Diphosphination of Electron Poor Alkenes

Article abstract of DOI:10.1021/om801179k

Studies of the reactions between an unsymmetrically substituted 1,1-diaminodiphosphine and electron poor alkenes revealed that, in contrast to the regioselective 1,2-addition of the P-P bond to α,β-unsaturated esters and nitriles with terminal double bond

Full text of DOI:10.1021/om801179k

1644
Organometallics 2009, 28, 1644–1651
Diphosphination of Electron Poor Alkenes
Imre Hajdo´k,† Falk Lissner,† Martin Nieger,‡ Sabine Strobel,† and Dietrich Gudat*,†
Institut fu¨r Anorganische Chemie, UniVersita¨t Stuttgart, Pfaffenwaldring 55, 70550 Stuttgart, Germany,
and Laboratory of Inorganic Chemistry, UniVersity of Helsinki, A. I. Virtasen aukio 1, Helsinki, Finland
ReceiVed December 12, 2008
Studies of the reactions between an unsymmetrically substituted 1,1-diaminodiphosphine and electron
poor alkenes revealed that, in contrast to the regioselective 1,2-addition of the P-P bond to R,ꢀ-unsaturated
esters and nitriles with terminal double bonds, ethyl(vinyl)ketone reacted via 1,4-addition and
R,ꢀ-unsaturated esters or ketones with internal double bonds failed to react at all, presumably owing to
the deactivating influence of the alkyl groups. Reaction of 1 with maleic N-phenylimide proceeded
stereoselectively under cis-addition but diesters of maleic and fumaric acid gave mixtures of diastereomeric
1,2-bisphosphines. The addition products were characterized by 31P NMR before being converted into
palladium complexes that were isolated and comprehensively characterized by spectroscopic data and in
most cases by X-ray diffraction studies. Monitoring the reactions of 1 with maleic and fumaric diesters
by NMR revealed that both E/Z-isomerization of alkene starting materials and epimerization of stereogenic
centers in 1,2-bisphosphines take place and allow isolation from the mixtures of diastereomeric ligands
of complexes featuring a uniform stereochemistry of the C2 backbone.
Scheme 1a
Introduction
Bidentate ligands are widely used in organometallic and
coordination chemistry as well as in catalysis. As a rational way
to their synthesis, additions to alkenes or alkynes that allow
simultaneous introduction of two donors to an organic backbone
have recently attracted attention, and elaborated protocols are
now known for the stereo- and even enantioselective dihy-
droxylation1 or diamination2 of olefins to give O,O- and N,N-
ligands. Analogous approaches to P,P-donor ligands, which are
likewise of great significance, are limited although it has been
reported that derivatives with two like phosphine fragments can
be accessed via double metathesis of activated 1,2-disubstituted
olefins,3 or via addition of the P-P bond of tetramethyldiphos-
phine to the activated double bonds of 1,3-butadiene or
fluoroalkenes.4 Although the latter reaction is long known, it
does not seem to have been widely used, presumably owing to
the need to employ hazardous starting materials, or the fact that
the additions to butadiene and substituted olefins do not occur
stereoselectively but yield mixtures of E/Z-isomers or diaster-
eomers, respectively.4 More recently, the double phosphination
of alkynes via radical induced E-stereoselective addition of
tetraphenyldiphosphine5 or stepwise transition-metal-catalyzed
addition of two molecules of diphenylphosphine oxide and
1
2
a
R ) 2,6-Me2C6H4 (1a, 2), Mes (1b, 3a,b); R ) CN (3a), CO2Me
(3b).
subsequent reduction of the formed tertiary bis(phosphine
oxides)6 have been demonstrated, and double Pt-catalyzed
hydrophosphination of a 1,3-diene was reported to give a
bidentate 1,2-bis(dialkylphosphino)ethane derivative;7 however,
all three reactions are limited to the synthesis of bidentate ligands
with two like R2P groups. A more general approach that allows
a specific one-step synthesis of chelating 1,2-bis-phosphines with
both identical8 and different8-10 phosphine donor moieties
featuring a large variety of P substituents has lately been found
in the Z-stereospecific addition reaction of diphosphines to
activated alkynes (Scheme 1, (a)). As we had demonstrated some
time ago, the more reactive 1,1-diamino-diphosphines may
undergo similar addition reactions to activated alkenes to give
1,2-bisphosphines featuring two donor sites with different
* To whom correspondence should be addressed. Fax: +49 711
68564241. E-mail: gudat@iac.uni-stuttgart.de.
† Universita¨t Stuttgart.
‡ University of Helsinki.
(1) (a) Kolb, H. C.; VanNieuwenhze, M. S.; Sharpless, K. B. Chem.
ReV. 1994, 94, 2483. (b) Sharpless, K. B. Angew. Chem. 2002, 114, 2126;
Angew. Chem., Int. Ed. 2002, 41, 2024.
(2) Muniz, K. New J. Chem. 2005, 29, 1371.
