Reaction of a 6-dimethylaminopentafulvene with the Mes2PCH 2CH2B(C6F5)2 frustrated Lewis Pair

Article abstract of DOI:10.1002/chem.201101937

The frustrated Lewis pair Mes₂PCH₂CH ₂B(C₆F₅)₂ reacts readily with 6-dimethylamino-6-methylfulvene at room temperature to yield the trans-1-[B(C₆F₅)₂]-2-[CH₂CH ₂PMes₂] disubstituted fulvene derivative 9 that features an internal N-B contact. Thermolysis (80 °C in toluene) results in a complete isomerization to the respective 1-[B(C₆F₅) ₂]-3-[CH₂CH₂PMes₂] isomer 10. Both compounds were characterized by using X-ray diffraction. A reaction scheme is formulated to rationalize the specific formation of these compounds, involving a retro-hydroboration/hydroboration sequence. The reaction of the 6-dimethylaminofulvene with HB(C₆F₅)₂ yielded the corresponding parent compound 13 that was also characterized by X-ray diffraction. Copyright

Full text of DOI:10.1002/chem.201101937

DOI: 10.1002/chem.201101937
Reaction of a 6-Dimethylaminopentafulvene with the
Mes2PCH2CH2B(C6F5)2 Frustrated Lewis Pair
AHCTUNGTNRUENG
Bao-Hua Xu,[a] Cornelia M. Mçmming,[a] Roland Frçhlich,[a, b] Gerald Kehr,[a] and
Gerhard Erker*[a]
Abstract: The frustrated Lewis pair
Mes2PCH2CH2B(C6F5)2 reacts readily
with 6-dimethylamino-6-methylfulvene
tive
1-[B
G
reaction scheme is formulated to ra-
tionalize the specific formation of these
compounds, involving a retro-hydro-
G
isomer 10. Both compounds were char-
acterized by using X-ray diffraction. A
at room temperature to yield the trans-
ACHTUNGTRENNUNG
1-[BACHTUNGTRENNUNG(C6F5)2]-2-[CH2CH2PMes2] disub-
Keywords: frustrated Lewis pair ·
stituted fulvene derivative 9 that fea-
tures an internal N–B contact. Ther-
molysis (808C in toluene) results in a
complete isomerization to the respec-
ACHTUNGTRENNUNG
hydroboration
· reaction mecha-
sponding parent compound 13 that was
also characterized by X-ray diffraction.
nisms · retro-hydroboration · X-ray
diffraction
Introduction
With the dimethylaminodihydropentalene system (3) the
À
FLP 1 reacts in a very unusual way to yield the C C bond
The ethylene-bridged frustrated Lewis pair[1] (FLP)
cleaved product 6 [Eq. (2)]. In this unique reaction only the
À
Mes2PCH2CH2B
(C6F5)2 (1)[2] undergoes a variety of remark-
electrophilic [R BACTHNGUTERN(NUG C6F5)2] alkyl borane section of 1 is uti-
À
able reactions with unsaturated substrates. This includes ad-
dition reactions to alkenes[3] and alkynes,[4] addition to car-
bonyl groups, and to nitroso compounds.[5] The P/B FLP
even adds (reversibly) to carbon dioxide[6] and undergoes a
1,1-P/B addition reaction to nitric oxide (NO) to yield a
novel type of a persistent N-oxyl radical, the new P/B-FLP
NO system.[7]
lized. Consequently, other R BACTHUGNTERN(NUG C6F5)2 reagents undergo this
À
C C bond cleavage transformation as well. The reaction se-
quence was shown to proceed through addition of R
(C6F5)2 (e.g., 4) to the nucleophilic fulvene five-membered
À
B
G
carbocyclic ring, eventually followed by migration of the
boron-bound R group.[9,10]
The FLP (1) was shown to undergo a series of interesting
reactions with pentafulvenes, especially with regard to
À
carbon–carbon bond formation and C C s-bond activation.
