Chromium (iii)-bis(iminophosphoranyl)methanido complexes: Synthesis, X-ray crystal structures and catalytic ethylene oligomerization

Article abstract of DOI:10.1039/b904619d

Bis(aminophoshonium) salts derived from bis(diphenylphosphino)methane were prepared and triply deprotonated with potassium hexamethyldisilazane to yield the corresponding bis(iminophosphoranyl)methanides, which were then subjected to coordination with Cr^IIICl₃(THF)₃. Binuclear complexes of type [(HC(PPh₂NR)₂Cr(μ-Cl)(Cl)) ₂] (R = iPr, tBu) with an octahedral coordination geometry and a long C-Cr bond were obtained and structurally characterized. In the case of R = o-MeO-C₆H₄, a monomeric species featuring no C-Cr bond is observed. Preliminary evaluation of catalytic activities of these complexes in ethylene oligomerization and polymerization is reported.

Full text of DOI:10.1039/b904619d

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PAPER
www.rsc.org/njc | New Journal of Chemistry
Chromium (III)-bis(iminophosphoranyl)methanido complexes: synthesis,
X-ray crystal structures and catalytic ethylene oligomerizationw
ab
a
a
a
Christian Klemps, Antoine Buchard, Romaric Houdard, Audrey Auffrant,
a
a
a
b
Nicolas Mezailles, Xavier Frederic Le Goff, Louis Ricard, Lucien Saussine,
´ ´ ´
b
a
Lionel Magna and Pascal Le Floch*
Received (in Montpellier, France) 6th March 2009, Accepted 18th May 2009
First published as an Advance Article on the web 17th June 2009
DOI: 10.1039/b904619d
Bis(aminophoshonium) salts derived from bis(diphenylphosphino)methane were prepared and
triply deprotonated with potassium hexamethyldisilazane to yield the corresponding
bis(iminophosphoranyl)methanides, which were then subjected to coordination with
III
Cr Cl
3
(THF)
3
. Binuclear complexes of type [(HC(PPh
2
NR)
2 2
Cr(m-Cl)(Cl)) ] (R = iPr, tBu) with
an octahedral coordination geometry and a long C–Cr bond were obtained and structurally
characterized. In the case of R = o-MeO-C , a monomeric species featuring no C–Cr bond is
6
H
4
observed. Preliminary evaluation of catalytic activities of these complexes in ethylene
oligomerization and polymerization is reported.
Introduction
catalysis. Comparatively, these ligands have received very little
attention compared to imines, their carbon analogs, and have
10,11
The development of transition metal catalysts for ethylene
oligomerization and polymerization is still a growing area of
research, since a-olefins are widely used in a variety of
industrial processes, ranging from co-monomers in the
synthesis of low density polyethylene to intermediates for
been rarely exploited in catalysis.
However, since these
ligands exhibit different electronic and steric properties with
regard to imines, namely the absence of a real p-system and a
positively charged phosphorus center making the nitrogen
atom a harder donor, iminophosphorane complexes deserve
much interest. Thus, having developed a straightforward route
to bis(iminophosphoranes) and their anionic derivatives
1
synthetic lubricants, plasticizers and surfactants. In this
context, chromium-based catalysts have attracted much
attention due to their potential in selective oligomerization
processes, in which the nature of the obtained olefinic oligomers
can be easily modified by fine tuning the metal coordination
12
starting from bis(aminophosphonium) derivatives, we were
interested in evaluating the potential of such ligands in oligo-
merization reactions. Thus we report here on the synthesis and
complete characterization of three bis(iminophosphorane)-
methanido chromium(III) complexes and discuss the preliminary
results of their activity in ethylene oligomerization.
2
sphere. Thus, chromium complexes bearing bidentate PBP,
3
4
5
tridentate SBPBS, SBNBS, PBNBP, NBNBN, and
6
PBPBO ligands were found to give mainly trimers. Not only
is the nature of the coordinating atoms determining for the
selectivity of the oligomerization process, but also the nature
of their substituents and the link between these coordination
sites. Indeed, diphosphinoamine (PBNBP) chromium complexes
catalyze ethylene tri- and tetramerization if the nitrogen atom
Results and discussion
Deprotonation of bis(aminophosphonium) salts, and
7
coordination to CrCl (THF)
3 3
bears ether groups whereas with other substituents on this
atom, the same type of ligand induces a higher selectivity
8
towards tetramerization. As we recently demonstrated
Monoanionic derivatives of bis(iminophosphorane) were
conveniently obtained by triple deprotonation of the corres-
ponding bis(aminophosphonium) salts 1a–c (Scheme 1), the
latter being prepared in a two-step synthesis starting from
bis(diphenylphosphino)methane, bromine, and the corresponding
the potential of iminophosphorane-based ligands in ethylene
9
oligomerization, we pursue a research program dedicated
to the use of iminophosphorane ligands in homogeneous
1
2
primary amine RNH
2
, as described earlier.