(3) (a) Holz, J.; Monsees, A.; Jiao, H.; You, J.; Komarov, I. V.; Fischer,
C.; Drauz, K.; Bo¨rner, A. J. Org. Chem. 2003, 68, 1701. (b) Holz, J.; Zayas,
O.; Jiao, H.; Baumann, W.; Spannenberg, A.; Monsees, A.; Riermeier, T. H.;
Almena, J.; Kadyrov, R.; Bo¨rner, A. Chem.-Eur. J. 2006, 12, 5001.
(4) (a) Hewertson, W. I.; Taylor, C. J. Chem. Soc. C 1970, 1990. (b)
Brandon, R.; Haszeldine, R. N.; Robinson, P. J. J. Chem. Soc., Perkin Trans.
2 1973, 1301. (c) Cooper, P.; Fields, R.; Haszeldine, R. N. J. Chem. Soc.,
Perkin Trans. 2 1975, 702.
(6) Allen Jr, A.; Ma, L.; Lin, W. Tetrahedron Lett. 2002, 43, 3707.
(7) Kovacik, I.; Scriban, C.; Glueck, D. S. Organometallics 2006, 25,
536.
(8) Dodds, D. L.; Haddow, M. F.; Orpen, A. G.; Pringle, P. G.;
Woodward, G. Organometallics 2006, 25, 5937.
(9) Burck, S.; Gudat, D.; Nieger, M. Angew. Chem. 2007, 119, 2977;
Angew. Chem., Int. Ed. 2007, 46, 2919.
(5) Sato, Z. A.; Yorimitsu, H.; Oshima, K. Angew. Chem. 2005, 117,
1722; Angew. Chem., Int. Ed. 2005, 44, 1694.
(10) Burck, S.; Hajdo´k, I.; Nieger, M.; Bubrin, D.; Schulze, S.; Gudat,
D. Z. Naturforsch. 2009, 64b, 63.
10.1021/om801179k CCC: $40.75
2009 American Chemical Society
Publication on Web 02/20/2009

Alkene Diphosphination
Organometallics, Vol. 28, No. 6, 2009 1645
Scheme 2a
satisfactorily purified; consequently, these compounds were only
characterized by spectroscopic studies and directly converted
into metal complexes by reaction with (cyclooctadiene)palla-
dium dichloride. The complexes formed were easily isolated in
pure form by crystallization and characterized by comprehensive
spectroscopic and analytical data and in several cases by single-
crystal X-ray diffraction studies.
In view of the objective to elucidate stereochemical aspects
of the diphosphination of alkenes, we began our studies by using
cyclic alkenes as reactants as here the Z-stereochemistry is fixed
by the ring structure, and analysis of the products should allow
the determination of whether the phosphine fragments add to
the same side, or to opposite sides, of the double bond. The
chosen substrates comprised cyclopentenone, cyclohexenone,
and the cyclic lactones coumarin and 5,6-dihydro-2H-pyran-2-
one, all featuring an internal double bond activated by a single
carbonyl or ester function. Reactions were performed by
refluxing mixtures of 4 and alkene for prolonged times in
toluene, and the conversion was monitored by 31P NMR
spectroscopy. In all cases, the absence of any visible reaction
under addition of the diphosphine to the double bond was noted,
and beside signals of species resulting from hydrolysis or
unspecific decomposition,10,11 only those of unreacted 4 were
observed. The same outcome was observed upon treatment of
the alkene substrates with the more reactive diphosphines 1a,b.
In contrast, a smooth reaction occurred between 4 and ethyl-
(vinyl)ketone featuring a terminal double bond. The 31P NMR
spectrum of the reaction mixture displayed a single AX pattern
attributable to the addition product, indicating that a regiose-
lective reaction had occurred. The product was trapped with
(cod)PdCl2 to give a palladium complex, which was isolated in
moderate yield after crystallization.
The constitution of both the free phosphine and its complex
were established by multinuclear (1H, 31P, 13C) one- and two-
dimensional NMR spectroscopy (the spectra of the phosphine
were recorded directly from the reaction mixture), and the
composition of the complex was further confirmed by elemental
analysis. The results of the structure elucidation are somewhat
surprising as the initial product was identified as 1,3-bis(pho-
sphine) 5 (Scheme 2) which is formed via 1,4-addition of the
P-P bond of 4 to the R,ꢀ-unsaturated ketone, rather than the
expected8-10 1,2-addition product. Crucial findings in support
of this assignment are the observation of 13C NMR signals of a
quaternary and a protonated olefinic carbon atom with a large
chemical shift difference that is attributable to the atoms of an
enolic double bond and the observed isochronicity of the two
protons of the adjacent methylene group, which rules out that
1,2-addition to the alkene double bond with concomitant
formation of a stereogenic center had occurred. In line with the
course of the addition is also the observation of a JPP coupling
constant that is an order of magnitude smaller than in the
previously reported 1,2-bisphosphines 2, 3.9,10 On the basis of
the assignment of the ligand structure, the species formed upon
reaction with (cod)PdCl2 is formulated as chelate complex 6.14
1
a
R ) CH2C(CH3)3, R ) Et (10), Me (11).