We had found that 1 reacts with 6,6-dimethylpentafulvene in
a slow reaction over several days to yield the FLP-addition
product (2) to the fulvene [6+4] dimer [Eq. (1)].[8]
In the reaction of the aminofulvene derivative 3 with
Piersꢀ borane [HBACTHNUTRGNEUNG
(C6F5)2],[11] a competing reaction pathway
is favored. Here, the cleavage of dihydrogen at the stage of
the addition products is the dominant pathway, leading to 7
[Eq. (3)].[10]
[a] Dr. B.-H. Xu, Dr. C. M. Mçmming, Dr. R. Frçhlich, Dr. G. Kehr,
Prof. Dr. G. Erker
Organisch-Chemisches Institut der Universitꢁt Mꢂnster
Corrensstrasse 40, 48149 Mꢂnster (Germany)
Fax : (+49)251-83-36503
E-mail: erker@uni-muenster.de
[b] Dr. R. Frçhlich
We have now treated the 6-dimethylaminopentafulvene
X-ray structure analyses
substrate (8)[12] with the Mes2PCH2CH2B
ACTHNUGTRNE(UNG C6F5)2 frustrated
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201101937.
Lewis pair (1) and found a third variant of product forma-
1826
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Chem. Eur. J. 2012, 18, 1826 – 1830

FULL PAPER
tion inside this general reaction scheme. This features some
closely related branches, which were followed either under
kinetically or thermodynamically controlled conditions.
These observations will be described in this article. This
work has led to a better understanding of the possibly com-
peting pathways in these related model systems that may
bered ring system of compound 9 shows a pair of olefinic
1H NMR signals at d=5.96 and 5.79 ppm (7H, 6H) with a
3
vicinal coupling constant of JH-H =5.5 Hz. The adjacent sa-
1
À
À
À
turated [B] CH CH R unit shows H NMR features at d=
2.81 ppm (broad, CH[B]; d13C=44.2 (broad)) and d=
1.89 ppm (d13C=51.1 (d, JP-C =15.3 Hz)), respectively.
3
À
À
proceed either with C C or C H bond formation or cleav-
age.
The X-ray crystal structure analysis of 9 (see Figure 1)
À
confirms that the B C s bond of the reagent 1 was cleaved
À
B
during the reaction and that the resulting
N
Results and Discussion
The FLP 1 was prepared in situ by hydroboration of di-
ACHTUNGTRENNUNGmesitylvinylphosphine with HBCAHUTNGTRNEN(UGN C6F5)2 at ambient tempera-
ture in pentane (15 min).[2] A solution of the 6-dimethylami-
nofulvene reagent (8) in dichloromethane was added and
the mixture stirred for 12 h. During this time a gray-white
precipitate had formed that was collected by filtration to
give approximately 40% yield of the new product 9 (see
Scheme 1). A close inspection of the NMR spectra revealed
Figure 1. Molecular structure of compound 9. Selected bond lengths [ꢄ]
À
À
À
À
and angles [8]: C1 B2 1.630(2), C1 C5 1.505(2), C1 C8 1.547(2), B2 N3
À
À
À
À
1.700(2), N3 C4 1.499(2), C4 C5 1.328(3), C5 C6 1.452(3), C6 C7
À
À
À
À
1.333(3), C7 C8 1.511(2), C8 C9 1.526(2), C9 C10 1.533(2), C10 P1
1.855(2); B2-C1-C5 100.7(1), B2-C1-C8 127.2(2), C5-C1-C8 103.7(1), C1-
B2-N3 96.1(1), B2-N3-C4 102.1(1), N3-C4-C5 109.3(2), C4-C5-C6
135.7(2), C4-C5-C1 115.7(2), C1-C5-C6 108.3(2), C5-C6-C7 109.2(2), C6-
C7-C8 112.9(2), C7-C8-C1 102.3(1), C7-C8-C9 116.7(2), C1-C8-C9
112.6(1), C8-C9-C10 114.7(2), C9-C10-P1 107.3(1).
Scheme 1.
