Reactions of topologically related "nacnacH-CN" and "p-nacnacH-CN" Chelate ligand systems with HB(C6F 5)2

Article abstract of DOI:10.1021/om200116q

The chelate bis-imine nacnacH-CN (1) and its bis-phosphinimine analogue P-nacnacH-CN (2) are shown to have similar reactivities with HB(C ₆F₅)₂. In a 1:1 stoichiometry simple Lewis acid/Lewis base adducts are observed: HB(

Full text of DOI:10.1021/om200116q

ARTICLE
pubs.acs.org/Organometallics
Reactions of Topologically Related “nacnacH-CN” and “P-nacnacH-CN”
Chelate Ligand Systems with HB(C6F5)2
Kirsten Spannhoff,† Rene Rojas,*,‡ Roland Fr€ohlich,† Gerald Kehr,† and Gerhard Erker*,†
†Organisch-Chemisches Institut, Universit€at M€unster, Corrensstrasse 40, 48149 M€unster, Germany
‡Departamento de Química Inorgꢀanica, Facultad de Química, Pontificia Universidad Catꢀolica de Chile, Casilla 306, Santiago-22, Chile
S Supporting Information
b
ABSTRACT: The chelate bis-imine nacnacH-CN (1) and its bis-
phosphinimine analogue P-nacnacH-CN (2) are shown to have similar
reactivities with HB(C6F5)2. In a 1:1 stoichiometry simple Lewis acid/
Lewis base adducts are observed: HB(C6F5)2 just adds to the nitrile
functionality to yield compounds 3 and 6, respectively. With two molar
equivalents of HB(C6F5)2, both systems 1 and 2 react at 70 °C with
reduction of the nitrile group to an imine that is in both reactions found
to be coordinated to a second equivalent of the HB(C6F5)2 Lewis acid.
The remaining B(C6F5)2 unit becomes part of a six-membered
heterocycle, where it is found to be coordinated to the pair of (C-
NAr) (4) or (P-NPh) (7) units. Heating of the nacnacH-CN/HB-
(C6F5)2 adduct 3 results in a disproportionation reaction yielding a
mixture of the heterocycle (4) and the borane-free starting material 1.
In marked contrast, the thermolysis of the P-nacnacH-CN/HB-
(C6F5)2 adduct (6) yields a new product (8), generated via an
intramolecular ꢀPh2PdNPh vs ꢀCHdNH exchange at the boron
center and a formal “Umpolung” of a hydridic to a protic hydrogen atom. The compounds 3, 4, 6, 7, and 8 were characterized
spectroscopically and by X-ray diffraction.
’ INTRODUCTION
’ RESULTS AND DISCUSSION
The 2,4-bis(N-arylimino)pentane system (“nacnacH”) shows a
very rich coordination chemistry in the monoanionic state.1,2 The
closely related 3-cyano substituted “nacnacH-CN” derivative 1 has
recently been shown to form zirconium complexes [(nacnac-
CN)CpZrCl2] that effectively use the cyano group as an anchor to
attach a Lewis acid upon ZieglerꢀNatta catalyst activation.3,4
Bis(diphenylphosphinimino)methane (“P-nacnacH”) is topo-
logically related to the nacnacH system. It forms closely related
metal coordination complexes in the monoanionic state.5,6 The
high acidity of the central PdCH-P unit allows for a facile second
deprotonation and consequently for the formation of very
interestingly structured metallabicyclic frameworks.7,8 The in-
stallation of a central cyano substituent eliminates the possibility
for a secondary deprotonation pathway. Consequently, bis-
(diphenylphosphinimino)acetonitrile (2) (“P-nacnacH-CN”)8
is topologically closely related to nacnacH-CN (1). This beha-
vior was illustrated in a series of reactions of 1 and 2 with the
strong Lewis acid HB(C6F5)2 [“Piers’ borane”],10 which will be
described in this account. This study revealed a marked differ-
ence in the reactivity of a topological pair of HB(C6F5)2 reaction
products that eventually revealed a remarkable new reaction
mode of the phosphorus-derived system.
Reaction of [nacnacH-CN] (1) with HB(C6F5)2. We decided
to investigate the nacnacH-CN ligand system 1 as one basis for
this study. Its unsymmetrical N-aryl substitution pattern repre-
sents a close to ideal set for combining sufficient reactivity
with steric and electronic product stabilization. The ligand 1
was prepared as recently described by us,3 namely, by selective
condensation of acetyl acetone with 2,6-diisopropylaniline in a
1:1 stoichiometry followed by treatment with aniline. The 3-CN
substituent was then subsequently introduced by treatment with
p-toluolsulfonylcyanide.11 Ligand system 1 was then reacted with
Piers’ borane HB(C6F5)2. Stirring of the reaction mixture for one
hour at room temperature in toluene eventually yielded the
adduct 3 [i.e., 1-HB(C6F5)2] as a colorless crystalline solid in
85% isolated yield. Single crystals of 3 suitable for X-ray crystal
structure analysis were obtained from toluene/pentane by the
diffusion method.
The X-ray crystal structure analysis of compound 3 features a
U-shaped nacnacH section of the framework. The internal
bonding situation is found to be slightly unsymmetrical. The
Received: February 7, 2011
Published: March 25, 2011
r
2011 American Chemical Society
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C1ꢀN1 bond (1.315(3) Å) is markedly longer than the opposite
C3ꢀN2 linkage (1.282(3) Å), and consequently, the C1ꢀC2
bond (1.415(3) Å) is shorter than the C2ꢀC3 bond (1.458(3)
Å). The internal angles and dihedral angles of this subunit are
within the expected range for such species (e.g., N1ꢀC1ꢀC2
119.4(2)°, C1ꢀC2ꢀC3 125.2(2)°, N2ꢀC3ꢀC2 118.5(2)°,
N1ꢀC1ꢀC2ꢀC3 2.1(4)°). Carbon atom C2 is trigonal planar
(sum of the bonding angles at C2 360.0°). The HB(C6F5)2 Lewis
acid is found to be coordinated to the nitrogen atom (N3) of the
cyano substituent12 that is attached at the central carbon atom
(C2) of the nacnacH framework (see Figure 1). The boron
atom shows a distorted tetrahedral coordination geometry with
typical bond angles of 111.8(2)° (N3ꢀB1ꢀC41), 108.6(2)°
(N3ꢀB1ꢀC51), and 111.3(2)° (C41ꢀB1ꢀC51). The C2, C5,
N3, B1 unit is close to linear (angles C2ꢀC5ꢀN3 178.7(3)°,
C5ꢀN3ꢀB1 175.7(2)°). The C5ꢀN3 bond length (1.146(3)
Å) is within the typical CtN triple bond range. Interestingly, the
parent system 1 is found to be nearly unperturbed upon adduct
formation with HB(C6F5)2 as observed in 3.
