The Cα-deprotonated iminophosphorane Ph 2P(CH2Py)(NSiMe3) as an N,N-chelating ligand for iron and zinc

Article abstract of DOI:10.1002/ejic.200400318

The iminophosphorane Ph₂P(CH₂Py)(NSiMe₃) (Py = NC₅H₄) is deprotonated at the C_α- position in a reaction with [M{N(SiMe₃)₂}₂] (M = Fe²⁺, Zn²⁺) to give metallaspirocycles in which the metal cations are N,N-chelated by the ring- and imino-nitrogen atoms of both monoanionic ligands. The molecular structures of [M{Ph₂P(CHPy) (NSiMe₃)}₂] [M = Fe (1), Zn (2)] are discussed and general trends in the bonding of the [Ph₂P(CHPy)(NSiMe₃)] ^- anion on metal coordination are deduced. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Full text of DOI:10.1002/ejic.200400318

FULL PAPER
The Cα-Deprotonated Iminophosphorane Ph2P(CH2Py)(NSiMe3)
as an N,N-Chelating Ligand for Iron and Zinc
Alexander Murso[a] and Dietmar Stalke*[a]
Keywords: Chelates / Hypervalent compounds / Iminophosphoranes / Iron / N ligands
The iminophosphorane Ph2P(CH2Py)(NSiMe3) (Py = NC5H4)
Zn (2)] are discussed and general trends in the bonding of
the [Ph2P(CHPy)(NSiMe3)]− anion on metal coordination are
is deprotonated at the Cα-position in
a reaction with
[M{N(SiMe3)2}2] (M = Fe2+, Zn2+) to give metallaspirocycles deduced.
in which the metal cations are N,N-chelated by the ring- and
imino-nitrogen atoms of both monoanionic ligands. The mo-
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
lecular structures of [M{Ph2P(CHPy)(NSiMe3)}2] [M = Fe (1),
Germany, 2004)
Introduction
polarisability. Recently, Leung et al. reported some main-
group metal complexes of iPr2P(CH2Py)(NSiMe3) and [2,6-
(Me3SiNPiPr2CH2)2(cy-C5H3N)], obtained by depro-
tonation with organolithium compounds, alkylmagnesium
compounds or group-14 amides. Metathesis with group-14
halides gave 1,3-dimetallacyclobutanes (Scheme 1).[9,10]
In the literature the imino nitrogen atom is commonly
described as a two-electron σ-donor with only minor π-ac-
ceptor properties.[1] However, we recently reported the
syntheses and coordination modes of the iminophos-
phorane Ph2P(CH2Py)(NSiMe3) (Py ϭ NC5H4) and its
anion in alkali metal complexes and provided experimental
evidence that the PϭN bond in iminophosphoranes has to
be regarded as a PϩϪNϪ single bond with high electrostatic
contributions,[11] as already predicted from theoretical in-
vestigations.[12,13] Thus, we found both lone pairs at the sp3-
hybridized imino nitrogen atom in [(Et2O)Li{Ph2P-
(CHPy)(NSiMe3)}] to be directed towards the cation.
Hence, the metalϪimino nitrogen interactions cannot be re-
garded as simple 2e-donor bonds (Figure 1).
Iminophosphoranes of the general type R3PNRЈ are
valuable building blocks in organometallic and organic
syntheses.[1] Their reactivity is mainly due to the inherent
polarity of the phosphorusϪnitrogen bond, which makes
them reactive towards both electrophilic and nucleophilic
reagents.[2] In silylated iminophosphoranes, R3PNSiMe3,
the SiϪN bond is cleaved in reactions with main-group[3] or
transition-metal halides,[4] resulting in the [R3PN]Ϫ building
block, which has similar steric and electronic characteristics
to the ubiquitous cyclopentadienyl ligand.[5] In addition,
the incorporation of heteroaromatic substituents at the
phosphorus centre instead of commonly used alkyl or phe-
nyl groups alters and augments the reactivity and coordi-
nation modes of iminophosphoranes. In reactions of pyri-
dyl-substituted iminophosphoranes and amino(imino)phos-
phoranes with organolithium compounds and lithium am-
ides reduction of the phosphorus() centre by PϪC or PϪN
bond cleavage is observed to give phosphanylamides or
phosphanides.[6] Likewise, transiminations are observed
when treating iminophosphoranes with imines.[7]
Additionally, P-alkyl-substituted iminophosphoranes can
easily be deprotonated to give attractive building blocks for
metallacycles.[8] The introduction of alkyl bridges between
the phosphorus atom and the donating heterocycle in the
ligand periphery of iminophosphoranes provides not only
the opportunity of a higher geometrical adaptability by a
wider bite but can also allow the formation of anionic spec-
ies. Delocalisation of the carbanionic charge to the donat-
ing atoms would enable the ligand to respond to the various
requirements of metal atoms with their different radii and
This bifurcated 4e-coordination pattern and the sidearm
donation capability of the pyridyl nitrogen atom in the
[Ph2P(CHPy)(NSiMe3)]Ϫ anion prompted us to investigate
reactions of the iminophosphorane Ph2P(CH2Py)(NSiMe3)
with transition metal amides [M{N(SiMe3)2}2]. In this con-
tribution we report the complexes of divalent iron and zinc
(M ϭ Fe, Zn).