À
À
CH2CH2 PMes2 components were added to the adjacent
former fulvene ring carbon atoms (C1 and C8, see Figure 1).
They are found in trans-orientation at the carbocyclic five-
that the product was admixed with a small amount of the
isomer 10. Subsequent heating of 9 in toluene solution for
12 h at 808C resulted in a practically complete conversion of
9 to the isomer 10, which upon cooling precipitated from
the solution. Compound 10 was isolated in >90% yield as
an off-white solid. Both the kinetic isomer 9 and its thermo-
dynamic rearrangement product 10 were characterized by
X-ray diffraction, C,H,N elemental analysis and by spectros-
copy.
À
membered ring system (C1 B2: 1.630(2) ꢄ, dihedral angle
C9-C8-C1-B2 À100.8(2)8). The boron atom in compound 9
À
is four-coordinated with a B2 N3 bond length of 1.700(2) ꢄ
(angles C1-B2-N3 96.1(1)8, B2-N3-C4: 102.1(1)8). The bicy-
clic core of compound 9 contains two carbon–carbon double
bonds (C6 C7 1.333(3) ꢄ, C4 C5: 1.328(3) ꢄ).
The cis-arrangement of the 8H and 1B(C6F5)2 groups at
À
À
AHCTUNGTRENNUNG
The kinetic reaction product 9 contains a pair of chiral
centers (C1, C8). Both in solution and in the crystal (see
below) we observe only a single diastereomer. This is char-
À
the five-membered carbocycle in 9 indicates that this section
of the product might have been formed by a hydroboration
reaction.[15] Scheme 2 sketches a possible pathway, utilizing
acterized by a trans orientation of the
BACHTUNGTERNNU(G C6F5)2 and
À
À
CH2CH2 PMes2 substituents at the central framework. We
1
observe the H/13C{1H} NMR signals of a pair of diastereo-
topic mesityl substituents at phosphorus (31P{1H}: d=
À21.8 ppm). Also the hydrogen atoms at the adjacent
À
À
CH2CH2 [P] unit are pairwise diastereotopic as are the
methyl groups at nitrogen (1H: d=2.01, 1.61 ppm; 13C{1H}:
d=46.1, 43.4 ppm) and also the C6F5 groups at boron (for
details see the Supporting Information). The 11B{1H} NMR
signal is relatively sharp and in a range as expected for four-
À
coordinate boron, formed by internal N B interaction
(11B{1H}: d= +4.6 ppm).[13,14] The carbocyclic five-mem-
Scheme 2.
Chem. Eur. J. 2012, 18, 1826 – 1830
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www.chemeurj.org
1827

G. Erker et al.
the initial R-B
N
framework. The carbocyclic subunit features the C6=C7
double bond (1.342(5) ꢄ); the heterocyclic compound con-
tains the C4=C5 carbon–carbon double bond (1.325(4) ꢄ)
that we had analogously already observed in the formation
of 6 from 3 [see Eq. (2)]. However, in the reaction of 8 with
1, retro-hydroboration[16] (to form 12a) followed by hydro-
boration using the in situ formed HB
9 seems to be the prevailing pathway.
As a reference reaction we treated the aminofulvene 8
separately with HB(C6F5)2 and obtained the respective prod-
À
and the newly formed N B linkage (1.697(4) ꢄ).
À
In contrast to 9, the pair of FLP derived
B
G
À
À
CH2CH2 PMes2 substituents is found 1,3-attached at the
carbocyclic ring of the heterobicyclic core of the thermody-
namic isomer 10 (see Figure 3). The framework of 10 con-
uct 13. The reaction went to completion within 3 h in pen-
tane solution at room temperature. Crystallization at À358C
gave the hydroboration product 13 in close to 90% yield as
light-yellow crystalline material. The structural analysis re-
vealed that the regioselectivity of the attachment of the hy-
droboration reagent was very effectively determined by the
À
NMe2 functionality of the substrate. The hydroboration
took place regioselectively at the pentafulvene C=C double
À
bond syn-positioned to the NMe2 donor substituents (see
Scheme 3 and Figure 2).
