Activation of polarized phosphorus-phosphorus bonds by alkynes: Rational synthesis of unsymmetrical 1,2-bisphosphine ligands and their complexes

Article abstract of DOI:10.1515/znb-2009-0109

The reactions of 1,1-diamino-2,2-diphenyl-substituted diphosphines featuring various degrees of P-P bond polarization with different alkynes were investigated. All diphosphines reacted with alkynes carrying one or two electron withdrawing carboxylic ester moieties under cleavage of the P-P bond and stereospecific phosphinyl-phosphination at the triple bond to give unsymmetrical ethane-1,2-bisphosphines. Several of the products were further converted into chelate complexes upon reaction with group-10 metal dihalides. All isolated compounds were characterized by analytical and spectroscopic data, and several of the new ligands and complexes by single-crystal X-ray diffraction studies.

Full text of DOI:10.1515/znb-2009-0109

Activation of Polarized Phosphorus–Phosphorus Bonds by Alkynes:
Rational Synthesis of Unsymmetrical 1,2-Bisphosphine Ligands and
Their Complexes
Sebastian Burcka, Imre Hajdo´ka, Martin Niegerb, Denis Bubrina, Simon Schulzea,
and Dietrich Gudata
a Institut fu¨r Anorganische Chemie, Universita¨t Stuttgart, Pfaffenwaldring 55, 70550 Stuttgart,
Germany
b Laboratory of Inorganic Chemistry, University of Helsinki, A. I. Virtasen aukio 1, Helsinki, Finland
Reprint requests to Prof. Dr. Dietrich Gudat. Fax: +49 711 685 64241.
E-mail: gudat@iac.uni-stuttgart.de
Z. Naturforsch. 2009, 64b, 63 – 72; received September 29, 2008
Dedicated to Professor Otto J. Scherer on the occasion of his 75th birthday
The reactions of 1,1-diamino-2,2-diphenyl-substituted diphosphines featuring various degrees of
P–P bond polarization with different alkynes were investigated. All diphosphines reacted with alkynes
carrying one or two electron withdrawing carboxylic ester moieties under cleavage of the P–P bond
and stereospecific phosphinyl-phosphination at the triple bond to give unsymmetrical ethane-1,2-
bisphosphines. Several of the products were further converted into chelate complexes upon reaction
with group-10 metal dihalides. All isolated compounds were characterized by analytical and spectro-
scopic data, and several of the new ligands and complexes by single-crystal X-ray diffraction studies.
Key words: Bidentate Ligands, Phosphines, Chelate Complexes, Addition Reaction, Insertion
Introduction
Bidentate ligands have a long standing reputation
in organometallic and coordination chemistry and are
widely applied in catalysis. As a rational way to their
synthesis, additions to alkenes or alkynes that allow
simultaneous introduction of two donors to an or-
ganic backbone have recently attracted attention. The
largest progress in this field has been made for O,O-
and N,N-ligands where protocols for stereo- and even
enantioselective dihydroxylation [1] or diamination of
olefins [2] were worked out. Approaches to P,P-donor
ligands, which are likewise of great significance, via
diphosphination of organic precursors are scarce [3],
but symmetrical derivatives can be accessed via double
metathesis of 1,2-disubstituted olefins [4]. In addition,
we have some time ago established that the unsymmet-
rical 1,2-bisphosphines2, 3 are easily accessible by ad-
dition of the polarized P–P bond of the diphosphine 1
to electron-poor alkenes (Scheme 1) [5]. Whereas the
flexible backbones of 2, 3 do not impose stringent spa-
tial constraints on the donor centers, the rigid skeletons
of 1,2-bisphosphinyl-ethenes can serve as scaffolds
that allow specific preorganization of the coordination
Scheme 1.
sites [6]. Quite interestingly, two approaches to stereo-
specific syntheses of such ligands via diphosphina-
tion of alkynes have recently been reported. Thus, Os-
hima et al. [7] prepared symmetrical E-1,2-bis(diphen-
ylphosphino)ethenes via the radical-promoted addition
of tetraphenyldiphosphine to alkynes, and Pringle et
al. [8] synthesized both symmetrical and unsymmetri-
cal Z-1,2-bis(phosphinyl)ethenes through the addition
of diphosphines to electron-poor acetylene mono- and
c
0932–0776 / 09 / 0100–0063 $ 06.00 ꢀ 2009 Verlag der Zeitschrift fu¨r Naturforschung, Tu¨bingen · http://znaturforsch.com
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64
S. Burck et al. · Activation of Polarized Phosphorus-Phosphorus Bonds by Alkynes
Scheme 2.
dicarboxylates. The latter reaction applies also to the Results and Discussion
N-heterocyclic diphosphine 4 which adds to ethyl pro-
Synthesis and characterization of unsymmetrical
diphosphines
piolate to produce Z-5 (Scheme 1) [9]. Similar hybrid
bisphosphines which exhibit two donor sites with dif-
ferent electronic properties have received interest as
ligands for specific applications in catalysis [10].
Although the formation of 5 is without doubt fa-
cilitated by the P–P bond polarization and the result-
ing high chemical reactivity of the precursor 4 [5], the
findings by Pringle et al. [8] suggest that the reaction
scheme is more general. It was therefore of interest to
establish if the addition to alkynes applies also to 1,1-
The diphosphines used in this study comprise the
N-heterocyclic compounds 4 [9] and 6, and the acyclic
derivative 7 [11] (see Scheme 2). These species were
chosen to represent diaminophospheniumfragments of
decreasing cation stability, and are expected to exhibit
a decreasing degree of P–P bond polarization and con-
comitantly lower reactivities [5].
Compound 6 [Np = neopentyl], which was previ-
diamino-diphosphines with less reactive P–P bonds, ously unknown, was prepared by condensation of the
and if these compounds react likewise with symmet- appropriate chlorophosphine precursor with diphen-
rically substituted, nonpolar acetylene derivatives. We yl(trimethylsilyl)phosphine and characterized by ele-
present here a full account of the studies of the addi- mental analysis and spectroscopic studies (see Exper-
tion reactions of polarized diphosphines to acetylene imental Section). The results of single-crystal X-ray
carboxylates, the complexation of the formed ligands diffraction studies of 4 (space group P212121) and 6
by divalent group-10 metals, and the spectroscopic (space group P21/c) are listed in Table 1, and the
and structural characterization of starting materials and molecular structures are displayed in Fig. 1 (4) and
products.
Fig. 2 (6), respectively. The unit cell of 4 contains two
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S. Burck et al. · Activation of Polarized Phosphorus-Phosphorus Bonds by Alkynes
Table 1. Crystal structure data for 4, 6, and 11.