The IR spectrum of the borane adduct 3 shows a sharp CtN
stretching band at ν~ = 2268 cmꢀ1, which is shifted by ν~ =
76 cmꢀ1 to higher wave numbers as compared to its parent ligand
system 1. This is what would be expected from simple addition of
a nitrile to a strong Lewis acid: sharing of the nitrogen lone pair
with the boron atom effectively reduces the electronic repulsion
between nitrogen and carbon to make the CtN triple bond in 3
slightly stronger.13
Treatment of 1 with two molar equivalents of HB(C6F5)2 at
70 °C (12 hours) led to complete conversion to 4, which was
isolated from the reaction mixture in 76% yield. Single crystals of
4 were obtained at ambient temperature from toluene/pentane
by the diffusion method.
The X-ray crystal structure analysis of compound 4 confirms
that the nitrile functionality of the starting material was reduced
to an imine under the forcing conditions. We find a ꢀCHdNH
functional group (C7ꢀN8 attached to the ligand framework at
carbon atom C4). One equivalent of the intact borane HB-
(C6F5)2 first forms a Lewis acid/Lewis base adduct16 with the
nitrogen atom of this newly generated imine (N8ꢀB9 1.568(4)
Å, angles C7ꢀN8ꢀB9 125.3(2)°, C4ꢀC7ꢀN8 127.1(2)°,
dihedral angle C4ꢀC7ꢀN8ꢀB9 167.7(3)°). It is assumed that
the reduction of the nitrile of the imine functionality is facilitated
by the second equivalent of HB(C6F5)2. Deprived of a hydride,
the residual B(C6F5)2 unit is trapped nearly symmetrically to
both distal nitrogens of the nacnac chelate system (N2ꢀB1
1.582(3) Å, N6ꢀB1 1.593(3) Å, angle N2ꢀB1ꢀN6 101.3(2)°).
The resulting six-membered heterocycle adopts a distorted boat-
shaped conformation. The boron atom is arranged markedly
outside the central N2C3 unit (θ C4ꢀC5ꢀN6ꢀB1 19.0(3)°,
C4ꢀC3ꢀN2ꢀB1 ꢀ19.3(3)°). The central N2C3 unit is found
In the 1H NMR spectrum of 3 we see the NꢀH resonance at δ
15.03 (in [D2]-dichloromethane), while a broad BꢀH signal is
observed at δ 4.06. The 11B NMR spectrum features a typical
four-coordinate boron resonance (δ ꢀ18.0), which is supported
by a characteristically small Δδ(p,m) C6F5 chemical shift
difference14 in the 19F NMR spectrum [δ ꢀ134.8 (o), ꢀ159.9
(p), ꢀ165.3 (m)]. The system 3 exhibits a pair of characteristic
13C NMR resonances for the CdNꢀAr units (δ13C: 170.0,
167.8) and the C2 resonance at δ 75.6.
The adduct 3 was generated in situ from 1 plus HB(C6F5)2 in a
1:1 molar ratio in toluene and was then heated at 70 °C for three
hours. This revealed the formation of a mixture of the new com-
pound 4 with ca. one equivalent of the free starting material 1.15
Scheme 1
Figure 1. Molecular structure of HB(C6F5)2 adduct 3.
Scheme 2
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Figure 2. View of the molecular structure of the product 4 (toluene
solvate was omitted for clarity).
Scheme 3
Figure 3. Molecular structure of the [(P-nacnacH-CN)HB(C6F5)2]
adduct 6.
as previously described by us starting from the cyano-substituted
dppm system 5,17 which in turn was obtained in a convenient
one-pot double phosphorylation of acetonitrile using n-butyl-
lithium and ClPPh2. Compound 2 (“P-nacnacH-CN”) was then
prepared by 2-fold Staudinger reaction of 5 with phenylazide (see
Scheme 3).18
Compound 2 was reacted with one molar equivalent of HB-
(C6F5)2 at ꢀ78 °C (two hours) and worked up at 0 °C, yielding
the adduct 6 in 76% isolated yield. Single crystals of 6 suited for
X-ray crystal structure analysis were obtained from a toluene/
pentane solution at ꢀ35 °C via the gas diffusion method. This
analysisshows thatthe Lewis acidHB(C6F5)2 has justadded tothe
external nitrile nitrogen atom. The boron atom has taken up a
distorted tetrahedral coordination geometry in the adduct. It
features bond angles of 107.1(2)° (N3ꢀB1ꢀC71), 106.4(2)°
(N3ꢀB1ꢀC81), and 114.4(2)° (C71ꢀB1ꢀC81). The N3ꢀB1
bond length is found to be at 1.568(3) Å. The C2ꢀN3 triple bond
is short (1.151(2) Å), and the C1ꢀB1 moiety is linear (C1ꢀ
C2 1.379(3) Å, angles C1ꢀC2ꢀN3 179.8(2)°, C2ꢀN3ꢀB1
172.3(2)°). The central carbon atom C1 of the framework is
trigonal planar (sum of the bonding angles 359.9°). The central
N2P2C unit is not delocalized. It exhibits a bond length alternation
with a slightly longer N1ꢀP1 (1.637(2) Å) and a shorter N2dP2
linkage (1.584(2) Å). Consequently, the P1ꢀC1 bond (1.746(2)
Å) is shorter than the adjacent P2ꢀC1 linkage (1.779(2) Å)
As expected, the adduct 6 shows a ν(CtN) stretching band
(~ν = 2235 cmꢀ1) that is shifted to higher wave numbers as
compared to its free precursor 2 (~ν = 2157 cmꢀ1). The adduct 6
features a 11B NMR resonance at δ ꢀ18.5 and 19F NMR signals at
δꢀ134.0 (o), ꢀ160.2 (p), andꢀ164.9 (m) fortheC6F5 substituents
to be delocalized (N6ꢀC5 1.334(3) Å, N2ꢀC3 1.324(3) Å,
C4ꢀC5 1.430(3) Å, C4ꢀC3 1.434(3) Å).
In the NMR spectrum of 4 the typical signals for the [B]ꢀimine
unit [1H: δ 8.64 dNH; δ 8.50 (NdCHꢀ); 13C: δ 164.2] and a
1
broad [B]ꢀH H NMR resonance of this unit at δ 3.74 are
observed. The central N2C3 moiety features a pair of CdN 13
C
NMR signals at δ 170.7/167.7 and the central C4 resonance at δ
111.4. At 213 K two nonidentical pairs of C6F5 groups at boron
were monitored in the 19F NMR spectra. Under these conditions,
some o/o0 and m/m0 pairs are differentiated due to hindered
BꢀC6F5 rotation (for further information see the Experimental
Section and the Supporting Information).
