiplanar conformation. The boron center at its end is
pseudotetrahedrally coordinated to C8, the ipso carbon atoms
of a pair of -C6F5 groups (B-C31: 1.636(5) Å, B-C41:
We then set out to study the chemistry of the analogous
bifunctional iridium/boron systems but encountered some
remarkable differences between these two series. The synthesis
was started with the reaction of the (Cp-allyl)lithium reagent
(6) with the (COD)Ir chloride dimer [(COD)IrCl]2 (5b) to give
(Cp-CH2-CHdCH2)Ir(COD) (10) as expected (see Scheme
3). Its subsequent hydroboration reaction with HB(C6F5)2 was
carried out under similar conditions to those in the Rh series,
only that pentane was chosen as the solvent. Addition of
HB(C6F5)2 to (Cp-allyl)Ir(COD) (10) at room temperature gave
(14) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson,
D. G.; Taylor, R. J. Chem. Soc., Dalton Trans. 1989, 1–83.

Pair of (COD)CpRh and –Ir Complexes
Organometallics, Vol. 27, No. 10, 2008 2331
Figure 3. Dynamic 19F NMR spectra of complex 13 (564.2 MHz in CD2Cl2).
a bright yellow solution, from which a white solid began to
precipitate immediately. After the solution had completely
decolorized, the white precipitate was collected and isolated in
85% yield. The subsequent analysis, including an X-ray crystal
structure analysis of the product, revealed that we had not
isolated the [Ir/B] system (11) with an extended -(CH2)3
B(C6F5)2 substituent but rather its ring-closed zwitterionic
hydrido-Ir/borate isomer (13).
1
Product 13 features a set of four different COD -CHd H
NMR signals (in CDCl3 at 228 K: δ 4.64, 4.49, 3.77, and 3.57).
There is a trimethylene unit (13C NMR: δ 23.9, 22.4 20.1)
connected to boron. The 11B NMR shift (δ -16.9) is in a typical
borate anion range. There are only three Cp (i.e., C5H3) 1H NMR
resonances (δ 5.80, 5.58, 5.24). Corresponding 13C NMR signals
of the CH(Cp) groups were located at δ 87.6, 89.4, and 83.2.
One of the former Cp-H hydrogens is now found bonded to
Figure 4. Projection of the molecular structure of complex 13.
1
the iridium center. The Ir-H H NMR resonance was located
far “upfield” at δ -11.91.15
We thus conclude that 13 contains a borata-six-membered
heterocyclic ring anellated with the Cp framework at iridium.
Consequently, the -C6F5 substituents at boron are different, i.e.,
positioned cis or trans to iridium. In addition this crowded
structural situation has led to an increased rotational barrier
around both B-C6F5 vectors, so that the 19F NMR spectrum at
low temperature (208 K) features two pairs of diastereotopic
o-fluorine resonances of the pair of -C6F5 substituents (δ
-130.2/-135.7, -131.5/-132.9) in addition to one pair of p-F
resonances (δ -162.2, -163.4) and two pairs of m-F signals
(δ -164.7/-164.9, -165.8/-166.3) of the diastereotopic -C6F5
groups. We note that the small ∆(δ m-F)-(δ p-F) separation is
very typical of a tetraorganylborate-type structure. Increasing
the NMR monitoring temperature leads to coalescence of pairs
of o-F and m-F 19F NMR resonances (see Figure 3). As expected
the p-F NMR signals do not show coalescence behavior. From
this temperature-dependent dynamic 19F NMR behavior Gibbs
Figure 5. Molecular structure of complex 14a.
activation energies of ∆Gqrot(233 K) ≈ 10.1 ( 0.2 kcal mol-1
were estimated for the hindered rotation around the cis- and
trans-B-C6F5 vectors16 in complex 13.
The structural description of compound 13 was confirmed
by an X-ray crystal structure analysis (single crystals were
(15) Peterson, T. H.; Golden, J. T.; Bergman, R. G. J. Am. Chem. Soc.
2001, 123, 455–462. Heinekey, D. M.; Hinkle, A. S.; Close, J. D. J. Am.
Chem. Soc. 1996, 118, 5353–5361. Pedersen, A.; Tilset, M. Organometallics
1993, 12, 3064–3068. Sowa, J. R.; Angelici, R. J. J. Am. Chem. Soc. 1991,
113, 2537–2544. Heinekey, D. M.; Millar, J. J. M.; Koetzle, T. F.; Payne,
N. G.; Zilm, K. W. J. Am. Chem. Soc. 1990, 112, 909–919. See for a
comparison: Ahlers, W.; Erker, G.; Fröhlich, R.; Peuchert, U. J. Organomet.
Chem. 1999, 578, 115–124.
(16) Ahlers, W.; Temme, B.; Erker, G.; Fröhlich, R.; Fox, T. J.
Organomet. Chem. 1997, 527, 191–201.

2332 Organometallics, Vol. 27, No. 10, 2008
Herrmann et al.
Scheme 4
Figure 6. Molecular structure of complex 14b.
obtained from a concentrated toluene solution). In complex 13
the iridium atom is coordinated to the pair of CC double bonds
of the 1,5-cyclooctadiene ligand (bond lengths Ir1A-C11A:
2.209(5) Å [data of the independent molecule B in square
brackets: Ir1B-C11B: 2.218(5) Å], Ir1A-C12A: 2.185(6) Å
[2.208(5)Å],C11A-C12A:1.378(9)Å[1.393(7)Å],Ir1A-C15A:
2.208(5) Å [2.190(5) Å], Ir1A-C16A: 2.216(5) Å [2.200(5)
Å], C15A-C16A: 1.393 (9) Å [1.395(8) Å]). It is η5-bonded
to a disubstituted C5H3 ligand (Ir-C(Cp) bond lengths within
2.183(5) and 2.288(4) Å [2.183(5) and 2.304(5) Å]), and it is
bonded to a hydrogen atom (Ir1A-H1A: 1.51(5) Å, Ir1B-H1B:
1.49(5) Å). A six-membered borata-heterocyclic ring system is
anellated with the Cp ring. The C1A-C6A bond length is
1.494(7) Å [1.498(7) Å], and the C5A-B1A bond length
amounts to 1.656(7) Å [1.645(7) Å]. The anellated heterocycle
features a distorted shallow twist conformation (C1A-C5A:
1.451(7) Å [1.459(7) Å], angles C6A-C1A-C5A: 123.7(4)°
[124.6(4)°] and C1A-C5A-B1A: 122.5(4)° [121.3(4)°]). The
boron center in complex 13 is four-coordinate (bond angles
C5A-B1A-C8A: 104.9(4)° [106.2(4)°], C21A-B1A-C31A:
111.9(4)° [105.0(4)°]).