65
4
6
11
14
15
16
Formula
C30H30N2P2
C28H36N2P2
C30H44N2O4P2
C35H36Cl2N2
NiO2P2·C4H8O
780.31
C35H36Cl2N2O2 C35H36Cl2N2O2
P2Pd · CH3CN
P2Pt · 2.5 C6H6
Mr
480.50
462.53
558.61
796.95
1039.86
Crystal size, mm3
Crystal system
Space group
0.35×0.25×0.15 0.50×0.40×0.30 0.40×0.30×0.30 0.24×0.12×0.06 0.35×0.30×0.25 0.15×0.10×0.05
orthorhombic
P212121(no.19)
11.3554(2)
13.9318(2)
32.6862(6)
90
monoclinic
P21/c (no. 14)
9.443(1)
14.537(2)
19.256(3)
90
95.25(1)
90
2632.2(6)
4
triclinic
monoclinic
P21/n (no.14)
11.9078(3)
17.5373(4)
17.8602(5)
90
102.596(1)
90
3639.99(16)
4
monoclinic
P21/n (no. 14)
12.1862(2)
17.1731(3)
17.3631(3)
90
101.627(1)
90
3559.10(11)
4
monoclinic
P21/c (no. 14)
12.3158(2)
17.3500(2)
22.1891(4)
90
102.465(1)
90
4629.58(12)
4
¯
P1 (no. 2)
˚
a, A
11.612(3)
15.054(4)
18.606(5)
89.85(4)
88.466(7)
79.73(3)
3199.2(14)
4
˚
b, A
˚
c, A
α, deg
β, deg
90
90
γ, deg
3
˚
V, A
5170.99(15)
8
1.234
0.189
2032
Z
Dcalcd, g cm−3
µ(MoKα ), cm−1
F(000), e
hkl range
1.167
0.183
992
1.160
0.170
1200
1.424
0.809
1632
1.487
0.799
1632
1.492
3.256
2092
−14 ≤ h ≤ +10 −11 ≤ h ≤ +11 −7 ≤ h ≤ +12
−14 ≤ h ≤ +13 −11 ≤ h ≤ +15 −15 ≤ h ≤ +15
−17 ≤ k ≤ +15 −17 ≤ k ≤ +17 −17 ≤ k ≤ +17 −19 ≤ k ≤ +20 −22 ≤ k ≤ +19 −22 ≤ k ≤ +20
−40 ≤ l ≤ +37
−22 ≤ l ≤ +22
−22 ≤ l ≤ +22
−21 ≤ l ≤ +18
−22 ≤ l ≤ +13
−28 ≤ l ≤ +28
θ
max, deg
26
25
25
25
27.5
27.5
Refl. measured
Refl. unique
Rint
24209
9839
0.042
621
20650
4632
0.038
289
11630
11021
22136
6407
0.067
446 / 6 restraints 429
0.039/0.070
17734
7744
0.033
28892
10371
0.058
520 / 17 restraints
0.034/0.065
Param. refined
705
0.051/0.149
R(F) [for I ≥ 2σ(I)] 0.036/0.062
0.071/0.174
0.025/0.064
/wR(F2) (all refl.)
x (Flack)
0.01(5)
0.917
–
–
–
–
–
GoF (F2)
1.056
0.982
0.883
1.037
0.910
∆ρfin (max/min),
0.177/ −0.199
1.017/ −0.614
0.36/ −0.387
0.524/ −0.316
0.585/ −0.426
1.170/ −1.338
−3
˚
e A
Fig. 1. Molecular structure of one of the crystallographically
independent molecules in crystalline 4 (H atoms omitted for
clarity; displacement ellipsoids at the 50 % probability level);
Fig. 2. Molecular structure of 6 (H atoms omitted for clar-
ity; displacement ellipsoids at the 50 % probability level);
˚
˚
selected bond lengths (A): P1–N2 1.712(3), P1–N5 1.693(3),
selected bond lengths (A) (values for the second molecule
P1–P2 2.312(1).
in brackets): P1–N2 1.712(2) [1.711(2)], P1–N5 1.719(2)
[1.717(2)], P1–P2 2.320(1) [2.321(1)].
apart from the presence of substantially lengthened
˚
˚
P–P bonds (4: 2.320(1), 2.321(1) A; 6: 2.312(1) A)
crystallographically independent molecules with simi-
lar metrical parameters which differ merely in the tor-
sional orientation of the peripheral aryl substituents.
Both molecular structures lack any special features
whose values exceed significantly the corresponding
bond length in 7 (2.250(1) A [11]). The bond lengthen-
ing had previously been identified as a typical feature
˚
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66
S. Burck et al. · Activation of Polarized Phosphorus-Phosphorus Bonds by Alkynes
of CC-unsaturated N-heterocyclic diphosphines and is dition of polarized diphosphines to electron-deficient
closely related to their high chemical reactivity [5]. In alkenes [5].
According to 31P NMR spectroscopic studies the re-
action of 4 with methyl tetrolate took a similar course
as with methyl propiolate and produced as the ma-
jor product a species which displayed very similar
31P NMR data (AX-type spectrum with δA = 80.4,
δX = −29.4, JAX = 255 Hz) as 5 and 8, and was on
this basis assigned formula 9. Complete conversion of
the starting materials required in this case much more
these terms, the equal P–P bonds in 4 and 6 suggest
that formal replacement of the double bond in 4 by an
annulated benzene ring in 6 exerts only a subtle effect
on the electronic structure.
Reactions with electron deficient alkynes
The reactions of 4 and 6 with ethyl propiolate
◦
proceeded smoothly at 0 C or r. t. Monitoring by
◦
31P NMR spectroscopy confirmed that both reactions
yielded a single addition product together with side-
products (diphenylphosphineand phosphorous acid di-
amides) arising from hydrolysis of the starting diphos-
phines [5], thus indicating that the addition step is
both completely regio- and stereoselective. Whereas
the 1,2-bisphosphine 5 was isolated in pure form af-
ter crystallization from pentane, 8 failed to crystal-
lize and was only identified in situ by NMR spec-
forcing conditions (heating to 60 C for 36 h), and no
attempts toward isolation of the product were made.
The reaction of 4 with phenylacetylene, which lacks an
electron-withdrawing substituent, was very complex;
NMR studies indicated the formation of products aris-
ing from hydrolysis and decomposition of the starting
material but gave no evidence for a specific reaction
under addition of the P–P bond.