Reaction of the [P-nacnacH-CN] System 2 with HB(C6F5)2.
The cyano-substituted bis-phosphinimine system 2 was prepared
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on boron. It shows a triplet structure for the 13C NMR P2C signal at
δ 21.4 (1JPC = 134.1 Hz) and a single 31P NMR resonance at δ 27.2.
In the 1H NMR spectrum of 6 there are two sets of phenyl groups,
one for the NꢀPh and one for the PꢀPh in an integral ratio of 1:2.
The broad BꢀH resonance is observed at δ 4.05.
The P-nacnacH-CN system 2 was then reacted with two molar
equivalents of HB(C6F5)2. Similar to the reaction between
nacnacH-CN and Piers’ borane, this reaction required heating
to 70 °C to proceed. After heating the reaction mixture of 2 plus
two equivalents of HB(C6F5)2 for three hours at this temperature
in toluene, 7 was isolated as a pale solid in 84% yield upon
workup. Its structure is analogous to 4, which was isolated from
the reaction of 1 with two equivalents of HB(C6F5)2 (see above).
This was revealed from the typical spectroscopic data (see
below), the CHN elemental analysis, and the result of the
X-ray crystal structure analysis (single crystals were obtained
from toluene).
The crystal structure analysis shows that the nitrile function-
ality of 7 was reduced by treatment with HB(C6F5)2 under the
applied reaction conditions. An imine bonded to the central
carbon atom C1 of the N2P2C framework (C1ꢀC2 1.407(4) Å,
C2ꢀN3 1.302(4) Å, angle C1ꢀC2ꢀN3 129.0(3)°) was ob-
served. The newly formed imine functional group is coordinated
to an intact HB(C6F5)2 Lewis acid moiety (N3ꢀB2 1.573(4) Å,
angles N3ꢀB2ꢀC91 109.0(2)°, N3ꢀB2ꢀC101 107.1(2)°,
C91ꢀB2ꢀ
C101 116.4(2)°). The remaining B(C6F5)2 unit has lost its
hydride (that was used in the reduction of the ꢀCN function to
give the imine) and is found to be symmetrically bonded by both
N1 and N2 inside the delocalized BN2P2C six-membered-ring
structure of 7 (B1ꢀN1 1.584(4) Å, B1ꢀN2 1.588(4) Å, P1ꢀN1
1.628(2) Å, P2ꢀN2 1.633(2) Å, P1ꢀC1 1.749(3) Å, P2ꢀC1
1.744(3) Å, angles N1ꢀB1ꢀN2 112.7(2)°, P1ꢀC1ꢀP2
124.4(2)°). The central six-membered heterocycle is slightly
boat-shaped (dihedral angles C1ꢀP2ꢀN2ꢀB1 4.3(3)° and
P2ꢀN2ꢀB1ꢀN1 ꢀ7.0(4)°).
Figure 4. View of the molecular structure of compound 7.
Compound 7 features a pair of 11B NMR signals at δ ꢀ0.3 and
ꢀ14.7, respectively. An AX spin pattern is observed in the 31P
NMR spectrum, with resonances at δ 36.9 and 25.4 (2JPP = 18.0
Hz). At 233 K pairs of o, p, and m 19F NMR signals of the
[N]BH(C6F5)2 unit and a total of four o-C6F5 19F NMR
resonances of the central endocyclic B(C6F5)2 unit were mon-
itored (for details see Experimental Section and the Supporting
Information). The imine 13C NMR resonance of compound 7
occurs at δ 165.0 (δ1H = 7.33), and the corresponding [B]-
NHd 1H NMR resonance is found at 6.00 (corresponding broad
BꢀH signal at δ 2.94).
The Unusual Reactivity of Compound 6. The thermolysis of
the P-nacnacH-CN/HB(C6F5)2 adduct 6 was investigated, in the
same way as we had done for the nacnacH-CN/HB(C6F5)2
adduct 3 (see above). However, in contrast to the P-nacnacH-
CN/HB(C6F5)2 and nacnacH-CN/HB(C6F5)2 results so far,
here we encountered a remarkable difference.
The adduct 6 was heated for 26 h at 80 °C in toluene. Workup
of the reaction mixture resulted in a mixture of the unusual
product 8 and the starting material 2 in a ratio of 7:1 in a
combined 64% yield. Compound 8 was unambiguously char-
acterized from its spectroscopic data and the result of the X-ray
crystal structure analysis (single crystals were obtained from the
DMSO solution at room temperature).
Figure 5. View of the molecular structure of the thermolysis product 8.
imine functionality by HB(C6F5)2. However, we have not
isolated the single imine product due to extensive rearrangement
that takes place during the thermolysis reaction (see Figure 5 and
Scheme 4). This resulted in the formation of a six-membered
heterocycle that contains a boron atom, two nitrogen atoms, and
a phosphorus atom. In contrast to the previously observed
The X-ray crystal structure analysis revealed that the nitrile
functionality of the starting material 6 had been reduced to an
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Scheme 4
related products and the general structural appearance in both
series are certainly noteworthy.
The similarity between the nacnacH-CN and P-nacnacH-CN
systems abruptly ends in the behavior of the mono-HB(C6F5)2
adducts (3 and 6, respectively) upon thermolysis. The nacnacH-
CN/HB(C6F5)2 system typically undergoes ligand dispropor-
tionation to enter the typical nacnacH-CN plus two equivalents
of HB(C6F5)2 chemistry to eventually yield ca. equal amounts of
the two-boron-containing heterocycle 4 and the boron-free
starting material 1.
The thermally initiated reaction of the P-nacnacH-CN/HB-
(C6F5)2 adduct 6 is markedly different. It probably commences
with ꢀCtN to ꢀCHdNH reduction, but here the small and
reactive imino group takes up an active part in the subsequent
rearrangement course (see the Supporting Information). It is an
unexpected interesting consequence of this ready rearrangement
that it generates a situation that ultimately results in a possibility
to achieve a novel “Umpolungsreaction” of the former BꢀH
hydrogen to a protic hydrogen situation potentially via an
incipient nitrenium-like reactive intermediate.
reaction products, in this series one of the phosphorus atoms is
no longer found within the central heterocycle core, but it has been
converted to a simple ꢀPPh2 substituent attached at a carbon
atom of the central BN2PC2 core. The boron center is found to be
four-coordinate. It is bonded to a pair of C6F5 groups and the
nitrogen atoms N1 and N3 (B1ꢀN1 1.570(3) Å, B1ꢀN3
1.550(3) Å, angle N1ꢀB1ꢀN3 108.0(2)°), respectively. The ring
parameters continue with the N1ꢀP1 linkage (1.640(2) Å), the
short ylidic P1ꢀC1 bond (1.738(2) Å), and the C1ꢀC2 bond
(1.405(3) Å). The C2ꢀN3 bond (1.342(2) Å) then closes the
ring structure. Carbon atom C2 bears the newly formed N2(H)Ph
substituent (C2ꢀN2 1.367(2) Å). This unit should be regarded as
a delocalized cationic amidinium substructure.
