First dibenzophospholyl(diphenylphosphino)methane - Borane hybrid P-(η2-BH3) ligand: Synthesis and rhodium(I) complex

Article abstract of DOI:10.1021/om900684w

The first dibenzophospholyl(diphenylphosphino)methane-borane hybrid ligand has been prepared from a Pd-catalyzed reaction of (chloromethyl) diphenylphosphine-borane with the dibenzophospholyl anion. This borane precursor is readily synthesized using a pro

Full text of DOI:10.1021/om900684w

6288 Organometallics 2009, 28, 6288–6292
DOI: 10.1021/om900684w
First Dibenzophospholyl(diphenylphosphino)methane-Borane
Hybrid P-(η2-BH3) Ligand: Synthesis and Rhodium(I) Complex
§
,§
†,‡
Duc Hanh Nguyen,†,‡ Hugo Laureano, Sylvain Juge,* Philippe Kalck,
ꢀ
ꢀ
Jean-Claude Daran,†,‡ Yannick Coppel,†,‡ Martine Urrutigoity,†,‡ and
Maryse Gouygou*,†,‡
†CNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de Narbonne, F-31077 Toulouse, France,
‡
§
ꢀ
ꢀ
Universite de Toulouse, UPS, INPT, LCC, F-31077 Toulouse, France, and Institut de Chimie Moleculaire
de l’Universiteꢀ de Bourgogne, UMR CNRS 5260, 9, Avenue Alain Savary BP 47870,
21078 Dijon Cedex, France
Received August 3, 2009
The first dibenzophospholyl(diphenylphosphino)methane-borane hybrid ligand has been pre-
pared from a Pd-catalyzed reaction of (chloromethyl)diphenylphosphine-borane with the dibenzo-
phospholyl anion. This borane precursor is readily synthesized using a promising new reaction of
diphenylphosphine-borane with dichloromethane, under phase transfer catalysis (PTC) conditions.
The dibenzophospholyl(diphenylphosphino)methane-borane acts as a chelating P-(η2-BH3) ligand
to afford an air-stable Rh(I) complex. The X-ray crystal structure of this complex shows complexa-
tion of both benzophospholyl and borane moieties.
Recently the reaction of phosphine-boranes with transi-
tion-metal complexes has attracted particular attention,
owing to their possible dehydrogenation under mild catalytic
conditions,1 making it as a promising H2 source. In addition,
phosphine-boranes could also be used without previous
decomplexation to prepare various transition-metal com-
plexes by ligand exchange or by a reaction with the corre-
sponding metal salts.2,3 Using this methodology, phosphine-
boranes allow one to prepare chiral or achiral complexes
with phosphorus ligands which cannot be prepared by alter-
native approaches or purified in their trivalent form.2,3 On
the other hand, phosphine-boranes carry out the complexa-
tion by their BH3 group with the formation of three-center-
two-electron M-H-B bonds, as illustrated by the com-
plexes [Mn(η5-C5H5)(η1-H3B PMe3)(CO)2] (1),4 [(Rh(η2-H3B
Bis(diphenylphosphino)methane-borane (dppm BH3) stabi-
3
lizes the labile M H3B bond toward its η1 or η2 coordina-
3 3 3
tion mode, but until to date only dppm-borane has been
reported so far.5-8
In order to extend the chemistry of these complexes, we
were interested in the design and synthesis of modulable
chelating phosphine-borane ligands by introduction of a
phosphole group9 which possesses different steric and elec-
tronic effects with respect to the phosphine. As part of our
ongoing program on phosphine-borane derivatives used as
electrophilic or nucleophilic building blocks,10 we investi-
gated the synthesis of phospholyl(diphenylphosphino)-
methane ligands using a promising new reaction producing
a methano bridge via the formation of a P-C bond, starting
from a (chloromethyl)diphenylphosphine-borane as pre-
cursor.
3
3
3
dppm)(η4-C8H12)][PF6] (2),5 and [Ru(η5-C5H5)(η1-H3B
dppm)]PF6] (3)6 (Figure 1).
We report herein the synthesis of the first dibenzo-
phospholyl(diphenylphosphino)methane-borane and its
use for the preparation of a new hybrid P-(η2-BH3)-
rhodium(I) complex.
*To whom correspondence should be addressed. E-mail: Sylvain.Juge@
u-bourgogne.fr (S.J.); Maryse.Gouygou@lcc-toulouse.fr (M.G.).
(1) Clark, T. J.; Lee, K.; Manners, I. Chem. Eur. J. 2006, 12, 8634.
Results and Discussion
ꢀ
(2) Brodie, N.; Juge, S. Inorg. Chem. 1998, 37, 2438.