These results indicate that the hydroboration reaction of 10
with HB(C6F5)2 probably initially leads to the regioselective
formation of the hydroboration product 11. This, however, seems
to be unstable under the applied reaction conditions with regard
to an attack of the strong boron electrophile on its “own”
electron-rich adjacent Cp ring. This initial step of an electrophilic
aromatic substitution reaction17 sequence probably generates the
reactive intermediate 12. Complex 12 has two attractive
pathways for stabilization with re-formation of the aromatic
Cp-π-electron sextet: Rupture of the newly formed C-B bond
would lead back to 11; deprotonation would lead to 13. This
pathway is followed with the iridium atom serving as a metal
base18 to abstract the adjacent proton from the substituted
cyclopentadiene ligand in 12 to form the observed zwitterionic
iridium hydride complex 13 (see Scheme 3).
Thus, we observed the formation of the adduct 11 · THF upon
dissolving 13 in d8-THF. We deduce this from the absence of
1
the Ir-H H NMR resonance and the observation of a 2:2
intensity pair (AA′BB′ spin system) of η5-C5H4- H NMR
1
signals at δ 5.01, 4.92. Also, the typically increased molecular
symmetry gives rise to monitoring only two COD 13C NMR
signals [δ 47.2 (C9) and 34.7 (C10)] for 11 · THF.
This seems to be a rather common reaction mode for complex
13. Treatment with 1 molar equiv of 1-methylimidazole in
toluene at room temperature led to the rapid formation of the
donor adduct (14a) to the electrophilic boron center of the open
isomer (11). Complex 14a was isolated in ca. 80% yield from
the reaction mixture. It features the typical spectroscopic data
of a [(COD)IrCp-CH2CH2CH2B(C6F5)2]/1-methylimidazole ad-
duct (see Table 1 and Scheme 4). We observed 11B and 19F
NMR shifts characteristic of the B-N-type structure, a 2:2
intensity pair of C5H4- 1H NMR resonances (δ 5.00/4.72;
corresponding 13C NMR signals at δ 82.3, 80.2; C-ipso at δ
103.6) and only one pair of COD 13C NMR resonances (δ 47.3,
1
34.5, H NMR signals at δ 3.74, 2.21/1.97).
Complex 14a was characterized by X-ray diffraction (single
crystals were obtained from d6-benzene). The molecular struc-
ture of the iridium complex 14a is very similar to that of its
rhodium analogue 9a (see the values listed in Table 2 for a
comparison), only that the Ir-C(π) bond lengths seem to be
slightly shorter. Even the conformation of the -(CH2)3-[B]
tether is alike for the 14a/9a pair of complexes. Only some
conformational details around the [B]-1-methylimidazole unit
seem to be marginally different.
We have also treated complex 13 with 1-methylbenzimidazole
and isolated the open [B/N] adduct 14b (68% yield). It was
characterized spectroscopically (see Table 1) and by an X-ray
crystal structure analysis (see Figure 6 and Table 2).
Complex 13 even reacts with pyrrole, although this aromatic
five-membered heterocycle itself is not a donor ligand. However,
its nonaromatic 2H-pyrrole isomer19 is. In order to stabilize the
boron center in the open [Ir/B] isomer 11, isomerization to the
“isopyrrole” reagent is required. This has been known to be
effected20,21 by the strong boron Lewis acid B(C6F5)3.22,23
Consequently, the reaction of complex 13 with pyrrole took ca.
There is some evidence that the formation of 13 from 11 via
12 is reversible. Most of this evidence comes from trapping
reactions, i.e., the observation of reaction sequences where the
addition of a suitable donor ligand to 13 eventually results in
the rapid formation of the corresponding adduct of the elusive
bifunctional isomer 11.
(17) Döring, S.; Erker, G.; Fröhlich, R.; Meyer, O.; Bergander, K.
Organometallics 1998, 17, 2183–2187.
(19) Dubnikova, F.; Lifshitz, A. J. Phys. Chem. A 2001, 105, 3605–
3614. Smith, S. B. J.; Liu, R. J. Mol. Struct. (THEOCHEM) 1999, 491,
211–222. Bachrach, M. J. Org. Chem. 1993, 58, 5414–5421.
(20) Kehr, G.; Roesmann, R.; Fröhlich, R.; Holst, C.; Erker, G. Eur.
J. Inorg. Chem. 2001, 535–538. Kehr, G.; Fröhlich, R.; Wibbeling, B.; Erker,
G. Chem.-Eur. J. 2000, 6, 258–266.
(18) Werner, H.; Lippert, F.; Peters, K.; v. Schnering, H. G. Chem. Ber.
1992, 347–352. Werner, H. Angew. Chem. 1983, 95, 932–954. Angew.
Chem., Int. Ed. Engl. 1983, 22, 927–949. Werner, H. Pure Appl. Chem.
1982, 54, 177–188.

Pair of (COD)CpRh and –Ir Complexes
Organometallics, Vol. 27, No. 10, 2008 2333
Scheme 5
3 days at room temperature to go to completion. We have
isolated the corresponding open [Ir/B]-2H-pyrrole adduct 15 in
ca. 70% yield (see Scheme 5).
The NMR spectra of product 15 show the presence of a re-
formed C5H4-ring system [1H: δ 4.99 (2-H/5-H), δ 4.75 (3-H/
4-H)] and a symmetrically coordinated η4-COD ligand [1H: δ
3.74 (m, 4H, 9-H), δ 2.21/1.99 (m, 8H, 10-H); 13C: δ 47.3,
34.5]. No IrH resonance was observed. Most noteworthy are
the NMR resonances of the 2H-pyrrole isomer coordinated to
boron [1H: δ 3.49 (2H, CH2), δ 7.46, 5.37, 6.19 (14-H to 12-
H); 13C: δ 168.4 (C14), δ 153.5 (C12), δ 127.2 (C13)]. The
13C NMR signal of the “isopyrrole” CH2 group occurs at δ
64.8.20,24
Single crystals suitable for X-ray crystal structure analysis
were obtained from a toluene solution of 15 layered with
pentane. Complex 15 features the typical CpIr(COD) framework
(see Figure 7) that has a fully extended -(CH3-)3[B] unit
attached at the η5-C5H4 ring [Ir-C(Cp) bond lengths ranging
from 2.198(4) to 2.291(4) Å, Ir-C(COD) bond lengths within
2.105(4) to 2.141(4) Å]. The boron center in 15 is tetracoor-
dinated (C8-B9: 1.609(6) Å, B-C31 1.659(6) Å, B-C41:
1.656(6) Å). It has the 2H-pyrrole ligand coordinated via its
“imine-type” nitrogen atom (B-N10: 1.620(5) Å, angles
C8-B9-N10:107.6(3)°,B9-N10-C11:126.9(3)°,B9-N10–14:
126.1(3)°, C11-N10-C14: 107.0(4)°). The typical bond lengths
within the 2H-pyrrole unit20,24 amount to N10-C14: 1.324(5)
Å, C14-C13: 1.459(7) Å, C13-C12: 1.295(7) Å, C12-C11:
1.470(6) Å, and C11-N10: 1.396(5) Å. The bond angle at C11
is 107.4(4)° (N10-C11-C12).
