4,4,5,5-Tetraphenyl-1,3,2-dioxaborolane: A bulky borane for the transition metal catalysed hydroboration of alkenes

Article abstract of DOI:10.1002/ejic.200701066

4,4,5,5-Tetraphenyl-1,3,2-dioxaborolane (HBBzpin, 3) has been prepared in high yield by the addition of H₃B·SMe₂ to benzopinacol. HBBzpin is a relatively stable solid that reacts with a variety of alkenes under catalytic conditions t

Full text of DOI:10.1002/ejic.200701066

FULL PAPER
DOI: 10.1002/ejic.200701066
4,4,5,5-Tetraphenyl-1,3,2-dioxaborolane: A Bulky Borane for the Transition
Metal Catalysed Hydroboration of Alkenes
Claudia B. Fritschi,[a] Sophie M. Wernitz,[a] Christopher M. Vogels,[a] Michael P. Shaver,[a][‡]
Andreas Decken,[b] Andrew Bell,*[c] and Stephen A. Westcott*[a]
Dedicated to the memory of Professor Yoshihiko Ito
Keywords: Boranes / Catalysis / Hydroboration / Organoboronate esters / Borylrhodium complexes
4,4,5,5-Tetraphenyl-1,3,2-dioxaborolane (HBBzpin, 3) has
been prepared in high yield by the addition of H3B·SMe2 to
benzopinacol. HBBzpin is a relatively stable solid that reacts
with a variety of alkenes under catalytic conditions to give
tively. Addition of HBBzpin to RhCl(PPh3)3 gave Rh(H)-
Cl(BzBpin)(PPh3)2 (11) as the only new rhodium-containing
product. The complex 11 has been characterized by a
number of physical and analytical methods, including a sin-
air- and chromatography-stable organoboronate esters. Re- gle-crystal X-ray diffraction study.
actions of vinylarenes in the presence of catalytic amounts of
[Cp*IrCl2]2 gave the corresponding terminal products selec-
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
studied, however, is the use of alternate borane sources for
catalysed hydroboration reactions.[4] Indeed, pinacolborane
(4,4,5,5-tetramethyl-1,3,2-dioxaborolane or HBpin) is occa-
sionally used as a replacement for HBcat as the resulting
organoborane products are stable to air and chromatog-
raphy.[5] Unfortunately, these reactions can suffer from poor
selectivities or competing pathways (i.e. hydrogenation or
dehydrogenative borylations[6]). As such, we have investi-
gated the synthesis and use of bulky 4,4,5,5-tetraphenyl-
1,3,2-dioxaborolane (3) for its use in the catalysed hydro-
boration of alkenes in order to circumvent these shortcom-
ings.
Introduction
There has been considerable recent interest in the use of
transition metals to catalyse the hydroboration of alkenes
and alkynes.[1] Products obtained from these reactions can
have complementary or opposite chemo-, regio-, and/or
stereoselectivity to those generated by the uncatalysed vari-
ant. For instance, an elegant study by Männig and Nöth
demonstrated that the addition of catecholborane (HBcat;
cat = 1,2-O2C6H4) to 5-hexen-2-one proceeded readily at
room temperature to give the expected borate product 1
(Scheme 1), where addition of the borane has occurred at
the more reactive ketone functionality.[2] However, if the re-
action was carried out at lower temperatures in the presence
of a rhodium catalyst, e.g. RhCl(PPh3)3, they were able to
facilitate selective addition of HBcat to the less reactive al-
kene group to give the corresponding alkylboronate ester
2. Since this seminal discovery, a considerable amount of
research has focussed on investigating the mechanism and
scope of catalysed hydroboration reactions.[3] Much less
[a] Department of Chemistry, Mount Allison University,
Sackville, NB E4L 1G8, Canada
Fax: +1-506-364-2313
E-mail: swestcott@mta.ca
[b] Department of Chemistry, University of New Brunswick,
Fredericton, NB E3B 5A3, Canada
[c] Promerus LLC,
9921 Brecksville Road, Brecksville, Ohio 44141-3289, USA
[‡] Present address: Deparment of Chemistry, University of Prince
Edward Island,
Charlottetown, PE C1A 4P3, Canada
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
Scheme 1. Hydroboration of 5-hexen-2-one with catecholborane
(HBcat).