In order to establish if the polarized P–P bonds also
troscopy; purification and further characterization was, undergo addition to nonpolar alkynes we studied fur-
however, possible after conversion into a palladium ther the reactions of 4, 6, and 7 with symmetrically
complex (see below). The purity and constitution of 5 substituted diphenylacetylene and dimethyl acetylene-
were established by analytical and spectroscopic stud- dicarboxylate (DMAD), respectively. Whereas all
1
ies. The H and 13C NMR spectra contain, in addi- three phosphines did not react with diphenylacetylene,
tion to the signals attributable to the peripheral sub- addition of one equivalent of DMAD to a solution of
stituents at the phosphorus atoms and the carboxylic both 6 and even the less reactive 7 at r. t. resulted
ester group, the resonances of an olefinic proton and in a smooth reaction under quantitative (according to
two olefinic carbon atoms which are readily assigned 31P NMR) conversion of the starting materials into the
to the nuclei in the trisubstituted double bond; all three addition products 10 and 11. Both compounds were
signals are split into doublets of doublets as a conse- isolated in good yields after crystallization from hex-
quence of spin-coupling with the two 31P nuclei. The ane, and their purity and constitution were established
1
31P{ H} NMR spectra of both 5 and 9 display charac- by analytical and spectroscopic data. The dissymmet-
teristic AX-type patterns whose chemical shifts allow ric substitution of the central double bond by two un-
easy assignment of the PN2 (δ = 83 – 94) and PPh2 like phosphinyl units is reflected in the presence of
(δ = −25 – −26) groups. The unusually large values 1H and 13C NMR signals of two distinguishable es-
3
for JPP (166 – 188 Hz) imply that the couplings ex- ter moieties as well as, naturally, the observation of an
hibit a large through-space component [12, 13] which AX-type pattern with similar chemical shifts as for 5
1
requires a close spatial proximity of the nonbonding and 8 in the 31P{ H} NMR spectra. The assignment
electron pairs on the phosphorus atoms and is only of a Z-configuration at the central double bond was
3
feasible for a Z-configuration of the central double first derived from the finding of a similar size of JPP
bond. This assumption is backed by the observation of as in 5, 8 and the analogy to the products formed
3
similar values of JPP for Z-configurated ethene-1,2- by addition of alkyl/aryldiphosphines to DMAD [8],
bisphosphines derived from dimethyl acetylenedicar- and was unambiguously confirmed by the results of a
boxylate [8], and finally confirmed by single-crystal single-crystal X-ray diffraction study of 11 (Table 1,
X-ray diffraction studies of metal complexes of both Fig. 3). The crystals contain two crystallographically
products (see below) which also prove the attachment independent molecules which differ slightly in the tor-
of the carboxylic ester group to the carbon atom car- sional orientation of the peripheral substituents. The
rying the N-heterocyclic phosphinyl substituent. The bond lengths and angles are unexceptional, but the cen-
observed regioselectivity of the addition step mirrors tral double bonds exhibit perceptibly twisted confor-
in this respect the previously observed mode of ad- mations with dihedral angles between the coordination
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S. Burck et al. · Activation of Polarized Phosphorus-Phosphorus Bonds by Alkynes
67
phines excellent chelating ligands, we engaged in a
study of the coordination behavior of the ligands 5
and 8 by exploring their reactions with chlorides of
divalent group-10 metals. These salts were chosen as
attractive substrates for two reasons, viz. (i) the target
complexes can be considered to have great potential
to serve as pre-catalysts in catalytic transformations,
and (ii) comparison with known complexes of eth-
ene-1,2-bis-phosphinesderived from the addition of P-
aryl/alkyl-substituted diphosphines to DMAD [8] may
serve to probe the effects induced by formal replace-
ment of alkyl by amino substituents at one of the donor
centers on the coordination properties of the ligands.
In agreement with the anticipated behavior, quan-
titative complexation (according to the analysis of
31P NMR spectra of reaction mixtures) occurred when
solutions of the ligands and suitable metal salts were
combined at r. t., and the products 14 – 17 were readily
isolated after evaporation of the solvents and recrystal-
lization. Similar yields and purities of isolated com-
plexes were obtained regardless if the bisphosphine
ligands were employed in pure form, as crude prod-
ucts, or even as in situ formed species in the reac-
tion mixtures. Preliminary studies indicate that the last
approach offers a synthetically highly convenient ap-
proach to prepare the chelate complexes in one pot via
a cascade reaction starting from diphenyl(trimethylsil-
yl)phosphine (or, alternatively, lithium diphenylphos-
phide), an appropriate diamino(chloro)phosphine, an
activated acetylene, and a suitable metal halide.
Fig. 3. Molecular structure of one of the crystallographically
independent molecules in crystals of 11 (H atoms omitted for
clarity; displacement ellipsoids at the 50 % probability level);
˚
selected bond lengths (A) (values for the second molecule
in brackets): P1–N2 1.681(2) [1.694(2)], P1–N3 1.698(2)
[1.686(2)], P1–C30 1.877(2) [1.876(3)], P2–C40 1.850(3)
[1.854(2)], C30–C40 1.342(3) [1.344(3)].
plane of the two carbon atoms of 11◦ and 13◦, respec-
tively. No similar distortion is observed in analogous
compounds [8, 14], and its presence here is presumably
caused by the mutual interference between the bulky
peripheral substituents. The orientation of the phos-
phinyl groups implies that the phosphorus lone-pairs
point inwards toward each other, but are rotated out of
the plane of the central double bond, most likely as a
consequence of mutual electrostatic repulsion.
The reaction of 4 with DMAD at r. t. took a more
complicated course and gave a product mixture which
was assigned via analysis of 31P NMR spectra of re-
action mixtures to contain unreacted 4, the expected
addition product 12, and a further species presum-
ably formed by reaction of 4 with two equivalents of
DMAD. Investigations aiming at the exact identifica-
tion of this product and the mechanism of its formation
are still in progress; a comprehensive report of these
studies is beyond the scope of this work and will be
given elsewhere. It was found that formation of the 2 : 1
adduct could be largely avoided by conducting the re-
The identity and purity of the complexes 14 – 17 was
established by analytical and spectroscopic data and,
with exception of 17, by single-crystal X-ray diffrac-
tion studies. The 1H and 13C NMR data are simi-
lar to those of the free ligands and do not require
1
further discussion. The 31P{ H} NMR spectra differ
from those of the ligands in displaying large positive
coordination shifts (∆δ) which are typical for five-
membered ring chelate complexes [8]. Although the
magnitude of ∆δ varies strongly with the metal, the
values are always larger for the phosphorus atom in
the PPh2 moiety (∆δ = 62 – 88 vs. ∆δ = 4 – 41 for
PN2). The size of JPP is by one to two orders of
magnitude lower than in the free ligands, and the ob-
served values (2 – 20 Hz) are consistent with a cis-
arrangement of the phosphorus atoms. The size of
1JPtP for the phosphorus atom in the PPh2 moiety
of 16 (1JPtP = 3548 Hz) matches values found for
◦
action at low temperature (−78 C) and isolating the
crude product after warming to r. t. and evaporation of
all volatiles under reduced pressure. Although we did
not succeed in separating small amounts of remaining
starting materials and side products, and thus failed to
isolate 12 in pure form, the crude material could be
readily employed for further reactions such as the for-
mation of the palladium complex 13.
Metal complexes of unsymmetrical 1,2-bis-phosphino-
ethenes
Considering that the preorganization of the phos- platinum complexes of 1,2-di(alkyl/aryl)phosphinyl-
phorus donor moieties renders ethane-1,2-bisphos- ethenes (≈ 3500 Hz) [8] whereas the larger coupling
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68
S. Burck et al. · Activation of Polarized Phosphorus-Phosphorus Bonds by Alkynes
˚
Table 2. Selected bond lengths (A) and angles (deg) for 14 –
16 with estimated standard deviations in parentheses.