’ EXPERIMENTAL SECTION
General Procedures. All reactions were carried out under an inert
gas atmosphere (argon) in Schlenk-type glassware or in a glovebox.
Solvents were dried and distilled under argon prior to use. The following
instruments were used for the physical characterization of the com-
pounds. NMR: Varian Inova 500 (1H: 500 MHz, 13C: 126 MHz, 19F:
470 MHz, 31P: 202 MHz, 11B: 160 MHz), Bruker Unity Plus 600 (1H:
600 MHz, 13C: 151 MHz, 19F: 564 MHz, 31P: 243 MHz, 11B: 192 MHz).
Most NMR assignments were supported by additional 2D experiments.
Melting points: Ta-Instruments differential scanning calorimeter Q20
(heating rate: 10 °C/min). IR: Varian 3100 FT-IR spectrometer (KBr
pellet or ATR). Elemental analyses: Elementar Vario El III. X-ray
structure analysis: Data sets were collected with a Nonius KappaCCD
diffractometer. Programs used: data collection COLLECT (Nonius B.
V., 1998), data reduction Denzo-SMN (Z. Otwinowski, W. Minor,
Methods Enzymol. 1997, 276, 307ꢀ326), absorption correction Denzo
(Z. Otwinowski, D. Borek, W. Majewski, W. Minor, Acta Crystallogr.
2003, A59, 228ꢀ234), structure solution SHELXS-97 (G. M. Sheldrick,
Acta Crystallogr. 1990, A46, 467ꢀ473), structure refinement SHELXL-
97 (G. M. Sheldrick, Acta Crystallogr. 2008, A64, 112ꢀ122), graphics XP
(BrukerAXS, 2000). Graphics show the thermal ellipsoids with 50%
probability, R values are given for the observed reflections, wR2 values for
all reflections.
In solution compound 8 possesses a 13C NMR signal for the
“amidinium” carbon atom (C2)19 at δ 163.0. The adjacent “ylidic”
carbon atom C120 shows a 13C NMR resonance at δ 42.8 with a
pair of substantially different 1JPC coupling constants of 120.5 and
27.9 Hz.21 Typical of a borate center, three distinct resonances of 8
were observed in the 19F NMR spectrum [δ ꢀ132.5 (o), ꢀ160.0
(p), ꢀ165.3 (m)] with a relatively sharp 11B NMR signal atδ ꢀ4.1
(ν1/2 ≈ 50 Hz). There is a 31P NMR AX spin pattern observed for
the pair of phosphorus atoms in 8 (δ 37.6, δ ꢀ30.3, 2JPP = 170.1
Hz). The 1H NMR spectrum reveals a set of broad NꢀH resonances
at δ 6.40 ([B]NꢀH) and δ 5.87 ([C]NꢀH), respectively.
The presence of two NH units in compound 8 might give us a
clue to formulate how this unusual product might actually have
been formed starting from 6. Comparison of 6 and 8 reveals that
in principle the NH functionality has been carried through from 6
all the way to 8. The truly unusual feature of the 6 f 8 reaction is
that the hydridic [B]ꢀH hydrogen in 6 eventually must have
been converted to a protic [N]ꢀH hydrogen in 8.22 The detailed
mechanism of this unexpected reaction is not clear at present. For
a possible reaction pathway see the Supporting Information.
Synthesis of 3. Bis(pentafluorophenyl)borane, [HB(C6F5)2] (45
mg, 0.130 mmol, 1.04 equiv), intoluene (1 mL) was added toa solution of
13 (45 mg, 0.125 mmol) in toluene (3 mL). The reaction mixture was
stirred for one hour, and the volatiles were removed under vacuum,
redissolved in pentane, and filtered over Celite. Concentration of the
solution by slow evaporation of pentane gave 3 as a colorless crystalline
material in 85% yield (75 mg, 0.106 mmol). Single crystals of 3 suitable for
X-ray crystal structure analysis were obtained by slow diffusion of pentane
to toluene at room temperature. Mp (DSC): 127 °C. IR (KBr): ~ν/cmꢀ1
2430 (ν(BH), s), 2268 (ν(CtN), s). Anal. Calcd for C36H30BF10N3: C,
61.29; H, 4.29; N, 5.96. Found: C, 61.44; H, 4.48; N, 6.32. 1H NMR (600
MHz, CD2Cl2, 298 K): δ 15.03 (s, 1H, NH), 7.37 (m, 2H, m-Ph), 7.28
(m, 1H, p-Ar), 7.21 (m, 2H, m-Ar), 7.20 (m, 1H, p-Ph), 6.91 (m, 2H, o-
Ph), 4.06 (br, 1H, BH), 2.83 (hept, 2H, J = 6.9 Hz, HCiPr), 2.22 (s, 3H,
’ CONCLUSIONS
Our study reveals a number of quite remarkable similarities
between the conventional nacnacH-CN system 1 and its phos-
phorus analogue P-nacnacH-CN 2. Both have similar structures
and form analogously composed and structured adducts with the
strong Lewis acid HB(C6F5)2. In both these systems the HB-
(C6F5)2 Lewis acid binds to the ꢀCtN functional group
through the terminal nitrogen atom in a linear fashion, and the
adduct is “protected” from direct reduction by a substantial
activation barrier. Nevertheless, the CN groups of both the
systems are eventually reduced to the imine stage. Upon treat-
ment with two molar equivalents of HB(C6F5)2, the respective
heterocycles 4 and 7 are formed, respectively. In each instance,
one HB(C6F5)2 unit is used as a reduction equivalent, while the
second unit simply binds as a Lewis acid to the newly formed
imino group. The generation of these conceptually closely
MePh), 2.04 (s, 3H, MeAr), 1.24 (d, 6H, J = 6.9 Hz, MeiPr), 1.11 (d, 6H, J =
0
6.9 Hz, MeiPr ). 13C{1H} NMR (151 MHz, CD2Cl2, 298 K): δ 170.0
(CdNAr), 167.8 (CdNPh), 144.3 (i-Ph), 142.7 (o-Ar), 136.0 (i-Ar),
129.7 (m-Ph), 128.2 (p-Ar), 126.0 (p-Ph), 124.2 (m-Ar), 122.9 (o-Ph), n.