Figure 7. View of the molecular structure of complex 15.
Therefore, the obtained bifunctional system may potentially
be regarded as an intramolecular main group element/
transition metal “frustrated” Lewis acid/Lewis base pair,25
i.e., a pair where Lewis acid/Lewis base adduct formation
(and thus quenching of their properties) is prevented by their
steric bulk.26 This does not, however, prevent their single
components from reacting with other sterically less congested
Lewis or Brønsted acids or bases, which may explain some
of the sensitivity of the unique system 8. Consequently,
quenching of one of the reactive sites, here by adding
heterocyclic nitrogen donor ligands to boron, results in the
formation and isolation of very stable products.
The corresponding iridium system behaves in a more
complicated fashion. We must assume that the initial hydrobo-
ration product (11) is formed as well, but in this case it is
unstable with regard to an intramolecular electrophilic aromatic
substitution reaction17,23 at the adjacent Cp-Ir system to yield
13. Presently it is not completely clear why this apparently very
favorable reaction pathway has been observed for the iridium
example but not for the closely related rhodium case. It may
be that an increased metal basicity18 of the Ir system might be
a decisive factor.
The zwitterionic [Ir/B] system 13 is rather stable, but it is
prone to undergo the reverse ring-opening reaction, probably
initiated by proton transfer to the respective Cp ipso-carbon
adjacent to boron. Because of the specific equilibrium position
of the 13 a (12) a 11 system, reversal of the electrophilic
aromatic substitution reaction can be observed only in cases
where the product (11) on the disfavored side is effectively
removed from the equilibrium by a suitable scavenger. Imine-
type heterocyclic donor ligands serve this purpose very well.
The observation of the formation of 15 does point to the
possibility that the very minor equilibrium component (11)
can be actively involved in catalysis. In view of earlier
observations it is likely that in this system the pyrrole f
2H-pyrrole tautomerization is catalyzed20,21,24 by the reactive
trivalent boron Lewis acid in 11, which then subsequently
traps the obtained isopyrrole ligand.27 So it may be envisaged
that the pair of isomers in such systems (here 13/11) could
serve as specific catalyst or reagents in future chemical
transformations. This would give this type of observed
Conclusions
The hydroboration of the (COD)M(Cp-allyl) complexes 7 (M
) Rh) and 10 (M ) Ir) with the very electrophilic HB(C6F5)2
reagent proceeds with the expected “anti-Markovnikov” re-
gioselectivity.8,10 In both cases we generate a bifunctional group
9 metal/boron system. In the case of the Rh example the
formation of the product (8) could actually be followed and
the obtained compound characterized by NMR spectroscopy,
although the system 8 in our hands proved to be too sensitive
to be isolated as a pure compound.
Complex 8 contains a strongly electrophilic boron center.
The Rh(I) center in 8 on the other hand is electron-rich.
(21) Bonazza, A.; Camurati, I.; Guidotta, S.; Mascellari, N. S.; Resconi,
L. Macromol. Chem. Phys. 2004, 205, 319–333. Focante, F.; Camurati, I.;
Nanni, D.; Leardini, R.; Resconi, L. Organometallics 2004, 23, 5135–5141.
Guidotti, S.; Camurati, I.; Focante, F.; Angellini, L.; Moscardi, G.; Resconi,
L.; Leardini, R.; Nanni, D.; Mercandelli, P.; Sironi, A.; Beringhelli, T.;
Maggioni, D. J. Org. Chem. 2003, 68, 5445–5465.
(22) Massey, A. G.; Park, A. J. J. Organomet. Chem. 1966, 5, 218–
225. Pohlmann, J. L.; Brinkmann, F. E.; Tesi, G.; Donadio, R. E. Z.
Naturforsch. 1965, 20b, 1–4. Pohlmann, J. L.; Brinkmann, F. E. Z.
Naturforsch. 1965, 20b, 5–11. Massey, A. G.; Park, A. J. J. Organomet.
Chem. 1964, 2, 245–250. Massey, A. G.; Park, A. J.; Stone, F. G. A. Proc.
Chem. Soc. 1963, 212.
(25) Welch, G. C.; San Juan, R. R.; Masuda, J. D.; Stephan, D. W.
Science 2006, 314 (5802), 1124–1126. Welsh, G. C.; Stephan, D. W. J. Am.
Chem. Soc. 2007, 129, 1880–1881.
(26) Spies, P.; Erker, G.; Kehr, G.; Fröhlich, R.; Stephan, D. W. Chem.
Commun. 2007, 47, 5072–5074.
(23) Erker, G. Dalton Trans. 2005, 1883–1890.
(27) See for a related reaction: Vagedes, D.; Fröhlich, R.; Erker, G.
Angew. Chem. 1999, 111, 3561–3565. Angew. Chem., Int. Ed. 1999, 38,
3362–3365.
(24) Hill, M.; Kehr, G.; Fröhlich, R.; Erker, G. Eur. J. Inorg. Chem.
2003, 3583–3589.

2334 Organometallics, Vol. 27, No. 10, 2008
Herrmann et al.
added to bis(pentafluorphenyl)borane (28.6 mg, 0.08 mmol).
Subsequent NMR measurements showed a complete conversion
to 8. Isolation of the compound could not be achieved. Upon
drying in vacuo, a red oil was obtained, which quickly turned
brown. 8: 1H NMR (CD2Cl2, 499.8 MHz, 298 K): δ 5.04 (m,
2H, 2,5-H), 4.90 (m, 2H, 3,4-H), 3.72 (br, 4H, 9-H), 2.18 (ps t,
2H, 6-H), 2.12 (m, 6H, 8,10-H), 1.89 (m, 4H, 10-H′), 1.82 (qui,
3JHH ) 7.4 Hz, 2H, 7-H). 13C{1H} NMR (CD2Cl2, 126 MHz,
isomerization reaction a role extended from just a mere
protective reaction of a reactive bifunctional main group
element/transition metal system.
Experimental Section
General Information. All syntheses were performed using dried
solvents in an inert gas atmosphere (argon) using Schlenk-type
glassware or a glovebox. Solvents were dried and distilled prior to
use. The following instruments were used for physical characteriza-
tion of the compounds: melting points: DSC 2010 (TA-Instruments);
elemental analyses: Foss-Heraeus CHNO-Rapid; IR spectra: Varian
3100 FT-IR (Excalibur Series); NMR spectra: Bruker AC 200 P
(11B: 64.2 MHz), Bruker AMX400 (1H: 400.1 MHz, 13C: 100.6
MHz), Varian 500 MHz INOVA (1H: 499.8 MHz, 13C: 126 MHz,
19F: 470.2 MHz), and Varian UNITYplus 600 (1H: 599.6 MHz,
13C: 150.8 MHz, 19F: 564.2 MHz). 11B spectra were referenced to
an external Et2O · BF3 sample; 19F spectra were referenced to an
external CFCl3 sample. NMR assignments were supported by
additional 2D experiments. X-ray diffraction: Data sets were
collected with a Nonius KappaCCD diffractometer, equipped with
a rotating anode generator. Programs used: data collection COL-
LECT (Nonius B.V., 1998), data reduction Denzo-SMN (Z.