ꢁ
(3) Darcel, C.; Kaloun, E. B.; Merdes, R.; Moulin, D.; Riegel, N.;
^
ꢀ
Thorimbert, S.; Genet, J. P.; Juge, S. J. Organomet. Chem. 2001, 624,
333.
The hybrid dibenzophospholyl(diphenylphosphino)methane-
borane ligand 7 is prepared from the reaction of the
(4) Kakizawa, T.; Kawano, Y.; Shimoi, M. Organometallics 2001, 20,
3211. For other transition-metal complexes see (a) Shimoi, M.; Nagai, S. I.;
Ichikawa, M.; Kawano, Y.; Katoh, K.; Uruichi, M.; Ogino, H. J. Am. Chem.
Soc. 1999, 121, 11704. (b) Kawano, Y.; Yasue, T.; Shimoi, M. J. Am. Chem.
Soc. 1999, 121, 11744. (c) Yasue, T.; Kawano, Y.; Shimoi, M. Angew.
Chem., Int. Ed. 2003, 42, 1727. (d) Kawano, Y.; Yamaguchi, K.; Miyake,
S. Y.; Kakizawa, T.; Shimoi, M. Chem. Eur. J. 2007, 13, 6920.
(5) Ingleson, M.; Patmore, N. J.; Ruggiero, G. D.; Frost, C. G.;
Mahon, M. F.; Willis, M. C.; Weller, A. S. Organometallics 2001, 20,
4434.
(7) (a) Macias, R.; Rath, N. P.; Barton, L. Angew. Chem., Int. Ed.
1999, 38, 162. (b) Volkov, O.; Macas, R.; Rath, N. P.; Barton, L. Inorg. Chem.
2002, 41, 5837.
€
(8) Merle, N.; Frost, C. G.; Kociok-Kohn, G.; Willis, M. C.; Weller,
A. S. Eur. J. Inorg. Chem. 2006, 4068.
(9) (a) Mourgues, S.; Serra, D.; Lamy, F.; Vincendeau, S.; Daran,
J.-C.; Manoury, E.; Gouygou, M. Eur. J. Inorg. Chem. 2003, 2820.
(b) Lopez Cortes, J. G.; Ramon, O.; Vincendeau, S.; Serra, D.; Lamy, F.;
Daran, J.-C.; Manoury, E.; Gouygou, M. Eur. J. Inorg. Chem. 2006, 5148.
€
(6) (a) Merle, N.; Kociok-Kohn, G.; Mahon, M. F.; Frost, C. G.;
ꢀ
(10) Darcel, C.; Uziel, J.; Juge, S. In Phosphorus Ligands in Asym-
Ruggerio, G. D.; Weller, A. S.; Willis, M. C. Dalton Trans. 2004, 3883.
€
€
(b) Merle, N.; Frost, C. G.; Kociok-Kohn, G.; Willis, M. C.; Weller, A. S.
metric Catalysis: Synthesis and Applications; Borner, A., Ed.; Wiley-VCH:
J. Organomet. Chem. 2005, 690, 2839.
Weinheim, Germany, 2008; p 1211.
r
pubs.acs.org/Organometallics
Published on Web 10/12/2009
2009 American Chemical Society

Article
Organometallics, Vol. 28, No. 21, 2009 6289
Figure 1. Drawings of 1-3.
Scheme 1
dibenzophospholyllithium reagent 611 with (chloromethyl)-
diphenylphosphine-borane 5. The compound 5 was pre-
viously prepared in 75% yield, by the new reaction of
diphenylphosphine-borane
4
with dichloromethane,
under phase transfer catalysis (PTC) conditions (Scheme 1).
Noteworthy the direct reaction of the anion 6 with
the (chloromethyl)phosphine-borane 5 results in low yield
(<10%). Conversely, in the presence of 5% Pd(OAc)2/dppf,
the desired ligand 7is obtained in 52% isolated yield (Scheme 1).
The white solid dibenzophospholyl(diphenylphosphino)-
methane-borane ligand 7 is both air- and moisture-stable
and is fully characterized by conventional NMR techniques
1
(31P, H, 13C, 11B), mass spectrometry, and elemental ana-
lysis. The 31P{1H} NMR spectrum displays a doublet at
δ -29.7 ppm (2JPP=68.0 Hz) and a lower field broad signal
at δ 15.6 ppm, the latter being assigned to the PPh2 group
coordinated to borane. It is noteworthy that the BH3 group
does not migrate from the PPh2 moiety to the phospholyl
Figure 2. X-ray crystal structure of the hybrid ligand 7. Selec-
˚
ted bond lengths (A) and angles (deg):P(1)-B(1), 1.9085(17);
P(1)-C(11), 1.8106(13); P(1)-C(111), 1.8053(15); P(1)-C(121),
1.8014(14); P(2)-C(11), 1.8624(13); P(2)-C(21), 1.8169(14);
P(2)-C(24), 1.8088(14); P(1)-C(11)-P(2), 110.20(7); C(24)-
P(2)-C(21), 89.70(6).
