Investigation of the reactivity of hydroxyborate salts with group IV metal complexes: Synthesis and structural characterization of the zirconium and hafnium ionic complexes [PPN]+[Cp2MMe(OB(C 6F5)3)]-

Article abstract of DOI:10.1021/om2002798

The syntheses of some novel fluorinated and nonfluorinated hydroxyborate salts, [Q]⁺[HOB(C₆F₅)₃]^- and [Q]⁺[HOBPh₃]^- ([Q]⁺ = aprotic cation), are reported. The reactivities of both salts with group IV metal complexes were compared. The reaction of [PPN]⁺[HOB(C ₆F₅)₃]^- ([PPN]⁺ = bis(triphenylphosphoranylidene)ammonium) with Cp₂ZrMe₂ and Cp₂HfMe₂ resulted in the formation of the ionic complexes [PPN]⁺[Cp₂ZrMe(OB(C₆F₅) ₃)]^- and [PPN]⁺[Cp₂HfMe(OB(C ₆F₅)₃)]^- in high yields. These complexes were fully characterized, and the covalent characteristics of the M-O and B-O bonds were established by X-ray crystallographic structural determination.

Full text of DOI:10.1021/om2002798

ARTICLE
pubs.acs.org/Organometallics
Investigation of the Reactivity of Hydroxyborate Salts with Group IV
Metal Complexes: Synthesis and Structural Characterization of the
Zirconium and Hafnium Ionic Complexes [PPN]+[Cp2MMe(OB(C6F5)3)]ꢀ
Vinciane Kelsen,† Christophe Vallꢀee,*,† Erwann Jeanneau,‡ Christine Bibal,§ Catherine C. Santini,*,§
Yves Chauvin,§ and Hꢀelꢁene Olivier-Bourbigou†
†
ꢀ
IFP Energies Nouvelles, Rond-point de L’Echangeur de Solaize, BP 3, 69360, Solaize, France
‡Centre de Diffractomꢀetrie Henri Longchambon, Universitꢀe de Lyon, 43 Boulevard du 11 Novembre 1918,
69622 Villeurbanne Cedex, France
§Universitꢀe de Lyon, ICL, C2P2, UMR 5265 CNRS-ESCPE Lyon-Universitꢀe Lyon1, 43 Boulevard du 11 Novembre 1918,
69622 Villeurbanne Cedex, France
S Supporting Information
b
ABSTRACT: The syntheses of some novel fluorinated and
nonfluorinated hydroxyborate salts, [Q]+[HOB(C6F5)3]ꢀ and
[Q]+[HOBPh3]ꢀ ([Q]+ = aprotic cation), are reported. The
reactivities of both salts with group IV metal complexes were
compared. The reaction of [PPN]+[HOB(C6F5)3]ꢀ ([PPN]+ =
bis(triphenylphosphoranylidene)ammonium) with Cp2ZrMe2
and Cp2HfMe2 resulted in the formation of the ionic complexes
[PPN]+[Cp2ZrMe(OB(C6F5)3)]ꢀ and [PPN]+[Cp2HfMe(OB-
(C6F5)3)]ꢀ in high yields. These complexes were fully char-
acterized, and the covalent characteristics of the MꢀO and
BꢀO bonds were established by X-ray crystallographic struc-
tural determination.
’ INTRODUCTION
anions predominantly exist as the counterions of organometallic
complexes, such as [LnM]+[HOB(C6F5)3]ꢀ (where M = Cr, Fe,
Co,11 Ru,12 Mo,13 Ni,14 Pt,15,16 Pd,17 Ti,18 V,19 Zn20). These
complexes generally are the result of a protonolysis reaction by
the protic functional group of the associated cation (Scheme 1).
Direct reactions of the borate hydroxyl group that yield an
MꢀOꢀB core are seldom observed. Moreover, the nature of the
MꢀO and OꢀB bonds generally remains ill-defined. For example,
the aluminum derivative LAlOB(C6F5)3, in which L represents an
anionic β-diketiminato ligand, is formed by reaction of the borinic
The catalytic properties of organometallic complexes are
controlled by two factors: the identity of the metal center and
the nature of the coordinated ligands. Modifying the identity or
structure of the ligands coordinated to the metal center strongly
influences the rate of the catalyzed reaction and the selectivity
toward certain products.1 Thus, the search for new ligand
frameworks with unique electronic and steric properties remains
important. Boroxide ligands [OB(Mes)2]ꢀ (where Mes =
mesityl) have been described by several groups, and their
reactivity has been demonstrated with a number of different
metals.2ꢀ8 The π-accepting properties of these ligands, which are
facilitated by the presence of an empty p-orbital on the central
boron atom, are of interest for the development of catalyst
complexes. Such ligands are able to accept electron density from
the lone pair electrons of oxygen atoms, modifying the electronic
environment of the metal center. The reaction of the borinic acid
(Mes)2BOH with group IV metal complexes was recently
described, and these reactions were shown to produce boroxide
complexes, such as MCp2{OB(Mes)2}Cl (where M = Ti, Zr),
which displayed an MꢀOꢀB core.9,10
acid adduct H2O B(C6F5)3 (which is similar to [H]+[HOB-
3
(C6F5)3]ꢀ) with LAlMe2. The electronic characteristics of the
AlꢀO bond of LAlOB(C6F5)3 remain the subject of debate.21
X-ray diffraction data of this complex suggest that there are four
possible resonance structures that exhibit delocalization of a negative
charge on the aluminum, oxygen, and boron atoms (Scheme 2).
Furthermore, the reaction of H2O B(C6F5)3 with TaCp*R4
3
complexes was found to yield the oxo complex Cp*R2-
TadO B(C6F5)3, in which the tantalumꢀoxygen double
3 3 3
bond is datively coordinated to the boron atom.22 Finally,
Very few examples of boron-containing ligands have been
reported to date. In organometallic chemistry, hydroxyborate
Received: March 29, 2011
Published: July 28, 2011
r
2011 American Chemical Society
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Organometallics
ARTICLE
Scheme 1. Protonolysis of an MꢀX Bond by the Protic
Scheme 3. Synthesis of Hydroxyborate Salts
Functional Group of the [NuH]+ Cation
Scheme 2. Four Proposed Resonance Structures of the
AlꢀOꢀB Complex Frameworka
[BMIM]+, 1-butyl-2,3-dimethylimidazolium [BMMIM]+, 1-
ethyl-3-methylimidazolium [EMIM]+, 1,3-dibutylimidazolium
[BBIM]+, N,N-butylmethylpyrrolidinium [BMPy]+, tetrabutyl-
phosphonium [Bu4P]+, and tetraphenylphosphonium [Ph4P]+,
has been described previously.24 Following a similar metho-
dology, [PPN]+[Cl]ꢀ was added to a solution of tris(penta-
fluorophenyl)borane in methylene chloride to yield the chlor-
oborate salt [PPN]+[ClB(C6F5)3]ꢀ. The product of this reaction
was allowed to react with anhydrous LiOH without further purifi-
cation, affording the desired hydroxyborate species [PPN]+-
[HOB(C6F5)3]ꢀ (1), in excellent overall yield (95%). Colorless
crystals suitable for X-ray diffraction analysis were grown by the
slow diffusion of n-pentane into a concentrated solution of 1 in
methylene chloride.