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0
o. (CtN), 75.6 (CCN), 29.1 (HCiPr), 24.4 (MeiPr ), 22.5 (MeiPr), 19.4
(MePh), 19.1(MeAr), [C5F6 arenot listed]. 19FNMR(564 MHz, CD2Cl2,
298 K):δꢀ134.8 (m, 2F, o-C6F5), ꢀ159.9(t, 3JFF =20.8Hz, 1F, p-C6F5),
ꢀ165.3 (m, 2F, m-C6F5) [Δδ(p,m) = 5.4]. 11B{1H} NMR (192 MHz,
CD2Cl2, 298 K): δ ꢀ18.0 (br ν1/2 ≈ 450 Hz)
ꢀ78 °C. To this solution was added HB(C6F5)2 (117 mg, 0.338 mmol,
1.0 equiv) in dichloromethane (3 mL), and the reaction mixture was
stirred for two hours at ꢀ78 °C. After removing the solvent in vacuo at
0 °C, 6 was yielded as a pale powder (240 mg, 0.256 mmol, 76%). Single
crystals of 6 suitable for X-ray crystal structure analysis were obtained
through vapor diffusion of pentane into a solution of 6 in toluene at
ꢀ35 °C. Dec: 149 °C, mp 177 °C. IR (KBr): ν~/cmꢀ1 2419 (ν(BH), w),
2235 (ν(CtN), s). Anal. Calcd for C50H32BF10N3P2: C, 64.05; H, 3.44;
N, 4.48. Found: C, 63.78; H, 3.20; N, 4.44. 1H NMR (500 MHz, C6D6,
298 K): δ 11.15 (br, 1H, NH)t, 7.60 (m, 8H, o-PhP), 6.96 (m, 4H, p-
PhP), 6.91 (m, 4H, m-PhN), 6.88 (m, 8H, m-PhP), 6.78 (m, 4H, o-PhN),
6.69 (m, 2H, p-PhN), 4.05 (br, 1H, B-H), [t tentative assignment].
13C{1H} NMR (126 MHz, C6D6, 298 K): δ 148.1 (dm, 1JFC ≈ 235 Hz,
o-C6F5), 145.1 (i-PhN), 139.6 (dm, 1JFC ≈ 247 Hz, p-C6F5), 137.2 (dm,
1JFC ≈ 251 Hz, m-C6F5), 133.1 (p-PhP), 132.6 (m, o-PhP), 129.7 (m-
X-ray crystal structure analysis of 3: formula C36H30BF10N3, M = 705.44,
colorless crystal 0.25 ꢁ 0.20 ꢁ 0.05 mm, a = 9.1730(5) Å, b = 13.9793(6)
Å, c = 14.9065(7) Å, R = 66.006(2)°, β = 85.949(2)°, γ = 87.231(2)°, V =
1741.55(15) Å3, Fcalc = 1.345 g cmꢀ3, μ = 1.010 mmꢀ1, empirical
absorption correction (0.786 e T e 0.951), Z = 2, triclinic, space group
P1 (No. 2), λ = 1.54178 Å, T = 223(2) K, ω and j scans, 19 628 reflections
collected ((h, (k, (l), [(sin θ)/λ] = 0.60 Åꢀ1, 6016 independent (Rint
=
0.056) and 4539 observed reflections [I g 2 σ(I)], 460 refined parameters,
R = 0.053, wR2 = 0.144, max. (min.) residual electron density 0.22 (ꢀ0.24)
e Åꢀ3, hydrogen atom at N1 from difference Fourier calculations, the others
calculated and refined as riding atoms.
N
P
1
3
Ph ), 129.1 (m, m-Ph ), 127.4 (AXX0, JPC þ JP C = 99.5 Hz, i-PhP),
122.3 (t, 2JPC = 10.4 Hz, CtN)t, 121.2 (p-PhN), 121.1 (m, o-PhN), 118.8
(br, i-C6F5), 21.4 (t, 1JPC = 134.1 Hz, [P]2C), [t tentative assignment].
19F NMR (470 MHz, C6D6, 298 K): δ ꢀ134.0 (m, 2F, o-C6F5), ꢀ160.2
(m, 1F, p-C6F5), ꢀ164.9 (m, 2F, m-C6F5) [Δδ(p,m) = 4.7]. 31P{1H}
NMR (202 MHz, C6D6, 298 K): δ 27.2 (ν1/2 ≈ 3 Hz). 11B{1H} NMR
(160 MHz, C6D6, 298 K): δ ꢀ18.5 (ν1/2 ≈ 350 Hz).
0
Synthesis of 4. Bis(pentafluorophenyl)borane (60 mg, 0.17 mmol,
1.0 equiv) in toluene (1 mL) was added to a solution of 1 (61 mg, 0.170
mmol) in toluene (3 mL). The reaction mixture was stirred for one hour,
then warmed to 70 °C and kept at this temperature for three hours.
[After this time, 1H NMR spectroscopy shows the formation of
compound 4 plus free ligand 1.] Then one additional equivalent of
HB(C6F5)2 (60 mg, 0.170 mmol) in toluene (1 mL) was added to the
reaction mixture and kept at 70 °C for another 12 hours. Volatiles were
removed under vacuum, redissolved in pentane, and filtered over Celite.
Concentration of the solution by slow evaporation of pentane gave 4 as a
crystalline, colorless material in 76% yield (145 mg, 0.127 mmol). Single
crystals of 4 suitable for X-ray crystal structure analysis were obtained by
slow diffusion of pentane to toluene at room temperature. Mp (DSC):
155 °C. IR (KBr): ν~/cmꢀ1 3385 (ν(NH), s), 2406 (ν(BH), s), 2369.
X-ray crystal structure analysis of 6: formula C50H32BF10N3P2, M =
937.54, colorless crystal 0.40 ꢁ 0.30 ꢁ 0.30 mm, a = 12.8718(4) Å, b =
13.1734(4) Å, c = 16.1600(6) Å, R = 94.010(1)°, β = 109.163(2)°, γ =
119.124(3)°, V = 2171.72(15) Å3, Fcalc = 1.434 g cmꢀ3, μ = 1.641
mmꢀ1, empirical absorption correction (0.560 e T e 0.639), Z = 2,
triclinic, space group P1 (No. 2), λ = 1.54178 Å, T = 223(2) K, ω and j
scans, 27 024 reflections collected ((h, (k, (l), [(sin θ)/λ] = 0.60 Åꢀ1
,
7617 independent (Rint = 0.040) and 7028 observed reflections [I g
2σ(I)], 601 refined parameters, R = 0.043, wR2 = 0.115, max. (min.)
residual electron density 0.41 (ꢀ0.28) e Åꢀ3, hydrogen atoms at N1 and
B1 from difference Fourier calculations, the others calculated and refined
as riding atoms.