Results and Discussion
Syntheses
[14]
The reaction of the iron() amide [Fe{N(SiMe3)2}2]2
[a]
with the iminophosphorane Ph2P(CH2Py)(NSiMe3)[11] in a
1:2 ratio in polar solvents such as THF or Et2O results,
even at Ϫ78 °C, in dark-red to black solutions containing
Institut für Anorganische Chemie der Universität Würzburg,
Am Hubland, 97074 Würzburg, Germany
Fax: (internat.) ϩ 49-931-888-4619
E-mail: dstalke@chemie.uni-wuerzburg.de
4272
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DOI: 10.1002/ejic.200400318
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The Cα-Deprotonated Iminophosphorane Ph2P(CH2Py)(NSiMe3)
FULL PAPER
Scheme 1. Main-group metal complexes of iPr2P(CH2Py)(NSiMe3) (top) and [2,6-(Me3SiNPiPr2CH2)2(cy-C5H3N)] (bottom)
tion of the iminophosphorane with [Zn{N(SiMe3)2}2][15]
gives the isomorphous zinc derivative [Zn{Ph2P(CHPy)-
(NSiMe3)}2] (2; Scheme 2, right).
After workup, both complexes were isolated in high
yields and their molecular structures determined by X-ray
diffraction experiments. Both compounds 1 and 2 are insol-
uble in nonpolar solvents. The complexes were analysed by
IR spectroscopy and elemental analysis. For the iron com-
plex 1 no NMR spectroscopic data were available due to
its paramagnetic nature. The NMR resonances for the zinc
derivative 2 are given in the Exp. Sect.
Figure 1. Bifurcated donation of the valence shell charge concen-
trations derived from experimental charge density studies of the
imino nitrogen atom in [(Et2O)Li{Ph2P(CHPy)(NSiMe3)}]
Structure Discussion
The solid-state structure of 1 is depicted in Figure 2. The
central iron() cation is chelated by the nitrogen atoms
several products. In contrast, the addition of pure N1ϪN4 of the two ligands. The coordination sphere is best
[Fe{N(SiMe3)2}2]2 to the solid iminophosphorane Ph2P- described as a distorted tetrahedron with the angles at the
(CH2Py)(NSiMe3) at room temperature gives immediately iron cation varying from 100.92(8) to 124.40(8)°. In the me-
a red oily suspension of solid [Fe{Ph2P(CHPy)(NSiMe3)}2] tallaspirocycle, the two six-membered FeN2C2P rings adopt
(1) in liquid HN(SiMe3)2, formed by the Cα-deprotonation a distorted boat conformation, each with the deprotonated
of the iminophosphorane (Scheme 2, left). A similar reac- carbon atoms C1 and C22 displaced by, on average, 45 pm
Scheme 2. Syntheses of [Fe{Ph2P(CHPy)(NSiMe3)}2] (1) and [Zn{Ph2P(CHPy)(NSiMe3)}2] (2) in the reaction of Ph2P(CH2Py)(NSiMe3)
with the corresponding metal amide [M{N(SiMe3)2}2]2 (M ϭ Fe, Zn)
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A. Murso, D. Stalke
FULL PAPER
Figure 3. Solid-state structure of [Zn{Ph2P(CHPy)(NSiMe3)}2] (2);
selected bond lengths [pm] and angles [°]: ZnϪN1 201.70(15),
ZnϪN3 201.15(16), ZnϪN2 203.96(16), ZnϪN4 203.88(16),
P1ϪN1 160.92(16), P2ϪN3 161.43(16), N1ϪSi1 173.41(16),