14
15
16
M–P1
M–P2
2.133(1)
2.134(1)
2.194(1)
2.208(1)
1.693(2)
1.691(2)
1.848(3)
1.321(4)
1.809(3)
2.221(1)
2.212(1)
2.348(1)
2.363(1)
1.684(2)
1.682(2)
1.852(2)
1.330(2)
1.802(2)
2.200(1)
2.204(1)
2.345(1)
2.363(1)
1.683(3)
1.677(3)
1.859(4)
1.324(5)
1.793(4)
M–Cl1
M–Cl2
P1–N2
P1–N5
P1–C22
C22–C23
C23–P2
Fig. 5. Reduced structure of 15 showing only the atoms in the
chelate ring and directly attached substituents (displacement
ellipsoids at the 50 % probability level). The view axis is par-
allel to the least-squares plane defined by the PCCP fragment
of the chelate ring.
Both effects are manifested (apart from distortions in
the bond angles around the metal center discussed be-
low) in a dislocation of the metal atom out of the plane
formed by the remaining atoms in the chelate ring
and an additional torsional twist of the MCl2 unit (see
Fig. 5). As a consequence, the torsional angle φ be-
tween the P1–M–P2 and Cl1–M–Cl2 planes displays
a perceptible deviation from the ideal value of zero
which increases systematically with decreasing size of
M from approx. 12◦ in 16 (M = Pt) to 14◦ in 15 (M =
Pd) and 16◦ in 14 (M = Ni).
P1–M–P1
88.04(3)
87.08(2)
88.17(4)
Inspection of trends in individual bond lengths and
angles reveals that the P1–M and P2–M distances
in each single complex deviate neither significantly
from each other nor from distances in similar com-
plexes [6, 8, 15]. Even though the M–Cl bond lengths
compare in general also very well to standard bond
lengths [15], the two M–Cl bonds in a given complex
show a distinct influence of the trans-ligand, with the
M–Cl1 bond opposite to the PPh2 moiety being 1 –
2 pm shorter than the M–Cl2 bond (Table 2). Al-
together, these structural features compare well with
those of group-10 metal complexes containing eth-
ene-1,2-bisphosphine ligands with a mixed PPh2/PCy2
donor set but deviate from those with a PPh2/PtBu2
donor set where much more pronounced differences in
the P–M bonds were noticed [8].
The angular deviations from ideal metal coordina-
tion geometry are manifested in a widening of the
Cl1–M–P1 and Cl1–M–Cl2 and contraction of the
Cl2–M–P2 and P1–M–P2 angles. The P1–M–P2 an-
gle in all complexes remains fixed around 87 – 88◦ and
does not show a systematic response to the variation of
the M–P distances in chelate rings with different metal
Fig. 4. Molecular structure of 15 (H atoms and solvent
molecules omitted for clarity; displacement ellipsoids at the
50 % probability level). Selected bond lengths and angles are
listed in Table 2.
for the diazaphospholene phosphorus atom (1JPtP
=
4720 Hz) is attributable to the higher electronegativity
of the attached substituents.
Single crystals of 14 – 16 for X-ray diffraction stud-
ies were prepared by recry◦stallization from appropriate
solvent mixtures at −20 C. All compounds crystal-
lize in the monoclinic space groups P21/n (14, 15) and
P21/c (16), respectively, but differ in the number and
variety of incorporated solvent molecules (14: 1 THF,
15: 1 CH3CN, 16: 2.5 C6H6) and are thus not isostruc-
tural. All three crystals contain discrete molecules
without unusual intermolecular contacts. The molec-
ular structure of 15 is shown in Fig. 4 (those of 14 and
16 are virtually identical and are not displayed), and
additional data and selected bond lengths and angles
of all compounds are listed in Tables 1 and 2.
Comparison of the structural data of all complexes atoms. As similar P–M–P angles as in 14 – 16 have also
studied reveals that the common five-membered metal- been reported for both the related complexes prepared
chelate fragments exhibit closely similar features and by Pringle et al. [8] and for complexes cis-(PPh2P–
are characterized by a perceptible distortion of the ide- CH=CH–PPh2)MCl2 [6], and as the remaining struc-
ally square-planar coordination at the d8 M(II) center tural parameters in the ligand backbones of 15 – 17
and a non-planar conformation of the chelate rings. give no evidence for the presence of any peculiar steric
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S. Burck et al. · Activation of Polarized Phosphorus-Phosphorus Bonds by Alkynes
69
or electronic strain, we interpret these results as point- for 24 h. The precipitate formed was filtered off, the filtrate
evaporated under reduced pressure, and the residue dissolved
ing to a very strict bite angle preference of ligands con-
taining the ethene-1,2-bisphosphine motif.
in hexane (100 mL). Crystallization at −20 ◦C produced
◦
colorless crystals; yield 8.15 g (86 %). – M. p. 135 C. –
1H NMR (CDCl3): δ = 7.09 – 6.97 (m, 4 H, C6H4), 3.57
Conclusion
3
(d, 4 H, JPC = 16.3 Hz, CH2), 1.03 (s, 18 H, CH3). –
1
2
13C{ H} NMR (CDCl3): δ = 137.3 (d, JPC = 10.3 Hz,
In the present work it has been demonstrated
3
that unsymmetrical 1,1-diamino-diphosphinesundergo C6H4), 120.7 (s, C6H4), 111.1 (d, JPC = 1.8 Hz, C6H4),
54.5 (d, 2JPC = 11.2 Hz, CH2), 33.2 (d, 2JPC = 4.7 Hz, NC),
regio- and Z-stereospecific addition to electron-poor
28.1 (d, JPC = 3.2 Hz, CH3). – 31P{ H} NMR (CDCl3):
δ = 162.1. – C16H26N2PCl (312.82): calcd. C 61.43, H 8.38,
N 8.96; found C 61.94, H 8.38, N 8.92.
4
1
alkynes bearing at least one carboxylic ester function.
Both symmetrically and unsymmetrically substituted
alkynes undergo the reaction, and the addition is facili-
tated by an increasing degree of P–P bond polarization
in the diphosphine precursor and, in particular, the na-
ture of the co-substituent in the alkynes; replacement
of a hydrogen by a methyl group slows down the reac-
tion whereas introduction of a second electron with-
drawing carboxylic ester moiety has an accelerating
effect. The ethane-1,2-bisphosphines produce chelate
complexes with divalent ions of group-10 metals. As
a synthetically useful variant, the preparation of such
a complex can be conveniently carried out starting di-
rectly from the diphosphines by performing both the
alkyne insertion and complex formation in one pot.