electronic properties on a saturated C2-backbone (Scheme 1,
(b)).11 Hybrid chelating ligands of this type have received
interest as ligands for specific applications in catalysis.13
To establish if diphosphination of alkenes can provide a
practically useful access to hybrid 1,2-bisphosphines, we have
now studied reactions of a 1,1-diamino-diphosphine precursor
with a larger range of alkenes. Particular attention was given
to reactions with 1,2-disubstituted substrates where synfacial
or antifacial attachment of the phosphinyl fragments may give
rise to diastereomeric addition products, and evaluation of the
relative stereochemistry in the addition products allowed us to
decide if the addition step is stereospecific, like the diphosphi-
nation of alkynes,8-10 or not.
Results and Discussion
The addition reactions to alkenes described in this work were
conducted using the benzo-1,3,2-diazaphospholene derivative
4 (Scheme 2).10 This starting material was chosen because its
reactivity toward alkynes comes close to that of N-heterocyclic
phosphines with isolated rings like 1a,b but is easier to handle
due to its increased stability toward hydrolysis. Furthermore, it
was found that preparation of 4 via condensation of a chloro-
phosphine precursor with diphenyl(trimethylsilyl)phosphine and
subsequent reaction with alkenes could be conveniently per-
formed as one-pot reaction, thus eliminating the additional effort
and reduction in yield losses associated with workup and
isolation of the diphosphine. The 1,2-bisphosphines resulting
from the addition were obtained after evaporation of volatiles
as crude products in the form of viscous oils that could not be
Regarding that in the case of alkynes formal replacement of
an alkyl substituent by a second activating group overcomes
both the electronic deactivation and any possible steric hin-
drance10 and renders reactions under diphosphination of internal
triple bonds feasible, we studied further the reactions of 4 with
(11) Burck, S.; Gudat, D.; Nieger, M. Angew. Chem. 2004, 116, 4905;
Angew. Chem., Int. Ed. 2004, 43, 4801.
(12) Cullen, W. R.; Dawson, D. S. Can. J. Chem. 1967, 45, 2887.
(13) (a) Sakai, N.; Mano, S.; Nozaki, K.; Takaya, H. J. Am. Chem. Soc.
1993, 115, 7033. (b) Nozaki, K.; Sakai, N.; Nanno, T.; Higashijima, T.;
Mano, S.; Horiuchi, T.; Takaya, H. J. Am. Chem. Soc. 1997, 119, 4413. (c)
Yan, Y.; Zhang, X. J. Am. Chem. Soc. 2006, 128, 7198.
(14) Although this seems the most likely assignment, an alternative
molecular structure featuring a macrocyclic dinuclear complex arising from
coordination of two bidentate ligands to two palladium atoms cannot be
totally ruled out; furthermore, the configuration at the double bond was not
determined.

1646 Organometallics, Vol. 28, No. 6, 2009
Hajdo´k et al.
maleic anhydride and maleic N-phenylimide, respectively. In
both cases, 31P NMR studies revealed that complete conversion
of the starting diphosphine had occurred after one hour at
ambient temperature. The reaction with the imide produced a
single addition product which was detected by 31P NMR (AX
3
spin system, δ ) 115.3 (PN2), 4.9 (PPh2), JPP ) 2 Hz) and
directly trapped by reaction with (cod)PdCl2. The complex
formed was isolated by crystallization and characterized by
analytical and spectroscopic data and single-crystal X-ray
diffraction as 8 (Scheme 2). In contrast, the corresponding
reaction with maleic anhydride was unspecific and gave a
mixture of several addition products. We attribute this behavior
to the occurrence of consecutive ring-opening reactions of the
cyclic anhydride15,16 which are known to occur in similar
compounds in the presence of phosphines16 and are likely to
produce a mixture of cyclic as well as acyclic reaction products.
As we were neither able to isolate nor unambiguously identify
individual products, this reaction was not pursued further.
The identity of the complex 8 was unambiguously established
by analytical and spectroscopic (NMR, IR, ESI-MS) data. Key
to the structural assignment were the occurrence of a pseudo-
molecular ion peak in the (-)-ESI-MS and the observation of
the highly significant signals of the protons in the C2-backbone
which formed the AB-part of an ABXY spin system (X, Y )
31P) and showed HSQC- and HMBC-correlations to the aliphatic
carbon atoms of the C2-backbone and the adjacent imide
carbonyl groups, respectively. The31P{1H} NMR spectrum
displayed the expected AX-type pattern whose signals were
straightforwardly assigned to the PCN2 (δ31P 139.4) and PC3
(δ31P 96.0) phosphorus atoms. The pronounced deshielding of
both signals and the magnitude of JPP (24.5 Hz) are reliable
indicators for the presence of a five-membered chelate ring with
cis-arrangement of the two donor atoms at the metal,8-11 and
the presence of the N-phenylimido fragment was proven by the
presence of characteristic bands in the carbonyl region of the
IR spectrum and the expected signals in the aromatic and
Figure 1. Molecular structure of 8 (top) and reduced plot (bottom)
showing the alignment of the fused five-membered rings seen as a
projection along the central C29-C30 bond. H-atoms and cocrys-
tallized solvent molecules (1.4 CH2Cl2) were omitted for clarity;
50% probability ellipsoids. Selected bond lengths (Å) and angles
(deg): Pd-P1 2.1960(9), Pd-P2 2.2311(9), Pd-Cl2 2.3558(9),
Pd-Cl1 2.3689(9), P1-N1 1.665(3), P1-N2 1.671(3), P1-C29
1.903(4), P2-C30 1.851(4), C29-C30 1.527(5), P1-Pd-P2
89.30(3), P2-Pd-Cl2 88.46(3), P1-Pd-Cl1 88.96(3), Cl2-
Pd-Cl1-93.72(3).