N3ϪSi2 173.43(16), P1ϪC1 172.1(2), P2ϪC22 172.28(19), PϪCPh
av. 181.6, C1ϪC2 138.9(3), C22ϪC23 139.6(3), C2ϪN2 137.5(2),
C23ϪN4 137.5(2); P1ϪC1ϪC2 123.75(15), P2ϪC22ϪC23
123.35(15), P1ϪN1ϪSi1 131.10(10), P2ϪN3ϪSi2 128.80(10)
Figure 2. Solid-state structure of [Fe{Ph2P(CHPy)(NSiMe3)}2] (1);
selected bond lengths [pm] and angles [°]: FeϪN1 204.6(2), FeϪN3
204.2(2), FeϪN2 207.5(2), FeϪN4 207.9(2), P1ϪN1 161.2(2),
P2ϪN3 161.3(2), N1ϪSi1 173.7(2), N3ϪSi2 173.7(2), P1ϪC1
172.5(2), P2ϪC22 172.7(2), PϪCPh av. 182.2, C1ϪC2 139.4(3),
C22ϪC23 140.3(3), C2ϪN2 137.9(3), C23ϪN4 137.5(3);
P1ϪC1ϪC2 124.08(19), P2ϪC22ϪC23 123.42(19), P1ϪN1ϪSi1
132.07(12), P2ϪN3ϪSi2 129.83(12)
from the respective best NϪPϪCϪN plane (29 pm for the 182 pm for covalently bonded zinc amides to 231 pm for
Fe2ϩ cation). donor-base complexed dimethylzinc;[23] in 2 they are similar
The FeϪNimino distances (av. 204.4 pm) are equal within to ZnϪNimino interactions in the related zinc bis(iminopho-
their estimated standard deviations (esds). They are in the sphorane)methanides [Zn{HC(Ph2PNR}2X] [R ϭ Mes,
range typically found for iron() complexes in which the SiMe3; X ϭ Me, N(SiMe3)2, OCPh3], where the contacts
cation is coordinated to imino functions, for example in vary from 198.6 to 208.3 pm.[24] In the ortho-deprotonated
[Fe{(o-C6H4)Ph2PNSiMe3}2]
(211.1
pm),[16]
[Fe{2- [Zn(o-C6H4PPh2NSiMe3)2] the ZnϪN contacts are 14.4 pm
(RNPPh2)-6-RЈ(c-C5H3N)}Cl2] (R ϭ 2,6-Me2-C6H3, 2,6- longer (215.8 pm).[25] Thus, the Zn1ϪN1/3 contacts in 2 are
iPr2-C6H3; RЈ ϭ Ph, H2CPh, SiMe3; 204.8Ϫ206.7 pm)[17] in the range for covalently bonded zinc amides. The
or in the 12 VE iron() complex [Fe(H2CPh)- ZnϪNpy distances are identical (Zn1ϪN3/4: av. 203.92 pm)
{HC(CMeNAr)2}] (198.2 pm).[18] The FeϪNimino distances and only 2.5 pm longer than the ZnϪNimino interactions.
in 1 are about 24.4 pm shorter than in the dibromoiron() The average value quoted for ZnϪNpy contacts is 208.3
compound [{2,6-(Ph2PNSiMe3)Py}FeBr2], where the FeϪN pm.[26] To judge the covalent or dative character of the
contacts are on average 228.8 pm,[19] reflecting the pro- ZnϪNpy bonds, complex 2 is best compared with the
nounced amidic character of the FeϪNimino bonds.
bis(1,4-dihydropyridin-1-yl)bis(pyridine)zinc system:[27] the
It seems remarkable that the FeϪNpy distances in 1 (av. ZnϪNpy distances in 2 are 4.4 pm longer than the covalent
207.7 pm) are only 3.3 pm longer than the FeϪNimino con- bonds in bis(1,4-dihydropyridin-1-yl)bis(pyridine)zinc (197
tacts. They are much shorter than in the donor base coordi- pm), but 11.6 pm shorter than the dative ones (213 pm),
nated complexes [(H2NCH2Py)Fe][Br]2 (FeϪNpy: av. 222.3 clearly emphasising the amidic character of the ZnϪNpy
pm),[20] [(Hpy)2(H2O)4Fe][MeCO2]2 (221.3 pm)[21] or [Fe{2- interactions in 2.