Eur. J. Inorg. Chem. 2008, 779–785
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A. Bell, S. A. Westcott et al.
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Results and Discussion
Synthesis
taining this tetraphenylethylene glycol ester have been used
recently in the enantioselective synthesis of 1,5-anti- and
1,5-syn-diols.[8]
Similar selectivities were observed in reactions with 4-F-
C6H4CH=CH2 where the corresponding linear product 4-
F-C6H4CH2CH2BzBpin (7) was the only organoboronate
ester generated in the presence of [Cp*IrCl2]2. Compound
7 has been characterized by a number of physical methods
including a single-crystal X-ray diffraction study, and the
molecular structure is shown in Figure 1. The B–O bond
lengths of 1.361(3) and 1.371(3) Å are typical for three-co-
ordinate diorganyloxyboranes.[9] Indeed, the two short
bonds indicate that π-bonding between the oxygen lone
pairs and the empty p-orbital of the boron atom is signifi-
cant in compound 7. Bond lengths and angles within the
BzBpin group are similar to those reported for a related
ferrocene derivative.[10]
Compound 3 (HBBzpin) was prepared in 85% yield by
the addition of benzopinacol to a solution of H3B·SMe2
in toluene heated at reflux for 12 h and characterized by
multinuclear NMR spectroscopy (Scheme 2). HBBzpin is a
white solid that can be kept indefinitely at room tempera-
ture under nitrogen. A broad peak in the 11B NMR spec-
trum at δ = 27 ppm and a broad singlet at δ = 4.95 ppm in
1
the H NMR spectrum are consistent with chemical shifts
found for other bulky diorganyloxyboranes. Interestingly,
attempts to prepare this compound using H3B·THF re-
sulted in a mixture of products.[4a] Compound 3 is remark-
ably stable, and all attempts to add this borane to a number
of unsaturated molecules at room temperature proved un-
successful.
Scheme 2. Synthesis of 4,4,5,5-tetraphenyl-1,3,2-dioxaborolane (3).
Catalysed Hydroborations
We therefore decided to examine the metal-catalysed hy-
droboration of 3 in the presence of the metal complexes
RhCl(PPh3)3, Rh(acac)(dppb), [Rh(cod)(dppb)]BF4, and
[Cp*IrCl2]2 [acac = acetylacetonato, cod = 1,5-cyclo-
octadiene, dppb = 1,4-bis(diphenylphosphanyl)butane] with
a number of alkenes. Although RhCl(PPh3)3 is frequently
used to catalyse hydroborations with HBcat and HBpin, all
efforts to use this complex to facilitate the addition of
HBBzpin to 4-vinylanisole (4-MeOC6H4CH=CH2) at room
temperature failed. Reactions with Rh(acac)(dppb) gave a
mixture of branched [4-MeOC6H4CH(BzBpin)CH3 (4),
20%] and linear [4-MeOC6H4CH2CH2(BzBpin) (5),
45%] hydroboration products, as well as a small amount
Figure 1. Perspective view of a molecule of 7 with atom labelling
scheme. Thermal ellipsoids are drawn at the 50% probability level,
and hydrogen atoms are omitted for clarity. Selected bond lengths
[Å] and angles [°]: B(1)–O(1) 1.361(3), B(1)–O(2) 1.371(3), B(1)–
C(1) 1.557(3), C(1)–C(2) 1.543(3), C(6)–F(1) 1.370(3); O(1)–B(1)–
O(2) 112.72(18), O(1)–B(1)–C(1) 122.57(19), O(2)–B(1)–C(1)
124.71(19), C(2)–C(1)–B(1) 112.47(19).