1
carbonyl regions of the H and 13C NMR spectra.
The constitutional assignment derived from the spectroscopic
data was confirmed by a single-crystal X-ray diffraction study
(Figure 1) which disclosed also a cis-arrangement of the
phosphine-donor moieties attached to the imide ring (although
JPP and 3JHH were measured from the 31P and 1H NMR spectra,
the conformation could not be reliably derived due to the lack
of suitable reference compounds). The C29-C30 (1.527(5) Å)
and P2-C30 (1.851(4) Å) bonds in the ligand are normal single
bonds whereas the P1-C29 distance (1.903(4) Å) is somewhat
lengthened. The distorted square planar coordination of the metal
atom and the values of the Pd-P and Pd-Cl bond lengths (cf.
caption to Figure 1 a) in 8 match closely the corresponding
features found in the complex 910 (Chart 1) where the chelate
ligand exhibits an unsaturated C2-backbone, and in other related
bis(phosphine) chelate complexes of palladium.8
Chart 1a
a
R ) CH2C(CH3)3.
The chelate bite angle in 8 (89.30(3)°) is close to the ideal
angle of 90° and thus slightly larger than in 9 (87.08(2)°10),
indicating presumably a less strict rigidity of the chelate ligand.
The Cl2 atom is dislocated out of the palladium coordination
plane formed by the remaining donor atoms but the resulting
torsional twist between the P1-Pd-P2 and Cl1-Pd-Cl2 planes
(torsional angle φ ) 9°) is less pronounced than in 9 (φ ) 14°).
Both the PdP2C2 chelate ring and the cyclic imide ring in 8
display twist-conformations. The cis-annulation of the two five-
membered rings induces a perceptible deviation from an
optimum staggered conformation of the substituents at the
C29-C30 bond which is common to both rings (Figure 1
bottom), leading to substantial contraction of the dihedral angles
P1-C29-C30-P2 (-26°), C32-C29-C30-C31 (-16°), and
H29-C29-C30-H30 (-27°, using the calculated positions of
the hydrogen atoms), with respect to the “unstrained” value of
60°.
(15) van Doorn, J. A.; Frijns, J. H. G.; Meijboom, N. J. Chem. Soc.,
Perkin Trans. 2 1990, 479.
(16) Avey, A.; Schut, D. M.; Weakley, T. J. R.; Tyler, D. R. Inorg.
Chem. 1993, 32, 233.
If one considers that the reactions of 4 with maleic N-
phenylimide and (cod)PdCl2 yield exclusively a single NMR-
spectroscopically detectable diastereomer of both the ligand 7

Alkene Diphosphination
Organometallics, Vol. 28, No. 6, 2009 1647
Figure 3. Molecular structure of 11; H atoms and cocrystallized
solvent molecules (1.5 DMF) omitted for clarity; 50% probability
ellipsoids; only one of two positions for the disordered neopentyl
group shown. Selected bond lengths (Å) and angles (deg): P2-Pd43
2.191(2), P22-Pd43 2.227(2), Pd43-Cl45 2.352(2), Pd43-Cl44
2.363(2), N1-P2 1.666(5), P2-N3 1.667(6), P2-C20 1.857(7),
C20-C21 1.518(10), C21-P22 1.870(7), P2-Pd43-P22 88.73(6),
P22-Pd43-Cl45 89.42(6), P2-Pd43-Cl44 87.59(6), Cl45-Pd43-
Cl44 94.89(6), P2-Pd43-Cl45 171.92(7), P22-Pd43-Cl44
173.87(6).