2-Diphenylphosphino-1,3-bis(neopentyl)-2,3-dihydro-1H-
benzo[1,3,2]diazaphosphole (6)
Diphenyl(trimethylsilyl)phosphine (1.11 g, 4.3 mmol)
was added dropwise to a stirred solution of 2-chloro-1,3-
bis(neopentyl)-2,3-dihydro-1H-benzo[1,3,2]diazaphosphole
(1.35 g, 4.3 mmol) in anhydrous THF (5 mL). Stirring was
continued for 24 h after the addition was complete, and
the solution was then evaporated under reduced pressure.
Recrystallization of the residue from toluene (5 mL) at
−20 ◦C produced yellow crystals of m. p. 118 ◦C; yield
1.42 g (71 %). – 1H NMR (C6D6): δ = 7.65 (m, 4 H,
o-C6H5), 7.12 – 6.96 (m, 6 H, m/p-C6H53), 6.77 (m, 2 H,
C6H4), 6.55 (m, 2 H, C6H4), 3.14 (dd, JPH = 15.5 Hz,
Experimental Section
3
2JHH = 12.9 Hz), 2.66 (dd, 2 H, JPH
=
2JHH = 15.5 Hz,
CH2), 0.83 (s, 18 H, CH3). – 13C{ H} NMR (C6D6): δ =
1
All manipulations were carried out under an atmosphere
of dry argon using standard vacuum line techniques. Sol-
vents were dried by standard procedures. NMR spectra
were recorded on Bruker Avance 400 (1H: 400.1 MHz,
13C: 100.5 MHz, 31P: 161.9 MHz) or Avance 250 (1H:
250.1 MHz, 13C: 62.8 MHz, 31P: 101.2 MHz) NMR spec-
trometers at 303 K; chemical shifts are referenced to ext.
TMS (1H, 13C) or 85 % H3PO4 (Ξ = 40.480747 MHz, 31P).
Coupling constants are given as absolute values; i, o, m,
p denote the positions in phenyl and 2,6-dimethylphenyl
(DMP, denoted as C6H3) rings, benzannulated rings are de-
noted as C6H4, and 1H and 13C NMR signal assignments
141.1 (d, 2JPC = 8.6 Hz, C6H4), 136.8 (dd, JPC = 26.5 Hz,
1
2JPC = 8.3 Hz, i-C6H5), 134.6 (dd, JPC = 17.2 Hz, JPC
=
3
2
3
5.0 Hz, o-C6H5), 128.4 (d, JPC = 6.4 Hz, m-C6H5), 127.8
(s, p-C6H5), 119.0 (s, C6H4), 109.8 (s, C6H4), 55.1 (dd,
2
3
3JPC = 12.5 Hz, JPC = 1.8 Hz, CH2), 34.2 (dd, JPC
=
2.7 Hz, 4JPC = 1.4 Hz, NC), 28.2 (d, 5JCP = 3.3 Hz, CH3). –
31P{ H} NMR (C6D6): δ = 148.6 (d, 1JPP = 265 Hz, N2P),
1
−16.5 (d, 1JPP = 265 Hz, PPh2). – MS: m/z (%) = 462.2 (15)
[M]+, 277.1 (100) [M–PPh2]+. – C28H36N2P2 (462.55):
calcd. C 72.71, H 7.85, N 6.06; found C 72.72, H 7.80,
N 6.02.
1
are based on analysis of 2D H,13C gsHSQC and gsHMBC
Z-2-[1,3-Bis-(2ꢀ,6ꢀ-dimethylphenyl)-2,3-dihydro-1H-1,3,2-
diazaphospholyl]-3-diphenylphosphanyl-acrylic acid ethyl
ester (5)
spectra. EI-MS: Varian MAT 711, 70 eV. ESI-MS: Bruker
Daltonics microTOF-Q. Elemental analysis: Perkin-Elmer
24000CHN/O Analyzer. Melting points were determined in
sealed capillaries.
Ethyl propiolate (196 mg, 2.0 mmol) was added drop-
wise under stirring to a cooled (0 ◦C) solution of 4 (960 mg,
2.0 mmol) in toluene (20 mL). Stirring was continued for 1 h
after the addition was complete. The solution was then con-
2-Chloro-1,3-bis(neopentyl)-2,3-dihydro-1H-benzo[1,3,2]
diazaphosphole
PCl3 (4.58 g, 33.4 mmol) was added dropwise to a centrated under reduced pressure to a total volume of 5 mL,
stirred solution of benzene-1,2-bis(neopentyl)amine (7.52 g, pentane◦(3 mL) was added, and the resulting solution stored
30.3 mmol) and triethylamine (6.75 g, 66.7 mmol) in CH3CN at −20 C. The product precipitated as a colorless powder
◦
(150 mL ) at 0 ◦C. After the addition was complete, the solu- of m. p. 105 C which was collected by filtration and dried
1
tion was allowed to warm to r. t., and stirring was continued in vacuum; yield 985 mg (85 %). – H NMR (CDCl3): δ =
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70
S. Burck et al. · Activation of Polarized Phosphorus-Phosphorus Bonds by Alkynes
7.42 (dd, 1 H, 2JPH = 1.0 Hz, 3JPH = 26.8 Hz, HC=), 7.16 – 148.0 (dd, 1JPC = 28.7 Hz, 2JPC = 14.0 Hz, =C), 142.0 (dd,
7.06 (m, 6 H, m/p-C6H5), 7.03 (m, 4 H, o-C6H5), 6.98 (s, 1JPC = 22.3 Hz, 2JPC = 7.2 Hz, =C), 141.5 (d, 2JPC = 8.5 Hz,
3
6
1
2
6 H, C6H3), 5.86 (dd, 2 H, JPH = 2.3 Hz, JPH = 0.6 Hz, C6H4), 136.7 (dd, JPC = 13.2 Hz, JPC = 7.8 Hz, i-C6H5),
N-CH), 4.24 (q, 2 H, JHH = 7.2 Hz, CH2), 2.31 (s, 12 H, 134.3 (dd, 3JPC = 21.2 Hz, 5JPC = 0.7 Hz, m-CH), 129.1 (s,
3
o-CH3), 1.32 (t, 3 H, 3JHH = 7.2 Hz, CH3). – 13C{ H} NMR
p-C6H5), 128.6 (d, 3JPC = 7.3 Hz, o-C6H5), 118.8 (s, C6H4),
1
(CDCl3): δ = 167.3 (dd, JPC = 10.0 Hz, 4.7 Hz, C=O), 153.4 109.3 (s, C6H4), 55.1 (d, 2JPC = 13.9, CH2), 51.4 (s, OCH3),
(dd, 1JPC = 41.2 Hz, 2JPC = 20.0 Hz, =CH), 151.9 (dd, 1JPC
=
50.9 (s, OCH3), 33.9 (d, JPC = 2.6 Hz, CCH3), 28.0 (d,
3
85.9 Hz, JPC = 19.5 Hz, =C), 140.3 (d, JPC = 16.6 Hz, 4JCP= 2.9 Hz, CCH3). – 31P{ H} NMR (C6D6): δ = 96.3
i-C6H3), 138.1 (dd, 1JPC = 11.1 Hz, 5JPC = 7.1 Hz, i-C6H5), (d, 3JPP = 184 Hz, N2P), −13.5 (d, 3JPP = 184 Hz, PPh2). –
136.6 (d, 4JPC = 1.9 Hz, m-C6H3), 132.2 (dd, 2JPC = 19.5 Hz, MS (EI, 70 eV): m/z (%) = 604.3 (17) [M]+, 277.2 (100). –
5JPC = 1.1 Hz, o-C6H5), 128.4 (s, m-C6H3), 128.0 (s, m- C34H42N2O4P2 (604.67): calcd. C 67.54, H 7.00, N 4.63;
C6H5), 127.9 (s, p-C6H5), 125.5 (d, 5JPC = 1.7 Hz, p-C6H3), found C 67.43, H 7.42, N 4.55.