Otwinowski, W. Minor, Methods Enzymol. 1997, 276, 307-326),
absorption correction SORTAV (R. H. Blessing, Acta Crystallogr.
1995, A51, 33-37; R. H. Blessing, J. Appl. Crystallogr. 1997, 30,
421-426) and Denzo (Z. Otwinowski, D. Borek, W. Majewski,
W. Minor, Acta Crystallogr. 2003, A59, 228-234), structure
solution SHELXS-97 (G. M. Sheldrick, Acta Crystallogr. 1990,
A46, 467-473), structure refinement SHELXL-97 (G. M. Sheldrick,
Universität Göttingen, 1997), graphics XP (BrukerAXS, 2000).
(2-Propenyl)cyclopentadienyllithium,28 bis(pentafluorophenyl)-
borane,9 chloro(1,5-cyclooctadiene)rhodium dimer,29 and chloro(1,5-
cyclooctadiene)iridium dimer30 were prepared according to literature
procedures.
1
1
298 K): δ 147.3 (dm, JCF ) 247 Hz, o-C6F5), 143.7 (dm, JCF
1
) 254 Hz, p-C6F5), 137.9 (dm, JCF ) 251 Hz, m-C6F5), 114.6
1
1
(br, i-C6F5), 106.3 (d, JRhC ) 3.8 Hz, C1), 86.9 (d, JRhC ) 3.8
Hz, C2,5), 85.7 (d, 1JRhC ) 3.8 Hz, C3,4), 64.3 (d, 1JRhC ) 14.2
Hz, C9), 32.7 (C10), 32.5 (br, C8), 30.9 (C6), 27.4 (C7). 19F
NMR (d6-benzene, 282.4 MHz, 298 K): δ -129.8 (m, 4F,
3
o-C6F5), -147.4 (t, JFF ) 21.0 Hz, 2F, p-C6F5), -160.9 (m,
4F, m-C6F5). 11B{1H} NMR (d6-benzene, 64.2 MHz, 300 K): δ
[ppm] 72.6 (ν1/2 ) 720 Hz).
Reaction of in Situ-Generated Complex 8 with 1-Methyl-
imidazole; Formation of the Adduct 9a. At room temperature a
solution of complex 7 (14.7 mg, 0.05 mmol) in toluene (5 mL)
was added to bis(pentafluorophenyl)borane (16.1 mg, 0.05 mmol).
The suspension was stirred for several minutes until all solids were
dissolved. Then the solution was added to 1-methylimidazole (3.8
mg, 0.05 mmol). Upon addition, the color of the reaction mixture
changed from dark red to orange. Subequently the solvent was
removed in vacuo and the residue washed with pentane (5 mL).
After removing the solvent in vacuo the product was yielded as a
pale yellow solid (12.5 mg, 36%). Crystals suitable for X-ray
diffraction were obtained from a solution of 9a in dichloromethane-
d2 in a NMR tube after one week. Mp: 204 °C. Anal. Calcd for
C32H28BF10N2Rh (744.3): C, 51.64; H, 3.79; N, 3.76. Found: C,
1
52.18; H, 3.88; N 3.78. H NMR (CDCl3, 599.6 MHz, 298 K): δ
7.69 (br, 1H, 11-H), 7.16 (br, 1H, 14-H), 6.90 (m, 1H, 13-H), 5.09
(m, 2H, 2,5-H), 4.91 (m, 2H, 3,4-H), 3.77 (s, 3H, 15-H), 3.69 (br,
3
4H, 9-H), 2.11(m, 4H, 10-H), 2.06 (t, JHH ) 6.3 Hz, 2H, 6-H),
1.86 (m, 4H, 10-H′), 1.22 (m, 2H, 8-H), 1.19 (m, 2H, 7-H). 13C{1H}
Reaction of [(COD)RhCl]2 (5a) with [allyl-Cp]Li (6); Prepa-
ration of 7. At room temperature THF (30 mL) was added carefully
to a mixture of compound 5a (978 mg, 1.98 mmol) and allylcy-
clopentadienyllithium (6) (445 mg, 4.0 mmol). The resulting
solution was stirred overnight. The solvent was removed in vacuo
and the residue taken up in pentane (100 mL). The suspension was
filtered over neutral alumina and washed with pentane (200 mL).
The solvent of the combined organic phases was removed in vacuo,
and a yellow oil was yielded (849 mg, 67.7%). Anal. Calcd for
C16H21Rh (316.2): C, 60.77; H, 6.69. Found: C, 61.42; H, 6.88. 1H
NMR (d6-benzene, 400.1 MHz, 298 K): δ 5.91 (ddt, 3JHH ) 16.7,
10.0, 6.7 Hz, 1H, 7-H), 5.00 (m, 2H, 8-H), 4.96 (m, 2H, 2,5-H),
1
NMR (CDCl3, 150.8 MHz, 298 K): δ 147.9 (dm, JCF ) 236 Hz,
1
1
o-C6F5), 138.9 (dm, JCF ) 248 Hz, p-C6F5), 137.0 (dm, JCF
)
250 Hz, m-C6F5), 136.0 (C11), 125.9 (C14), 121.7 (br, i-C6F5), 121.1
(C13), 107.3 (d, JRhC ) 3.6 Hz, C1), 86.8 (d, JRhC ) 3.4 Hz,
1
1
1
1
C2,5), 84.6 (d, JRhC ) 3.8 Hz, C3,4), 63.7 (d, JRhC ) 13.9 Hz,
C9), 35.3 (C15), 32.4 (C10), 31.2 (C6), 27.9 (C7), 23.1 (br, C8).
19F NMR (CDCl3, 564.2 MHz, 298 K): δ -133.3 (m, 4F, o-C6F5),
3
-159.6 (t, JFF ) 20.5 Hz, 2F, p-C6F5), -164.3 (m, 4F, m-C6F5).
11B{1H} NMR (CDCl3, 64.2 MHz, 300 K): δ -6.1 (ν1/2 ) 380
Hz). IR (KBr): ν 3184 (w), 3166 (w), 3144 (w), 2990 (m), 2993
(m), 2882 (m), 2853 (m), 2365 (w), 2345 (w), 1643 (m), 1558 (w),
1541 (w), 1517 (s), 1454 (s), 1363 (w), 1281 (m), 1113 (s), 1088
(s), 999 (w), 969 (s), 871 (w), 811 (m), 793 (m), 753 (m), 677 (m),
621 (w) [cm-1].