We have also investigated the hydroboration of a repre-
of the corresponding alkenyl boronate ester [4-MeO- sentative number of other substrates in the presence of
C6H4CH=CH(BzBpin) (6), 15%] and the hydrogenation [Cp*IrCl2]2, and the reactions proceeded selectively at room
product (4-MeOC6H4CH2CH3, 20% Scheme 3). Com- temperature to give the corresponding terminal products
pound 6 presumably arises from a dehydrogenative bo- (Figure 2). The new organoboronate ester products 4–10
rylation pathway, commonly observed as a competing reac- are air- and chromatography-stable and could easily be
tion in catalysed hydroborations. While reactions using transformed into the corresponding alcohols upon oxidat-
[Rh(cod)(dppb)]BF4 also gave a mixture of products, the ive workup. Reactions of 1-octene and norbornylene with 3
linear organoboronate compound 5 was the sole product could be catalysed by both Rh(acac)(dppb) and [Cp*IrCl2]2
(100% conversion) generated in reactions using catalytic to give the linear product exclusively, although those using
amounts (5 mol-%) of [Cp*IrCl2]2.[7] Related allenes con- the iridium catalyst were complete within hours, while reac-
Scheme 3. Catalysed hydroboration of 4-vinylanisole with 3.
780
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 779–785

Bulky Borane for Transition Metal Catalysed Hydroboration of Alkenes
tions with the rhodium catalyst took considerably longer the metal complexes used in the catalytic runs. Although no
(days in the case of norbornylene). Interestingly, the iridium reaction was observed with Rh(acac)(dppb) at room tem-
complex also catalysed the selective hydroboration of 5- perature in THF, addition of 3 to [Cp*IrCl2]2 resulted in a
hexen-2-one to give the organoboronate ester compound complex mixture of products, as several hydride peaks were
10. The sluggish nature of 3 towards uncatalysed reactions, observed in the 1H NMR spectra. Similar product distribu-
even in the presence of the ketone functionality in 5-hexen- tions have been reported previously for reactions with this
2-one, allowed for a selective catalysed addition at the al- iridium complex and HBcat.[7a] Reaction of 3 with
kene group. Similar selectivities have been reported in an RhCl(PPh3)3, however, gave the boryl(hydrido) complex
elegant study by Kabalka et al. for reactions using Rh(H)Cl(BzBpin)(PPh3)2 (11) as the sole rhodium-contain-
HBCy2.[11]
ing product. Interestingly, reactions of RhCl(PPh3)3, with
HBcat and HBpin are known to give several (phosphane)-
rhodium complexes, including the corresponding boryl-
rhodium species.[2,14] The synthesis and reactivity of boryl
transition metal complexes has been the subject of intense
investigations.[12,13]
Spectroscopic and analytical data for 11 are consistent
with its formulation. For instance, a doublet at δ =
40.4 ppm with JP–Rh = 124 Hz in the 31P{1H} NMR spec-
trum and a broad singlet at δ = 32 ppm in the 11B NMR
spectrum are similar to those observed in other borylrho-
1
dium species.[14] The H NMR spectrum shows a doublet
2
of triplets at δ = –14.34 ppm (1JH–Rh = 28.8 Hz, JH–P
=
Figure 2. Novel organoboronates generated from the catalysed hy-
droboration of alkenes with 3.
14.8 Hz) which suggests that the phosphane ligands are
magnetically equivalent. The structure of complex 11 has
been confirmed by a single-crystal X-ray diffraction study,
the results of which are shown in Figure 3. The molecular
structure of 11 consists of a 16-electron distorted square-
Reactions with Metal Complexes
In order to gain further insight into the reactivity of 3,
we investigated the stoichiometric addition of HBBzpin to
Figure 3. Perspective view of a molecule of 11 with atom labelling scheme. Thermal ellipsoids are drawn at the 50% probability level
with hydrogen atoms and a molecule of THF omitted for clarity. Selected bond lengths [Å] and angles [°]: Rh–B 1.963(4), Rh–P(2)
2.3227(13), Rh–P(1) 2.3236(13), Rh–Cl 2.4228(14), B–O(1) 1.385(4), B–O(2) 1.390(4); B–Rh–P(2) 95.74(12), B–Rh–P(1) 95.25(12), P(2)–
Rh–P(1) 163.49(3), B–Rh–Cl 108.66(10), P(2)–Rh–Cl 92.52(4), P(1)–Rh–Cl 95.60(4), O(1)–B–O(2) 111.3(3), O(1)–B–Rh 124.0(3), O(2)–
B–Rh 124.4(3).