Figure 2. Molecular structure of 10 (top) and reduced plot (bottom)
showing a projection along the C20-C21 bond. H atoms and one
cocrystallized solvent molecule (THF) were omitted for clarity; 50%
probability ellipsoids. Selected bond lengths (Å) and angles (deg):
N1-P2 1.680(4), N3-P2 1.669(4), P2-Pd43 2.2061(13), P22-Pd43
2.2411(13), Pd43-Cl44 2.3554(12), Pd43-Cl45 2.3612(13),
C20-C21 1.530(7), C20-P2 1.865(5), C21-P22 1.849(5),
P2-Pd43-P22 89.60(5), P2-Pd43-Cl44 88.04(5), P22-Pd43-Cl45
89.95(5), Cl44-Pd43-Cl45 93.23(5).
neopentyl moiety and one cocrystallized solvent molecule in
11 and is reflected in larger estimated standard deviations of
bond lengths and angles), a comparison of the molecular
structures allows to state beyond doubt that both compounds
display a mutual trans-arrangement of the protons at the five-
membered chelate ring and thus exhibit, regardless of the
different double bond configuration in the starting materials,
the same configuration of the C2 backbone.
and the palladium complex 8, and that it is further very unlikely
that coordination of the phosphine donors to palladium induces
configuration inversion at the carbon atoms, 7 is assumed to
show the same cis-annulation of the five-membered rings as
had been established for 8. In these terms, the addition of the
P-P bond of 4 to maleic imide may be considered like the
diphosphination of alkynes8-10 as a stereospecific reaction that
proceeds by synfacial attack of both phosphinyl fragments to
the double bond.
With the aim to extend the scope of the phosphinyl phos-
phination of activated alkenes, we also studied the addition of
4 to the acyclic esters dimethyl fumarate and diethyl maleate,
which are distinguished by Z- or E-configuration of the double
bond, respectively. The reactions took place upon prolonged
(6-11 h) heating to 65 °C, and the initially formed adducts
were trapped by complexation with (cod)PdCl2. A 31P NMR
survey revealed that in each reaction a single 1,2-bisphosphine
chelate complex had formed which was isolated in moderate
yield by crystallization and characterized by analytical and
spectroscopic data and single-crystal X-ray diffraction studies.
As the spectroscopic data of both products are very similar to
those of 8, the new compounds were likewise formulated as
bisphosphine chelate complexes formed by 1,2-addition of 4 to
the alkene and subsequent coordination to palladium (Scheme
2); these structural assignments were, as expected, confirmed
by single-crystal X-ray diffraction studies. Even if the general
quality of the final structural data of 11 (Figure 2) is somewhat
poorer than in the case of 10 (Figure 3; the deterioration is
presumably associated with the positional disorder of one
The distorted square-planar metal coordination environment
in both compounds is nearly identical with that in 8, including
the presence of very similar P-Pd-P bite angles (89.6(1)° for
10 and 88.7(1)° for 11) and a comparable twist between the
P2Pd and PdCl2 planes (dihedral angles φ ) 11° (10), 9° (11)).
The bonding parameters in the ligand are also very similar, even
though the P2-C20 bonds are not lengthened as in 8, and both
types of endocyclic P-C bonds (10: P2-C20 1.865(5), P22-C21
1.849(5) Å; 11: P2-C20 1.857(7), P22-C21 1.870(7) Å) are
now undistinguishable within experimental error. The absence
of a second fused ring allows a stronger twist of the chelate
ring, which is reflected in a larger displacement of the C20 and
C21 atoms out of the PdP2 planes (mean displacement values
are 0.19 Å in 8, 0.32 Å in 10, and 0.34 Å in 11). At the same
time, the torsional angles P2-C20-C21-P22 (44-47°) and
C35-C20-C21-C39 (approximately 65°) are larger than the
corresponding angles in 8, and both trends together suggest
structural relaxation toward a regular staggered conformation
at the C20-C21 bond. Values of 176-174° for the H20-
C20-C21-H21 torsional angles (evaluated using calculated
H-atom positions) reveal that the hydrogen substituents adopt
axial positions with respect to the five-membered chelate ring,
leaving the equatorial positions for the bulkier ester substituents.
To understand the specific formation of stereochemically
identical complexes via diphosphination of isomeric alkene
starting materials, reactions of diethyl maleate and dimethyl
fumarate with 4 and then with (cod)PdCl2 were followed by 1H
and 31P NMR. These studies revealed that the first step in the

1648 Organometallics, Vol. 28, No. 6, 2009
Hajdo´k et al.
Chart 2a
Scheme 3. Proposed Reaction Mechanism for the
Diphosphination of Acyclic Dialkyl Maleates/Fumarates
a
R ) Et (12a, 13a), Me (12b, 13b).
reaction of 4 and diethyl maleate involved isomerization of the
double bond to give the more stable diethyl fumarate, yielding
quantitative conversion within some 30 min at 60 °C. Maleate-
to-fumarate isomerizations are known and have been reported
to occur in the presence of acid,17 radical,18 or nucleophilic19
catalysts, and although tertiary phosphines do not yet seem to
have been used for this purpose,20 we believe that the isomer-
ization observed here is induced by nucleophilic attack of the
diphosphine on the electron deficient double bond. Subse-
quent reaction of the fumarates (either formed by preceding
isomerization or employed as substrate) with 4 produced two
new species that gave rise to characteristic AX-type patterns
in the 31P NMR spectra. On the basis of the observation that
both products display comparable chemical shifts as alkyne
derived bisphosphines like 2 (Scheme 1)9,10 but are distin-
guished by a similar deviation in the JPP coupling constants
as in E/Z-alkenylidene-1,2-bisphosphines,15,21 we assign these
species as 1,2-bisphosphines 12a (R ) Et, δ31P ) 122.1,
(the deviation of the diastereomeric ratio 10:10′ of approximately
30:6 from that of the free ligands 12b/13b proves that in this
case likewise substantial epimerization must have occurred22).