3
4.83 (m, 2H, 3,4-H), 3.84 (m, 4H, 9-H), 2.76 (d, JHH ) 6.7 Hz,
2H, 6-H); 2.24 (m, 4H, 10-H), 1.97 (m, 4H, 10-H′). 13C{1H} NMR
(d6-benzene, 100.6 MHz, 298 K): δ 137.5 (C7), 115.3 (C8), 104.5
1
(d,1JRhC ) 4.0 Hz, C1), 87.1 (d, JRhC ) 3.6 Hz, C2,5), 85.7 (d,
X-ray crystal structure analysis of 9a: formula C32H28-
BF10N2Rh, M ) 744.28, colorless crystal 0.20 × 0.20 × 0.15 mm,
a ) 10.321(1) Å, b ) 10.501(1) Å, c ) 14.223(1) Å, R ) 74.03(1)°,
ꢀ ) 74.60(1)°, γ ) 82.79(1)°, V ) 1426.5(2) Å3, Fcalc ) 1.733 g
cm-3, µ ) 0.692 mm-1, empirical absorption correction (0.874 e
1JRhC ) 4.0 Hz, C3,4), 64.0 (d, 1JRhC ) 14.1 Hz, C9), 33.0 (C10),
32.5 (C6). IR (KBr): ν 3077 (m), 2983 (s), 2928 (s), 2872 (s), 2824
(s), 2036 (w), 1970 (w), 1638 (m), 1447 (m), 1425 (m), 1361 (w),
1323 (m), 1238 (m), 1153 (m), 1035 (w), 993 (s), 913 (s), 868 (s),
789 (s), 778 (sh), 566 (m), 486 (m) [cm-1].
j
T e 0.903), Z ) 2, triclinic, space group P1 (No. 2), λ ) 0.71073
Å, T ) 198 K, ω and scans, 16 516 reflections collected ((h,
(k, (l), [(sin θ)/λ] ) 0.66 Å-1, 6764 independent (Rint ) 0.072)
and 5006 observed reflections [I g 2σ(I)], 416 refined parameters,
R ) 0.046, wR2 ) 0.112, max. residual electron density 0.74
(-1.07) e Å-3, hydrogen atoms calculated and refined as riding
atoms.
Reaction of Complex 7 with HB(C6F5)2; Generation of
Compound 8 (NMR-scale experiment). At room temperature a
solution of complex 7 (26.1 mg, 0.08 mmol) in deuterated
dichloromethane (1.5 mL) (alternatively in d6-benzene) was
(28) Lappert, M. F.; Pickett, C. J.; Riley, P. I.; Yarrow, P. I. W. J. Chem.
Soc., Dalton Trans. 1981, 805–813. Riemschneider, R. Z. Naturforsch. 1963,
18b, 641. Chang, B.-H.; Grubbs, R. H. ; Brubaker, C. H., Jr. J. Organomet.
Chem. 1985, 280, 365–376.
(29) Chatt, J.; Venanzi, L. M. J. Chem. Soc. 1957, 4735–4741.
(30) Herde, J. L.; Lambert, J. C.; Senoff, C. V.; Cushing, M. A. Inorg.
Synth. 1974, 15, 18–20.
Reaction of in Situ-Generated Complex 8 with 1-Methyl-
benzimidazole; Formation of Adduct 9b. At room temperature a
solution of complex 7 (57.9 mg, 0.18 mmol) in toluene (5 mL)
was added to bis(pentafluorophenyl)borane (63.3 mg, 0.18 mmol).
After stirring until all remaining solids were dissolved 1-methyl-

Pair of (COD)CpRh and –Ir Complexes
Organometallics, Vol. 27, No. 10, 2008 2335
benzimidazole (24.2 mg, 0.18 mmol) was added, whereupon the
solution turned from a red color to yellow-orange. Then the solvent
was removed in vacuo and the residue was washed with pentane
(5 mL). After removal of the solvent in vacuo the product was
obtained as a yellow powder (116.9 mg, 80.3%). Crystals suitable
for X-ray diffraction were obtained from a concentrated solution
of 9b in dichloromethane. Mp: 195 °C. Anal. Calcd for
C36H30BF10N2Rh · ½C7H8 (840.4): C, 56.45; H, 4.08; N, 3.33.
was isolated as a white powder (930 mg, 85.0%). Crystals suitable
for X-ray diffraction were obtained from a concentrated solution
of 13 in toluene. Mp: 152 °C. Anal. Calcd for C28H22BF10Ir (751.5):
C, 44.75; H, 2.95. Found: C, 44.36; H, 3.16. 1H NMR (CDCl3,
599.6 MHz, 228 K): δ 5.80 (m, 1H, 2-H), 5.58 (m, 1H, 3-H), 5.24
(m, 1H, 4-H), 4.64 (m, 1H, 14-H), 4.49 (m, 1H, 9-H), 3.77 (m,
1H, 10-H), 3.57 (m, 1H, 13-H), 2.34, 2.26 (each m, each 1H, 11-
H), 2.23, 2.08 (each m, each 1H, 15-H), 2.22, 2.09 (each m, each
1H, 16-H), 2.20, 2.16 (each m, each 1H, 12-H), 2.56, 1.84 (each
m, each 1H, 6-H), 1.58, 1.26 (each m, each 1H, 7-H), 1.01, 0.83
(each m, each 1H, 8-H), -11.91 (s, 1H, Ir-H). 13C{1H} NMR
(CDCl3, 150.8 MHz, 228 K): 110.5 (C1), 89.4 (C3), 87.6 (C2),
83.2 (C4), 69.5 (C9), 68.4 (C10), 65.7 (C14), 65.0 (C13), 33.1
(C15), 32.5 (C16), 31.8 (C12), 31.5 (C11), 23.9 (C6), 22.4 (C7),
20.1 (br, C8), n.o. (C5, C6F5). 19F NMR (CD2Cl2, 564.2 MHz, 208
K): δ -130.2, -135.7 (each m, each 1 F, o-C6F5A), -131.5, -132.9
1
Found: C, 56.34; H, 4.20; N, 3.71. H NMR (d6-benzene, 499.8
3
MHz, 298 K): δ 7.77 (dm, JHH ) 7.9 Hz, 1H, 19-H), 7.53 (br,
1H, 11-H), 6.90 (m, 1H, 18-H), 6.87 (m, 1H, 17-H), 6.48 (dm,
3JHH ) 8.2 Hz, 1H, 16-H), 5.13 (m, 2H, 2,5-H), 4.77 (m, 2H, 3,4-
H), 3.86 (br, 4H, 9-H), 2.31 (s, 3H, 15-H), 2.26 (m, 4H, 10-H),
2.16 (t, 3JHH ) 6.6 Hz, 2H, 6-H), 1.99 (m, 4H, 10-H′), 1.73 (br m,
2H, 8-H), 1.35 (m, 2H, 7-H). 13C{1H} NMR (d6-benzene, 126 MHz,
298 K): δ 148.9 (dm, 1JCF ) 236 Hz, o-C6F5), 141.3 (C11), 139.6
(dm, 1JCF ) 253 Hz, p-C6F5), 137.4 (dm, 1JCF ) 249 Hz, m-C6F5),
136.5 (C14), 132.9 (C13), 125.6 (C18), 125.3 (C17), 121.8 (br,
3
(each m, each 1 F, o-C6F5B), -162.2 (t, JFF ) 20.8 Hz, 1F,
p-C6F5A), -163.4 (t, 3JFF ) 20.8 Hz, 1F, p-C6F5B), -164.7, -164.9
(each m, each 1F, m-C6F5A), -165.8, -166.3 (each m, each 1F,
m-C6F5B). 11B{1H} NMR (CDCl3, 64.2 MHz, 300 K): δ -16.9
(ν1/2 ) 94 Hz). IR (KBr): ν 2961 (m), 2923 (m), 2853 (m), 2373
(w), 2157 (w), 1641 (m), 1512 (s), 1457 (vs), 1265 (s), 1082 (s),
1
i-C6F5), 116.8 (C19), 111.1 (C16), 107.3 (d, JRhC ) 3.7 Hz, C1),
1
1
87.6 (d, JRhC ) 3.4 Hz, C2,5), 85.5 (d, JRhC ) 3.9 Hz, C3,4),
64.4 (d, 1JRhC ) 14.1 Hz, C9), 32.9 (C10), 31.2 (C6), 30.9 (C15),
28.9 (C7), 21.9 (br, C8). 19F NMR (d6-benzene, 470.2 MHz, 298
3
K): δ -133.1 (m, 4F, o-C6F5), -158.8 (t, JFF ) 20.6 Hz, 2F,
964 (s), 804 (m), 768 (m), 643 (w) cm-1
.