Eur. J. Inorg. Chem. 2008, 779–785
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A. Bell, S. A. Westcott et al.
FULL PAPER
pyramidal[15] RhIII centre with trans-phosphane ligands and
the BzBpin group occupying the apical site. The relatively
small P(2)–Rh–P(1) angle of 163.49(3)° presumably arises
from steric crowding of the bulky BzBpin group. The Rh–
B distance of 1.963(4) Å is well within the range observed
for analogous Rh(Bcat) and -(Bpin) complexes.[14] Al-
though the hydrido ligand was not located in the X-ray
study, its presence is clearly indicated by the B–Rh–Cl angle
of 108.66(10)°, and from solution NMR spectroscopic data.
General Procedure for the Hydroboration of 4-Vinylanisole in the
Presence of Rh(acac)(dppb) as a Catalyst: In a typical reaction,
HBBzpin (50 mg, 0.13 mmol) in C6D6 (0.5 mL) was added to a
C6D6 solution (0.5 mL) of 4-vinylanisole (18 mg, 0.13 mmol) and
Rh(acac)(dppb) (1 mg, 0.0015 mmol). The reaction was allowed to
proceed for 18 h, at which point NMR spectroscopic data were
collected. Selected NMR spectroscopic data for 4-Me-
1
OC6H4CH(BBzpin)CH3 (4): H NMR: δ = 2.95 [q, J = 7.4 Hz, 1
H, CH(BBzpin)], 1.67 (d,
OC6H4CH=CH(BBzpin) (6): H NMR: δ = 8.02 (d, J = 18.5 Hz,
1 H, CH=CH), 6.61 (d, J = 18.5 Hz, 1 H, CH=CH) ppm.
J = 7.4 Hz, 3 H, CH3); 4-Me-
1
4-MeOC6H4CH2CH2(BBzpin) (5): A toluene solution (5 mL) of
HBBzpin (500 mg, 1.30 mmol) was added to a stirred toluene solu-
tion (1 mL) of 4-vinylanisole (187 mg, 1.40 mmol) and [Cp*IrCl2]2
(11 mg, 0.014 mmol). The reaction was allowed to proceed for 18 h
at which point the solvent was removed under vacuum to afford an
orange oil. The oil was dissolved in hot hexane (10 mL) and passed
through a small plug of silica. The volume of the solution was
decreased to 5 mL under vacuum, and the solution was then stored
Conclusions
4,4,5,5-Tetraphenyl-1,3,2-dioxaborolane (HBBzpin, 3)
has been prepared in high yield by the addition of
H3B·SMe2 to benzopinacol. HBBzpin is a relatively stable
solid that reacts with a variety of alkenes under catalytic
conditions to give the corresponding organoboronate esters.
The resulting products are stable to air and chromatography at –30 °C to afford an off-white precipitate after several days. The
solid was collected by suction filtration. Yield: 480 mg (72%); m.p.
131–133 °C. 1H NMR (in C6D6): δ = 7.31 (d, J = 8.2 Hz, 8 H, Ar),
7.16 (d, J = 8.4 Hz, 2 H, Ar), 6.94–6.85 (ov. m, 12 H, Ar), 6.79 (d,
J = 8.4 Hz, 2 H, Ar), 3.35 (s, 3 H, OCH3), 3.00 (t, J = 7.7 Hz, 2
H, CH2), 1.66 (t, J = 7.7 Hz, 2 H, CH2) ppm. 11B NMR (in C6D6):
δ = 35 (br.) ppm. 13C{1H} NMR (in C6D6): δ = 158.2, 143.1, 136.0,
129.3, 128.9, 127.3, 127.0, 113.9, 96.2, 54.6, 29.2, 13.4 (br., CB)
and can be readily converted into the alcohols upon oxidat-
ive workup. Addition of HBBzpin to RhCl(PPh3)3 gave
Rh(H)Cl(BzBpin)(PPh3)2 as the only new rhodium-contain-
ing product. We are in the process of examining the reactiv-
ity of this novel borylrhodium species as well as expanding
the scope of hydroborations using HBBzpin and will report
our findings in due course.