KHMDS
a
Laboratoire ‘‘He´te´roe´le´ments et Coordination’’, Ecole Polytechnique,
CNRS, 91128 Palaiseau cedex, France.
E-mail: lefloch@poly.polytechnique.fr; Fax: +33 (0)1 69 33 44 40;
Tel: +33 (0)1 69 33 44 00
IFP Lyon, Rond-point de l’echangeur de Solaize, BP 3,
b
69360 Solaize, France
w Electronic supplementary information (ESI) available: ORTEP plot
of the X-ray structure and important structural data of 3a as well as
crystal data for structures 3a–c, details of GC trace, DSC and polymer
melting points. CCDC reference numbers 651318–651320. For ESI
and crystallographic data in CIF or other electronic format see DOI:
10.1039/b904619d
Scheme 1 Synthesis of bis(iminophosphoranyl)methanides 2.
1
748 | New J. Chem., 2009, 33, 1748–1752
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(
KHMDS = potassium hexamethyldisilazane) was preferred
to nBuLi to achieve the proton abstraction, because of better
precipitation properties of the potassium bromide salt in THF,
which facilitates its removal. The deprotonation reaction
proceeded rapidly and its completeness was checked by
3
1
1
P{ H} NMR, the singlet at 33.5; 29.5; 36.9 corresponding
to 1a–c being replaced by a singlet at 16.0; 3.9; 11.5 ppm for
a–c. The potassium bis(iminophosphoranyl)methanides 2a–c
were thus obtained as pale yellow powders in high yields and
2
1
13
31
fully characterized by H, C and P NMR. However, they
were found to be too moisture sensitive to furnish satisfactory
3 3
elemental analyses. Addition of CrCl (THF) to THF solutions
of 2a–c afforded blue (3a and b) or brown (3c) complexes,
Fig. 2 X-Ray solid state structure of 3c. Hydrogen atoms have been
respectively. Due to the strong paramagnetic nature of the
3
octahedral d -Cr(III) center, no signals could be observed for
omitted for clarity. Ellipsoids are drawn at the 50% probability
˚
level. Bond distances (A) and angles (1): Cr1–N1 = 2.013(4),
Cr1–Cl1 = 2.3742(15), Cr1–Cl2 = 2.3641(15), Cr1–C1 = 3.366(6),
1
13
31
any of these complexes in H, C and P NMR. However, the
complete disappearance of the ligand signals is a sign of the
completeness of the reaction.
N1–P1
= 1.636(5), P2–N2 = 1.628(5), P2–C1 = 1.726(6),
P1–C1 = 1.702(6), Cr1–O1 = 2.087(4), Cl1–Cr1–Cl2 = 168.55(6),
N1–Cr1–Cl1 = 95.64(14), C1–Cr1–Cl2 = 118.0(11), P1–C1–P2 =
118.5(4), N1–Cr1–N2 = 101.55(19), O1–Cr1–O2 = 101.14(16).
Structural characterization of the complexes 3a–c
Single X-ray quality crystals of all complexes 3a–c could be
grown (see Experimental section for details). Views of one
molecule of 3b and 3c are shown in Fig. 1 and Fig. 2 along
with some important structural parameters (see ESIw for
details on the structure of 3a). 3a and b both present a dimeric
1
3
[(HC(PPh
2
NSiMe
3
)
2
)Cr(m-Cl)]
2
.
The CrÁ Á ÁCr separation
˚
˚
measured at 3.6360(5) A for 3a and 3.7231(8) A for 3b is
slightly greater than that reported by Stephan and Wei for the
1
3
TMS-substituted dimer. The distortion from an octahedral
geometry around each of the chromium central atoms is
evidenced by a Cl1–Cr1–C1 angle of 171.13(4)1 in 3a and
171.02(7)1 for 3b. As expected from their inherent similarity,
both structures present essentially identical structural features.