This methodology was extended to the synthesis of the non-
fluorinated salts [Q]+[HOBPh3]ꢀ, in which [Q]+ = [BMMIM]+
(4) and [PPN]+ (5), from triphenylborane. Chloroborate salts
[BMMIM]+[ClBPh3]ꢀ (2) and [PPN]+[ClBPh3]ꢀ (3) were
obtained by the addition of their corresponding salts [Q]+[Cl]ꢀ
to BPh3 in methylene chloride. Precipitation of these salts in
toluene produced white solids. 11B NMR spectra of the com-
pounds in CD2Cl2 exhibited broad peaks at 26.2 ppm for 2 and
19.4 ppm for 3. These boron resonances were surprisingly shifted
downfield when compared with their fluorinated analogues
[Q]+[ClB(C6F5)3]ꢀ (around ꢀ7 ppm), but these resonances
were not shifted as far downfield as that observed in the trico-
ordinated boron compound Ph2BCl (62.8 ppm).26
a L = β-diketiminato ligand.
it has been shown that Cp*2ZrOB(C6F5)3 results from a stepwise
reaction between [HNEt3]+[HOB(C6F5)3]ꢀ and Cp*2ZrMe2.
The nature of the ZrꢀOꢀB bonds of this complex has never
been discussed.23
The chemistry of hydroxyborate ligands deserves further
attention because this class of ligands possesses a variety of
potential electronic and steric properties. Hydroxyborate ligands
experience greater steric hindrance than boroxide ligands be-
cause of the tetracoordinate nature of the boron. The induced
anionic charge on the boron atom could be offset by the presence
of electron-withdrawing fluorine atoms that could act as “elec-
tron pumps”. Substitution of pentafluorophenyl rings by other
alkyl or aryl groups could yield an effective method for modifying
the electronic and steric properties of hydroxyborate ligands.
A limiting factor impeding the development of their chemistry
is related to their synthesis, i.e., the reaction of an amine with the
water adduct H2O B(C6F5)3 to produce [HNEt3]+[HOB-
3
(C6F5)3]ꢀ. In this salt, both NꢀH and OꢀH protons could
induce the cleavage of the MꢀC bond of alkyl complexes, as is
observed with the organometallic compound Cp*2ZrMe2.23
Initially, our aim was to develop a versatile, one-pot synthetic
method for preparing [Q]+[HOB(C6F5)3]ꢀ salts, in which [Q]+
represents an aprotic cation.24,25 Indeed, preliminary studies of
their reactivity with Cp2ZrMe2 demonstrated that protonolysis
of the ZrꢀMe bond and formation of the ionic complex
[Q]+[Cp2ZrMe(OB(C6F5)3)]ꢀ were taking place.24 However,
in the absence of X-ray crystallographic structural data for the
complex, the order of the ZrꢀO bond remained unclear.
In this paper, the syntheses of the fluorinated salt [PPN]+-
[HOB(C6F5)3]ꢀ ([PPN]+ = bis(triphenylphosphoranylidene)-
ammonium) and its nonfluorinated analogues, [BMMIM]+-
[HOBPh3]ꢀ ([BMMIM]+ = 1-butyl-2,3-dimethylimidazolium)
and [PPN]+[HOBPh3]ꢀ, are described. Spectroscopic features
of these complexes and their reactivity with Cp2ZrMe2 are
reported, and the properties of these hydroxyborate ligands are
compared. In addition, the synthesis of the ionic complex [Q]+-
[Cp2ZrMe(OB(C6F5)3)]ꢀ was significantly improved, and this
technique was applied to the synthesis of its hafnium analogue,
[PPN]+[Cp2HfMe(OB(C6F5)3)]ꢀ. These complexes were fully
characterized, and crystal structures of the complexes are also
reported and discussed.
In the second step of the synthesis, the chloroborate salts 2
and 3 were allowed to react with anhydrous LiOH. The products
of this reaction were the hydroxyborate salts [BMMIM]+-
[HOBPh3]ꢀ (4) and [PPN]+[HOBPh3]ꢀ (5), which were
recovered as a colorless viscous oil and a white powder, respec-
tively. 11B NMR spectra of these products revealed broadened
resonances around ꢀ0.80 ppm, similar to the chemical shift
observed in NMR spectra of the [HOBPh3]ꢀ anion, which
was associated with the cationic complex [(η6-Ar)(PCy3)-
RudPHMes*]+ (Ar = p-cymene, Mes* = 2,4,6-tri-tert-butylphe-
nyl, 1.43 ppm).27 The ꢀOH group appeared as a broad singlet at
0.70 ppm and at 0.49 ppm in the 1H NMR spectra of 4 and 5,
respectively. This hydroxyl functionality was shifted upfield
between 1 and 2 ppm as compared with the hydroxyl function-
alities in the fluorinated analogues [Q]+[HOB(C6F5)3]ꢀ. The
ꢀOH group in the nonfluorinated anion was observed to be less
acidic than those in the fluorinated analogues. This difference in
acidity may be explained by the strong electron-withdrawing
characteristics of the C6F5 aromatic rings. A second possible
explanation may involve the presence of intramolecular
F interactions in the fluorinated anion [HOB(C6F5)3]ꢀ
’ RESULTS AND DISCUSSION
The synthesis of the hydroxyborate salt [Q]+[HOB-
H
3 3 3
(vide infra), in which the F atoms donate electron density to the
proton. These electronic effects, notably because of the presence
(C6F5)3]ꢀ, in which [Q]+ = 1-butyl-3-methylimidazolium
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Organometallics
ARTICLE
of intramolecular H F interactions in the fluorinated anions,
tetramethylguanidino)benzene)). This BꢀO bond is longer than
that observed in the borinic acid (Mes)2BOH, which exhibits an
average BꢀO bond length of 1.368 Å.34 This difference is likely
due to the empty p-orbital of the tricoordinated boron atom of
borinic acid, which can accept lone pair electrons from the
oxygen atom. In the case of hydroxyborate anions, the boron
atom is not a π-electron acceptor.35 In compound 1, the hydroxyl
proton forms hydrogen bonds with two fluorine atoms located
on different C6F5 rings (H31ꢀF5: 2.279 Å, H31ꢀF6: 2.122 Å).