Anal. Calcd for C48H31B2F20N3 C7H8: C, 57.77, H, 3.44; N, 3.67.
3
Found: C, 57.33; H, 3.32; N, 4.02. 1H NMR (500 MHz, CD2Cl2, 213 K):
δ 8.64 (dd, 1H, J = 19.1, 6.1 Hz, NH), 8.50 (d, 1H, J = 19.1 Hz, N=CH),
7.33a, 7.29b, 7.15c, 7.12d, 6.75e (each m, each 1H, Ph), 7.21 (m, 1H, p-
Ar), 7.09 (m, 1H, m-Ar), 6.92 (m, 1H, m0-Ar), 3.74 (br, 1H, BH), 2.59
Synthesis of 7. The bis(phosphinimine) 2 (250 mg, 0.423 mmol)
and HB(C6F5)2 (292 mg, 0.854 mmol, 2.02 equiv) were dissolved in
toluene (6 mL) and stirred for three hours at 70 °C. After removing the
solvent under reduced pressure, the residue was washed with pentane
(25 mL) and dried in vacuo to yield 7 as a pale powder (458 mg, 0.357
mmol, 84%). Single crystals of 7 suitable for X-ray crystal structure
analysis were obtained from a toluene solution of 7 at room temperature.
Mp (DSC): 200 °C. IR (KBr): ν~/cmꢀ1 4062, 3373 (ν(NꢀH), s), 2397
(ν(BH), w). Anal. Calcd for C62H33B2F20N3P2: C, 58.02; H, 2.59; N,
3.27. Found:C, 58.12; H, 2.35;N, 3.49. 1H NMR(500 MHz, CD2Cl2, 233
0
(m, 1H, HCiPr(o )), 2.57 (s, 3H, MeAr), 2.47 (s, 3H, MePh), 2.14 (quint,
1H, J = 6.5 Hz, HCiPr(o)), 1.12 (d, 3H, J = 6.5 Hz, MeiPr(o)), 1.06 (d, 3H, J
0
0
= 6.5 Hz, MeiPr(o )), 1.04 (d, 3H, J = 6.5 Hz, MeiPr(o) ), 0.58 (d, 3H, J =
0
0
6.5 Hz, MeiPr(o ) ). 13C{1H} NMR (126 MHz, CD2Cl2, 213 K): δ 170.7
(CdNAr), 167.7 (CdNPh), 164.2 (NdCH), 145.4 (o0-Ar), 144.6 (o-
Ar), 141.5 (i-Ph), 136.8 (i-Ar), 129.3e, 128.45d, 128.38a, 128.1b, 124.8c
(Ph), (p-Ph), 128.9 (p-Ar), 125.1 (m-Ar), 124.0 (m0-Ar), 111.4 (CCdN),
0
0
29.4 (HCiPr(o )), 28.2 (HCiPr(o)), 26.9 (m, MeiPr(o )), 24.7 (MeiPr(o)),
0
0 0
24.3 (d, J = 11.7 Hz, MeiPr(o) ), 22.0 (m, MeAr), 21.1 (MeiPr(o ) ), 20.5
(MePh) [C5F6 not listed]. 19F NMR (470 MHz, CD2Cl2, 213 K): δ
ꢀ120.3 (o0), ꢀ130.6 (o), ꢀ154.3 (p), ꢀ164.5 (m), ꢀ166.4 (m0) (each
P(A)
K): δ 7.90 (m, 2H, o-Ph0 ), 7.81 (m, 2H, o-Ph0P(B)), 7.80 (m, 1H, p-
PhP(B)), 7.79 (m, 1H, p-PhP(A)), 7.65 (m, 1H, p-Ph0P(B)), 7.57 (m, 2H, m-
A
m, each 1H, C6F5 ) [Δδ(p,m) = 10.2, 12.1], ꢀ133.3 (o), ꢀ137.2 (o0),
PhP(B)), 7.55 (m, 2H, m-Ph0 ), 7.50 (m, 1H, p-Ph0P(A)), 7.44 (m, 2H,
P(B)
B
ꢀ158.2 (p), ꢀ164.5 (m), ꢀ166.3 (m0) (each m, each 1H, C6F5 )
m-Ph0P(A)), 7.43 (m, 2H, m-PhP(A)), 7.33 (ddd, 3JPH = 31.6 Hz, 3JPH
=
16.5 Hz, JHH = 18.0 Hz, 1H, dCH), 7.30 (m, 2H, o-PhP(B)), 7.11
(m, 2H, o-PhP(A)), 7.06 (m, 2H, p-PhN(B), p-PhN(A)), 7.04 (m, 1H, m0-
PhN(A)), 6.98 (m, 1H, m0-PhN(B)), 6.91 (m, 1H, o0-PhN(A)), 6.77 (m, 1H,
o0-PhN(B)), 6.72 (m, 1H, m-PhN(B)), 6.64 (m, 1H, m-PhN(A)), 6.00 (dd,
3JHH = 18.0 Hz, 3JHH(B) = 6.1 Hz, 1H, NH), 5.82 (m, 1H, o-PhN(B)), 5.55
(m, 1H, o-PhN(A)), 2.94 (br, 1H, BH). 13C{1H} NMR (126 MHz,
3
[Δδ(p,m) = 6.3, 8.1], ꢀ137.2 (2F, o), ꢀ160.8 (1F, p), ꢀ165.7 (2F, m)
(each m, C6F5C) [Δδ(p,m) = 4.9], ꢀ136.8 (2F, o), ꢀ160.8 (1F, p),
ꢀ165.4 (2F, m) (each m, C6F5D) [Δδ(p,m) = 4.6].