group during the reaction between BH3 P(CH2Cl)Ph2
3
and LiP(C6H4)2. The BH3 group appears as a doublet at
δ 1.34 ppm (2JHP(1)=15.9 Hz) in 1H{11B} NMR, whereas the
11B NMR spectrum displays a single broad resonance at
δ -38.3 ppm, characteristic of a phosphine-borane chemi-
cal shift.12 Finally, the 1H NMR spectrum exhibits a doublet
of doublet at δ 2.63 ppm (2JHP(1) =10.8 Hz, 2JHP(2) =2.1 Hz)
corresponding to the methylene bridge. The X-ray crystal
structure of the hybrid ligand 7 is shown in Figure 2 along
with selected bond distances and angles. The P(1)-B(1)
Scheme 2
˚
bond length is 1.9085(17) A. The H atoms attached to the
˚
boron atom were idealized with distances of 0.98 A and
treated as riding on the B atom. The P(1)-C(11)-P(2) angle
is 110.20(7)°. The C(21), C(22), C(23), and C(24) atoms of
the dibenzophosphole residue are planar, with the largest
˚
deviation from the mean plane being 0.044(2) A. The P(2)
The [Rh2(μ-Cl)2(COD)2] and [Rh(COD)2][CF3SO3] pre-
cursors were used to synthesize the corresponding complexes
with the hybrid ligand 7. The reaction of [Rh2(μ-Cl)2-
(COD)2] with 0.5 equiv of 7 in dichloromethane, using
AgBF4 as a halide abstracting agent, gave the rhodium
complex [Rh(COD){(η2-BH3-phosphine)(κ1-phosphole)}]BF4
(8a) in excellent yield (86% isolated), which is an air-
and moisture-stable solid (Scheme 2). An alternative
synthesis was also developed using the cationic pre-
˚
atom deviates from this plane by 0.140(1) A, as already
observed for other dibenzophosphole compounds.13 All
bond lengths and bond angles compare favorably to those
of other common dibenzophospholes.13
(11) Schenk, W. A.; Stubbe, M.; Hagel, M. J. Organomet. Chem.
1998, 560, 257.
(12) Bourumeau, K.; Gaumont, A. C.; Denis, J. M. Tetrahedron Lett.
1997, 38, 1923.
-
cursor [Rh(COD)2]þ (as its CF3SO3 salt) with a stoi-
(13) (a) Alyea, E. C.; Ferguson, G.; Gallager, J. F. Acta Crystallogr.
1992, C48, 959. (b) Lopez-Cortes, J. G.; Vincendeau, S.; Daran, J. C.;
Manoury, E.; Gouygou, M. Acta Crystallogr. 2006, C62, m188. (c) Mizuta,
T.; Iwakuni, Y.; Nakazono, T.; Kubo, K.; Miyoshi, K. J. Organomet. Chem.
2007, 692, 184.
chiometric amount of 7 in dichloromethane. Indeed,
the reaction led to the complex [Rh(COD){(η2-BH3-
phosphine)(κ1-phosphole)}][CF3SO3] (8b) in a very good

6290 Organometallics, Vol. 28, No. 21, 2009
Nguyen et al.
˚
fragment, i.e. Rh-Cg2 (C(6)-C(7) = 2.0012 (2) A). The
coordination of ligand 7 to the rhodium induces a slight
variation of the P(1)-C-P(2) angle (110.20(7)° versus
112.743(14)° for 7 and 8, respectively). Surprisingly, the
deviation of the P(2) atom from the C(21), C(22), C(23),
˚
C(24) mean plane increased (0.140(1) A for 7 versus
˚
0.1855(4) A for 8), whereas the phosphorus coordination
normally brings the phosphorus back in the plane of the
central cycle, as already observed in dibenzophosphole-
rhodium complexes.14
The 1H NMR spectral data at 188 K of the Rh complex 8a
confirm the molecular structure described above. In the
1H{11B,31P} NMR spectrum, a singlet15 at δ -1.41 ppm
corresponding to 2H of BH3 is observed, the third proton of
BH3 being included in a massif centered at 2.26 ppm with
1
four protons of the COD ligand. By 1D H EXSY experi-
ment with broadband decoupling of 11B and 31P, two sing-
lets15 for the three protons of BH3 (2.26 (1H) and -1.41 ppm
(2H)) could be observed and assigned to the terminal B-H
and to the bridging Rh-H-B, respectively.