A similar phenomenon has previously been described in the
3 3 3
were also observable using IR spectroscopy. The IR spectra of the
[Q]+[HOB(C6F5)3]ꢀ and [Q]+[HOBPh3]ꢀ compounds exhib-
ited a difference of about 60 cmꢀ1 between the two different
ν(OH) bands; the ν(OH) absorption bands were located at 3620
and 3617 cmꢀ1 for 4 and 5, respectively. The corresponding
ν(OH) absorptions of the [Q]+[HOB(C6F5)3]ꢀ salts were ob-
served in the range 3680ꢀ3700 cmꢀ1
.
[PPN]+ cations are known to favor the formation of crystalline
solids. It has been proposed that this property may arise from
interactions between cations in the solid state.28 This property
was observed when the molecular structure of compound 1,
shown in Figure 1, was resolved.29 Compound 1 crystallizes in
the triclinic space group P1 and is monomeric, in contrast to
bis(pentafluorophenyl)borinic acid, which has been shown to be
a cyclic trimer in the solid state.30 The BꢀO and OꢀH bond
lengths were determined to be 1.475 and 0.799 Å, respectively.
The length of the BꢀO bond is in the range of BꢀO bonds in
tris(pentafluorophenyl)hydroxyborate that have been cited in
the literature (1.500 Å in [7-azaindolium]+[HOB(C6F5)3]ꢀ,31
1.470 Å in [N-isoquinolinium]+[HOB(C6F5)3]ꢀ,32 1.466 Å in
[btmgbH]+[HOB(C6F5)3]ꢀ33 (btmgb = 1,2-bis(N,N,N0,N0-
compound [7-azaindolium]+[HOB(C6F5)3]ꢀ.31 These H
F
3 3 3
interactions may be the cause of the monomeric character of the
anion [HOB(C6F5)3]ꢀ. Bond lengths between boron B(1) and
Cipso (C(1), C(7), and C(13)) in compound 1 are an average of
1.668 Å. The lengths of these bonds are longer than the BꢀCipso
bonds observed in bis(pentafluorophenyl)borinic acid (average
BꢀCipso bond length of 1.612 Å) because of an increase in steric
hindrance around the boron atom in the hydroxyborate anion
of 1.
The reactivity of hydroxyborate anionic ligands with the
metallocene complex Cp2ZrMe2 was also investigated. We first
focused on the uncommon anion [HOBPh3]ꢀ, whose reactivity
has never been reported to the best of our knowledge.
The addition of one equivalent of 4 to a solution containing
Cp2ZrMe2 resulted in the formation of a small amount of white
precipitate (Scheme 4). This solid was separated by filtration and
was identified as an inorganic zirconium species on the basis of its
elevated melting point, which was greater than 430 °C. 1H NMR
analysis of the filtrate suggested that formation of the expected
complex, [BMMIM]+[Cp2ZrMe(OBPh3)]ꢀ (6, 50% according
to 1H integration), of the borate salt [BMMIM]+[MeBPh3]ꢀ (7,
1
28% according to H integration), and also of the bimetallic
complex (Cp2ZrMe)2(μ-O) (8, 22% according to 1H in-
tegration) had occurred. Toluene was used to extract 8 from
the mixture of products. Attempts to separate compound 6 from
compound 7 failed, likely because of the similar physical proper-
ties of these two compounds.
Complex 6 was identified by NMR resonances observed at
ꢀ0.04 ppm in the 1H NMR and at 13.2 ppm in the 13C NMR,
assigned to δZr-Me. This carbon chemical shift is located further
upfield than that of the fluorinated analogue complex
[BMMIM]+[Cp2ZrMe(OB(C6F5)3)]ꢀ (17.5 ppm).24 A similar
difference in chemical shifts is observed between complexes
Cp2ZrMe(OPh)36 (δ(13C) CH3 = 22.4 ppm) and Cp2ZrMe-
(OC6F5)37 (δ(13C) CH3 = 27.2 ppm). The downfield shift of the
methyl carbon resonance of the fluorinated complexes is con-
sistent with the presence of fluorine atoms, which withdraw
electron density from the phenyl rings and make the metal more
electropositive through an inductive effect. Similar to the fluorin-
ated analogue complex [BMMIM]+[Cp2ZrMe(OB(C6F5)3)]ꢀ,
Figure 1. Molecular structure of [PPN]+[HOB(C6F5)3]ꢀ (1) with
thermal displacement ellipsoids drawn at the 30% probability level.
Selected bond lengths (Å) and angles (deg): B(1)ꢀO(1) 1.476 (3),
B(1)ꢀC(1) 1.677 (3), B(1)ꢀC(7) 1.672 (3), B(1)ꢀC(13) 1.656 (3),
O(1)ꢀH(31) 0.799 (2), H(31)ꢀF(5) 2.286 (2), H(31)ꢀF(6) 2.125
(2), N(1)ꢀP(1) 1.579 (2), N(1)ꢀP(2) 1.581 (1), B(1)ꢀO(1)ꢀH(31)
106.2 (1) and P(1)ꢀN(1)ꢀP(2) 139.1 (1).
Scheme 4. Reaction of a Non-fluorinated Hydroxyborate Salt with Cp2ZrMe2
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Organometallics
ARTICLE
Scheme 5. Reaction of a Fluorinated Hydroxyborate Salt
with Cp2ZrMe2 and Cp2HfMe2
the protons of the cyclopentadienyl rings are detected at 5.75
ppm in the 1H spectrum, and the carbon atoms are detected at
109.4 ppm in the 13C NMR spectrum of the compound. The
boron resonance of the ꢀOBPh3 moiety in 6 is observed at 1.83
ppm in the 11B NMR spectrum, which is similar to the 11B NMR
chemical shift of the starting anion in 4 (ꢀ0.80 ppm).
Figure 2. Molecular structure of [PPN]+[Cp2ZrMe(OB(C6F5)3)]ꢀ
(9) with displacement ellipsoids drawn at the 30% probability level.
The unexpected anion [MeBPh3]ꢀ was identified by the
1
characteristic quadruplet peak located at 0.22 ppm in the H
NMR spectrum, which corresponds to its methyl group, and by
the resonance of its boron atom at ꢀ11.74 ppm in the 11B NMR
spectrum.38 Formation of this species may be the result of an
exchange reaction between a methyl ligand in the zirconium
complex and the hydroxyl group of the boron atom, resulting in
the formation of a [MeBPh3]ꢀ anion and Cp2Zr(Me)(OH). The
resulting complex, Cp2Zr(Me)(OH), could react further with
the starting complex, Cp2ZrMe2, to produce the dimeric complex
(Cp2ZrMe)2(μ-O) (8) and the inorganic zirconium species
during consecutive exchange reactions. In contrast, no traces of
[MeB(C6F5)3]ꢀ were detected in the reaction of fluorinated
[HOB(C6F5)3]ꢀ with Cp2ZrMe2.24 Two possible explanations
for the formation of [MeBPh3]ꢀ from the nonfluorinated ligand
are the lower acidity of the hydroxyl functional group of
[HOBPh3]ꢀ and the weakness of its BꢀO bond. According to
a previous report,39 the molecular structure of this anion
possessed a BꢀO bond length of 1.60 Å, remarkably longer than
that observed in [HOB(C6F5)3]ꢀ (1.475 Å).