Scheme 3.
Figure 3. A view of the molecular structure of compound 10. Selected
À
À
À
bond lengths [ꢄ] and angles [8]: C1 B2 1.620(3), C1 C5 1.497(3), C1 C8
À
À
À
À
1.538(3), B2 N3 1.713(3), N3 C4 1.500(3), C4 C5 1.334(3), C5 C6
À
À
À
À
1.449(3), C6 C7 1.339(3), C7 C8 1.515(3), C7 C9 1.497(3), C9 C10
1.529(3), C10 P1 1.861(2); B2-C1-C5 101.9(2), B2-C1-C8 126.5(2), C5-
C1-C8 102.9(2), C1-B2-N3 96.5(2), B2-N3-C4 102.5(2), N3-C4-C5
109.7(2), C4-C5-C6 135.1(2), C4-C5-C1 115.6(2), C1-C5-C6 109.0(2), C5-
C6-C7 109.8(2), C6-C7-C8 111.0(2), C6-C7-C9 129.0(2), C8-C7-C9
120.0(2), C7-C8-C1 104.3(2), C7-C9-C10 114.9(2), C9-C10-P1 108.5(1).
À
tains a similarly located pair of conjugated C=C double
À
À
bonds (C6 C7 1.339(3) ꢄ, C4 C5 1.334(4) ꢄ), but the
CH2CH2PMes2 substituent is now found attached at the
Figure 2. A projection of the molecular structure of the dimethylamino-
fulvene hydroboration product 13. Selected bond lengths [ꢄ] and angles
“central” carbocyclic CACHTNUTGRNEUNG
(sp2) carbon center (C7). The boron
atom in compound 10 is tetracoordinated; it features a B2
N3 bond length of 1.713(3) ꢄ.
Compound 10 contains a chiral center adjacent to boron
(C1). Therefore, we have observed the H NMR signals of a
À
À
À
À
[8]: C1 B2 1.628(4), C1 C5 1.515(4), C1 C8 1.543(4), B2 N3 1.697(4),
À
À
À
À
À
À
N3 C4 1.507(4), C4 C5 1.325(3), C5 C6 1.458(4), C6 C7 1.342(5), C7
C8 1.505(5); B2-C1-C5 100.7(2), B2-C1-C8 126.7(3), C5-C1-C8 103.6(2),
C1-B2-N3 96.5(2), B2-N3-C4 102.4(2), N3-C4-C5 109.1(2), C4-C5-C6
135.3(3), C4-C5-C1 115.9(3), C1-C5-C6 108.4(3), C5-C6-C7 108.6(3), C6-
C7-C8 113.4(3), C7-C8-C1 102.9(3).
1
pair of diastereotopic mesityl groups at phosphorus and an
AMX spin system for the 1H/8Ha/Hb protons. Also the
methyl groups at nitrogen are diastereotopic (1H: d=2.07,
1.70 ppm; 13C{1H}: d=46.1, 43.9 ppm) as is the pair of C6F5
substituents at boron (for details see the Supporting Infor-
mation). The boron NMR resonance of compound 10 was
found at d=4.4 ppm (11B{1H}) and the phosphorus NMR
signal is at d=À22.2 ppm (31P{1H}). Compound 10 features
13C NMR signals of the endocyclic conjugated diene unit at
d=125.5 (C4), 150.0 (C5), 119.1 (C6) and 162.9 ppm (C7).
It is likely that the thermodynamic product 10 is formed
in a similar sequence as 9, only that the isomeric fulvene
12b is involved as an intermediate. This may be formed by
À
1
The H NMR spectrum of compound 13 features the sig-
nals of the olefinic hydrogen atoms 6H and 7H at d=5.82
and 5.98 ppm, respectively. The 8-Ha/Hb hydrogen atoms
(d=2.49/1.56 ppm) are diastereotopic due to the newly
formed adjacent chirality center (1H: d=3.17 ppm). Conse-
quently, the C6F5 groups at boron are diastereotopic as are
the methyl groups at the nitrogen atom of the heterocyclic
N B containing five-membered ring (1H: d=2.06,
À
1.67 ppm). The 11B NMR resonance of compound 13 occurs
at d=4.6 ppm.