The variable-temperature 1H{11B,31P} NMR spectra, with
heating from 188 to 298 K, show that these two singlets
collapsed (Tc=238 K, ΔGq=41.4 ( 1 kJ/mol) into a doublet
at -0.09 ppm (JHRh = 15.0 Hz). As the three protons of
the BH3 group are equivalent, the η2-BH3 binding motif
observed in the solid state is not maintained in solution at
room temperature. This suggests that the BH3 group is
fluxional in solution at room temperature, as observed in
other rhodium complexes,4-8 due to the rapid exchange of
the three B-H bonds, their bonding to the Rh center
occurring through rotation around the P-B bond according
to the mechanism proposed by Barton.7
T1 measurements, obtained by the conventional inversion
recovery method, have been carried out. At all temperatures,
we observed an average T1 for the three protons of BH3,
showing that the exchange is fast on the T1 relaxation time
scale, even at 188 K where the exchange is slow on the
spectral time scale.
Figure 3. X-ray crystal structure of the cationic part of complex
˚
8. Selected bond lengths (A) and angles (deg): P(1)-B(1),
1.928(2); P(1)-C(1), 1.8102(4); P(2)-C(1), 1.8377; Rh(1)-B(1),
2.331(2); Rh(1)-H(1b), 1.96(3); Rh(1)-H(2b), 1.85(3); B(1)-
H(1b), 1.13(3); B(1)-H(2b), 1.24(3); B(1)-H(3b), 1.00(3);
Rh(1)-P(2), 2.24532(16); P(2)-C(1), 1.8377; Rh(1)-C(2),
2.27157(17); Rh(1)-C(3), 2.25416(17); Rh(1)-C(6), 2.121(2);
Rh(1)-C(7), 2.120(2); P(1)-C(1)-P(2), 112.743(14).
yield (92%). The complex 8a was fully characterized by NMR
spectroscopy, mass spectrometry, and elemental analysis.
The [BF4]- metathesis with the bulky [BPh4]- anion afforded
crystals of 8c suitable for the X-ray diffraction study.
The X-ray crystal structure of 8c was determined at 180 K
(Figure 3). The ligand binds to the metal center through the
phosphorus atom of the phosphole moiety and in a η2 mode
through the BH3 group, formally as two three-center-
two-electron bonds. All hydrogen atoms on the borane
were located and refined. The two bridging hydrogens
exhibit similar Rh-H distances within experimental error
The remaining observed 31P, 11B, and 13C resonances are
entirely consistent with the solid-state structure. The boron
chemical shift at δ -26.03 ppm (d, JBP=85.1 Hz), downfield
of that of ligand 7 (δ -38.31 ppm), is similar to Weller’s Rh
complex.5 In 31P NMR spectra, the doublet of doublet at
δ 47.52 ppm (dd, JP(1)Rh=139.7 Hz, JP(1)P(2)=68.9 Hz) and
the broad signal at δ 20.66 ppm, corresponding to the
phosphine-borane group, are shifted to lower fields. More-
over, the 31P-103Rh HMQC NMR spectrum at 298 K allows
the assignment of the doublet at δ -8258.4 ppm to the Rh
metal center.
In summary, we have described the synthesis of the
first dibenzophospholyl(diphenylphosphino)methane-borane
hybrid ligand prepared starting from (chloromethyl)diphe-
nylphosphine-borane. This compound acting as a building
block was easily prepared by the new reaction of diphenyl-
phosphine-borane with dichloromethane under PTC con-
ditions, which offers a promising route for the synthesis of
modified dppm’s. Dibenzophospholyl(diphenylphosphino)-
methane-borane acts as a P-(η2-BH3) chelating ligand
˚
˚
(Rh-H(1b) = 1.96(3) A; Rh-H(2b) = 1.85(3) A). These
distances compare well to those reported for other crystal-
lographically characterized rhodium-dppm(borane) com-
plexes.5,7 Due to these Rh H-B interactions, the corres-
ponding B-H bond distances (B-H(1b)=1.13(3) A; B-H-
(2b) = 1.24(3) A) are slightly longer than that found for the
3 3 3
˚
˚
˚
terminal B-H(3b) distance (1.00(3) A). The Rh B intera-
3 3 3
˚
tomic distance of 2.332 A is longer than the sum of the
˚
combined covalent radii of Rh and B (2.27 A) and is similar
˚
to those found in the rhodium complex 2 (2.313(3) A), which
is consistent with the absence of a direct Rh-B interaction.
The Rh metal center has a square-planar geometry defined
by the two centroids of the COD ligand and the P(2) and the
B(1) atoms. Moreover, the geometry of 8 can be viewed as a
trigonal bipyramid with one centroid and the H(1) and H(2)
atoms in the equatorial plane, the H(1)-Rh-H(2) angle
being small (60.7(12)°) (Figure 3).