(RNPPh2)-6-RЈ(cy-C5H3N)}Cl2] (R ϭ 2,6-Me2-C6H3, 2,6-
The geometrical parameters of the anionic ligands of
iPr2-C6H3; RЈ ϭ Ph, H2CPh, SiMe3; 218.4Ϫ222.9 pm),[17] both complexes 1 and 2 are almost equal. Thus, in the fol-
but similar to those in [Fe{C(H)(SitBuMe2)Py}2]2 (209.7 lowing discussion the averages are given; the exact param-
and 218.9 pm),[22] where the pyridyl nitrogen atom acts as eters are listed in the captions of Figures 1 and 2, respec-
a side-arm donor, like in 1.
tively.
The solid-state structure of the isomorphous zinc deriva-
The P1ϪC1 and P2ϪC22 bonds in 1 and 2 (av. 172.5
tive [Zn{Ph2P(CHPy)(NSiMe3)}2] (2) is shown in Figure 3. pm) are about 12 pm shorter than formal PϪC single bonds
The central zinc cation is fourfold coordinated by the ni- (185 pm);[28] they are in the range found for ylidic PϩϪCϪ
trogen atoms N1ϪN4 of the two anionic ligands. The coor- interactions (163Ϫ173 pm).[12,29] In addition, the C1/
dination polyhedron around the Zn2ϩ ion is a nearly ideal 22ϪC2/23 contacts (av. 139.6 pm) are 10 pm shorter than
tetrahedron [the angles vary from 103.70(6) to 111.31(6)°]. the corresponding bond length in the neutral starting mate-
Like in 1, both monoanionic [Ph2P(CHPy)(NSiMe3)]Ϫ rial Ph2P(CH2Py)(NSiMe3) (182.57 pm).[11] As a conse-
units act as bidentate N,N-chelates and the two six-mem- quence, the C2ϪN2 and C23ϪN4 bonds in the pyridyl sub-
bered rings of the metallaspirocycle each show a distorted stituents (average 137.6 pm) are 4.4 pm longer than in the
boat conformation. The displacement of the deprotonated starting material (133.17 pm).[11] The sum of the angles at
carbon atoms and the metal centre from the best plane of the imino nitrogen atoms in both complexes is about 360°,
the ligand (av. 45 pm for C1/C22 and 21 pm for Fe) is simi- illustrating a planar coordination sphere at these atoms. For
lar to 1.
the pyridyl nitrogen atoms N2 and N4, a marginal pyrami-
In 2, the distances between the zinc atom and the imino dal environment is observed, with a mean sum of the angles
nitrogen atoms N1 and N3 (av. 201.43 pm) are equal within of 355.5° in 1 and 356.3° in 2. All these parameters are
the esds. In general, ZnϪN contacts span a wide range from very similar to those found in the alkali metal derivatives
4274
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Eur. J. Inorg. Chem. 2004, 4272Ϫ4277

The Cα-Deprotonated Iminophosphorane Ph2P(CH2Py)(NSiMe3)
FULL PAPER
[(Et2O)Li{Ph2P(CHPy)(NSiMe3)}] and [{Ph2P(CH2Py)- atom decrease the electron density at the phosphorus cen-
(NSiMe3)}M{Ph2P(CHPy)(NSiMe3)}] (M ϭ Li, Na), con- tre. The almost invariant 15N NMR spectroscopic shift of
taining the same anion,[11] and to the related the imino nitrogen atoms in 2 (δ ϭ Ϫ348 ppm) and the
[(THF)Mg{2,6-(Me3SiNPiPr2CH)2(c-C5H3N)}].[10] In the iminophosphorane (δ ϭ Ϫ343 ppm) indicate that the charge
metallacyclobutanes [{2-[M{C(iPr2PNSiMe3)}]-6-[M{HC- density at this nitrogen atom is less affected by the depro-
(iPr2PNSiMe3)}X]}(c-C5H3N)]2 (M ϭ Sn, X ϭ Cl; M ϭ tonation. However, the 15N NMR resonance for the pyridyl
Pb, X ϭ N(SiMe3)2], which contain the mono- and di- ring nitrogen atoms in the anionic ligands of 2 (δ ϭ Ϫ182
anionic derivative of [2,6-(Me3SiNPiPr2CH2)2(c-C5H3N)], ppm) differs remarkably from that of the parent iminophos-
longer PϪCα(H) (av. 178.6 pm) and Cα(H)ϪCPy distances phorane (δ ϭ Ϫ61 ppm); it is considerably shifted to higher
(av. 147.3 pm) are found than in 1 and 2 due to the observed fields. This resonance is in the range observed earlier for the
[M]ϪCα bonds in addition to the [M]ϪN contacts.[10] [Ph2P(CHPy)(NSiMe3)]Ϫ anion and is in accordance with
Whereas in the metallacyclobutanes the negative charge is charge accumulation at the pyridyl ring nitrogen atoms.[11]
accumulated at the deprotonated carbon centres, in 1 and 2
it is delocalised over the [HCϪPy] backbone of the ligand,
Conclusion
leading to a perturbation of the aromatic ring systems and
charge accumulation at the pyridyl nitrogen atom. The in-
creased electron density in the pyridyl substituents leads to
a displacement of the metal cations from the ring plane
towards the π-density of the pyridyl substituent, which ex-
plains the short MϪNpy distances in 1 and 2.