Figure 3. Molecular structure of [PPN]+[Cp2HfMe(OB(C6F5)3)]ꢀ
(10) with displacement ellipsoids drawn at the 30% probability level.
completion. Slow diffusion of n-pentane into concentrated
solutions of 9 and 10 in methylene chloride produced colorless
and yellow crystals of the Zr and Hf species, respectively.
1
Compounds 9 and 10 were analyzed by H, 11B, 19F, and 13C
NMR spectroscopy, and their spectroscopic and structural
Reaction of [Q]+[HOB(C6F5)3]ꢀ with Cp2ZrMe2 allowed
isolation of the [Q]+[Cp2ZrMe(OB(C6F5)3)]ꢀ class of ionic
complexes. No side reaction leading to the formation of
[MeB(C6F5)3]ꢀ was observed.24 When [Q]+ was [BMIM]+,
[BMMIM]+, [EMIM]+, [BBIM]+, [BMPy]+, [Bu4P]+, or
[Ph4P]+, the ionic complexes were obtained as liquids, prevent-
ing X-ray characterization and confirmation of the exact nature of
their BꢀO and ZrꢀO bonds. In addition, the syntheses were
performed in toluene, producing a low yield (30ꢀ40%) of the
[Q]+[Cp2ZrMe(OB(C6F5)3)]ꢀ complexes.
To promote the crystallization of these ionic complexes,
[PPN]+ was used as the counterion, as it is known to promote
the crystallization of anions. In addition to this synthetic varia-
tion, the reaction was also carried out in methylene chloride
instead of toluene (Scheme 5). These modifications and the use
of a slight excess of Cp2ZrMe2 resulted in the isolation of
[PPN]+[Cp2ZrMe(OB(C6F5)3)]ꢀ (9) with a considerable in-
crease in the reaction yield (79%). The method developed here
was also extended to the synthesis of the hafnocene complex
[PPN]+[Cp2HfMe(OB(C6F5)3)]ꢀ (10). In the case of the
zirconocene Cp2ZrMe2, the reaction occurred at ꢀ25 °C within
2 h, whereas the reaction between 1 and Cp2HfMe2 was slower
and required 8 days of stirring at room temperature for
features were all found to be very similar.
Replacement of one of the methyl groups of the metallocene
compound Cp2MMe2 by the hydroxyborate ligand produced a
small downfield shift of the remaining methyl group by approxi-
mately 0.2 ppm in the 1H NMR spectra (ꢀ0.22 ppm for 9 and
ꢀ0.34 ppm for 10) when compared with the parent complexes of
the general formula Cp2MMe2. In addition, the 1H NMR
resonance of the Cp ligand is observed at approximately 5.70
ppm. In the 11B NMR spectra, the observed singlet is slightly
broadened as compared with the resonance of the hydroxyborate
anion. Only a small shift of the 11B NMR resonance peaks is
observed for both ionic metallocene complexes (ꢀ3.62 ppm for
9 and ꢀ3.06 ppm for 10). This negative 11B NMR chemical shift
is characteristic of the OB(C6F5)3ꢀ group with tetracoordination
of boron.40,41 The 19F NMR spectra exhibit the three predicted
sets of multiplets attributed to the ortho, meta, and para positions
of the aryl ring. The ortho-fluorine resonance was shifted slightly
upfield from ꢀ136 ppm to ꢀ133 ppm in the ionic metallocene
complexes. In the 13C NMR spectra of the complexes, the Cp
resonance remains largely unaffected (average shifts of 110 and
109 ppm for Cp2MMe2 and the grafted ionic complexes,
respectively), and the chemical shift of the Me resonance under-
goes a small downfield shift from 29.5 ppm to 17.5 ppm for the Zr
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Organometallics
ARTICLE
Table 1. Crystal Structure and Refinement Data for [PPN]+[HOB(C6F5)3]ꢀ (1), [PPN]+[Cp2ZrMe(OB(C6F5)3)]ꢀ (9), and
[PPN]+[Cp2HfMe(OB(C6F5)3)]ꢀ (10)
1
9
10
formula
C36H30NP2
C36H30NP2
C36H30NP2
3
3
3
C18HBF15O
1067.56
C29H13BF15ZrO
1303.01
C29H13BF15HfO
1390.28
fw
temperature (K)
cryst syst
space group
a (Å)
150
150
150
triclinic
triclinic
triclinic
P1
P1
P1
12.7244 (3)
14.0170 (4)
16.7119 (4)
67.3774 (9)
88.0710 (10)
64.5140 (10)
2452.33 (11)
2
12.4937 (3)
13.2762 (3)
18.9678 (4)
106.3210 (10)
100.3220 (10)
105.6740 (10)
2794.12 (11)
2
12.4775 (4)
13.2598 (5)
18.9597 (8)
106.314 (3)
100.432 (3)
105.730 (3)
2783.2 (2)
2
b (Å)
c (Å)
R (deg)
β (deg)
γ (deg)
V (Å3)
Z
Dcalc (Mg mꢀ3
abs coeff (mmꢀ1
)
1.446
1.549
1.659
)
0.19
0.35
2.03
θ range for data collection
no. of reflns collected
no. of indep reflns
0.4 to 27.9
11 718
0.4 to 27.9
25 025
3.39 to 29.55
70 499
11 718
13 340
14 119
reflns with I > 2σ(I)
7993
9638
12 171
no. of data/restrains/params
goodness of fit on F(x)
final R indices [I > 2σ(I)]
11 718/0/668
1.08(1)
13 340/0/775
1.12(1)
14 119/0/776
0.96(2)
R1 = 0.047,
wR2 = 0.050
R1 = 0.072,
wR2 = 0.089
0.37 and ꢀ0.28
R1 = 0.040,
wR2 = 0.040
R1 = 0.064,
wR2 = 0.068
0.45 and ꢀ0.50
R1 = 0.050,
wR2 = 0.120
R1 = 0.062,
wR2 = 0.12
2.31 and ꢀ2.52
R indices (all data)
largest diff peak and hole (e Åꢀ3
)
species and from 35.8 ppm to 20.3 ppm for the Hf species. These
values are within the range expected for neutral zirconium species,
such as Cp2Zr(Me)(OCMe2CH2CH2CHdCH2) (17.4 ppm for
Me and 110.4 ppm for Cp)42 and Cp2Zr(Me){O(C6H3)(CH3)-
CH2PPh2} (20.5 ppm for Me and 111.6 ppm for Cp).43
Table 2. Selected Bond Lengths (Å) and Angles (deg) for
[PPN]+[Cp2ZrMe(OB(C6F5)3)]ꢀ (9) and [PPN]+[Cp2HfMe-
(OB(C6F5)3)]ꢀ (10)
9
10
X-ray diffraction studies were performed on 9 and 10. Their
molecular structures are shown in Figures 2 and 3, respectively.