The differences observed for the Rh-COD bond lengths
reveal a differentiated trans influence for the benzophos-
pholyl and BH2 moeties. The Rh-Cg1 distance (C(2)-
(14) (a) Kessler, J. M.; Nelson, J. H.; Frye, J. S.; DeCian, A.; Fischer,
J. Inorg. Chem. 1993, 32, 1048. (b) Karas, J.; Huttner, G.; Heinze, K.;
Rutsch, P.; Zsolnai, L. Eur. J. Inorg. Chem. 1999, 405. (c) Chen, A. C.;
Allen, D. P.; Crudden, C. M.; Wang, R.; Decken, A. Can. J. Chem. 2005, 83,
943.
˚
C(3) = 2.1752 (2) A) trans to the benzophospholyl moiety
(15) The 1H-Rh coupling could not be observed at low temperature.
is significantly longer than those that are trans to the BH2

Article
Organometallics, Vol. 28, No. 21, 2009 6291
affording a stable Rh(I) complex, with coordination of both
the dibenzophospholyl and the borane moieties. Using
this methodology, the synthesis of P-chirogenic phospholyl-
(diphenylphosphino)methane-borane ligands and their
Rh(I) complex derivatives are currently in progress for
application in asymmetric catalysis.
121.489 MHz; δ (ppm)): 23.7 (m). HRMS (ESI): calcd for
C13H14BClP (Mþ - H) 247.0615, found 247.0638.
Dibenzophospholyl(diphenylphosphino)methane-Borane (7).
To a solution of 1-phenyldibenzophosphole (0.573 g, 2.2 mmol)
in THF (40 mL) was added at 0 °C metallic lithium in excess
(0.20 g). The reaction mixture was vigorously stirred for 1 h at
0 °C and then for 3 h at room temperature. After removal of the
unreacted lithium, the dark red solution was cooled at -20 °C
and anhydrous AlCl3 (0.8 mmol, 0.11 g) was added to neutralize
PhLi. The reaction mixture was warmed to room temperature
and stirred again for 30 min to afford the dibenzophospholyl
anion 6. To the anion was added at -78 °C a solution
of (chloromethyl)diphenylphosphine-borane 5 (0.50 g, 2.0
mmol) in THF (10 mL) and then a solution of Pd(OAc)2
(0.1 mmol, 0.022 g) and dppf (0.2 mmol, 0.11 g) in THF
(10 mL). After it was stirred for 48 h, the yellow reaction mixture
was concentrated to 5 mL and quenched with degassed H2O
(20 mL). The residue was extracted with dichloromethane (3 ꢀ
30 mL), and the combined extracts were dried over MgSO4
and then evaporated to afford a yellow solid. Purification
by silica gel column chromatography (eluent CH2Cl2/n-hexane
(50/50 or 40/60)) yielded 0.41 g (52%) of ligand 7 as a white solid.
Crystals suitable for an X-ray diffraction study were obtained by
recrystallization from an CH2Cl2/n-pentane solution at -20 °C.
Experimental Section
General Procedures. All reactions were carried out under an
argon atmosphere in dried glassware. Solvents were dried and
freshly distilled under an argon atmosphere over sodium/
benzophenone for THF, P2O5 for CH2Cl2, and CaH2 for n-pentane.
Thin-layer chromatography was performed on silica gel (60 F254
)
and visualized by UV, iodine, or permanganate treatment. Flash
chromatography was performed on silica gel (35-70 μm). All
1D and 2D NMR spectra data were recorded on Bruker DRX
300 or Advance 300-500 spectrometers with TMS as internal
reference for 1H and 13C, 85% phosphoric acid as external
reference for 31P, BF3 Et2O as external reference for 11B, and
3
Rh(acac)3 as external reference for 103Rh. T1 relaxation times
were mesured by the conventional inversion recovery method.
Mass spectral analyses were performed on Bruker ESI micro-
TOF-Q (HR) and TSQ 7000 Thermoquest instruments (DCI).
The m/z value of the major peak is given with the intensity as a
percentage of the base peak shown in brackets. Elemental
analyses were measured with a precision superior to 0.3% at
the Microanalysis Laboratory of the LCC at Toulouse. Com-
mercially available palladium(II) acetate, dppf, [Rh(COD)2]-
CF3SO3, silver trifluoroborate, and tetraphenylborate were
used as received. 1-Phenyldibenzophosphole,16 [Rh(μ-Cl)-
(COD)]2,17 and diphenylphosphine18 were prepared as de-
scribed.