The potential tetradentate coordination of 2c, owing to the
presence of two methoxy groups, is confirmed in the structure
3c. Complex 3c is indeed a monomeric species in the solid state
with a distorted octahedral geometry around the chromium
center. The methoxy groups occupy two equatorial coordination
1
3
structure similar to the one reported by Wei and Stephan for
the chromium(II) complex [((HC(PPh NSiMe Cr(m-Cl)) ].
2
3
)
2
2
The anionic nature of the bis(iminophosphoranyl)methanide
ligand was confirmed by the location and subsequent
refinement of the single proton in the X-ray structures.
Furthermore, both structures show coordination of the central
carbon atom to the chromium center with Cr1–C1 bond
˚
lengths of 2.2311(14) A (3a) and 2.185(3) A (3b), respectively.
˚
This length is intermediate between the short Cr1–C1 distance
˚
˚
sites with a very short average Cr1–O bond length of 2.091(4) A,
of 2.148(5) A found in the [C(PPh
2
NSiMe
3
)
˚
2
Cr]
2
bridging
1
carbene complex and the one of 2.264(3) A observed for
4
and thus complete the coordination sphere. The Cr–N
˚
˚
distances are 2.013(4) A and 1.999(5) A long, respectively.
Both nitrogen and oxygen atoms form an equatorial
coordination plane with a mean deviation of only 0.411. No
Cr1Á Á ÁC1 bond was observed in this structure. Moreover,
the Cr1–N1–P1–C1–P2–N2 ring system exhibits boat-like
geometry which strongly differs from the structures recorded
for 3a and b (Fig. 3). Such a structural element was observed
by Stephan and Wei for the second isomer in the solid state
1
3
structure of [(HC(PPh
2
NSiMe
3
)
2
)Cr(m-Cl)]
2
.
Nevertheless,
˚
there the Cr1Á Á ÁC1 distance of 2.921(3) A is much shorter
˚
than that of 3.366(6) A measured for 3c.
Fig. 1 X-Ray solid state structure of 3b which lies about an inversion
center. Hydrogen atoms have been omitted for clarity. Ellipsoids
are drawn at the 50% probability level. Ellipsoids are drawn at
˚
the 50% probability level. Bond distances (A) and angles (1):
Cr1–N1 = 2.100(2), Cr1–Cl1 = 2.4211(7), Cr1–Cl2 = 2.3971(7),
Cr1–C1
= 2.185(3), N1–P1 = 1.604(2), N2–P2 = 1.603(2),
P2–C1 = 1.764(2), P1–C1 = 1.750(3), Cl1–Cr1–Cl2 = 90.90(2),
N1–Cr1–Cl1 = 90.06(6), C1–Cr1–Cl2 = 171.02(7), P1–C1–P2 =
Fig. 3 Diagram of the bis(iminophosphoranyl)methanide geometry
on the Cr(III) center of 3b (left) and 3c (right).
122.92(15), N1–Cr1–N2 = 96.97(8).
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Ethylene oligomerization
Conclusions
The catalytic activities of the complexes 3a–c in
ethylene oligomerization and polymerization were investigated.
Experiments were carried at both 45 1C as well as 20 1C in the
presence of MAO (MAO = methylaluminoxane) with a
MAO/Cr ratio of 300 (or 600, run 3), and toluene as solvent.
The ethylene pressure was kept constant at 30 bar throughout
the catalytic run (0.5 h). The products of the catalytic
conversions were oligomers, mainly linear a-olefins
In conclusion, three bis(diphenylphosphino)methanido
chromium(III) complexes 3a–c were synthesized and fully char-
acterized. Depending on the nature of the nitrogen substituent,
two different structure types were obtained: a dimeric complex
containing a Cr–C1 bond and a monomeric species where the
chromium coordination is completed by two pendant oxygen
donors. 3a–c proved to be active catalysts for ethylene oligo-
merization and polymerization with activities up to 19789
mol(C H ) per mol(Cr). Future work will focus on rationalizing
(
Table 1), as detected by GC. Two important common
2
4
features of all catalyst precursors 3a–c were observed. First,
the productivity increased significantly when the oligomerization
reactions were carried out at lower temperatures. This effect
was most pronounced for 3a, for which the productivity
increased from 18 421 to 19 789 mol(C H ) per mol(Cr).
the observed product distribution using theoretical studies.