ppm. IR (nujol): ν = 2953, 2918, 2856, 1608, 1510, 1446, 1377,
˜
1344, 1306, 1242, 1176, 1034, 1011, 966, 881, 835, 808, 764, 750,
698, 658 cm–1. C35H31BO3 (510.47): calcd. C 82.35, H 6.13; found
C 82.30, H 5.77. CI-MS: m/z (%) = 510 (5) [M], 377 (12).
Experimental Section
4-F-C6H4CH2CH2(BBzpin) (7): A toluene solution (5 mL) of
HBBzpin (500 mg, 1.30 mmol) was added to a stirred toluene solu-
tion (1 mL) of 4-fluorostyrene (171 mg, 1.40 mmol) and
[Cp*IrCl2]2 (11 mg, 0.014 mmol). The reaction was allowed to pro-
ceed for 18 h at which point solvent was removed under vacuum
to afford an orange oil. The oil was dissolved in hot hexane
(10 mL) and passed through a small plug of silica. The volume of
the solution was decreased to 5 mL under vacuum, and the solution
was then stored at –30 °C to afford a white precipitate after several
days. The solid was collected by suction filtration. Yield: 510 mg
(79%); m.p. 124–125 °C. 1H NMR (in C6D6): δ = 7.30 (d, J =
8.2 Hz, 8 H, Ar), 6.97–6.76 (ov. m, 16 H, Ar), 2.86 (t, J = 7.7 Hz,
2 H, CH2), 1.54 (t, J = 7.7 Hz, 2 H, CH2) ppm. 11B NMR (in
C6D6): δ = 35 (br.) ppm. 13C{1H} NMR (in C6D6): δ = 161.7 (d,
General: Reagents and solvents were purchased from Aldrich
Chemicals and used as received. NMR spectra were recorded with
a JEOL JNM-GSX270 FT NMR (1H 270 MHz; 11B 87 MHz; 13C
68 MHz; 19F 254 MHz; 31P 109 MHz) spectrometer. Chemical
shifts (δ) are reported in ppm [relative to residual solvent peaks (1H
and 13C) or external BF3·OEt2 (11B), CF3CO2H (19F), and H3PO4
(31P)] and coupling constants (J) in Hz. Multiplicities are reported
as singlet (s), doublet (d), triplet (t), quartet (q), quintet (quint),
multiplet (m), broad (br.), and overlapping (ov.). Infrared spectra
were obtained using a Mattson Genesis II FT-IR spectrometer.
GC-MS analyses were conducted using a Varian Saturn 2000 MS,
coupled to a CP-3800 GC. The GC was equipped with the 1177
injection port with a CP-8410 liquid autoinjector connected to
an SPB-1 (Supelco) fused-silica column (30 mϫ0.25 mm
i.d.ϫ0.25 µm) attached to a 50 cm transfer line. Melting points
were determined using a Mel-Temp apparatus and are uncorrected.
Elemental analyses were performed by Guelph Chemical Laborato-
ries (Guelph, ON). Reactions were performed under dinitrogen.
JCF = 247 Hz, C-F), 143.0, 139.5 (d, JCF = 2 Hz), 129.8 (d, JCF
=
8 Hz), 128.8, 127.3, 127.1, 115.0 (d, JCF = 21 Hz), 96.2, 29.1, 13.2
(br., CB) ppm. 19F{1H} NMR (in C6D6): δ = –118.2 ppm. IR (nu-
jol): ν = 2931, 2856, 1597, 1446, 1377, 1340, 1242, 1219, 1176,
˜
1088, 1012, 964, 883, 841, 816, 750, 696, 660, 615, 542, 480 cm–1.