The X-ray crystal structure analysis of compound 13 (see
Figure 2) features
means of the isomeric R B
lowing a subsequent HBACHTUNRGTNE(UNG C6F5)2 retro-hydroboration/hydro-
ACHTUGNTREN(NUNG C6F5)2 addition product 11b fol-
a
typical N,B-heteroatom containing
1828
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ꢃ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2012, 18, 1826 – 1830

Reaction of a 6-Dimethylaminopentafulvene
FULL PAPER
Preparation of compound 10: A toluene solution (5 mL) of 9 (156 mg,
0.2 mmol) was heated to 808C for 12 h. Then the solution was cooled to
À308C and a white-gray solid began to precipitate. After standing at the
same temperature for 1 h, the solid was isolated by using cannula filtra-
tion and washed with pentane (3ꢅ2.5 mL). Removal of all volatiles in
vacuo yielded 10 (145 mg, 93%). Crystals suitable for X-ray crystal struc-
ture analysis were grown by diffusion of pentane to a saturated toluene
solution of 10 at À308C. For more experimental details and complete
characterization of 10, see the Supporting Information.
X-ray crystal structure analysis of 10: Formula C41H39BF10NP, M=777.51,
colorless crystal 0.35ꢅ0.13ꢅ0.05 mm; a=8.6311(6), b=14.9478(8), c=
Scheme 4.
15.3343(6) ꢄ;
a=97.013(4),
b=95.152(5),
g=106.168(5)8,
V=
1869.94(18) ꢄ3, 1calc =1.381 gcmÀ3, m=1.368 mmÀ1, empirical absorption
¯
correction (0.646ꢀTꢀ0.935), Z=2, triclinic, space group P1 (No. 2), l=
boration route (see Scheme 4; for a detailed Scheme see the
Supporting Information).
1.54178 ꢄ, T=223(2) K, w and f scans, 24354 reflections collected (Æh,
Æk, Æl), [(sinq)/l]=0.60 ꢄÀ1, 6413 independent (Rint =0.049) and 5440
observed reflections [Iꢁ2s(I)], 496 refined parameters, R=0.048, wR2 =
0.123, max. (min.) residual electron density 0.25 (À0.27) eꢄÀ3, hydrogen
atoms calculated and refined as riding atoms.
Conclusion
Preparation of compound 13: Compound 8 (27 mg, 0.2 mmol) and HB-
AHCTNUGTRE(GNUNN C6F5)2 (69 mg, 0.2 mmol) were dissolved in pentane (6 mL) and stirred
The here observed reaction pathway fits well into the over-
all picture as it had emerged from studying the reactions of
various RBACHTUNGTRENNUNG(C6F5)2 reagents with the aminodihydropentalene
for 3 h. The mixture was then crystallized at À358C to give yellow crys-
tals of 13 (84 mg, 87%). Crystals suitable for X-ray crystal structure anal-
ysis were grown from a pentane solution of 13 at À358C. Elemental anal-
ysis calcd (%) for C21H14BF10N: C, 53.54; H, 3.43; N, 2.81; found: C,
53.86; H, 3.57; N, 3.05. For more experimental details and complete char-
acterization of 13, see the Supporting Information.
analogues 3. In each case, the reaction was initiated by the
addition of borane to the fulvene five-membered ring, fol-
lowed by isomerization by means of sequential 1,5-hydrogen
shifts inside the newly formed cyclopentadiene system to
generate an electrophilic conjugated iminium moiety, which
was then able to accept the R-nucleophile from boron to
form the essential new carbon–carbon s bond. From that
step on, the ways to forming stable products may differ for
individual systems as demonstrated by our previous work
[see Eqs. (2) and (3)] and by the outcome of this study.