Experimental
2
4
General considerations
Secondly, all catalysts exhibited two distinct product distributions
in the liquid phase with one maximum production of 1-hexene
and a second tight distribution in the C14–C24 range. This
bimodal product distribution might be due to two competing
oligomerization mechanisms. The C –C fraction would
All manipulations were carried out under argon or nitrogen
using standard Schlenk or glove box techniques. Solvents were
dried according to standard procedures and distilled prior to
1
2
20
use. 1a, 2a, and CrCl
(THF)
were prepared as described
4
8
3
31
3
1
5
1
13
be produced by a metallacycle mechanism whereas the
higher C14–C24 fraction would be formed by a degenerative
before. H, C and P NMR spectra were recorded on a
Bruker Avance 300 spectrometer at 20 1C. Coupling constants
J are reported in Hz, chemical shifts in ppm. Elemental
analyses were performed at the Service d’analyse du CNRS,
Gif-sur-Yvette, France. MAO was obtained from Sigma-
Aldrich (10 wt% in toluene), ethylene from Air Liquide
1
6
polymerization mechanism. Further analysis of this fraction
reveals that neither a classic Schultz–Flory nor Poisson
distribution is present and only linear a-olefins with even
and uneven carbon number were formed as major products.
To further understand the origin of the olefins with uneven
carbon number, which might stem either from chain transfer
(
N25 grade). GC analyses were carried out using a Perichrom
PR2100 gas chromatograph equipped with a HP PONA
1
7,18
column (0.2 mm  50 m  0.5 mm).
to an Al–Me species
or from a metathesis mechanism
1
9
involving a bimetallic chromium species, a catalytic test
employing 600 eq. of MAO was carried out (run 3). However,
no significant change in the quantity of a-olefins with uneven
carbon number was observed. The relatively rapid enclosure of
the catalyst with polymeric material and thus deactivation of
the catalytic species under the chosen experimental conditions
is probably at the origin of the insensitivity towards a
changing MAO/Cr ratio and precludes further analysis in this
General procedure for the preparation of bis(iminophosphonium)
bromides 1b and c
1
2
In analogy to the procedure previously described, a solution
of bis(diphenyphosphino)methane (150 mg, 0.39 mmol) in
dichloromethane (10 mL) was cooled to À78 1C and bromine
(125 mg, 0.8 mmol, 40 mL) was added dropwise from a syringe.
The cold bath was removed and the reaction mixture was
allowed to warm to ambient temperature. A yellow-white
precipitate was observed. At À78 1C, the corresponding
primary amine (1.56 mmol) was added dropwise and the
reaction mixture was allowed to warm to ambient temperature,
upon which a white precipitate of ammonium bromide
formed. The salt was filtered off, and the filtrate dried
in vacuo. The solid residue was washed with THF
(2 Â 25 mL) to yield a white powder after drying in vacuo.
6
direction. Complex 3c shows the highest C -productivity along
with an a-selectivity of 95%, a result which may be ascribed to
the monomeric nature of the catalyst precursor, as observed
with other chromium-based catalytic systems for ethylene
8
oligomerization. Each of the catalytic runs produced a
polymeric fraction accounting for 15–23% of the total
production, whose quantity did not change significantly with
the reaction temperature.
Table 1 Ethylene oligomerization with complexes 3a–c (conditions: 30 bar C
2
H
4
, 8 mmol of Cr, 20 mL toluene, 0.5 h, MAO/Cr = 300)
Run Complex T/1C [1-C ] (%) [1-C ] (%) [1-C ] (%)
C
4
4
C
6
6
C
8
8
2 4
C14–C24 (%) Polymer (% ) TON/mol (C H ) per mol (Cr)
1
2
3
4
5
6
7
3a
3a
3a
3b
3b
3c
3c
45
20
20
45
20
45
20
2 [91]
3 [95]
2 [93]
2 [90]
2 [90]
6 [95]
6 [95]
8 [98]
3 [99]
5 [99]
5 [99]
2 [99]
3 [99]
3 [99]
3 [99]
69
65
66
69
66
63
61
18
16
17
19
23
15
16
18 421
19 789
19 258
16 841
17 892
18 266
18 973
11 [98]
10 [98]
5 [97]
6 [98]
13 [98]
14 [98]
a
a
MAO/Cr = 600.