1H NMR(298 K, CDCl3, 300.13 MHz;δ(ppm)): 7.88 (dd, 4JHH
=
=
0.6 Hz, 3JHH =7.5 Hz, 2H(3,30) of phosphole), 7.75 (m, 4JHH
3
1.2 Hz, JHH = 8.4 Hz, JHP = 1.5 Hz, 4H, CH, Ph), 7.40-7.58
(m, 10H, 4H(3,30,5,50) of phosphole and 6H of Ph), 7.25 (t,
3
3JHH = 7.2 Hz, JHP = 1.0 Hz, 1H, H(4 or 40) of phosphole),
3
3
7.24 (t, JHH = 7.2 Hz, JHP = 1.0 Hz, 1H, H(4 or 40) of
phosphole), 2.63 (dd, JHP(2)= 2.1 Hz, JHP(1) =10.8 Hz, 2H,
2
2
CH2), 1.34 (brq, JHB = 88.5 Hz, 3H, BH3). 1H{11B} NMR
1
1
(298 K, CDCl3, 300.13 MHz; selected δ (ppm)): 1.34 (d, JHP(1)
= 15.9 Hz, 3H, BH3). 31P{1H} NMR (298 K, CDCl3, 121.495
Diphenylphosphine-Borane (4).19 This compound was freshly
prepared before use. In a round-bottom flask at room tem-
perature were introduced THF (20 mL), diphenylphosphine
MHz; δ (ppm)): þ15.58 (br, P(1), PBH3), -29.70 (d, P(2), 2JPP
=
68.0 Hz). 13C{1H} NMR (298 K, CDCl3, 75.468 MHz; δ (ppm)):
143.53 (d, JCP = 1.8 Hz, C(2 or 20) of phosphole), 142.85 (t,
JCP =7.3 Hz, C(2 or 20) of phosphole), 132.45 (d, JCP =8.7 Hz,
Ph), 131.95 (d, JCP = 2.4 Hz, Ph), 130.58 (d, JCP = 22.4 Hz,
C(6,60) of phosphole), 129.81 (d, JCP = 55.3 Hz, Ph), 129.78
(d, JCP =55.2 Hz, Ph), 129.0 (s, C(5,50) of phosphole), 128.93 (d,
JCP = 10.1 Hz, Ph), 127.59 (d, JCP = 7.3 Hz, CH(4,40) of
phosphole), 121.33 (s, CH(3,30) of phosphole), 27.82 (dd,
JCP =33.0, JCP =40.4 Hz, CH2). 11B{1H} NMR (298 K, CDCl3,
96.294 MHz; δ (ppm)): -38.44 (d, 1B, JBP =40.7 Hz). MS (DCI,
NH3; m/z (%)): 397.2 (100%) [M þ H]þ. Anal. Calcd for
BC25H23P2: C, 75.79; H, 5.85. Found: C, 75.61; H, 5.99.
(2.0 g, 10.7 mmol, 1 equiv), and then BH3 SMe2 (1.2 mL,
3
12.8 mmol). After it was stirred for 3 h, the mixture was hydro-
lyzed with H2O (10 mL) and extracted with 3 ꢀ 10 mL of AcOEt.
The organic phases were dried over MgSO4, and the solvent was
evaporated. The crude product was purified by flash chromato-
graphy over silica gel using AcOEt/petroleum ether (1/3) as
eluent, affording pure 4 (1.85 g; yield 86%) as a white solid. 1H
NMR (298 K, CDCl3, 300.13 MHz; δ (ppm)): 7.66-7.72 (m,
4H, H arom), 7.44-7.57 (m, 6H, H arom), 6.33 (qd, 1H, 1JPH
=
379 Hz, 3JHH = 7 Hz, PH), 0.50-1.50 (br q, 3H, 1JBH = 87 Hz,
BH3). 31P NMR (298 K, CDCl3, 121.489 MHz; δ (ppm)):
1.3 (m).
Rhodium Complex (8). A solution of the ligand 7 (0.059 g,
0.149 mmol) in CH2Cl2 (10 mL) was added to a solution of [Rh2-
(μ-Cl)2(COD)2] (0.037 g, 0.075 mmol) in CH2Cl2 (10 mL) at
0 °C. The reaction mixture was stirred at this temperature for
15 min and then AgBF4 (0.032 g, 0.164 mmol) was introduced
and the resulting mixture was warmed to room temperature and
stirred for 14 h. The solution was filtered and concentrated, and
n-pentane was added to afford 8a as a yellow-green solid.