Metal bis(trimethylsilyl)amides easily deprotonate the im-
inophosphorane Ph2P(CH2Py)(NSiMe3) at the methylene
bridge to furnish N,N-chelating monoanionic ligands coor-
dinating to the metal atom through the pyridyl and the im-
ino nitrogen atoms. The negative charge is delocalised over
the [HCϪPy] backbone of the ligand, increasing the elec-
tron density in the pyridyl rings. Thus, the metal cations are
shifted towards the π-density of the pyridyl rings. On metal
coordination, the PϪN and SiϪN bonds in the ligands get
simultaneously elongated, due to the decay of the electro-
static contributions in the PϩϪNϪ and SiϩϪNϪ bonds. Ad-
ditionally, we found shorter MϪNimino contacts than ex-
pected for MǟN donor bonds. These geometrical para-
meters show that the imino nitrogen atom cannot be regarded
as a simple two-electron donor. The MϪNimino distances in
complexes 1 and 2 reflect a high ionic contribution to the
bonding. This leads to a description of the imino nitrogen
atom between a monoanionic two- and four-electron donat-
ing centre.
The PϪN bonds in 1 and 2 are, on average, 161.2 pm
long. They are at the upper end of the range found for PϪN
bonds in iminophosphoranes (147Ϫ162 pm)[30] and reflect
the trend of PϪN bond elongation on weakening the elec-
trostatic PϩϪNϪ interaction because of the presence of the
adjacent deprotonated Cα position and the additional N-
metal coordination.[9,11,31] The SiϪN distances in 1 and 2
are, on average, 173.6 pm long and are therefore about 5.5
pm longer than in the neutral iminophosphorane
Ph2P(CH2Py)(NSiMe3) (168.08 pm).[11] Similar changes in
SiϪN bond lengths have been found in the alkali-metal de-
rivatives of Ph2P(CH2Py)(NSiMe3)[11] and in bis(iminophos-
phorane)methanides[32] with regard to the parent starting
materials.[33] The long SiϪN bonds found in 1 and 2 are a
result of the strong interactions of the negatively charged
imino nitrogen atoms with the doubly charged cations, re-
ducing the electrostatic contributions in the SiϪN interac-
tions.