2
2
1
2
5
119.7 (dd, JPC = 5.9 Hz, JPC = 0.4 Hz, N-CH), 60.7 (s,
4
CH2), 19.1 (d, JPC = 4.4 Hz, o-CH3), 13.9 (s, CH3). –
2-[Bis(diisopropylamino)phosphino]-3-diphenylphosphino-
Z-but-2-ene-dicarboxylic acid dimethyl ester (11)
31P NMR (CDCl3): δ = 83.2 (dd, JPP = 188.0 Hz, JPH
=
3
3
3
3
27.2 Hz, N2P), −25.9 (dt, JPP = 188.0 Hz, JPH = 6.9 Hz,
PPh2). – MS (EI, 70 eV, 420 K): m/z (%) = 578.2 (0.1) [M]+,
392.1 (53) [M–C12H11P]+, 295.1 (7) [M–C17H16O2P]+,
185.0 (33) [M–C23H26N2O2P]+, 108.0 (33) [C6H5P]+. –
C35H36N2O2P2 (578.63): calcd. C 72.65, H 6.27, N 4.84;
found C 72.28, H 6.31, N 4.62.
DMAD (180 mg, 1.27 mmol) was added dropwise to a
stirred and cooled (0 ◦C) solution of 7 (530 mg, 1.27 mmol)
in anhydrous THF (10 mL). The solution was allowed to
warm to r. t. after the addition was complete, and the stir-
ring was continued for 24 h. The solution was then evap-
orated under reduced pressure, the residue extracted with
hexane (20 mL), and filtered. Pure 12 was obtained in only
Reaction of 4 with tetrolic acid methyl ester
◦
23 % yield upon storage of the filtrate at −20 C, but the
Diphosphine 4 (240 mg, 0.5 mmol) and tetrolic acid product is generated quantitatively in situ (as shown by
methyl ester (49 mg, 0.5 mL) were dissolved in anhydrous 31P NMR) and used for further reactions. – M. p. 122.3 ◦C. –
THF (10 mL) and the solution refluxed for 36 h. Quan- 1H NMR (C6D6): δ = 7.73 (m, 4 H, o-C6H5), 7.15 – 6.99
3
3
titative conversion of the starting diphosphine into 9 (ma- (m, 6 H, m/p-C6H5), 3.84 (dsept, JPH = 12.1 Hz, JHH
=
jor product) besides varying (minor) amounts of hydroly- 6.3 Hz, 4 H, NCH), 3.41 (s, 3 H, OCH3), 2.96 (s, 3 H, OCH3),
sis products (diphenylphosphine and phosphorous acid di- 1.28 (d, 3JHH = 6.3 Hz, 12 H, CH3), 1.24 (d, 3JHH = 6.3 Hz,
amides) was confirmed by 31P NMR spectroscopy. No at- 12 H, CH3). – 13C{ H} NMR (C6D6): δ = 169.6 (dd, JPC
=
1
tempt toward isolation of the product was made. – 31P NMR 12 Hz, 1.8Hz, C=O), 167.4 (dd,JPC = 12.3 Hz, 3.2 Hz, C=O),
(THF): δ = 80.4 (d, JPP = 255 Hz, N2P), −29.4 (d, 3JPP
=
157.8 (dd, JPC = 40.1, 33.0 Hz, =C), 142.2 (dd, JPC = 45.9,
3
1
2
255 Hz, PPh2).
32.8 Hz, =C), 136.5 (dd, JPC = 15.1 Hz, JPC = 6.3 Hz, i-
C6H5), 134.0 (dd, 3JPC = 20.6 Hz, 6JPC = 0.7 Hz, m-C6H5),
128.4 (d, 2JPC = 14.6 Hz, o-C6H5), 128.2 (s, p-C6H5), 51.6
(s, OCH3), 50.9 (s, OCH3), 48.6 (d, 2JPH = 13.3, NCH), 24.4
2-[1,3-Bis(neopentyl)-2,3-dihydro-1H-benzo[1,3,2]diaza-
phospholyl]-3-diphenylphosphino-Z-but-2-ene-dicarboxylic
(dd,1JPC = 6.9 Hz, JPC = 4.3 Hz, CH3), 24.1 (d, JPC
=
=
2
3
acid dimethyl ester (10)
6.6 Hz, CH3). – 31P{ H} NMR (C6D6): δ = 64.9 (d, 2JPP
1
180 Hz, N2P), −13.7 (d, 2JPP = 180 Hz, PPh2). – MS ((+)-
ESI): m/z (%) = 581.3 (100) [M+Na]+. – C30H44N2O4P2
(558.64): calcd. C 64.50, H 7.94, N 5.01; found C 64.32,
H 7.87, N 4.87.