However, all these pathways have a common origin, which
X-ray crystal structure analysis of 13: Formula C21H14BF10N, M=481.14,
light yellow crystal 0.17ꢅ0.15ꢅ0.15 mm, a=15.1034(3), b=15.6593(4),
c=16.4607(4) ꢄ, V=3893.10(16) ꢄ3, 1calc =1.642 gcmÀ3, m=1.457 mmÀ1
,
empirical absorption correction (0.790ꢀTꢀ0.811), Z=8, orthorhombic,
space group Pbca (No. 61), l=1.54178 ꢄ, T=223(2) K, w and f scans,
27558 reflections collected (Æh, Æk, Æl), [(sinq)/l]=0.60 ꢄÀ1, 3376 inde-
pendent (Rint =0.093) and 2342 observed reflections [Iꢁ2s(I)], 301 re-
fined parameters, R=0.044, wR2 =0.114, max. (min.) residual electron
density 0.18 (À0.18) eꢄÀ3, hydrogen atoms calculated and refined as
riding atoms.
À
À
involves C C or C H s-bond formation/s-bond cleavage at
the activated p framework involving the respective borane
reagent.
Acknowledgements
Financial support from the Deutsche Forschungsgemeinschaft is grateful-
ly acknowledged.
Experimental Section
Preparation of compound 9: Mes2PCH=CH2 (50 mg, 0.17 mmol) and HB-
ACHTUNGTRENNUNG(C6F5)2 (58 mg, 0.17 mmol) were dissolved in pentane (2 mL) and stirred
[1] Reviews: a) D. W. Stephan, G. Erker, Angew. Chem. 2010, 122, 50–
81; Angew. Chem. Int. Ed. 2010, 49, 46–76; b) G. Erker, Organome-
tallics 2011, 30, 358–368; c) P. P. Power, Nature 2010, 463, 171–177;
d) D. W. Stephan, Org. Biomol. Chem. 2008, 6, 1535–1539; e) D. W.
Stephan, Dalton Trans. 2009, 3129–3136; f) D. W. Stephan, S.
Greenberg, T. W. Graham, P. Chase, J. J. Hastie, S. J. Geier, J. M.
Farrell, C. C. Brown, Z. M. Heiden, G. C. Welch, M. Ullrich, Inorg.
Chem. 2011, 50, 12338–12348; g) W. E. Piers, A. J. V. Marwitz, L. G.
Mercier, Inorg. Chem. 2011, 50, 12252–12262.
[2] a) P. Spies, G. Erker, G. Kehr, K. Bergander, R. Frçhlich, S.
Grimme, D. W. Stephan, Chem. Commun. 2007, 5072–5074; b) P.
Spies, S. Schwendemann, S. Lange, G. Kehr, R. Frçhlich, G. Erker,
Angew. Chem. 2008, 120, 7654–7657; Angew. Chem. Int. Ed. 2008,
47, 7543–7546.
[3] a) T. Voss, J.-B. Sortais, R. Frçhlich, G. Kehr, G. Erker, Organome-
tallics 2011, 30, 584–594; b) J.-B. Sortais, T. Voss, G. Kehr, R. Frçh-
lich, G. Erker, Chem. Commun. 2009, 7417–7418; c) J. S. J. McCa-
hill, G. C. Welch, D. W. Stephan, Angew. Chem. 2007, 119, 5056–
5059; Angew. Chem. Int. Ed. 2007, 46, 4968–4971; d) C. M. Mçm-
ming, G. Kehr, R. Frçhlich, S. Grimme, G. Erker, J. Am. Chem. Soc.