Experimental Section
General Remarks: All manipulations were performed under dry N2
with Schlenk techniques or in an argon-filled glovebox. All solvents
were dried with Na/K alloy and distilled prior to use. IR spec-
troscopy was performed with a Bruker IFS 25 spectrometer. NMR
spectra were recorded at room temperature with a Bruker DRX
300 spectrometer at 300.1 (1H), 75.5 (13C), 121.5 (31P), 59.6 (29Si)
and 30.4 MHz (1H,15N HMBC). Chemical shifts are given as δ val-
Spectroscopic Investigations
The IR spectra of 1 and 2 show signals at 1360 cmϪ1 for
both complexes. These signals are in the range found for
PϪN stretching modes (1140Ϫ1370 cmϪ1),[1,34] and are
shifted 11 cmϪ1 to higher wavenumbers relative to the start-
ing iminophosphorane (νPN ϭ 1349 cmϪ1). A similar shift
to higher wavenumbers was detected unambiguously by
DFT assignment earlier from the starting material
Ph3PNSiMe3 (νPN ϭ 1319 cmϪ1) to the ortho-metallated
[(Et2O)Li(o-C6H4PPh2NSiMe3)}2] (νPN ϭ 1328 cmϪ1).[35]
Due to the presence of a d6 FeII centre in a tetrahedral
coordination, no NMR spectroscopic data could be ob-
tained for the paramagnetic iron complex 1. In the 31P
NMR spectrum of 2, the phosphorus nuclei resonate at δ ϭ
26.4 ppm. Like for the alkali-metal derivatives of
Ph2P(CH2Py)(NSiMe3),[11] deprotonation at the Cα atom
results in a downfield shift from the resonance of the start-
ing iminophosphorane (δ ϭ Ϫ0.32 ppm). The negative
1
ues relative to [D8]toluene for H, 13C and to external formamide
1
for H,15N HMBC NMR, H3PO4 (85%) for 31P and to SiMe4 for
29Si NMR. Elemental analyses were performed by the Microanaly-
tisches Labor der Universität Würzburg.
[Fe{Ph2P(CHPy)NSiMe3}2] (1): Pure, liquid [Fe{N(SiMe3)2}2]2
(0.26 g, 0.69 mmol) was added by syringe to solid Ph2P(CH2Py)(N-
SiMe3) (0.50 g, 1.37 mmol) in a drybox. The suspension turned red
immediately. It was stirred at room temp. for 1 h, then 20 mL of
hexane was added and the suspension was stirred for an additional
2 h. After evaporation of the solvent and formed HN(SiMe3)2 in
vacuo, 0.99 g (1.27 mmol, 93%) of red solid 1 was isolated. To crys-
tallise 1, the red powder was dissolved in hexane/Et2O (2:1). After
3 d, red blocks, suitable for an X-ray diffraction experiment, were
charge and metal coordination at the P-bound nitrogen obtained. IR: νPN ϭ 1360 cmϪ1. C42H48FeN4P2Si2 (782.81): calcd.
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A. Murso, D. Stalke
FULL PAPER
C 64.44, H 6.18, N 7.16; found C 64.36, H 6.21, N 7.12. M.p.
(DTA) 258 °C.
Acknowledgments
This work was supported by the Deutsche Forschungsgemeinschaft
(SFB 347 and the Graduiertenkolleg 690 Electron Density Ϫ The-
ory and Experiment).
[Zn{Ph2P(CHPy)NSiMe3}2] (2): [Zn{N(SiMe3)2}2] (0.29 g,
0.75 mmol) was dissolved in 10 mL of Et2O and added slowly to a
solution of Ph2P(CH2Py)(NSiMe3) (0.50 g, 1.37 mmol) in 25 mL
of Et2O at room temp. After stirring of the yellow solution for 2 h,
the volume of the solvent was reduced. Storage of the solution at
4 °C overnight yielded 0.54 g (0.68 mmol, 91%) of 2 as yellow
plates. IR: νPN ϭ 1360 cmϪ1. 1H NMR: δ ϭ 0.17 (s, 18 H, SiMe3),
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3
[3]
[4]
3J4,3 ϭ 8.8, 3J4,5 ϭ 6.6 Hz, 2 H, 4-H), 7.12 (d, J6,5 ϭ 5.6 Hz, 2 H,
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6-H), 7.01Ϫ7.06 (m, 12 H, m-, p-PhH), 7.73Ϫ7.91 (m, 8 H, o-PhH)
ppm. 13C NMR: δ ϭ 4.7 (d, 3JSi,C ϭ 3.8 Hz, SiMe3), 59.2 (d, C-1),
106.5 (s, C-5), 120.2 (d, C-3), 134.8 (s, C-4), 146.9 (s, C-6), 166.6
(d, C-2), 128.5 (m-PhC), 131.0 (p-PhC), 133.1 and 133.4 (o-PhC),
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2
138.2 (i-PhC) ppm. 29Si NMR: δ ϭ 1.32 (d, JSi,P ϭ 1.8 Hz) ppm.
1H,15N-HMBC NMR: δ ϭ Ϫ348 (NSiMe3), Ϫ182 (PyN) ppm. 31
P
[5c]
D. W. Stephan, F. Guerin, R. E. v.
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85.8120(10), β ϭ 81.1290(10), γ ϭ 79.9010(10)°, V ϭ 1.9845(2)
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