DMAD (130 mg, 0.93 mmol) was added dropwise to a
stirred solution of 6 (430 mg, 0.93 mmol) in anhydrous THF
(10 mL). Stirring was continued for 30 min after the addi-
tion was complete, and the solution was then evaporated un-
der reduced pressure. The residue was extracted with hexane
(20 mL) and filtered. Pure 10 was obt◦ained in only 22 % yield
upon storage of the filtrate at −20 C, but the product can
be generated quantitatively in situ (as shown by 31P NMR)
2-[1,3-Bis-(2,6-dimethylphenyl)-2,3-dihydro-1H-1,3,2-di-
azaphospholyl]-3-diphenylphosphino-2-butene dicarb-
oxyclic acid dimethylester (12) and its dichloropalladium
complex 13
and used for further reactions. – M. p. 118 C. – 1H NMR
◦
(C6D6): δ = 7.68 (m, 4 H, o-C6H5), 7.2 – 6.95 (m, 6 H, m/p-
C6H5), 6.72 (m, 2 H, C6H4), 6.61 (m, 2 H, C6H4), 3.33 (dd,
A solution of 4 (249 mg, 0.4 mmol) in THF (10 mL) was
3JPH = 15.6, 2JHH =15.1, 2 H, CH2), 3.06 (dd, JPH = 19.8, cooled to −78 ◦C. DMAD (57 mg, 0.4 mmol) was added un-
3
2JHH = 15.1, 2 H, CH2), 2.98 (s, 3 H, OCH3), 2.85 (s, 3 H, der stirring, and the mixture was stirred for 3 h at the same
OCH3), 0.91 (s, 18 H, CH3). – 13C{ H} NMR (C6D6): δ = temperature after the addition was complete. The resulting
1
168.7 (d, JPC = 2 Hz, C=O), 166.0 (d, JPC = 4 Hz, C=O), solution was then allowed to warm to r. t., and the forma-
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S. Burck et al. · Activation of Polarized Phosphorus-Phosphorus Bonds by Alkynes
71
1
tion of 12 as main product was verified by 31P NMR [δ = 3JHH = 7.2 Hz, CH3). – 13C{ H} NMR (CDCl3): δ = 162.4
3
3
84.3 (d, JPP = 220 Hz), −13.3 (d, JPP = 220 Hz)]. (Cy- (dd, 3JPC = 32.0 Hz, 2JPC = 3.4 Hz, C=O), 143.6 (d, 1JPC
=
=
clooctadiene)palladium dichloride (115 mg, 0.4 mmol) was 3.5 Hz), 139.8 (broad s), 138.2 (dd, JPC = 16.9 Hz, 3JPC
1
then added, the solution stirred for further 10 h, and finally 2.1 Hz, =C), 137.5 (d, JPC = 6.5 Hz), 135.3 (broad s), 133.9
3
evaporated to dryness. The residue was treated with toluene (d, JPC = 11.4 Hz), 132.5 (d, JPC = 2.9 Hz), 130.9 (broad
(4 mL), the resulting suspension filtered, and the remaining s), 129.4 (d, JPC = 12.1 Hz), 128.9 (broad s), 128.2 (d, JPC
=
1
2
solid residue of 13 dried in vacuum; yield 272 mg (85 %). – 1.3 Hz), 127.0 (dd, JPC = 61.9 Hz, JPC = 0.8 Hz, =CH),
2
M. p. 264 ◦C. – 1H NMR (CD3CN): δ = 7.70 – 7.60 (m, 122.8 (d, JPC = 3.4 Hz, N-CH), 63.2 (s, OCH2), 21.5 (s,
3
1
4 H, o-C6H5), 7.50 – 7.00 (m, 12 H), 6.40 (d, 2 H, JPH
=
o-CH3), 20.7 (s, o-CH3), 14.5 (s, CH3). – 31P{ H} NMR
14.2 Hz, N-CH), 3.86 (s, 3 H, OCH3), 3.56 (s, 3 H, OCH3), (CDCl3): δ = 108.6 (d, 2JPP = 20.0 Hz, N2P), 62.2 (d, 2JPP
=
2.63 (s, 6 H, o-CH3), 2.25 (s, 6 H, o-CH3). – 13C{ H} NMR 20.0 Hz, PPh2). – MS: (EI, 70 eV, 480 K): m/z (%) = 756.1
1
(CD3CN): δ = 163.1 (d, JPC = 61 Hz, C=O), 162.9 (d, JPC
55 Hz, C=O), 138.6 (d, JPC = 3.6 Hz), 137.3 (d, JPC
=
=
(0.1) [M]+, 295.1 (14) [C17H26O2PdCl2]+, 249.1 (100). –
C35H36N2O2P2PdCl2 (755.96) · CH3CN: calcd. C 56.57,
6.6 Hz), 135.9 (d, JPC = 1.9 Hz), 134.3 (d, JPC = 11.9 Hz), H 5.36, N 3.38; found C 56.08, H 5.23, N 3.28.
133.0 (d, JPC = 3.1 Hz), 130.1 (d, JPC = 1.0 Hz), 129.0 (dd,
JPC = 8.2 Hz, 1.8 Hz), 128.9 (d, JPC = 11 Hz), 128.2 (s),
(Z-2-[1,3-Bis-(2ꢀ,6ꢀ-dimethylphenyl)-2,3-dihydro-1H-1,3,2-
diazaphospholyl]-3-diphenylphosphanyl-acrylic acid ethyl
128.1 (d, JPC = 1.7 Hz), 123.1 (d, JPC = 2.9 Hz, N-CH), 53.6
ester)dichloro platinum(II) (16)
(s, OCH3), 53.3 (s, OCH3), 20.4 (s, CH3), 20.3 (s, CH3). –
31P{ H} NMR (CD3CN): δ = 105.9 (d, JPP = 17.4 Hz,
1
Yield 284 mg (87 %). – M. p. 151 ◦C. – 1H NMR (C6D6):
2
N2P), 77.5 (d, JPP = 17.4 Hz, PPh2). – C36H36N2O4P2PdCl2
(799.97)·0.5 CH3CN: calcd. C 54.16, H 4.61, N 4.27; found
54.17, H 4.61, N 4.37.
δ = 7.46 – 7.33 (m, 4 H, o-C6H5), 7.18 (dd, 1 H, JPH
=
65.4 Hz, 3JPH = 11.7 Hz, =CH), 6.90 – 6.68 (m, 12 H), 5.62
(d, 2 H, 3JPH = 15.5 Hz, N-CH), 4.03 (q, 2 H, 3JHH = 7.1 Hz,
CH2), 2.90 (s, 6 H, o-CH3), 2.13 (s, 6 H, o-CH3), 0.93 (t,
General procedure for the reaction of 4 with metal(II) salts
3 H, JHH = 7.1 Hz, CH3). – 31P{ H} NMR (C6D6): δ =
3
1
2
1
Ligand 4 (231 mg, 0.4 mmol) and one equiv. of the
appropriate metal salt (anhydrous NiCl2, (COD)PdCl2, or
(COD)PtCl2) were mixed with THF (10 mL) and the sus-
pension diluted with CH3CN until all solids had dissolved.
Storing the formed clear solutions at −20 ◦C gave red crys-
tals of the complexes which were collected by filtration and
dried in vacuum.
86.7 (d, JPP = 3.7 Hz, JPtP = 4720 Hz, N2P), 35.7 (d,
1
1
2JPP = 3.7 Hz, JPtP = 3548 Hz, PPh2). – 195Pt{ H} NMR
(C6D6): δ = −4420 (dd, 1JPtP = 4720, 3548 Hz). – MS (EI,
70 eV, 430K): m/z (%) = 844.1 (0.4) [M]+, 808.1 (0.3) [M–
Cl]+, 773.1 (0.6) [M–2 Cl]+. – C35H36N2O2P2PtCl2: calcd.
C 49.77, H 4.30, N 3.32; found C 49.76, H 4.51, N 3.56.