C34H28BFO2 (498.43): calcd. C 81.93, H 5.67; found C 81.96, H
5.55. CI-MS: m/z (%) = 500 (3) [M]+, 422 (19).
4,4,5,5-Tetraphenyl-1,3,2-dioxaborolane (HBBzpin) (3): Benzopina-
col (4.00 g, 10.91 mmol) was added as a solid to a stirred solution
of BH3·SMe2 (6.0 mL of a 2.0  toluene solution) over a period of
30 min. The mixture was heated to reflux for 12 h at which point
the solvent was removed under vacuum. Upon washing with hex-
ane (3ϫ5 mL), HBBzpin was collected as a white solid by suction
1-OctylBBzpin (8): A toluene (5 mL) solution of HBBzpin (500 mg,
1.30 mmol) was added to a stirred toluene solution (1 mL) of 1-
octene (156 mg, 1.40 mmol) and [Cp*IrCl2]2 (11 mg, 0.014 mmol).
The reaction was allowed to proceed for 18 h at which point solvent
was removed under vacuum to afford an orange oil. The oil was
dissolved in hexane (5 mL) and passed through a small plug of
silica. The solvent was then removed under vacuum to afford an
1
filtration. Yield: 3.50 g (85%); m.p. 132–135 °C. H NMR (C6D6):
δ = 7.33–7.29 (m, 8 H, Ar), 6.89–6.80 (ov. m, 12 H, Ar), 4.95 (br.
s, 1 H, HB) ppm. 11B NMR (C6D6): δ = 27 (br.) ppm. 13C{1H}
NMR (C6D6): δ = 142.5, 128.8, 127.4, 127.1, 96.4 ppm. IR (N2,
1
nujol): ν = 3059, 2960, 2899, 2870, 2602, 1493, 1446, 1379, 1344,
orange oil. Yield: 460 mg (72%). H NMR (in C6D6): δ = 7.41 (d,
˜
1215, 1190, 1176, 953, 881, 746, 696, 627 cm–1. C26H21BO2 J = 8.2 Hz, 8 H, Ar), 6.99–6.86 (ov. m, 12 H, Ar), 1.80 (quint, J =
(376.28): calcd. C 82.99, H 5.64; found C 82.62, H 6.00.
782
7.9 Hz, 2 H, CH2), 1.47–1.26 (ov. m, 12 H), 0.89 (t, J = 6.9 Hz, 3
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Bulky Borane for Transition Metal Catalysed Hydroboration of Alkenes
H, CH3) ppm. 11B NMR (in C6D6): δ = 34 (br.) ppm. 13C{1H}
NMR (in C6D6): δ = 143.3, 128.9, 127.4, 127.0, 96.0, 32.7, 32.0,
with Paratone-N oil, mounted using a glass fibre and frozen in the
cold stream of the goniometer. A hemisphere of data was collected
with a Bruker AXS P4/SMART 1000 diffractometer using ω- and
θ-scans with a scan width of 0.3° and exposure times of 10 (7)
29.6, 29.5, 24.3, 22.8, 14.1, 11.5 (br., CB) ppm. IR (nujol): ν =
˜
3059, 3027, 2927, 2856, 1601, 1493, 1446, 1379, 1327, 1225, 1176,
1080, 1036, 1003, 978, 887, 752, 700, 629 cm–1. C34H37BO2 and 40 s (11). The detector distances were 5 cm. The data were
(488.52): calcd. C 83.59, H 7.65; found C 83.25, H 7.94. CI-MS:
reduced[16a] and corrected for absorption.[16b] The structures were
solved by direct methods (7) or Patterson methods (11) and refined
by full-matrix least squares on F2.[16c] The THF molecule in 11
was disordered over two positions, and the site occupancies were
determined as 0.56 [O(63)–C(67)] and 0.44 [O(63Ј)-C(67Ј)] and
fixed in subsequent refinement cycles. All non-hydrogen atoms were
refined using anisotropic displacement parameters. Hydrogen
atoms were found in Fourier difference maps and refined using
isotropic displacement parameters. THF hydrogen atoms were in-
cluded in calculated positions and refined using a riding model.