Such epimerization processes are documented for both succinic
acid derived bisphosphines15 and bisphosphonates23 and are
reported to occur under acid catalysis. Observation of this
process during conversion of 12, 13 to the Pd-complexes 10,
11 suggests that epimerization can either also be promoted by
a soft Lewis acid such as Pd2+ or by side-products (diamino-
phosphine oxides) that are weak acids. As the isomerization
between meso- and dl-isomers of the free bisphosphines must
be regarded as reversible under the reaction conditions,23 the
observed isomer ratios close to 1:1 suggest that both diastere-
omers are similar in energy. This is obviously no longer true
under the additional constraint imposed by the chelate ring
formation in 10, 11, and we presume that the preference of the
ester groups for equatorial positions allows the minimization
of the conformational strain and thus provides an energetical
driving force for the observed isomerization.
Altogether, the observed course of the reaction between 4
and dialkyl maleates or fumarates suggests that the initial
addition of the diphosphine to the electron deficient double bond
is no stereospecific process like the reaction with alkynes.8-10
A consistent mechanism for reactions involving diphosphination
of alkenes which is compatible with all experimental observa-
tions reported in this study can be proposed by postulating that
initial attack of 4 on the electron deficient double bond produces
zwitterionic intermediates A1, A2 (Scheme 3), which resemble
the well-known betaines formed by action of tertiary phosphines
on electron deficient alkenes.24
3
3
3.1, JPP ) 10.2 Hz)/12b (R ) Me, δ31P ) 122.1, 3.5, JPP
3
) 9 Hz) and 13a (R ) Et, δ31P ) 116.9, -5.0, JPP ) 130
Hz)/13b (R ) Me, δ31P ) 116.6, -5.5, 3JPP ) 131 Hz) (Chart
2).
The isomer ratios were close to 1:1 and did not change
significantly even upon prolonged heating. Formation of the
addition products was accompanied by the formation of side
products (typically <10-20%, mostly diphenyl phosphine and
diaminophosphine oxides) arising from hydrolysis of 4 during
the reaction. Subsequent addition of (cod)PdCl2 to the reaction
mixture resulted in the disappearance of the signals of both pairs
of bisphosphines and the appearance of the signals of palladium
chelate complexes. Whereas in the reaction of 4 with dimethyl
fumarate only the resonances of the isolable complex 11 were
observed, the mixture obtained from 4 and diethyl maleate
displayed beside the signals of 10 (δ31P ) 132.5, 66.4, JPP
)
15.6 Hz) those of a small amount of a second transient species
(δ31P ) 142.9, 73.5, JPP ) 23.1 Hz), which we attribute to an
isomeric complex 10′ derived from the ligand 12a with a cis-
configuration of the ester substituents at the chelate ring.
Conversion of a mixture of the ligands 12a/13a featuring
either meso- or dl-configuration of the carbon atoms in the
alkylidene unit, into the same complex 11 requires that
configuration inversion of at least one carbon atom took place
(17) (a) Jordan, P. M.; Spencer, J. B.; Corina, D. L. J. Chem. Soc., Chem.
Commun. 1986, 911. (b) Janus, E.; Łozy˙ns´ki, M.; Pernak, J. Chem. Lett.
2006, 35, 210.
(18) Baag, M. M.; Kar, A.; Argade, N. P. Tetrahedron 2003, 59, 6489.
(19) Zhan, Y.; Ning, Z. Yunnan Nongye Daxue Xuebao 2006, 21, 239.
(20) The use of other phosphorus containing compounds than tertiary
phosphines as isomerization catalysts has been reported in case of the partial
isomerization (25% conversion) of maleic to fumaric dimethyl ester in the
presence of an iron diphosphenyl complex and was explained by a similar
mechanism as proposed in this work. Weber, L.; Frebel, M.; Boese, R.
Chem. Ber. 1990, 123, 733.
(21) (a) Carty, A. J.; Johnson, D. K.; Jacobson, S. E. J. Am. Chem. Soc.
1979, 101, 5612. (b) Colquhoun, I. J.; McFarlane, W. J. Chem. Soc., Dalton
Trans. 1982, 1915. (c) Hietkamp, S.; Stelzer, O. Inorg. Chem. 1984, 23,
258.
(22) It was not established if the observation of a mixture of the isomers
10/10′ owes to incomplete equilibration, or represents actually the composi-
tion of the equilibrium mixture.
(23) Balaraman, E.; Kumara Swamy, K. C. Synthesis 2004, 3037.
(24) (a) Gimbert, C.; Moreno-Manas, M.; Perez, E.; Vallribera, A.
Tetrahedron 2007, 63, 8305. (b) He, Z.; Tang, X.; Chen, Y.; He, Z. AdV.