p-C6F5), -164.1 (m, 4F, o-C6F5). 11B{1H} NMR (d6-benzene, 64.2
MHz, 300 K): δ -6.4 (ν1/2 ) 530 Hz). IR (KBr): ν 3749 (w), 3129
(w), 2926 (m), 2871 (m), 2826 (m), 2373 (w), 1644 (m), 1554 (m),
1516 (s), 1458 (vs), 1278 (m), 1198 (m), 1091 (s), 967 (s), 869
(w), 777 (w), 746 (m), 688 (w), 500 (w) [cm-1].
X-ray crystal structure analysis of 13: formula C28H22BF10Ir,
M ) 751.47, colorless crystal 0.25 × 0.20 × 0.10 mm, a )
11.8637(2) Å, b ) 13.7856(2) Å, c ) 16.3812(4) Å, R )
105.611(1)°, ꢀ ) 90.657(1)°, γ ) 108.065(1)°, V ) 2439.88(8)
Å3, Fcalc ) 2.046 g cm-3, µ ) 5.567 mm-1, empirical absorption
j
X-ray crystal structure analysis of 9b: formula C36H30-
BF10N2Rh · CH2Cl2, M ) 879.27, yellow crystal 0.35 × 0.25 ×
0.15 mm, a ) 9.319(1) Å, b ) 11.981(1) Å, c ) 17.343(1) Å, R
) 109.96(1)°, ꢀ ) 94.35(1)°, γ ) 100.45(1)°, V ) 1769.9(3) Å3,
Fcalc ) 1.650 g cm-3, µ ) 0.718 mm-1, empirical absorption
correction (0.337 e T e 0.606), Z ) 4, triclinic, space group P1
scans, 25 816
(No. 2), λ ) 0.71073 Å, T ) 198 K, ω and
reflections collected ((h, ( k, ( l), [(sin θ)/λ] ) 0.67 Å-1, 11 794
independent (Rint ) 0.055) and 8702 observed reflections [I g
2σ(I)], 727 refined parameters, R ) 0.039, wR2 ) 0.094, max.
residual electron density 1.61 (-1.82) e Å-3, two almost identical
independent molecules in the asymmetric unit, hydrogen atoms at
Ir from difference Fourier calculations, others calculated and refined
as riding atoms.
j
correction (0.787 e T e 0.900), Z ) 2, triclinic, space group P1
(No. 2), λ ) 0.71073 Å, T ) 198 K, ω and
scans, 16 583
reflections collected ((h, ( k, ( l), [(sin θ)/λ] ) 0.67 Å-1, 8451
independent (Rint ) 0.064) and 7024 observed reflections [I g
2σ(I)], 479 refined parameters, R ) 0.057, wR2 ) 0.158, max.
residual electron density 1.07 (-1.76) e Å-3, hydrogen atoms
calculated and refined as riding atoms.
Reaction of Complex 13 with Methylimidazole; Formation
of Adduct 14a. After stirring a solution of complex 13 (67.6 mg,
0.09 mmol) and methylimidazole (7.4 mg, 0.09 mmol) in toluene
(3 mL) for 10 min, the solvent was removed in vacuo and the
residue was washed with pentane (5 mL). The solvent was removed,
the residue was dried in vacuo, and the product was isolated as a
white powder (61.5 mg, 82.0%). Crystals suitable for X-ray
diffraction were obtained from a solution of 14a in deuterated
benzene. Mp: 200 °C. Anal. Calcd for C32H28BF10N2Ir (833.6): C,
46.11; H, 3.39; N, 3.36. Found: C, 46.22; H, 3.40; N, 3.35. 1H
NMR (d6-benzene, 499.8 MHz, 298 K): δ 7.00 (s, 1H, 11-H), 6.71
(s, 1H, 14-H), 5.44 (m, 1H, 13-H), 5.00 (m, 2H, 2,5-H), 4.72 (m,
Reaction of [(COD)IrCl]2 (5b) with [allyl-Cp]Li (6); Prepara-
tion of Complex 10. A solution of allylcyclopentadienyllithium
(6) (340 mg, 3.03 mmol) in tetrahydrofuran (20 mL) was added to
a solution of complex 5b (980 mg, 1.46 mmol) in tetrahydrofuran
(20 mL). The reaction mixture was refluxed for 60 min. Then the
solvent was removed in vacuo and the residue was taken up in
pentane (100 mL). Short column chromatography over neutral
alumina (pentane) yielded the product as a colorless oil after
removal of the solvent (969 mg, 82.0%). Anal. Calcd for C16H21Ir
(405.6): C, 47.38; H, 5.22. Found: C, 47.84; H, 5.29. 1H NMR
3
2H, 3,4-H), 3.74 (m, 4H, 9-H), 2.35 (t, JHH ) 7.9 Hz, 2H, 6-H),
3
(d6-benzene, 400.1 MHz, 298 K): δ 5.83 (ddt, JHH ) 16.8, 10.1,
2.21 (m, 4H, 10-H), 1.97 (m, 4H, 10-H′), 1.91 (s, 3H, 15-H), 1.50
6.8 Hz, 1 H, 7-H), 4.96 (dm, 3JHH ) 16.8 Hz, 1 H, 8-H), 4.94 (dm,
(m, 2H, 7-H), 1.44 (m, 2H, 8-H). 13C{1H} NMR (d6-benzene, 126
3JHH ) 10.1 Hz, 1 H, 8-H′), 4.85 (m, 2 H, 2,5-H), 4.76 (m, 2 H,
MHz, 298 K): δ 148.5 (dm, JCF ) 242 Hz, o-C6F5), 139.6 (dm,
1
3
3,4-H), 3.74 (m, 4 H, 9-H); 2.77 (d, JHH ) 6.8 Hz, 2 H, 6-H),
1JCF ) 252 Hz, p-C6F5), 137.7 (dm, 1JCF ) 254 Hz, m-C6F5), 135.7
(C11), 125.2 (C14), 122.4 (br, i-C6F5), 120.8 (C13), 103.6 (C1),
82.3 (C2,5), 80.2 (C3,4), 47.3 (C9), 34.5 (C10), 33.4 (C15), 31.4
(C6), 28.5 (C7), 24.4 (br, C8). 19F NMR (d6-benzene, 564.2 MHz,
298 K): δ -133.4 (m, 4F, o-C6F5), -159.0 (t, 3JFF ) 20.7 Hz, 2F,
p-C6F5), -164.1 (m, 4F, m-C6F5). 11B{1H} NMR (d6-benzene, 64.2
MHz, 300 K): δ -5.5 (ν1/2 ) 427 Hz). IR (KBr): ν 3446 (br),
3183 (w), 3164 (w), 3096 (w), 2974 (m), 2933 (m), 2917 (m), 2853
(m), 1643 (m), 1557 (w), 1541 (w), 1517 (s), 1455 (s), 1280 (m),
2.21 (m, 4 H, 10-H), 1.96 (m, 4 H, 10-H′). 13C{1H} NMR (d6-
benzene, 100.6 MHz, 298 K): δ 137.4 (C7), 115.6 (C8), 100.4 (C1),
82.3 (C2,5), 80.7 (C3,4), 47.3 (C9), 34.5 (C10), 31.9 (C6). IR (KBr):
ν 3461 (br), 3076 (w), 2967 (s), 2921 (s), 2872 (s), 2325 (s), 1637
(w), 1429 (w), 1318 (m), 1236 (w), 991 (m), 910 (s), 838 (s), 567
(w), 497 (m) cm-1
.