1
750 | New J. Chem., 2009, 33, 1748–1752
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Compound 1b. Yield: 166 mg (0.24 mmol, 62%) (Found: C
7.75, H 6.08, N 3.99%. C33 requires C 57.57, H
.15, N 4.07%); dP{1H} (121.5 MHz, CDCl ) 29.5 (s, P); d
nitrogen stream. Data were collected at 150.0(1) K on a
5
6
H42Br
2
2
N P
2
Nonius Kappa CCD diffractometer using a Mo-Ka (l =
˚
0.71073 A) X-ray source and a graphite monochromator. All
3
H
2
(
300 MHz, CDCl ) 0.96 (18H, s, C(CH ) ), 6.60 (2H, t, J
3
data were measured using phi and omega scans. The crystal
22
3 3
PH
2
structures were solved using SIR97 and SHELXL-97.
1
1
6.5, N-H), 6.96 (2H, s, PCH P), 7.60 (8H, m, o-CH(PPh )),
2
2
3
.73 (4H, t, J
4
7.0, p-CH(PPh )), 8.07 (8H, dd, J 11.5,
23
7
Molecular drawings were made using ORTEP-III.
HH
2
HP
3
J
HH 8.0, 8H, m-CH(PPh
1
2
)); d
P), 31.1 (s, C(CH
C
(75.5 MHz, CDCl
3
) 25.6
General procedure for the preparation of the complexes 3a–c
(
t, JCP 64.5, PCH
2
3
)
3
), 56.4 (s, C(CH
2
3
)
3
),
1
1
21.6 (d,
J
CP 102.0, ipso-C(PPh
3
2
)), 129.2 (dd,
CP 6.5, m-CH(PPh
JCP 6.7,
3 3
In THF (5 mL), CrCl (THF) (24 mg, 0.063 mmol) was added
o-CH(PPh
2
)), 134.4 (dd,
J
2
)), 134.8
to a solution of the corresponding bis(iminophosphoranyl)-
methanide 2 (0.063 mmol) resulting in an immediate color
change of the reaction mixture. After 1 h of stirring, the
reaction mixture was centrifuged and the supernatant solution
was dried in vacuo. The solid residue was finally washed with
petroleum ether 40/65 (2 Â 5 mL).
(
s, p-CH(PPh )).
2
Compound 1c. Yield: 159 mg (0.28 mmol, 72%) (Found C
5
9.36, H 4.92, N 3.37%. C H Br N O P requires C 59.41,
3
9
38
2
2
2 2
H 4.86, N 3.55%); dP{1H} (121.5 MHz, CDCl ) 36.9 (s, P); d
3
H
2
(
300 MHz, CDCl
3
) 3.11 (6H, s, OCH
3
), 5.78 (2H, t, JHP 14.5,
HH 7.0, N-CCH), 6.86 (4H, m,
)), 7.57
3
PCH
2
P), 6.31 (2H, d,
J
Compound 3a. Yield: 38 mg (0.029 mmol, 92%) of a dark
N-CCHCHCH), 7.36–7.48 (12H, m, o, p-CH(PPh
2
blue powder. X-Ray quality crystals were obtained by
3
3
(
3
2H, d,
JHH 7.0, C(OCH
3
)CH), 8.29 (8H, dd,
J
HH 9.0,
PH 9.4, NH); d
P), 54.4
overnight standing of
a concentrated dichloromethane
2
J
J
HH 7.5, m-CH(PPh
75.5 MHz, CDCl
s, OCH
s, ipso-C(PPh )), 124.5 (s, N-CC(OCH )CH), 125.6
2
)), 9.55 (2H, d,
C
solution of 3a. C H Cl Cr N P : calcd. C 60.01, H 5.69,
6
2
70
4
2
4 4
1
(
(
(
(
3
) 30.5 (t,
JCP 60.9, PCH
2
N 4.51%; found C 60.14, H 5.42, N 4.27%.
3
), 111.0 (s, N-CCH), 121.8 (s, N-CCHCH), 122.4
Compound 3b. Yield: 36 mg (0.026 mmol, 84%) of a
blue powder. X-Ray quality crystals were obtained by
overnight standing of a concentrated THF solution of 3b.
2
3
2
s, C(OCH )CHCH), 125.8 (s, N-C), 129.5 (d, JCP 8.0,
3
3
o-CH(PPh )), 132.2 (d, JCP 7.0, m-CH(PPh )), 148.5
2
2
66 4 2 4 4
C H78Cl Cr N P : calcd. C 61.12, H, 6.06, N 4.32%; found C
(
s, C(OCH )).