CCDC-659156 and -659157 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
m/z (%) = 489 (14) [M]+, 412 (87).
NorbornylBBzpin (9): A toluene solution (5 mL) of HBBzpin
(1.20 g, 3.19 mmol) was added to a stirred toluene solution (1 mL)
of norbornylene (300 mg, 3.19 mmol) and [Cp*IrCl2]2 (25 mg,
0.031 mmol). The reaction was allowed to proceed for 18 h at which
point the solvent was removed under vacuum to afford an orange
oil. The oil was dissolved in hexane (10 mL) and passed through a
small plug of silica. The volume of the solution was decreased to
5 mL under vacuum, and the solution was then stored at –30 °C to
afford a white precipitate after several days. The solid was collected
by suction filtration. Yield: 1.15 g (77%); m.p. 116–117 °C. 1H
NMR (in C6D6): δ = 7.39 (d, J = 8.2 Hz, 8 H, Ar), 6.95–6.85 (ov.
m, 12 H, Ar), 2.78 (br. s, 1 H), 2.31 (br. s, 1 H), 2.13 (m, 1 H),
1.71–1.20 (ov. m, 8 H) ppm. 11B NMR (in C6D6): δ = 34 (br.) ppm.
13C{1H} NMR (in C6D6): δ = 143.3, 128.8, 127.4, 127.0, 96.1, 39.2,
Table 1. Crystallographic data collection parameters for 7 and 11.
7
11·THF
38.6, 37.0, 32.7, 32.6, 29.4, 25.8 (br., CB) ppm. IR (nujol): ν =
˜
2964, 2908, 2861, 1599, 1493, 1460, 1446, 1410, 1375, 1311, 1227,
1173, 1016, 976, 885, 843, 748, 700, 658, 633, 607 cm–1. C33H31BO2
(470.45): calcd. C 84.25, H 6.66; found C 83.97, H 6.82. CI-MS:
m/z (%) = 470 (10) [M], 393 (72).
Empirical formula
Formula mass
Crystal dimensions [mm]
Crystal system
Space group
Z
C34H28BFO2
498.37
0.40ϫ0.20ϫ0.15 0.23ϫ0.15ϫ0.05
monoclinic
P21/n
4
C66H59BClO3P2Rh
1111.24
triclinic
¯
P1
CH3C(O)(CH2)4BBzpin (10):
A toluene solution (5 mL) of
2
HBBzpin (760 mg, 2.04 mmol) was added to a stirred toluene solu-
tion (1 mL) of 5-hexen-2-one (200 mg, 2.04 mmol) and
[Cp*IrCl2]2 (16 mg, 0.020 mmol). The reaction was allowed to pro-
ceed for 18 h at which point the reaction mixture was passed
through a small plug of silica. Removal of the solvent under vac-
uum afforded a colourless oil which was triturated with MeOH
(3ϫ2 mL), and the resulting white solid was collected by suction
filtration. Yield: 0.75 g (77%); m.p. 118–120 °C. 1H NMR (in
C6D6): δ = 7.41–7.37 (m, 8 H, Ar), 6.96–6.83 (ov. m, 12 H, Ar),
1.94 (t, J = 7.2 Hz, 2 H, CH2), 1.66–1.61 (ov. m, 4 H, CH2), 1.61
(s, 3 H, CH3), 1.26 (t, J = 7.2 Hz, 2 H, CH2) ppm. 11B NMR (in
C6D6): δ = 33 (br.) ppm. 13C{1H} NMR (in C6D6): δ = 206.0
[C(O)], 143.2, 128.8, 127.4, 127.1, 96.1, 43.0, 29.0, 26.5, 23.8, 11.3
a [Å]
b [Å]
c [Å]
α [°]
β [°]
γ [°]
11.714(3)
19.266(5)
12.181(3)
90
105.319(3)
90
2651.4(11)
1.249
173(1)
Mo-Kα (λ = 0.71073 Å)
0.080
18167
5905
455
10.483(6)
12.899(7)
22.037(12)
105.452(8)
91.188(8)
103.838(7)
2777(3)
1.329
Volume [Å3]
Dcalcd. [mg m–3]
T [K]
173(1)
Radiation
µ [mm–1]
0.460
18981
11967
916
0.96–27.50
1.040
0.0429
0.1165
0.821/–0.528
Total reflections collected
Total unique reflections
No. of variables
θ [°]
(br., CB) ppm. IR (nujol): ν = 3057, 2943, 2877, 1716 (C–O), 1597,
˜
2.03–27.50
1.062
0.0439
0.1164
1493, 1446, 1381, 1321, 1263, 1173, 1034, 980, 885, 756, 700, 660,
633 cm–1. C32H31BO3 (474.44): calcd. C 81.00, H 6.60; found C
80.69, H 6.92. CI-MS: m/z (%) = 474 (12) [M].