Crystallographic data for both compounds are summarized in
Table 1, and selected bond lengths and angles are shown in
Table 2. In the solid state, 9 and 10 are monomeric and crystallize
in the triclinic space group P1.
M(1)-O(1)
1.912 (2)
1.452 (3)
2.330 (2)
2.2579 (3)
2.2557 (2)
1.589 (2)
1.578 (2)
161.0 (2)
128.12 (1)
109.86 (5)
110.15 (5)
137.4 (1)
99.07 (8)
1.922 (3)
1.445 (6)
2.308 (5)
2.2350 (2)
2.2358 (2)
1.582 (4)
1.584 (4)
160.2 (3)
128.21 (1)
109.4 (1)
110.1 (1)
137.4 (3)
99.2 (2)
O(1)ꢀB(1)
M(1)-C(55)
M(1)ꢀCp1
M(1)ꢀCp2
P(1)ꢀN(1)
For complex 9, the ZrꢀO bond length of 1.912 Å is equal to
that observed in Cp*2ZrOB(C6F5)3.23 This bond length is also
similar to the ZrꢀO single bond described in the bimetallic
complex [(Cp2ZrMe)2(μ-O)]44 (1.948 Å) and greater than the
ZrdO bond length in the complex CpEt*2Zr(O)(NC5H5)
(CpEt* = η-C5Me4Et) (1.804 Å),45 suggesting that a ZrꢀO bond
order of 1 is present in compound 9. Furthermore, this ZrꢀO
bond is in the same range as that of ZrꢀOꢀB bonds described in
the neutral complex [Zr{OB(Mes)2}3(μ-OH)]2 (average ZrꢀO
bond length of 1.955 Å).9 The BꢀO bond length of 1.452 Å is in
the same range as that of the hydroxyborate anion (BꢀO bond
length of 1.475 Å) and is longer than that of [Zr{OB(Mes)2}3-
(μ-OH)]2 (average BꢀO bond length of 1.370 Å). All of these
structural data confirmed that zirconium is linked to the hydro-
xyborate anion via a simple covalent bond.
P(2)ꢀN(1)
M(1)ꢀO(1)ꢀB(1)
Cp1ꢀM(1)ꢀCp2
Cp1ꢀM(1)ꢀO
Cp2ꢀM(1)ꢀO
P(1)ꢀN(1)ꢀP(2)
C(55)ꢀM(1)ꢀO(1)
The ZrꢀMe and average ZrꢀCp bond lengths are 2.331 and
2.26 Å, respectively, which are slightly longer than those ob-
served in Cp2ZrMe2 (ZrꢀMe bond lengths of 2.280 and 2.273 Å;
average ZrꢀCp bond lengths of 2.23 Å). This increase in the
bond length is likely due to steric hindrance present in the
complex that is induced by the bulky hydroxyborate group. In 9,
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Organometallics
ARTICLE
no interactions are observed between the zirconium center and
the fluorine atoms in C6F5, in contrast to the results reported by
Siedle.23
C, H, N elemental analysis of samples was performed by the Service
Central d’Analyses of CNRS (Vernaison, France) and by the Mikroa-
nalytisches Labor Pascher (Remagen, Germany).
The structure of [PPN]+[Cp2HfMe(OB(C6F5)3)]ꢀ (10) is
very similar to that of the analogous zirconium complex 9.
The HfꢀO bond length of 1.927 Å is similar to that observed
in the homobimetallic complex (Cp2HfMe)2(μ-O) (average
HfꢀO bond length of 1.943 Å)46 and is in the same range as
those observed in LAl(Me)(μ-O)Hf(Me)Cp2 (L = CH(N(Ar)-
X-ray diffraction data were collected on a Nonius KappaCCD
diffractometer using Mo KR radiation (λ = 0.71073 Å). Data were
collected using ψ scans. The structures were solved by direct methods
using SIR97 software,48 and refinement was performed by a full-matrix
least-squares analysis on F or F2. No absorption correction was used.
Synthesis of [PPN]+[HOB(C6F5)3]ꢀ (1). A solution of [PPN]+-
[Cl]ꢀ (8.75 mmol, 5.025 g) in methylene chloride (25 mL) was added to
a solution of B(C6F5)3 (8.75 mmol, 4.480 g) in methylene chloride
(25 mL) at room temperature. After stirring overnight, the reaction
mixture was concentrated to one-half of the original volume and then
added via a cannula to a suspension of anhydrous LiOH (10.5 mmol,
251 mg) in 20 mL of methylene chloride. Five days of stirring at room
temperature were necessary to allow the reaction to proceed to
completion. The white LiCl precipitate was then filtered, and the solvent
was removed under vacuum to leave 1 as a white powder (8.31 mmol,
8.871 g).
(CMe))2, Ar = 2,6-iPr2C6H3)45 (1.919 Å) and Hf(OB(Mes)2)4
10
(1.902 and 1.916 Å). In 10, the BꢀO bond length (1.437 Å) is
10
slightly shorter than that observed in 1 (1.475 Å) but is longer
than that observed in the boroxide complex Hf(OB(Mes)2)4
(average BꢀO bond length of 1.388 Å). In addition, the HfꢀMe
bond length (2.312 Å) is similar to those observed in the
homobimetallic complex (Cp2HfMe)2(μ-O)46 (average HfꢀMe
47
bond length of 2.350 Å) and in LAl(Me)(μ-O)Hf(Me)Cp2
(2.281 Å).
The covalent character of the MꢀO and OꢀB bonds in ionic
complexes 9 and 10 was demonstrated via analysis of their
molecular structures. These data support the relevance of con-
sidering hydroxyborate anions to be a novel class of ligands for
organometallic complexes. In addition to the uniqueness of their
electronic and steric properties, the presence of an anionic charge
on the boron atom may present new opportunities for the
immobilization of complexes in ionic liquids.
1
Yield: 95%. H NMR (300 MHz, CD2Cl2) (δ, ppm): 1.67 (s, 1H,
OH); 7.40ꢀ7.55 (m, 24H, CH o-, m-Ph); 7.60ꢀ7.70 (m, 6H, CH p-Ph).