2009, 131, 12280–12289; the related theoretical analysis see e) A.
for 15 min. After addition of 8 (22.8 mg, 0.17 mmol), the solution turned
green and a white-gray powder started to precipitate. The reaction mix-
ture was stirred overnight and the precipitate was isolated by using can-
nula filtration. The powder was washed with pentane (3ꢅ2 mL) and
dried in vacuo to afford a mixture of 9 and 10 (49 mg, 37%) in a 4:1
ratio. Crystals suitable for the X-ray crystal structure analysis were ob-
tained by diffusion of heptane into a benzene solution of 9. Elemental
analysis calcd (%) for C41H39BF10NP: C, 63.33; H, 5.06; N, 1.80; found:
C, 62.82; H, 5.37; N, 1.78. For more experimental details and complete
characterization of 9, see the Supporting Information.
X-ray crystal structure analysis of 9: Formula C41H39BF10NP, M=777.51,
light yellow crystal 0.30ꢅ0.25ꢅ0.15 mm; a=9.9865(2), b=12.7434(2), c=
16.0365(3) ꢄ;
a=71.832(1),
b=77.233(1),
g=87.728(1)8,
V=
1890.21(6) ꢄ3, 1calc =1.366 gcmÀ3, m=0.153 mmÀ1, empirical absorption
¯
correction (0.956ꢀTꢀ0.977), Z=2, triclinic, space group P1 (No. 2), l=
0.71073 ꢄ, T=223(2) K, w and f scans, 15606 reflections collected (Æh,
Æk, Æl), [(sinq)/l]=0.66 ꢄÀ1, 8536 independent (Rint =0.043) and 7338
observed reflections [Iꢁ2s(I)], 496 refined parameters, R=0.057, wR2 =
0.153, max. (min.) residual electron density 0.35 (À0.27) eꢄÀ3, hydrogen
atoms calculated and refined as riding atoms.
Chem. Eur. J. 2012, 18, 1826 – 1830
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www.chemeurj.org
1829

G. Erker et al.
Stirling, A. Hamza, T. A. Rokob, I. Papai, Chem. Commun. 2008,
3148–3150; f) Y. Guo, S. Li, Eur. J. Inorg. Chem. 2008, 2501–2505.
[4] a) C. Appelt, H. Westenberg, F. Bertini, A. W. Ehlers, J. C. Sloot-
weg, K. Lammertsma, W. Uhl, Angew. Chem. 2011, 123, 4011–4014;
Angew. Chem. Int. Ed. 2011, 50, 3925–3928; b) A. Stute, G. Kehr,
R. Frçhlich, G. Erker, Chem. Commun. 2011, 47, 4288–4290;
c) M. A. Dureen, C. C. Brown, D. W. Stephan, Organometallics
2010, 29, 6422–6432; d) M. A. Dureen, C. C. Brown, D. W. Stephan,
Organometallics 2010, 29, 6594–6607; e) C. Chen, F. Eweiner, B.
Wibbeling, R. Frçhlich, S. Senda, Y. Ohki, K. Tatsumi, S. Grimme,
G. Kehr, G. Erker, Chem. Asian J. 2010, 5, 2199–2208; f) C. Chen,
R. Frçhlich, G. Kehr, G. Erker, Chem. Commun. 2010, 46, 3580–
3582; g) C. Jiang, O. Blacque, H. Berke, Organometallics 2010, 29,
125–133; h) M. A. Dureen, D. W. Stephan, J. Am. Chem. Soc. 2009,
131, 8396–8397; i) T. Voss, C. Chen, G. Kehr, E. Nauha, G. Erker,
D. W. Stephan, Chem. Eur. J. 2010, 16, 3005–3008.
b) D. J. Parks, W. E. Piers, G. P. A. Yap, Organometallics 1998, 17,
5492–5503.
[12] a) K. Hafner, K. H. Vçpel, G. Ploss, C. Kçnig, Liebigs Ann. Chem.
1963, 661, 52–75; b) K. Hafner, G. Schulz, K. Wagner, Liebigs Ann.
Chem. 1964, 678, 39–53; c) K. Hafner, K. H. Vçpel, G. Ploss, C.
Kçnig, Org. Synth. 1967, 47, 52–54.