Preparation of Complex 13. At room temperature a solution
of bis(pentafluorophenyl)borane (500 mg, 1.45 mmol) in pentane
(15 mL) was added to a solution of complex 10 (587 mg, 1.45
mmol) in pentane (15 mL). The color of the reaction mixture turned
a bright yellow, and precipitation of a white powder started. After
stirring until the solution was completely decolorized, the precipitate
was collected and washed with pentane (20 mL). The pure product
1113 (s), 1088 (s), 959 (s), 810 (m), 779 (w), 751 (m). cm-1
.
X-ray crystal structure analysis of 14a: formula C32H28-
BF10IrN2, M ) 833.57, colorless crystal 0.30 × 0.30 × 0.25 mm,
a ) 10.335(1) Å, b ) 10.481(1) Å, c ) 14.273(1) Å, R ) 74.01(1)°,
ꢀ ) 74.64(1)°, γ ) 83.01(1)°, V ) 1431.2(2) Å3, Fcalc ) 1.934 g

2336 Organometallics, Vol. 27, No. 10, 2008
Herrmann et al.
cm-3, µ) 4.758 mm-1, empirical absorption correction (0.329 e
by layering a solution of 15 in toluene with pentane. Mp: 142 °C.
j
T e 0.383), Z ) 2, triclinic, space group P1 (No. 2), λ ) 0.71073
Anal. Calcd for C32H27BF10NIr (818.6): C, 46.95; H, 3.32; N, 1.71.
1
Å, T ) 198 K, ω and scans, 16 873 reflections collected ((h, (
k, ( l), [(sin θ)/λ] ) 0.67 Å-1, 6964 independent (Rint ) 0.043)
and 6540 observed reflections [I g 2 e (I)], 416 refined parameters,
R ) 0.028, wR2 ) 0.070, max. residual electron density 0.75
(-1.97) e Å-3, hydrogen atoms calculated and refined as riding
atoms.
Found: C, 47.19; H, 3.56; N, 1.56. H NMR (d6-benzene, 599.6
3
MHz, 298 K): δ 7.46 (s, 1H, 14-H), 6.19 (d, JHH ) 5.4 Hz, 1H,
3
12-H), 5.37 (d, JHH ) 5.4 Hz, 1H, 13-H), 4.99 (m, 2H, 2,5-H),
4.75 (m, 2H, 3,4-H), 3.74 (m, 4H, 9-H), 3.49 (br, 2H, 11-H), 2.30
3
(t, JHH ) 7.6 Hz, 2H, 6-H), 2.21 (m, 4H, 10-H), 1.99 (m, 4H,
10-H′), 1.39 (m, 2H, 7-H), 1.19 (m, 2H, 8-H). 13C{1H} NMR (d6-
benzene, 150.8 MHz, 298 K): δ 168.4 (C14), 153.5 (C12), 148.3
(dm, 1JCF ) 239 Hz, o-C6F5), 139.4 (dm, 1JCF ) 250 Hz, p-C6F5),
137.5 (dm, 1JCF ) 255 Hz, m-C6F5), 127.2 (C13), 121.3 (br, i-C6F5),
103.3 (C1), 82.2 (C2,5), 80.3 (C3,4), 64.8 (C11), 47.3 (C9), 34.5
(C10), 31.4 (C6), 28.4 (C7), 24.5 (br, C8). 19F NMR (d6-benzene,
Reaction of Complex 13 with 1-Methylbenzimidazole; For-
mation of Adduct 14b. After stirring a solution of complex 13
(126.7 mg, 0.17 mmol) and methylbenzimidazole (22.3 mg, 0.17
mmol) in toluene (10 mL) for 10 min the solvent was removed in
vacuo. The remaining solid was washed with pentane (10 mL), the
solvent was removed, and the residue was dried in vacuo. The
product was isolated as a white powder (100.4 mg, 68.0%). Crystals
suitable for X-ray diffraction were obtained by gas phase diffusion
of pentane into a solution of 14b in toluene. Mp: 189 °C. Anal.
Calcd for C36H30BF10NIr (883.6): C, 48.93; H, 3.42; N, 3.17. Found:
C, 48.91; H, 3.52; N, 3.55. 1H NMR (d6-benzene, 499.8 MHz, 298
K): δ 7.79 (d, 3JHH ) 8.3 Hz, 1H, 19-H), 7.55 (s, 1H, 11-H), 6.89
564.2 MHz, 298 K): δ -133.4 (m, 4F, o-C6F5), -158.2 (t, 3JFF
)
20.5 Hz, 2F, p-C6F5), -163.6 (m, 4F, m-C6F5). 11B{1H} NMR (d6-
benzene, 64.2 MHz, 300 K): δ -5.3 (ν1/2 ) 290 Hz). IR (KBr): ν
3446 (br), 2920 (m), 2866 (w), 1644 (m), 1517 (m), 1456 (s), 1380
(w), 1277 (w), 1089 (s), 1013 (m), 1277 (w), 1118 (m), 1089 (s),
1013 (w), 963 (s), 909 (w), 813 (m), 699 (w) cm-1
.