(Z-2-(1,3-dineopentyl-1H-benzo[1,3,2]diazaphosphol-
2(3H)-yl)-3-(diphenylphosphino)acrylic acid ethyl ester) (8)
and its dichloropalladium complex 17
(Z-2-[1,3-Bis-(2ꢀ,6ꢀ-dimethylphenyl)-2,3-dihydro-1H-1,3,2-
diazaphospholyl]-3-diphenylphosphanyl-acrylic acid ethyl
ester)dichloro nickel(II) (14)
Ethyl propiolate (96 mg, 0.97 mmol) was added to a
stirred solution of 6 (450 mg, 0.97 mmol) in THF (10 mL),
and the mixture was stirred for 0.5 h at r. t. after the addition
was complete. The formation of 8 as the main product was
Yield 252 mg (89 %). – M. p. 145 ◦C. – 1H NMR (C6D6):
3
δ = 7.46 (d, broad, JPH = 7.5 Hz, 4 H, o-C6H5), 6.98 –
6.70 (m, 12 H), 5.60 (s, broad, 2 H N-CH), 3.91 (q, 2 H,
3JHH = 7.2 Hz, CH2), 2.98 (s, broad, 6 H, o-CH3), 2.12 (s,
verified by 31P NMR [δ = 94.4 (d, JPP = 166 Hz), −25.4
2
3
2
broad, 6 H, o-CH3), 0.83 (t, 3 H, JHH = 7.2 Hz, CH3). –
(d, JPP = 166 Hz)]. A solution of (COD)PdCl2 (270 mg,
31P{ H} NMR (C6D6): δ = 112.2 (broad s, N2P), 50.6
1
0.97 mmol) in CH2Cl2 (25 mL) was then added dropwise.
The solution was stirred for further 0.5 h after the addi-
tion was complete and was then evaporated to dryness. The
residue was extracted with diethyl ether (20 mL), the result-
ing suspension filtered, and the remaining red solid residue
of crude 17 recrystallized at −20 ◦C from Et2O/CH2Cl2
(1 : 1), yield 380 mg (53 %). – 1H NMR (C6D6): δ = 7.94
(broad s, PPh2). – MS (EI, 70 eV, 430 K): m/z (%) = 576.3
(2) [M–NiCl2]+, 295.1 (100) [M–C17H16O2PNiCl2]+. –
C35H36N2O2P2NiCl2 (708.23)·C4H8O: calcd. C 60.03,
H 5.68, N 3.59; found C 60.72, H 5.78, N 3.46.
(Z-2-[1,3-Bis-(2ꢀ,6ꢀ-dimethylphenyl)-2,3-dihydro-1H-1,3,2-
diazaphospholyl]-3-diphenylphosphanyl-acrylic acid ethyl
ester)dichloro palladium(II) (15)
2
3
(m, 4 H, o-C6H5), 7.95 (dd, 1 H, JPH = 73.4 Hz, JPH
10.7 Hz, =CH), 7.66 (m, 2 H, p-C6H5), 7.56 (m, 4 H, m-
=
Yield 253 mg (84 %). – M. p. 162 ◦C. – 1H NMR (CDCl3): C6H53), 6.97 (m, 2 H, C6H4), 6.94 (m, 2 H, C6H4), 4.04 (q,
3
δ = 7.27 – 6.78 (m, 14 H), 6.69 – 6.53 (m, 2 H), 5.95 (d, 2 H, 2 H, JHH = 7.1 Hz, CH2), 3.81 (dd, 2 H, JPH = 18.1 Hz,
3JPH = 13.9 Hz, N-CH), 4.12 (q, 2 H, 3JHH = 7.2 Hz, CH2), 2JHH = 15.7 Hz, CH2), 3.43 (dd, 2 H, JPH
=
2JHH
=
=
3
3
2.47 (s, 6 H, o-CH3), 1.80 (s, 6 H, o-CH3), 1.11 (t, 3 H, 15.4 Hz, CH2), 0.89 (s, 18 H, CH3), 0.74 (t, 3 H, JHH
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72
S. Burck et al. · Activation of Polarized Phosphorus-Phosphorus Bonds by Alkynes
1
7.1 Hz, CH3). – 13C{ H} NMR (C6D6): δ = 160.4 (d, JPC
=
tion parameters, and results of the analyses are listed in Ta-
40 Hz, C=O), 149.7 (d, 1JPC = 46 Hz, 2JPC = 34 Hz, =CH), ble 1. Direct Methods (SHELXS-97) [16] were used for struc-
1
2
2
143.7 (dd, JPC = 34 Hz, JPC = 12 Hz), 141.5 (d, JPC
=
ture solution, refinement was carried out using SHELXL-97
8.5 Hz, C6H4), 134.3 (d, JPC = 11.8 Hz, o-C6H5), 133.3 (full-matrix least-squares on F2) [16], and hydrogen atoms
2
4
3
(d, JPC = 2.9 Hz, p-C6H5), 129.6 (d, JPC = 11.9 Hz, m- were refined using a riding model. A semi-empirical ab-
C6H5), 127.4 (dd, JPC = 57.4 Hz, 2JPC = 1.0 Hz, i-C6H5), sorption correction from equivalent reflections was applied
1
2
120.9 (s, C6H4), 110.8 (d, JPC = 6.0 Hz, C6H4), 63.3 (s, for 14 – 16; max./min. transmission was 0.9115 / 0.8382 (14),
OCH2), 61.7 (d, 2JPC = 8.3 Hz, CH2), 33.9 (d, 3JP1C= 2.0 Hz, 0.8036 / 0.7759 (15), 0.7612 / 0.6456 (16).
CCH3), 29.1 (s, CCH3), 13.1 (s, CH3). – 31P{ H} NMR
CCDC 703435 (4), CCDC 703436 (6), CCDC 703760
(11), CCDC 703437 (14), CCDC 703438 (15) and CCDC
(C6D6): δ = 137.1 (d, 2JPP = 20.9 Hz, N2P), 63.9 (d, 2JPP
=
20.9 Hz, PPh2). – MS ((–)-ESI): m/z (%) = 773.1 (100) 703439 (16) contain the supplementary crystallographic
[M+Cl]−. – C33H42N2O2P2PdCl2 (737.98): calcd. C 53.71, data for this paper. These data can be obtained free of
H 5.74, N 3.80; found C 51.82, H 5.35, N 3.43.
charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data request/cif.
X-Ray structure determination
Acknowledgements
The crystal structure determinations of 4, 6, 11, 14·THF,
15·CH3CN, and 16·2.5C6H6, were performed on a Nonius
KappaCCD diffractometer at 123(2) K (for 4, 6, 14 – 16),
or on a Syntex P4 diffractometer at 173(2) K for 11, using
We thank Dr. J. Opitz, J. Trinkner and K. Wohlbold (Insti-
tut fu¨r Organische Chemie, Universita¨t Stuttgart) for record-
ing the mass spectra. The Deutsche Forschungsgemeinschaft
is acknowledged for financial support.
˚
MoKα radiation (λ = 0.71073 A). Crystal data, data collec-
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˚
˚
deviations: P–Ni 2.15 0.03 A; P–Pd 2.24 0.02 A;
˚
˚
P–Pt 2.22 0.02 A; Ni–Cl 2.21 0.05 A; Pd–Cl 2.37
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Unauthenticated
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