Synth. Catal. 2006, 348, 413. (c) Stewart, I. C.; Bergman, R. G.; Toste,
F. D. J. Am. Chem. Soc. 2003, 125, 8696. (d) Galkin, V. I.; Bakhtiyarova,;
Yu., V.; Polezhaeva, N. A.; Galkina, I. V.; Cherkasov, R. A.; Krivolapov,
D. B.; Gubaidullin, A. T.; Litvinov, I. A. Russ. J. Gen. Chem. 2002, 72,
384. (e) Gololobov, Y. G.; Pinchuk, V. A.; Thoennessen, H.; Jones, P. G.;
Schmutzler, R. Phosph., Sulfur, Silicon Rel. Elem. 1996, 115, 19.

Alkene Diphosphination
Organometallics, Vol. 28, No. 6, 2009 1649
Table 1. Crystallographic Data and Summary of Data Collection and Refinement for 8, 10, and 11
8
10
11
Formula
Formula weight
Crystal size
Crystal system, space grp.
Unit cell dimensions
C38H43Cl2N3O2P2Pd - 1.4 CH2Cl2
927
C36H48Cl2N2O4P2Pd - THF
884.11
C34H44Cl2N2O4P2Pd - 1.5 DMF
893.60
0.27 × 0.11 × 0.08 mm
0.11 × 0.07 × 0.06 mm
0.40 × 0.30 × 0.20 mm
Monoclinic, C2/c
Monoclinic, P21/c
Monoclinic, C2/c
a ) 31.8659(7) Å b ) 15.3565(4) Å c ) a ) 11.1613(2) Å b ) 14.9247(4) Å c ) a ) 23.899(2) Å b ) 14.033(1)
20.4915(4) Å ꢀ ) 124.458(1)°
8268.1(3) Å3
24.8530(6) Å ꢀ ) 92.592(2)°
4135.75(17) Å3
4, 1.42 Mg/m3
0.700 mm-1
Å c ) 25.170(2) Å ꢀ ) 94.36(1)°
Volume
8417.0(11) Å3
8, 1.41 Mg/m3
0.690 mm-1
3712
Z, Fcalc
8, 1.49 Mg/m3
µ
0.87 mm-1
F(000)
3344
1840
θ range for data collection
3.6 to 28.3°
Completeness of data for θ ) 25° 99.4%
1.6 to 28.3°
99.4%
3.0 to 25.0°
99.6%
Limiting indices
-42 e h e 42, -20 e k e 19, -27 e l -14 e h e 14, -19 e k e 19, -33 e l -28 e h e 28, -16 e k e 16, -29
e 27
e 33
e l e 28
Reflections collected/unique
Absorption Correction
Max./min. transmission
Data/restraints/parameters
Goodness-of-fit on F2
R1 [I > 2σ(I)]
78598/10258 [Rint ) 0.124]
19314/10203 [Rint ) 0.079]
54901/7421 [Rint ) 0.025]
numerical
empirical
semiempirical from equivalents
0.9278 and 0.7815
10258/0/674
1.092
0.933 and 0.965
10203/0/510
1.022
0.8621 and 0.7485
7421/123/466
1.055
0.070
0.056
0.114
0.069
0.137
wR2 R (all data)
0.171
Largest diff. peak and hole
0.842 and -1.037 e Å-3
1.374 and -0.874e Å-3
1.410 (in disordered dmf) and -0.986
e Å-3
The intermediates derived from acyclic alkenes may rapidly
interconvert via C-C bond rotation and carbanion inversion.
Reversal of the adduct formation under cleavage of the
diphosphine regenerates the starting material and, all processes
being reversible, allows for the eventual conversion of maleic
into more stable fumaric esters. Alternatively, shift of a cationic
phosphenium (PN2+) fragment to the carbanion center of the
intermediates produces the addition products 12, 13. The betaine
derived from maleic imide cannot undergo C-C bond rotation
due to the constraints of the cyclic structure, and synfacial shift
of the phosphenium fragment gives a single 1,2-bisphosphine
with a fixed configuration at the carbon atoms. Finally, as acid
catalyzed epimerization of succinic esters, which provides a
pathway for a later direct interconversion between diastereomers
10/11 or 12/13, is known to occur via the enol-form of one
ester moiety,23 we presume that a possible Lewis-catalyzed
variant of this reaction may proceed via a similar pathway by
coordination of a Lewis acid to the ester, deprotonation at carbon
(possibly promoted by a basic phosphine moiety) to give a metal
enolate, and reprotonation from the reverse side.
presumably as a consequence of the rigidity induced by the
cyclic substrate structure.
Experimental Section
All manipulations were carried out under an atmosphere of dry
argon using standard vacuum line techniques. Solvents 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 spectrometers at 303 K; chemical shifts are referenced to
ext. TMS (1H, 13C) or 85% H3PO4 (ꢀ ) 40.480747 MHz, 31P).
Coupling constants are given as absolute values; i, o, m, p denote
the positions in phenyl rings. EI-MS: Varian MAT 711, 70 eV.