X-ray crystal structure analysis of 4: formula C48H31B2F20N3 C7H8,
3
M = 1143.51, colorless crystal 0.10 ꢁ 0.07 ꢁ 0.05 mm, a = 16.0952(4) Å,
b = 10.0282(3) Å, c = 31.9122(9) Å, β = 90.840(1)°, V = 5150.3(2) Å3,
calc = 1.475 g cmꢀ3, μ = 1.206 mmꢀ1, empirical absorption correction
2
F
CD2Cl2, 233 K): δ 165.0 (d, JPC = 14.4 Hz, dCH), 138.3
2
(i-PhN(B)), 137.5 (i-PhN(A)), 134.7 (d, JPC = 8.8 Hz, o-PhP(B)), 134.2
(0.889 e T e 0.942), Z = 4, monoclinic, space group P2/c (No. 13), λ =
1.54178 Å, T = 223(2) K, ω and j scans, 71 703 reflections collected (
(h, (k, (l), [(sin θ)/λ] = 0.60 Åꢀ1, 8989 independent (Rint = 0.084)
and 6613 observed reflections [I g 2σ(I)], 734 refined parameters, R =
0.051, wR2 = 0.140, max. (min.) residual electron density 0.43 (ꢀ0.31) e
(d, 2JPC = 10.1 Hz, o-PhP(A)), 134.0 (d, 4JPC = 1.5 Hz, p-PhP(A)), 133.9
(d, 4JPC = 2.3 Hz, o-PhN(A)), 133.73 (d, 4JPC = 1.7 Hz, p-PhP(B)), 133.66
(m, o0-PhN(A)), 133.66 (m, o0-PhN(B)), 133.39 (m, p-Ph0P(A)), 133.37
2
4
(m, o-PhN(B)), 133.23 (dd, JPC = 11.2 Hz, JPC = 3.6 Hz, o-Ph0P(A)),
ꢀ3, hydrogen atoms at N8 and B9 from difference Fourier calculations,
133.16 (m, p-Ph0P(B)), 133.0 (dd, JPC = 11.2 Hz, JPC = 3.5 Hz, o-
2
4
Å
the others calculated and refined as riding atoms.
Ph0P(B)), 130.7 (d, 1JPC = 106.6 Hz, i-Ph0P(B)), 129.3 (d, 3JPC = 12.3 Hz,
Synthesis of 6. The bis(phosphinimine) 29 (200 mg, 0.338 mmol,
1.0 equiv) was dissolved in dichloromethane (3 mL) and cooled to
m-Ph0P(B)), 129.2 (d, JPC = 11.8 Hz, m-Ph0 ), 128.7 (m0-PhN(B)),
3
P(A)
128.6 (m0-PhN(A)), 128.5 (d, 3JPC = 12.4 Hz, m-PhP(A)), 128.3 (d, 3JPC
=
2382
dx.doi.org/10.1021/om200116q |Organometallics 2011, 30, 2377–2384

Organometallics
ARTICLE
12.3 Hz, m-PhP(B)), 127.9 (m-PhN(B)), 127.7 (m-PhN(A)), 127.45, 127.41
(p-PhN(B), p-PhN(A)), 127.36 (d, 1JPC = 104.8 Hz, i-Ph0P(A)), 123.5 (d,
1JPC = 101.2 Hz, i-PhP(B)), 119.9 (d, 1JPC = 100.3 Hz, i-PhP(A)), 44.4 (dd,
1JPC = 119.2, 113.2 Hz, [P]2C), [C5F6 not listed]. 19F NMR (470 MHz,
CD2Cl2, 233 K): δ ꢀ129.9 (o0), ꢀ131.6 (o), ꢀ158.3 (p), ꢀ164.7 (m),
99.151(3)°, V = 2147.98(15) Å3, Fcalc = 1.450 g cmꢀ3, μ = 1.659 mmꢀ1
,
empirical absorption correction (0.543 e T e 0.852), Z = 2, triclinic,
space group P1 (No. 2), λ = 1.54178 Å, T = 223(2) K, ω and j scans,
28 040 reflections collected ((h, (k, (l), [(sin θ)/λ] = 0.60 Åꢀ1, 7444
independent (Rint = 0.051) and 6595 observed reflections [I g 2σ(I)],
602 refined parameters, R = 0.042, wR2 = 0.105, max. (min.) residual
electron density 0.32 (ꢀ0.32) e Åꢀ3, hydrogen atom at N2 from
difference Fourier calculations, the others calculated and refined as
riding atoms.
A
ꢀ165.5 (m0) (each m, each 1F, C6F5 ) [Δδ(p,m) = 6.4, 7.2], ꢀ130.0 (o),
ꢀ131.3 (o0), ꢀ158.4 (p), ꢀ165.7 (m), ꢀ164.7 (m0) (each m, each 1F,
B
C6F5 ) [Δδ(p,m) = 7.3, 6.3], ꢀ135.2 (2F, o), ꢀ160.8 (1F, p), ꢀ165.3 (2F,
m) (each m, C6F5C) [Δδ(p,m) = 4.5], ꢀ136.0 (2F, o), ꢀ161.1 (1F, p),
ꢀ165.5 (2F, m) (each m, C6F5D) [Δδ(p,m) = 4.4]. 31P{1H} NMR (202
MHz, CD2Cl2, 233 K): δ 36.9 (d, 2JPP = 18.0 Hz, 1P, ν1/2 = 11.6 Hz), 25.4
(d, 2JPP = 18.0 Hz, 1P, ν1/2 = 13.1 Hz). 11B{1H} NMR (160 MHz, CD2Cl2,
233 K): δ ꢀ0.3 (N2B, ν1/2 = 400 Hz), ꢀ14.7 (BH, ν1/2 = 500 Hz).
’ ASSOCIATED CONTENT
S
Supporting Information. Text and figures giving further
b
X-ray crystal structure analysis of 7: formula C62H33B2F20N3P2
experimental and spectroscopic details and CIF files (3, 4, 6, 7, 8)
giving crystallographic data. This material is available free of
charge via the Internet at http://pubs.acs.org.
3
C7H8, M = 1375.61, colorless crystal 0.30 ꢁ 0.20 ꢁ 0.15 mm, a =
14.8112(4) Å, b = 22.0942(6) Å, c = 19.1294(5) Å, β = 105.550(2)°, V =
6030.8(3) Å3, Fcalc = 1.515 g cmꢀ3, μ = 1.628 mmꢀ1, empirical
absorption correction (0.641 e T e 0.792), Z = 4, monoclinic, space
group P21/n (No. 14), λ = 1.54178 Å, T = 223(2) K, ω and j scans,
’ AUTHOR INFORMATION
50 565 reflections collected ((h, (k, (l), [(sin θ)/λ] = 0.60 Åꢀ1
,
Corresponding Author
*E-mail: rrojasg@uc.cl; erker@uni-muenster.de.
10 698 independent (Rint = 0.062) and 8675 observed reflections [I g
2σ(I)], 854 refined parameters, R = 0.059, wR2 = 0.165, max. (min.)
residual electron density 0.88 (ꢀ0.46) e Åꢀ3, hydrogen atoms calculated
and refined as riding atoms.