GoF on F2
R1[a] [IϾ2σ(I)]
wR2[b] (all data)
Largest diff peak/hole [eÅ–3] 0.185/–0.241
Rh(H)Cl(PPh3)2(BBzpin) (11): A THF solution (2 mL) of HBBzpin
(162 mg, 0.43 mmol) was added to a stirred THF suspension
(5 mL) of RhCl(PPh3)3 (400 mg, 0.43 mmol). The reaction was al-
lowed to proceed for 18 h at which point a white precipitate was
collected by suction filtration. Yield: 225 mg (50%); m.p. 144–
a] R1 = Σ||Fo| – |Fc||/Σ|Fo|. [b] wR2 = {Σ[w(Fo – Fc ) ]/Σ[Fo4]}1/2
,
)
2
2 2
[
where w = 1/[σ2(Fo2) + (0.0307·P)2 + (0.7756·P)] (7), w = 1/[σ2(Fo
2
+ (0.0515·P)2 + (0.7756·P)] (11), where P = [max(Fo2,0) + 2·Fc ]/3.
2
Supporting Information (see footnote on the first page of this arti-
cle): Crystal data for complexes 7 and 11 and selected NMR spec-
troscopic data for complexes 3–11.
1
146 °C (dec.). H NMR (in CDCl3): δ = 7.64 (m, 12 H, Ar), 7.31
(t, J = 7.4 Hz, 8 H, Ar), 7.18 (t, J = 7.4 Hz, 12 H, Ar), 6.97 (t, J
= 7.4 Hz, 4 H, Ar), 6.86 (t, J = 7.4 Hz, 8 H, Ar), 6.73 (d, J =
1
2
7.4 Hz, 6 H, Ar), –14.34 (dt, JHRh = 28.8, JHP = 14.8 Hz, 1 H,
RhH) ppm. 11B NMR (in CDCl3): δ = 32 (br.) ppm. 13C{1H} NMR
(in CDCl3): δ = 143.0, 134.7 (t, JCP = 6 Hz), 132.7 (t, JCP = 23 Hz),
129.9, 129.0, 128.1 (t, JCP = 5 Hz), 126.9, 126.3, 96.2 ppm. 31P{1H}
NMR (in CDCl3): δ = 40.4 (d, JPRh = 124 Hz) ppm. IR (N2, nujol):
Acknowledgments
Thanks are gratefully extended to the Canada Research Chairs Pro-
gramme, Canadian Foundation for Innovation-Atlantic Innovation
Fund, Natural Science and Engineering Research Council of
Canada, Promerus LLC, and Mount Allison University for finan-
cial support and anonymous reviewers for helpful comments.
ν = 3037, 2897, 2854, 1599, 1479, 1464, 1433, 1379, 1215, 1149,
˜
1095, 1026, 999, 958, 908, 883, 789, 748, 692, 634 cm–1.
C62H51BClO2P2Rh (1039.34): calcd. C 71.64, H 4.96; found C
71.58, H 5.03.
X-ray Crystallography: Crystals of 7 and 11 (Table 1) were grown
from saturated THF solutions at 5 °C. Single crystals were coated
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Received: October 2, 2007
Published Online: December 18, 2007
Eur. J. Inorg. Chem. 2008, 779–785
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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