X-ray crystal structure analysis of 15: formula C32H27BF10IrN,
M ) 818.56, light yellow crystal 0.15 × 0.10 × 0.03 mm, a )
10.2691(1) Å, b ) 19.2190(2) Å, c ) 14.5208(2) Å, ꢀ )
96.108(1)°, V ) 2849.58(6) Å3, Fcalc ) 1.908 g cm-3, µ ) 4.776
mm-1, empirical absorption correction (0.534 e T e 0.870), Z )
4, monoclinic, space group P21/c (No. 14), λ ) 0.71073 Å, T )
223 K, ω and scans, 18 649 reflections collected ((h, (k, (l),
[(sin θ)/λ] ) 0.66 Å-1, 6795 independent (Rint ) 0.051) and 5072
observed reflections [I g 2σ(I)], 406 refined parameters, R ) 0.033,
3
4
(ddd, JHH ) 8.3, 7.3 Hz, JHH ) 1.2 Hz, 1H, 18-H), 6.85 (ddd,
3JHH ) 8.3, 7.3 Hz, 4JHH ) 1.2 Hz, 1H, 17-H), 6.45 (d, 3JHH ) 8.3
Hz, 1H, 16-H), 5.00 (m, 2H, 2,5-H), 4.71 (m, 2H, 3,4-H), 3.72 (m,
3
4H, 9-H), 2.27 (t, JHH ) 7.3 Hz, 2H, 6-H), 2.22 (s, 3H, 15-H),
3
2.20 (m, 4H, 10-H), 1.96 (m, 4H, 10-H′), 1.71 (br t, JHH ) 8.3
Hz, 2H, 8-H), 1.36 (m, 2H, 7-H). 13C{1H} NMR (d6-benzene, 126
MHz, 298 K): δ 148.7 (dm, 1JCF ) 237 Hz, o-C6F5), 141.2 (C11),
1
1
139.6 (dm, JCF ) 281 Hz, p-C6F5), 137.6 (dm, JCF ) 257 Hz,
m-C6F5), 136.3 (C14), 132.8 (C13), 125.5 (C18), 125.3 (C17), 121.6
(br, i-C6F5), 117.0 (C19), 111.1 (C16), 103.4 (C1), 82.4 (C2,5),
80.4 (C3,4), 47.4 (C9), 34.4 (C10), 31.0 (C6), 30.8 (C15), 28.7
(C7), 22.7 (br, C8). 19F NMR (d6-benzene, 470.2 MHz, 298 K): δ
wR2 ) 0.072, max. residual electron density 1.14 (-1.22) e Å-3
hydrogen atoms calculated and refined as riding atoms.
,
Reaction of Complex 13 with THF; Formation of Adduct
11 · THF (NMR-scale experiment). A solution of complex 13 (24
mg, 0.03 mmol) in deuterated tetrahydrofuran was characterized
3
-132.9 (m, 4F, o-C6F5), -158.3 (t, JFF ) 21 Hz, 2F, p-C6F5),
-163.8 (m, 4F, m-C6F5). 11B{1H} NMR (d6-benzene, 64.2 MHz,
300 K): δ -5.9 (ν1/2 ) 650 Hz). IR (KBr): ν 3122 (w), 2935 (br),
2874 (m), 2825 (m), 2379 (w), 2313 (w), 1649 (m), 1557 (m), 1517
(s), 1459 (s), 1260 (m), 1093 (m), 971 (m), 803 (w), 751 (w), 691
1
1
by H, 13C, 11B, and 19F experiments. H NMR (d8-THF, 499.8
MHz, 298 K): δ 5.01 (m, 2H, 2,5-H), 4.92 (m, 2H, 3,4-H), 3.49
(m, 4H, 9-H), 2.15 (m, 2H, 6-H), 1.94 (m, 4H, 10-H), 1.74 (m,
4H, 10-H′), 1.22 (m, 4H, 7,8-H). 13C{1H} NMR (d8-THF, 126
(w) cm-1
.
1
X-ray crystal structure analysis of 14b. formula C36H30-
BF10IrN2 · ½C7H8, M ) 929.70, colorless crystal 0.20 × 0.20 ×
0.20 mm, a ) 9.378(1) Å, b ) 11.921(1) Å, c ) 17.189(1) Å, R
) 70.04(1)°, ꢀ ) 79.63(1)°, γ ) 79.52(1)°, V ) 1761.6(3) Å3,
Fcalc ) 1.753 g cm-3, µ ) 3.876 mm-1, empirical absorption
MHz, 298 K): δ 149.0 (dm, JCF ) 243 Hz, o-C6F5), 140.5 (dm,
1JCF ) 250 Hz, p-C6F5), 137.9 (dm, 1JCF ) 251 Hz, m-C6F5), 119.0
(br, i-C6F5), 104.1 (C1), 82.7 (C2,5), 80.6 (C3,4), 47.2 (C9), 34.7
(C10), 31.7 (C6), 28.2 (C7), 24.4 (br, C8). 19F NMR (d8-THF, 470.2
MHz, 298 K): δ -133.7 (m, 4F, o-C6F5), -159.9 (t, 3JFF ) 20 Hz,
2H, p-C6F5), -165.4 (m, 4F, m-C6F5). 11B{1H} NMR (d8-THF,
64.2 MHz, 300 K): δ 6.6 (ν1/2 ) 720 Hz).
j
correction (0.511 e T e 0.511), Z ) 2, triclinic, space group P1
(No. 2), λ ) 0.71073 Å, T ) 223 K, ω and
scans, 19 840
reflections collected ((h, ( k l), [(sin θ)/λ] ) 0.67 Å-1, 8469
independent (Rint ) 0.046) and 7102 observed reflections [I g
2σ(I)], 505 refined parameters, R ) 0.035, wR2 ) 0.081, max.
residual electron density 1.19 (-1.30) e Å-3, hydrogen atoms
calculated and refined as riding atoms.
Acknowledgment. Financial support from the Fonds der
Chemischen Industrie and the Deutsche Forschungsgemein-
schaft is gratefully acknowledged.
Reaction of Complex 13 with Pyrrole; Formation of the
2H-Pyrrole Adduct 15. After stirring a solution of complex 13
(48.7 mg, 0.06 mmol) and pyrrole (4.3 mg, 0.06 mmol) in toluene
(5 mL) for three days at room temperature, the solvent was removed
in vacuo. The residue was washed with pentane (10 mL) and dried
in vacuo. The product was obtained as an off-white powder (35
mg, 71.0%). Crystals suitable for X-ray diffraction were obtained
Supporting Information Available: CIF files giving details of
the X-ray crystal structure analysis (9a, 9b, 13, 14a, 14b, and 15)
and text giving additional information about spectroscopic data.
This material is available free of charge via the Internet at
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OM800195D