’ ACKNOWLEDGMENT
Synthesis of 8. The bis(phosphinimine) 2 (100 mg, 0.180 mmol,
1.0 equiv) was dissolved in dichloromethane (3 mL) and cooled to
ꢀ78 °C. To this solution was added HB(C6F5)2 (62.2 mg, 0.180 mmol,
1.0 equiv) in dichloromethane (3 mL), and the reaction mixture was
stirred for two hours at ꢀ78 °C. After removing the solvent in vacuo at
0 °C, the reaction mixture was dissolved in toluene (5 mL) and heated
for 26 h at 80 °C. Filtration over a Whatman filter and removal of the
solvent under reduced pressure produced a residue, which was washed
with pentane (30 mL) and dried in vacuo to yield a product mixture of 8
and 2 in a ratio of 7:1 [determined from the 31P NMR spectrum] as a
pale solid (118 mg, 0.116 mmol, 64%). Single crystals of 8 suitable for
X-ray crystal structure analysis were obtained from a dimethylsulfoxide
solution of 8 at room temperature. Mp (DSC): 166 °C. IR (KBr): ν~/
cmꢀ1 3404, 3362 (ν(NꢀH), s), 2158 (ν(CtN), s of 2). Anal. Calcd for
C388H255B7F70N24P16: C, 65.14; H, 3.59; N, 4.70. Found: C, 65.23; H,
2.82; N, 4.49 [for a mixture of 8 and 2 = 7 (C50H32BF10N3P2):1
(C38H31N3P2)]. 1H NMR (500 MHz, CD2Cl2, 298 K): δ 7.74 (m, 4H,
o-PhPN), 7.61 (m, 2H, p-PhPN), 7.43 (m, 4H, m-PhPN), 7.27 (m, 2H, p-
PhP), 7.23 (m, 2H, m-PhN), 7.19 (m, 4H, m-PhP), 7.14 (m, 1H, p-PhN),
6.97 (m, 4H, o-PhP), 6.93 (m, 1H, p-PhNB), 6.86 (m, 2H, m-PhNB), 6.77
(m, 2H, o-PhNB), 6.41 (m, 2H, o-PhN), 6.40 (br, 1H, dNH), 5.87 (br,
1H, NHPh). 13C{1H} NMR (126 MHz, CD2Cl2, 298 K): δ 163.0 (d,
2JPC = 9.3 Hz, NdC), 147.8 (dm, 1JFC ≈ 239 Hz, o-C6F5), 142.4 (t, J =
Financial support from the Deutsche Forschungsgemeinschaft
and the Fonds der Chemischen Industrie is gratefully acknowl-
edged. R.R.G. acknowledges support by FONDECYT project
No. 1100286 and thanks the Alexander von Humboldt-Stiftung
for a fellowship.
’ REFERENCES
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Lappert, M. F.; Severn, J. R. Chem. Rev. 2002, 102, 3031–3065; (b)
Coates, G. W.; Moore, D. R. Angew. Chem. 2004, 116, 6784–6806;
Angew. Chem., Int. Ed. 2004, 43, 6618–6639; (c) Holland, P. L. Acc.
Chem. Res. 2008, 41, 905–914; (d) Mindiola, D. J. Angew. Chem. 2009,
121, 6314–6316; Angew. Chem., Int. Ed. 2009, 48, 2–5.
(2) Recent examples of nacnac-derived complexes and their applica-
tions: (a) Hayes, P. G.; Piers, W. E.; McDonald, R. J. Am. Chem. Soc.
2002, 124, 2132–2133; (b) Badiei, Y. M.; Krishnaswamy, A.; Melzer,
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J. L. J. Am. Chem. Soc. 2007, 129, 12372–12373; (e) Yu, Y.; Sadique,
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Soc. 2008, 130, 6624–6638; (f) Badiei, Y. M.; Dinescu, A.; Dai, X.;
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120, 10109–10112; (g) West, N. M.; White, P. S.; Templeton, J. L.
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2.4 Hz, i-PhNB), 139.4 (dm, 1JFC ≈ 247 Hz, p-C6F5), 137.4 (dm, 1JFC
≈
243 Hz, m-C6F5), 136.5 (dd, 1JPC = 13.7 Hz, 3JPC = 8.6 Hz, i-PhP), 136.1
(d, 4JPC = 2.0 Hz, i-PhN), 134.2 (dd, 2JPC = 9.5 Hz, 5JP C = 1.8 Hz, o-
0
PhPN), 132.5 (d, 4JPC = 2.9 Hz, p-PhPN), 131.8 (d, 2JPC = 17.8 Hz, o-
PhP), 131.5 (br, o-PhNB), 130.1 (m-PhN), 129.6 (dm, 1JPC = 103.5 Hz, i-
PhPN), 129.1 (d, 3JPC = 5.7 Hz, m-PhP), 128.6 (p-PhP), 128.4 (d, 3JPC
=
12.6 Hz, m-PhPN), 128.2 (d, J = 1.7 Hz, m-PhNB), 126.7 (p-PhN), 126.0
(d, J = 2.2 Hz, p-PhNB), 124.8 (o-PhN), 42.8 (dd, 1JPC = 120.5 Hz, 1JPC
=
27.9 Hz, PdC), n.o. (i-C6F5). 19F NMR (470 MHz, CD2Cl2, 298 K): δ
≈ ꢀ132.5 (m, 2F, o-C6F5), ꢀ160.0 (m, 1F, p-C6F5), ꢀ165.3 (m, 2F, m-
C6F5) [Δδ(p,m) = 5.3]. 31P{1H} NMR (202 MHz, CD2Cl2, 298 K): δ
37.6 (d, 2JPP = 170.1 Hz, 1P, PdN, ν1/2 = 5.1 Hz), ꢀ30.3 (d, 2JPP = 170.1
Hz, 1P, P, ν1/2 = 2.0 Hz). 11B{1H} NMR (160 MHz, CD2Cl2, 298 K): δ
ꢀ4.1 (ν1/2 ≈ 50 Hz).
(3) Cabrera, A. R.; Schneider, Y.; Valderrama, M.; Fro€hlich, R.; Kehr,
G.; Erker, G.; Rojas, R. S. Organometallics 2010, 29, 6104–6110.
(4) See for a comparison: (a) Scott, S. L.; Peoples, B. C.; Yung, C.;
Rojas, R. S.; Khanna, V.; Sano, H.; Suzuki, T.; Shimizu, F. Chem.
X-ray crystal structure analysis of 8: formula C50H32BF10N3P2, M =
937.54, colorless crystal 0.42 ꢁ 0.20 ꢁ 0.10 mm, a = 10.4591(4) Å, b =
11.6827(4) Å, c = 19.1693(9) Å, R = 101.833(2)°, β = 105.781(4)°, γ =
2383
dx.doi.org/10.1021/om200116q |Organometallics 2011, 30, 2377–2384

Organometallics
ARTICLE
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