Workup with diethyl ether (3 ꢀ 10 mL) give the clean product
(0.089 g, 86%). 1H NMR (298 K, CD2Cl2, 500.33 MHz; δ
(ppm)): 7.97 (dd, JHH=7.8 Hz, 3JHP=0.9 Hz, 1H, CH (3 or 30)
(Chloromethyl)diphenylphosphine-Borane (5).20 In a round-
bottom flask at room temperature were introduced diphe-
nylphosphine-borane 417 (54 mg, 0.25 mmol, 1 equiv), tetra-
butylammonium bromide (8 mg, 0.025 mmol, 10 mol %),
dichloromethane (0.4 mL), finely crushed potassium carbonate
(70 mg, 0.5 mmol, 2 equiv), and finally 25 μL of H2O. After the
mixture was stirred for 12 h, the end of the reaction was
controlled by 31P no lock NMR and the salts were removed by
filtration over silica using dichloromethane as solvent. The
solvent was evaporated and the crude product purified by flash
chromatography over silica gel using toluene as eluent, affording
pure 5 (yield 78%) as a white oil. Rf = 0.65 (toluene).
1H NMR (298 K, CDCl3, 300.13 MHz; δ (ppm)): 7.63-7.67
(m, 4H, H arom), 7.42-7.48 (m, 6H, H arom), 4.02 (d, 2H, J =
3.3 Hz, CH2), 0.50-1.50 (m, 3H, BH3). 31P NMR (298 K, CDCl3,
of phosphole), 7.96 (dd, JHH =7.8 Hz, 3JHP =0.9 Hz, 1H, CH-
3
(3 or 30) of phosphole), 7.70-7.75 (m, JHH = 6.2 Hz, JHP
1.1 Hz, 6H, 4Hortho þ 2Hpara, Ph), 7.66 (td, JHP=1.4 Hz, JHH
=
=
8.7 Hz, 1H, CH (4 or 40) of phosphole), 7.64 (td, JHP =1.4 Hz,
HH = 8.7 Hz, 1H, CH (4 or 40) of phosphole), 7.58-7.62 (m,
J
JHH = 7.5 Hz, 4Hmeta, Ph), 7.39 (d, JHH = 7.7 Hz, 1H, CH-
(6 or 60) of phosphole), 7.38 (d, JHH=7.1 Hz, 1H, CH(6 or 60) of
phosphole), 7.33 (td, JHP =4.0 Hz, JHH =1.0, 7.5 Hz, 1H, CH-
(5 or 50) of phosphole), 7.32 (td, JHP=4.0 Hz, JHH=1.0, 7.5 Hz,
1H, CH(5 or 50) of phosphole), 5.88 (br, 2H, CH, COD), 3.30
(br, 2H, CH, COD), 2.82 (t, JHP(1) = JHP(2) = 11.8 Hz, 2H,
P(1)CH2P(2)), 2.39-2.45 (m, 2H, CH2, COD), 2.23-2.30
(16) Affandi, S.; Green, R. L.; Hsich, B. T.; Holt, M. S.; Nelson, J. H.;
Alyena, E. C. Synth. React. Inorg. Met.-Org. Chem. 1987, 17, 307.
(17) Chatt, J.; Venanzi, L. M. J. Chem. Soc. 1957, 4735.
(18) Wittenberg, D.; Giman, H. J. Org. Chem. 1958, 23, 1063.
(19) McKinstry, L.; Livinghouse, T. Tetrahedron 1995, 51, 7655.
(20) Antczak, M. L.; Montchamp, J. L. Org. Lett. 2008, 10, 977.

6292 Organometallics, Vol. 28, No. 21, 2009
Nguyen et al.
(m, 4H, CH2, COD), 2.12-2.18 (m, 2H, CH2, COD), -0.11 (bd,
1JHB=109.7 Hz, 3H, BH3). 1H{11B,31P} NMR (298 K, CD2Cl2,
500.33 MHz; selected δ (ppm)): -0.09 (d, 3H, JHRh =15.0 Hz,
SHELXL-97.22 All H atoms attached to carbon were introduced
in idealized positions and treated as riding on their parent atoms
in the calculations. H atoms attached to boron were located in
difference Fourier syntheses; their coordinates were refined
using restraints, and their isotropic thermal parameters were
related to the boron atom. Drawings of the molecules were
realized with the help of ORTEP3.23
1
BH3). EXSY-1D H{11B,31P} NMR (188 K, CD2Cl2, 500.33
MHz; δ (ppm)): 2.26 (s, 1H, terminal H, BH3), -1.41 (s, 2H,
bridging H, BH3). 1H{11B} NMR (298 K, CD2Cl2, 300.13 MHz;
selected δ (ppm)): -0.09 (t, JHP = JHRh = 11.7 Hz, 3H, BH3).