[13] For HB
Kehr, G. Erker, Eur. J. Inorg. Chem. 2010, 849–853; b) K. Spann-
hoff, R. Rojas, R. Frçhlich, G. Kehr, G. Erker, Organometallics
ACHTNUGTNER(NGNU C6F5)2 adduct examples see: a) I. Peuser, R. Frçhlich, G.
AHCTUNGTRENNUNG
2011, 30, 2377–2384.
[14] For a comparison (BACTHNUTRGNE(UNG C6F5)3 adduct), see the selected examples:
a) S. J. Geier, A. L. Gille, T. M. Gilbert, D. W. Stephan, Inorg.
Chem. 2009, 48, 10466–10474; b) A. Bernsdorf, H. Brand, R. Hell-
mann, M. Kçckling, A. Schulz, A. Villinger, K. Voss, J. Am. Chem.
Soc. 2009, 131, 8958–8970; c) S. J. Geier, D. W. Stephan, J. Am.
Chem. Soc. 2009, 131, 3476–3477; d) S. Mitu, M. C. Baird, Organo-
metallics 2006, 25, 4888–4896; e) R. Choukroun, C. Lorber, D.
de Caro, L. Vendier, Organometallics 2006, 25, 4243–4246; f) S. A.
Llewellyn, M. L. H. Green, A. R. Cowley, Dalton Trans. 2006, 1776–
1783.
[5] C. M. Mçmming, G. Kehr, B. Wibbeling, R. Frçhlich, G. Erker,
Dalton Trans. 2010, 39, 7556–7564.
[6] C. M. Mçmming, G. Kehr, R. Frçhlich, S. Grimme, D. W. Stephan,
G. Erker, Angew. Chem. 2009, 121, 6770–6773; Angew. Chem. Int.
Ed. 2009, 48, 6643–6646.
[15] For the hydroboration reaction with HBACTHUNRGTNEUNG(C6F5)2 see Ref. [11] and
[7] A. J. P. Cardenas, B. J. Culotta, T. H. Warren, S. Grimme, A. Stute,
R. Frçhlich, G. Kehr, G. Erker, Angew. Chem. 2011, 123, 7709–
7713; Angew. Chem. Int. Ed. 2011, 50, 7567–7571.
[8] a) C. M. Mçmming, G. Kehr, R. Frçhlich, G. Erker, Chem.
Commun. 2011, 47, 2006–2007; for a comparison see b) B. Ueber-
sax, M. Neuenschwander, Chimia 1981, 35, 400–402 and references
cited therein.
[9] B.-H. Xu, G. Kehr, R. Frçhlich, G. Erker, Chem. Eur. J. 2010, 16,
12538–12540.
[10] B.-H. Xu, G. Kehr, R. Frçhlich, S. Grimme, G. Erker, J. Am. Chem.
Soc. 2011, 133, 3480–3491.
also: a) W. E. Piers, T. Chivers, Chem. Soc. Rev. 1997, 26, 345–354;
b) D. J. Parks, W. E. Piers, Tetrahedron 1998, 54, 15469–15488;
c) R. E. v. H. Spence, W. E. Piers, Organometallics 1995, 14, 4617–
4624; d) P. Spies, G. Kehr, K. Bergander, B. Wibbeling, R. Frçhlich,
G. Erker, Dalton Trans. 2009, 1534–1541.
[16] The retro-hydroboration was also observed in a) M. Scheideman, G.
Wang, E. Vedejs, J. Am. Chem. Soc. 2008, 130, 8669–8676; b) B.
Wrackmeyer, O. L. Tok, Appl. Organomet. Chem. 2007, 21, 531–
538; c) H. H. Karsch, G. Hanika, B. Huber, J. Riede, G. Mꢂller, J.
Organomet. Chem. 1989, 361, C25–C29.
[11] a) D. J. Parks, R. E. v. H. Spence, W. E. Piers, Angew. Chem. 1995,
107, 895–897; Angew. Chem. Int. Ed. Engl. 1995, 34, 809–811;
Received: June 22, 2011
Published online: January 3, 2012
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