11B NMR (96.3 MHz, CD2Cl2) (δ, ppm): ꢀ4.10. 19F NMR (282 MHz,
CD2Cl2) (δ, ppm): ꢀ135.8 (d, 6F, 3JFF = 21.6 Hz, o-F); ꢀ163.0 (t, 3F,
3JFF = 19.6 Hz, p-F); ꢀ166.5 (m, 6F, m-F). 13C NMR (75 MHz,
CD2Cl2) (δ, ppm): 127.4 (dd, 1JPC = 107.9 Hz, P-C); 129.8 (m, m-CH);
132.5 (m, o-CH); 134.1 (t, 4JPC = 1.3 Hz, p-CH); 136.7 (dm, 1JCF = 247
Hz, C-F); 138.4 (dm, 1JCF = 242 Hz, C-F); 148.3 (dm, 1JCF = 240 Hz,
C-F). IR: ν(OH) = 3698 cmꢀ1. Anal. Calcd for C54H31BF15NOP2: C,
60.75; H, 2.93; N, 1.31. Found: C, 60.91; H, 2.95; N, 1.27. HRMS (ESI),
positive mode: [PPN]+ 538.1849, calculated for [C36H30NP2]+
538.1853; negative mode: [HOB(C6F5)3]ꢀ 528.9887, calculated for
[C18HBF15O]ꢀ 528.9881.
’ CONCLUSIONS
In this paper, the reactivities of the fluorinated and nonfluori-
nated hydroxyborate anions [Q]+[HOB(C6F5)3]ꢀ and [Q]+-
[HOBPh3]ꢀ with Cp2ZrMe2 were compared. The decreased
acidity and the weaker BꢀO bond of [HOBPh3]ꢀ compared
with its fluorinated analogue led to the formation of multiple
products as the result of an exchange reaction involving the
methyl group of the zirconium complex and the hydroxyl group
of the borate ligand. In contrast, selective protonolysis of the
MꢀMe bond (where M = Zr and Hf) is observed between
[PPN]+[HOB(C6F5)3]ꢀ (1) and Cp2ZrMe2 or Cp2HfMe2, pro-
ducing the ionic complexes [PPN]+[Cp2ZrMe(OB(C6F5)3)]ꢀ
(9) and [PPN]+[Cp2HfMe(OB(C6F5)3)]ꢀ (10) in high yields.
The covalent character of the MꢀO and OꢀB bonds in both
complexes is confirmed by analysis of their molecular structures.
Investigation of the reactivity of the fluorinated hydroxyborate
anions with other metals is underway.
Synthesis of [BMMIM]+[ClBPh3]ꢀ (2). A solution of[BMMIM]+
[Cl]ꢀ (3.5 mmol, 660 mg) in methylene chloride (10 mL) was added to a
solution of BPh3 (5.95 mmol, 1.441 g) in methylene chloride (10 mL) at
room temperature. After 8 h of stirring, the reaction mixture was
concentrated to one-half the original volume and then slowly added via
a cannula to 30 mL of toluene at room temperature to precipitate the
chloride compound [BMMIM]+[ClBPh3]ꢀ. The white precipitate was
filtered, washed with 2 ꢁ 20 mL of toluene, and then dried under vacuum
to leave 2 as a white solid (3.40 mmol, 1.463 g).
1
Yield: 97%. H NMR (300 MHz, CD23Cl2) (δ, ppm): 0.95 (t, 3H,
3JHH = 7.4 Hz, CH3); 1.33 (sextet, 2H, JHH = 7.4 Hz, CH2); 1.70
3
(quintet, 2H, JHH = 7.7 Hz, CH2); 2.41 (s, 3H, CH3); 3.63 (s, 3H,
CH3); 3.91 (t, 2H, 3JHH = 7.5 Hz, CH2); 7.11 (d, 1H, 3JHH = 2.0 Hz,
CH); 7.13ꢀ7.23 (m, 9H, CH BPh); 7.24 (d, 1H, 3JHH = 2.3 Hz, CH);
7.40ꢀ7.49 (m, 6H, CH BPh). 11B NMR (96.3 MHz, CD2Cl2) (δ, ppm):
26.2 (broad). 13C NMR (75 MHz, CD2Cl2) (δ, ppm): 10.2 (CH3);
13.6 (CH3); 19.9 (CH2); 31.9 (CH2); 35.8 (CH3); 48.9 (CH2); 121.2
(CH); 123.1 (CH); 126.4 (CH BPh); 126.8 (CH BPh); 135.6 (CH
BPh); 143.7 (C(CH3)). Anal. Calcd for C27H32BClN2: C, 75.27;
H, 7.49; N, 6.50. Found: C, 74.80; H, 7.74; N, 6.56. MS (ESI), positive
mode: [BMMIM]+ 153.1385, calculated for [C9H17N2]+ 153.1392;
negative mode: [ClBPh3]ꢀ 277.0962, calculated for [C18H15BCl]ꢀ
277.0955.
’ EXPERIMENTAL SECTION
All manipulations were performed using either a glovebox or high
vacuum line techniques. Starting materials were purchased from Aldrich
and Strem Chemicals. B(C6F5)3 was treated with Me3SiCl and sublimed
prior to use. Solvents were purchased from SDS and dried using a solvent
purification system (SPS-M-Braun). The water content of these solvents
was periodically determined by Karl Fischer titration.
Synthesis of [PPN]+[ClBPh3]ꢀ (3). Compound 3 was obtained as
a white solid using the same procedure as described for compound 2,
substituting [PPN]+[Cl]ꢀ for [BMMIM]+[Cl]ꢀ.
1H NMR (300 MHz), 11B NMR (96.3 MHz), 19F{1H} NMR (282
MHz), and 13C{1H} NMR (75 MHz) spectra were recorded on a Bruker
AC 300 MHz instrument at room temperature. Deuterated solvent
(CD2Cl2) was purchased from Eurisotop. Chemical shifts are reported
in ppm vs SiMe4 in 1H and 13C NMR spectra, vs BF3 in diethyl ether for
11B NMR spectra, and vs CCl3F in 19F NMR spectra. All coupling
constants are reported in hertz.
1
Yield: 96%. H NMR (300 MHz, CD2Cl2) (δ, ppm): 7.09 (t, 3H,
3
3JHH = 6.9 Hz, CH p-BPh); 7.16 (t, 6H, JHH = 7.3 Hz, CH m-BPh);
7.40ꢀ7.55 (m, 30H, 24 CH o, m Ph PPN+ + 6 CH o-BPh); 7.60ꢀ7.70
(m, 6H, CH p Ph). 11B NMR (96.3 MHz, CD2Cl2) (δ, ppm): 19.4
(broad). Anal. Calcd for C54H45BClNP2: C, 79.47; H, 5.56; N, 1.72.