31P{1H} NMR (298 K, CD2Cl2, 202.537 MHz; δ (ppm)): þ47.52
(dd, 1JP(1)Rh =139.8 Hz, 2JP(1)P(2) =68.9 Hz, P(2)), þ20.66 (br,
P(1)). 11B{1H} NMR (298 K, CD2Cl2, 160.526 MHz; δ (ppm)):
-1.08 (b, BF4-), -26.03 (d, 1JBP=85.1 Hz, BH3). 103Rh NMR
Crystal Data for 7. C25H23BP, Mw = 354.4, monoclinic,
˚
˚
a = 10.7285(3) A, b = 14.9875(4) A, c = 13.2512(3) A, V =
˚
3
˚
2122.08(10) A , T=180(2) K, space group P21/c (No. 14), Z=4,
μ(Mo KR) = 0.134 mm-1, 18 819 reflections measured, 5266
unique reflections (Rint =0.024) which were used in all calcula-
tions. The final R and Rw(F2) values were 0.0477 and 0.1028,
respectively (all data).
(298 K, CD2Cl2, 15.8112 MHz; δ (ppm)): -8258.40 (d, 1JRhP
=
73.8 Hz). 13C{1H} NMR (298 K, CD2Cl2, 100.613 MHz; δ
(ppm)): 142.58 (d, JCP = 9.8 Hz, C(2,20) of phosphole), 133.40
(d, JCP = 2.7 Hz, Ph), 132.85 (d, JCP = 1.81 Hz, C(4,40) of
phosphole), 132.39 (d, JCP=10.7 Hz, Ph), 131.00 (d, JCP=15.0 Hz,
C(6,60) of phosphole), 129.91 (d, JCP =11.5 Hz, Ph), 129.10 (d,
JCP =11.1 Hz, C(5,50) of phosphole), 124.72 (d, JCP =64.7 Hz,
C(1 or 10) of phosphole), 124.67 (d, JCP =64.8 Hz, C(1 or 10) of
phosphole), 122.34 (d, JCP = 6.1 Hz, C(3 or 30), phosphole),
106.67 (dd, JCRh =10.3 Hz, JCP =6.0 Hz, CH, COD), 74.78 (d,
Crystal Data for 8c. C57H33B2P2Rh, Mw = 926.48, triclinic,
˚
˚
˚
a = 11.9261(5) A, b = 14.1919(7) A, c = 14.6192(6) A, R =
3
˚
87.739(3)°, β=84.475(3)°, γ=69.165(3)°, V=2301.78(18) A ,
T = 180(2) K, space group P1 (No. 2), Z = 2, μ(Mo KR) =
0.479 mm-1, 42 266 reflections measured, 13 334 unique reflec-
tions (Rint=0.027), which were used in all calculations. The final
R and Rw(F2) values were 0.0408 and 0.1039, respectively
(all data).
JCP = 13.1 Hz, CH, COD), 33.42 (CH2, COD), 33.39 (CH2,
COD), 28.55 (dd, JCP(1)=11.5 Hz, JCP(2)= 42.7 Hz, P(1)CH2P-
(2)), 28.18 (CH2, COD), 28.17 (CH2, COD). MS (FAB, MNBA;
m/z (%)): 607 (100%) [M]þ. Anal. Calcd for C33B2H35F4P2Rh:
C, 57.10; H, 5.08. Found: C, 57.20; H, 5.98. Crystals suitable for
an X-ray diffraction study were obtained by metathesis of a
dichloromethane solution of 8a with excess NaBPh4, filtration,
and crystallization by slow evaporation of dichloromethane to
afford 8c.
Acknowledgment. We are grateful to the CNRS, the
ꢁ
“Ministere de l’Education Nationale et de la Recherche”,
and the ANR program 07-BLAN-0292-01 MetChirPhos)
for financial support, a Ph.D. fellowship (to H.L.), and
a postdoctoral grant (to D.H.N.). S.J. also thanks
Prof. P. Harvey for his help with the preparation of
this paper and Ms. M. J. Ondel and M. J. Penouilh
(University of Bourgogne) for their technical support
and mass spectroscopy, respectively.
X-ray Diffraction Studies. A single crystal of each compound
was mounted under inert perfluoro polyether at the tip of a glass
fiber and cooled in the cryostream of an Oxford-Diffraction
XCALIBUR CCD diffractometer for 7 or in the cryo-
stream of a Bruker APEX2 CCD diffractometer for 8c. Data
were collected using monochromatic Mo KR radiation (λ =
Supporting Information Available: A figure giving variable-
temperature 1H{11B,31P} NMR spectra, a table giving T1 mea-
surements, and CIF files giving X-ray crystallographic data for
compounds 7 and 8c. This material is available free of charge via
the Internet at http://pubs.acs.org.
˚
0.710 73 A).
The structures were solved by direct methods (SIR97)21
and refined by least-squares procedures on F2 using
(21) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.;
Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.;
Spagna, R. SIR97: a program for automatic solution of crystal struc-
tures by direct methods. J. Appl. Crystallogr. 1999, 32, 115–119.
(22) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112–122.
(23) Farrugia, L. J. ORTEP-3 for Windows. J. Appl. Crystallogr.
1997, 30, 565.