3
6
0.97, H 6.22, N 4.19%.
General procedure for the preparation of the
bis(iminophosphoranyl)methanides 2b and c
Compound 3c. Yield: 43 mg (0.055 mmol, 87%) of a
brown powder. X-Ray quality crystals were obtained by
KHMDS (38 mg, 0.19 mmol) was added to a suspension
of 0.063 mmol of the corresponding bis(iminophosphonium)
bromide 1 in THF (5 mL). The reaction mixture immediately
became clear taking a pale yellow color. Precipitating potassium
bromide was removed by centrifugation and the supernatant
solution dried in vacuo to yield a pale yellow powder.
overnight standing of a concentrated THF solution of 3c.
39 2 2 2 2
C H35Cl CrN O P : calcd. C 62.58, H 4.71, N 3.74%; found
C 62.41, H 4.88, N 3.59%.
General oligomerization procedure
All catalytic reactions were carried out in a magnetically
stirred stainless steel autoclave (120 mL) equipped with a
pressure gauge and needle valves for injection of chemicals.
The interior of the autoclave was protected from corrosion by
a Teflon/protective coating and a glass liner. A typical reaction
was performed by introducing into the reactor under nitrogen
atmosphere the complex (4 mmol in the case of the dimeric
complexes 3a and b, 8 mmol in the case of 3c) and toluene
(20 mL). After injection of the MAO solution (300 eq.), the
reactor was immediately brought to the desired working
pressure, and continuously fed by ethylene using a reserve
bottle. The reaction was stopped by shutting off the ethylene
supply and cooling down the system to À70 1C. After the
pressure in the reactor has decreased to atmospheric pressure,
the reaction was quenched by adding 1 mL of methanol.
n-Heptane used as internal standard was also introduced and
the mixture was analyzed by quantitative GC, first calibrated
with authentic samples (except in the case of butenes for which
the calibration was based on the response factor of n-pentane).
Compound 2b. Yield: 34 mg (0.061 mmol, 98%). dP{1H}
(
121.5 MHz, [D
.89 (18H, s, C(CH
16H, m, o-CH, m-CH(PPh
8
]-THF) 3.9 (s, P); d
H
(300 MHz, [D
8
]-THF)
), 1.05 (1H, t, JHP 3.0, PCHP), 7.12
)), 7.79 (8H, m, p-CH(PPh )); d
2
0
3 3
)
(
(
(
(
(
2
2
C
3
75.5 MHz, [D ]-THF) 35.8 (dd, JCP 5.5, C(CH ) ), 52.1
8
3 3
2
s, C(CH ) ), 127.5 (dd,
3
J
CP
5.5, o-CH(PPh )), 128.5
2
3
3
s, p-CH(PPh )), 133.2 (dd, JCP 4.5, m-CH(PPh )), 146.2
2
2
1
d, J 87.5, ipso-C(PPh )).
CP
2
Compound 2c. Yield: 41 mg (0.062 mmol, 99%); dP{1H}
121.5 MHz, [D ]-THF) 11.5 (s, P); (300 MHz,
]-THF) 2.07 (1H, s, PCHP), 3.48 (6H, s, OCH ),
.12–6.45 (8H, m, C(OCH )CHCHCHCH), 6.94 (12H, m, o,
(
8
d
H
[
D
8
3
6
3
p-CH(PPh )), 7.78 (8H, m, m-CH(PPh )); d (75.5 MHz,
2
2
C
1
[
D ]-THF) 11.6 (t, J 120.0, PCHP), 55.9 (s, OCH ), 112.5
8 CP 3
(
s, C(OCH )CHCH), 114.3 (s, N-CCHCH), 121.9
3
3
s, C(OCH )CH), 122.6 (dd, JCP 7.0, N-CCH), 128.1 (dd,
(
2
3
3
J
CP 5.5, o-CH(PPh
.0, m-CH(PPh )), 140.5 (d, JCP 101.0, ipso-C(PPh
s, N-C), 153.6 (dd, JCP 11.0, N-CC(OCH
2
)), 129.3 (s, p-CH(PPh
2
)), 132.2 (dd, JCP
1
4
2
2
)), 145.6
3
(
3
)).
Notes and references
X-Ray crystallography
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