Found: C, 78.45; H, 5.48; N, 1.68.
Mass spectra were collected on an Agilent 6890 N apparatus with an
Agilent 5975B inert XL EI/CI MSD mass spectrometer.
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ARTICLE
Synthesis of [BMMIM]+[HOBPh3]ꢀ (4). A solution of
[BMMIM]+[ClBPh3]ꢀ (1.16 mmol, 500 mg) in methylene chloride
(10 mL) was added to a suspension of anhydrous LiOH (1.392 mmol, 33
mg) in methylene chloride (10 mL) at room temperature. After stirring
overnight, the white LiCl precipitate was filtered, and the solvent was
removed under vacuum to leave [BMMIM]+[HOBPh3]ꢀ as a colorless,
viscous oil (1.16 mmol, 478 mg).
Synthesis of [PPN]+[Cp2MeZrOB(C6F5)3]ꢀ (9). A solution of
[PPN]+[HOB(C6F5)3]ꢀ (0.64 mmol, 679 mg) in methylene chloride
(3 mL) was added dropwise to a solution of Cp2ZrMe2 (0.79 mmol, 198
mg, 1.2 equiv) in methylene chloride (3 mL) at ꢀ25 °C. After stirring for
2 h at room temperature, the yellow solution was concentrated and then
washed with 25 mL of toluene. The pale brown oil obtained after
decanting the supernatant was washed a second time with toluene. The
solvent was removed under vacuum to leave 9 as a pale brown oil (0.51
mmol, 665 mg). Slow diffusion of n-pentane into a concentrated
solution of 9 in methylene chloride yielded colorless crystals.
Yield: >99%. 1H NMR (300 MHz, CD2Cl2) (δ, ppm): 0.70 (s, 1H,
OH); 0.92 (t, 3H, 3JHH = 7.3 Hz, CH3); 1.21 (sextuplet, 2H, 3JHH = 7.6
Hz, CH2); 1.51 (q, 2H, 3JHH = 7.3 Hz, CH2); 1.96 (s, 3H, CH3); 3.11 (s,
3H, CH3); 3.5 (t, 2H, 3JHH = 7.5 Hz, CH2); 6.59 (d, 1H, 3JHH = 2.2 Hz,
CH); 6.63 (d, 1H, 3JHH = 2.2 Hz, CH); 6.88 (m, 3H, CH p-BPh); 7.00
(m, 6H, CH m-BPh); 7.31 (m, 6H, CH o-BPh). 11B NMR (96.3 MHz,
CD2Cl2) (δ, ppm): ꢀ0.81. 13C NMR (75 MHz, CD2Cl2) (δ, ppm): 9.6
(CH3); 13.6 (CH3); 19.9 (CH2); 31.9 (CH2); 35.3 (CH3); 48.5 (CH2);
120.9 (CH); 122.9 (CH); 123.3 (CH p-BPh); 126.5 (CH m-BPh);
133.5 (CH o-BPh); 143.1 (C(CH3)). IR: ν(OH) = 3620 cmꢀ1. Anal.
Calcd for C27H33BN2O: C, 78.64; H, 8.07; N, 6.79. Found: C, 74.19; H,
8.08; N, 6.76.
Yield: 79%. 1H NMR (300 MHz, CD2Cl2) (δ, ppm): ꢀ0.22 (s, 3H,
CH3); 5.73 (s, 10H, CH Cp); 7.40ꢀ7.55 (m, 24H, CH o, m Ph);
7.59ꢀ7.69 (m, 6H, CH p Ph). 11B NMR (96.3 MHz, CD2Cl2) (δ, ppm):
ꢀ3.62. 19F NMR (282 MHz, CD2Cl2) (δ, ppm): ꢀ133.0 (m, 6F, o-F);
ꢀ163.78 (t, 3F, 3JFF = 19.8 Hz, p-F); ꢀ167.0 (m, 6F, m-F). 13C NMR
(75 MHz, CD2Cl2) (δ, ppm): 17.5 (CH3, Zr-Me); 109.6 (CH Cp);
127.4 (dd, 1JPC = 108.2 Hz, P-C); 129.8 (m, m-CH); 132.5 (m, o-CH);
134.1 (t, 4JPC = 1.7 Hz, p-CH); 136.7 (dm, 1JCF = 247 Hz, C-F); 138.3
1
1
(dm, JCF = 242 Hz, C-F); 148.1 (dm, JCF = 240 Hz, Cꢀ-F). Anal.
Calcd for C65H41BF15NOP2Zr: C, 59.92; H, 3.33; N, 1.07. Found: C,
59.84; H, 3.18; N, 1.12.
Synthesis of [PPN]+[HOBPh3]ꢀ (5). Compound 5 was obtained
as a white solid using the same procedure as described for compound 4,
substituting [PPN]+[ClBPh3]ꢀ for [BMMIM]+[ClBPh3]ꢀ.
Synthesis of [PPN]+[Cp2MeHfOB(C6F5)3]ꢀ (10). A solution of
[PPN]+[HOB(C6F5)3]ꢀ (0.197 mmol, 210 mg) in methylene chloride
(1 mL) was added dropwise to a solution of Cp2HfMe2 (0.295 mmol,
100 mg, 1.5 equiv) in methylene chloride (1 mL) at room temperature.
After stirring for 8 days, the solvent was removed under vacuum to yield
a yellow powder. This powder was washed with 10 mL of toluene. The
pale brown oil obtained after decanting the supernatant was washed a
second time with toluene. The solvent was removed under vacuum to
leave 10 as a pale brown powder (0.165 mmol, 230 mg). Slow diffusion
of n-pentane into a concentrated solution of 10 in methylene chloride
yielded yellow crystals.
Yield: >99%. 1H NMR (300 MHz, CD2Cl2) (δ, ppm): 0.49 (s, 1H,
OH); 6.90 (t, 3H, 3JHH = 7.3 Hz, CH p-BPh); 7.04 (t, 6H, 3JHH = 7.3 Hz,
CH m-BPh); 7.29 (d, 6H, 3JHH = 7.9 Hz, CH o-BPh); 7.40ꢀ7.55 (m,
24H, CH o, m Ph); 7.60ꢀ7.70 (m, 6H, CH p Ph). 11B NMR (96.3 MHz,
CD2Cl2) (δ, ppm): ꢀ0.82. 13C NMR (75 MHz, CD2Cl2) (δ, ppm):
123.3 (CH p-BPh3); 126.5 (CH m-BPh3); 127.4 (dd, 1JPC = 108.1 Hz,
P-C); 129.8 (m, m-CH); 132.5 (m, o-CH); 133.4 (CH o-BPh3); 134.1
(t, 4JPC = 1.3 Hz, p-CH). Anal. Calcd for C54H46BNOP2: C, 81.31; H,
5.81; N, 1.72. Found: C, 79.98; H, 5.90; N, 1.64.
Synthesis of [BMMIM]+[Cp2MeZrOBPh3]ꢀ (6). A solution of
[BMMIM]+[HOBPh3]ꢀ (4) (0.63 mmol, 258 mg) in methylene
chloride (8 mL) was added dropwise to a solution of Cp2ZrMe2 (0.63
mmol, 163 mg) in methylene chloride (8 mL) at ꢀ25 °C. After stirring
for 2 h at room temperature, the reaction mixture was filtered to remove
the small amount of white precipitate that formed during the reaction.
Two different liquid phases were observed upon addition of 20 mL
of toluene. The colorless top phase contained (Cp2ZrMe)2(μ-O), and
the light yellow bottom phase contained a mixture of [BMMIM]+-
[Cp2MeZrOBPh3]ꢀ (6) and [BMMIM]+[MeBPh3]ꢀ (7). Attempts to
separate 6 from 7 failed.
1
Yield: 84%. H NMR (300 MHz, CD2Cl2) (δ, ppm): ꢀ0.34 (s, 3H,
CH3); 5.70 (s, 10H, CH Cp); 7.40ꢀ7.55 (m, 24H, CH o, mPh); 7.60ꢀ7.69
(m, 6H, CH p Ph). 11B NMR (96.3 MHz, CD2Cl2) (δ, ppm): ꢀ3.62. 19
F
NMR (282 MHz, CD2Cl2) (δ, ppm): ꢀ132.94 (m, 6F, o-F); ꢀ163.90 (t,
3
3F, JFF = 19.9 Hz, p-F); ꢀ167.03 (m, 6F, m-F). 13C NMR (75 MHz,
CD2Cl2) (δ, ppm): 20.3 (CH3, Zr-Me); 109.1 (CH Cp); 127.4 (dd, 1JPC
=
108.2 Hz, P-C); 129.8 (m, m-CH); 133 (m, o-CH); 134.1 (t, 4JPC = 1.4 Hz,
p-CH); 136.8 (dm, 1JCF = 247 Hz, C-F); 138.3 (dm, 1JCF = 243 Hz, C-F);
148.2 (dm, 1JCF = 238 Hz, C-F). Anal. Calcd for C65H41BF15NOP2Hf: C,
56.15; H, 3.12; N, 1.01. Found: C, 56.21; H, 3.11; N, 1.02.
1
Spectral Characterization of 6. H NMR (300 MHz, CD2Cl2) (δ,
3
ppm): ꢀ0.04 (s, 3H, CH3); 0.96 (t, 3H, JHH = 7.3 Hz, CH3); 1.26
’ ASSOCIATED CONTENT
(sextuplet, 2H, 3JHH = 8.0 Hz, CH2); 1.58 (quintuplet, 2H, 3JHH = 8.0
Hz, CH2); 1.97 (s, 3H, CH3); 3.17 (s, 3H, CH3); 3.59 (t, 2H, 3JHH = 7.6
Hz, CH2); 5.75 (s, 10H, CH Cp); 6.49 (d, 1H, 3JHH = 2.1 Hz, CH); 6.58
(d, 1H, 3JHH = 2.2 Hz, CH); 6.82 (m, 3H, CH p-Ph); 6.89 (m, 6H, CH
Ph); 7.04 (m, 6H, CH Ph). 11B NMR (96.3 MHz, CD2Cl2) (δ, ppm):
1.83. 13C NMR (75 MHz, CD2Cl2) (δ, ppm): 9.6 (CH3); 13.2 (CH3,
Zr-Me); 13.7 (CH3); 19.9 (CH2); 31.8 (CH2); 35.4 (CH3); 48.9
(CH2); 109.4 (CH, Cp); 121.0 (CH; 122.6 (CH); 122.7 (CH Ph);
126.1 (CH Ph); 134.0 (CH Ph); 143.2 (C(CH3)).
S
Supporting Information. CIF files providing X-ray crys-
b
tallographic data for 1, 9, and 10 are available free of charge via
the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: santini@cpe.fr (Tel: (+33)472431810); christophe.vallee@
ifpen.fr (Tel: (+33)437702153).
1
Spectral Characterization of 7. H NMR (300 MHz, CD2Cl2) (δ,
3
ppm): 0.22 (q, 3H, 2JBH = 3.9 Hz, CH3); 0.95 (t, 3H, JHH = 7.2 Hz,
CH3); 1.28 (sextuplet, 2H, 3JHH = 8.0 Hz, CH2); 1.60 (quintuplet, 2H,
3JHH = 7.4 Hz, CH2); 2.04 (s, 3H, CH3); 3.24 (s, 3H, CH3); 3.64 (t, 2H,
3JHH = 7.4 Hz, CH2); 6.55 (d, 1H, 3JHH = 2.2 Hz, CH); 6.63 (d, 1H,
3JHH = 2.2 Hz, CH); 6.82 (m, 3H, CH o-Ph); 6.97 (m, 6H, CH Ph); 7.29
’ ACKNOWLEDGMENT
The authors wish to thank IFP Energies Nouvelles (Lyon,
France) and the ANRT for financial support.
(m, 6H, CH Ph). 11B NMR (96.3 MHz, CD2Cl2) (δ, ppm): ꢀ11.74. 13
C
NMR (75 MHz, CD2Cl2) (δ, ppm): 9.4 (CH3); 13.30 (q, CH3, B-Me);
13.6 (CH3); 19.9 (CH2); 31.9 (CH2); 35.3 (CH3); 48.7 (CH2); 121.0
(CH); 122.0 (CH Ph); 122.6 (CH); 126.0 (q, CH Ph); 134.7 (d, CH
Ph); 143.3 (C(CH3)); 167.6 (q, C Ph).
’ REFERENCES
(1) van Leeuwen, P. W. N. M. Homogeneous Catalysis, Understanding
the Art; Kluwer Academic Publishers: Dordrecht, 2004.
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ARTICLE
(2) Zhao, P. J.; Incarvito, C. D.; Hartwig, J. F. J. Am. Chem. Soc. 2007,
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(3) Birch, S. J.; Boss, S. R.; Cole, S. C.; Coles, M. P.; Haigh, R.;
Hitchcock, P. B.; Wheatley, A. E. H. Dalton Trans. 2004, 3568.
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(35) The comparison between the anion [HOB(C6F5)3]ꢀ and
(C6F5)2BOH was not relevant because its trimeric structure revealed
an interaction between oxygen and a boron atom of a second molecule,
which undoubtedly increased the BꢀO bond length. Conversely,
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