Elemental analysis: Perkin-Elmer 24000CHN/O Analyzer. Melting
points were determined in sealed capillaries.
[2-(1-Diphenylphosphino-pent-2-ene-3-oxy)-(1,3-dineopentyl-1,2-
dihydro-benzo[c][1,3,2]diazaphosphole) Dichloro Palladium (6).
Ethyl(vinyl)ketone (90 mg, 1.07 mmol) was added to a solution of
4 (470 mg, 1.02 mmol) in THF (8 mL). After stirring the mixture
for 24 h, a solution of (cod)PdCl2 (280 mg, 0.98 mmol) in CH2Cl2
(15 mL) was added, and stirring was continued for one more hour.
Volatiles were then removed in vacuum and the residue dispersed
in Et2O (20 mL). The brown suspension formed was filtered, and
Conclusions
1
The results of the reactions described in this work together
with those of a previous study11 shed light on the scope as well
as the regio- and stereochemistry of the addition of unsym-
metrical diphosphines to electron poor alkenes. It has been
demonstrated that the diphosphines react with R,ꢀ-unsaturated
esters and nitriles11 featuring a terminal double bond, or with
derivatives of maleic and fumaric acid, under 1,2-addition to
give 1,2-bisphosphines, and with a terminal R,ꢀ-unsaturated
ketone under 1,4-addition. The reactions require more forcing
conditions than additions to alkynes but those involving
asymmetrically substituted alkenes are likewise regiospecific and
connect the more nucleophilic phosphinyl moiety to the terminal
position.11 The addition is suppressed by the presence of alkyl
or aryl substituents at the double bond, presumably due to
electronic deactivation. The addition to maleic or fumaric
diesters is not stereospecific but yields a mixture of dl- and meso-
isomers which epimerize, however, to give complexes with a
uniform trans-arrangement of the ester moieties upon complex-
ation to Pd(II). In contrast, the cis-stereochemistry of the double
bond is conserved during the addition of 4 to maleic imide,
the residue dried in vacuum, yield 410 mg (56%), mp 192 °C; H
NMR (CD2Cl2): δ ) 7.91 (m, 4 H, o-C6H5), 7.61 (m, 2 H, p-C6H5),
7.55 (m, 4 H, m-C6H5), 6.99 (m, 2 H, C6H4), 6.96 (m, 2 H, C6H4),
3
3
3
4.95 (q, 1 H, JPH ) JHH ) 7 Hz, )CH), 4.26 (dd, 2 H, JPH
)
3
3
13.2 Hz, JHH ) 15.3 Hz, NCH2), 3.42 (dd, 1 H, JPH ) 21.4 Hz,
3
2
2JHH ) 15.4 Hz, NCH2), 3.36 (ddd, 2 H, JPH ) 14 Hz, JPH ) 7
3
3
3
Hz, JHH ) 7 Hz, PCH2), 1.98 (ddq, 2 H, JHH ) 13.9 Hz, JHH
)
2
7.1 Hz, JPH ) 1.1 Hz, CH2), 1.10 (s, 18 H, CCH3), 0.78 (t, 3 H,
3JHH ) 7.0 Hz, CH3); 13C{1H}-NMR (CD2Cl2): δ ) 154.7 (t, JPC
2
2
) 10.1 Hz, OC)), 139.3 (d, JPC ) 2.1 Hz, C6H4), 134.0 (d, JPC
4
) 10.2 Hz, o-C6H5), 132.0 (d, JPC ) 2.9 Hz, p-C6H5), 130.4 (d,
1JPC ) 56.3 Hz, i-C6H5), 129.0 (d, 2JPC ) 11.4 Hz, m-C6H5), 120.8
(s, C6H4), 111.1 (d, 3JPC ) 5.3 Hz, C6H4), 103.8 (dd, JPC ) 7.8 Hz,
2
3
5.9 Hz, )CH), 61.3 (d, JPC ) 10.4 Hz, CH2), 34.0 (d, JPC ) 1.0
1
4
Hz, CCH3), 29.5 (s, CCH3), 28.7 (dd, JPC) 30.3 Hz, JPC ) 6.9
3
Hz, CH2P), 28.2 (d, JPC ) 1.7 Hz, CH2CH3), 11.0 (s, CH2CH3);
31P{1H} NMR (CD2Cl2) δ ) 91.5 (d, JPP ) 32.7 Hz, N2P), 11.2
3
3
(d, JPP ) 32.7 Hz, PPh2); IR νj ) 3057 (w), 2952 (m), 1690 (w),
1594 (w), 1479 (s), 1435 (s),1397 (w), 1363 (m), 1268 (m), 1137
(m), 1100 (m), 1031 (m), 957 (m), 917 (s), 837 (s), 741 (s), 687
(s), 624 (m), 506 (s) cm-1; (-)-ESI MS: m/e (%): 759.26 (100)

1650 Organometallics, Vol. 28, No. 6, 2009
Hajdo´k et al.
[M + Cl-]; C33H44Cl2N2OP2Pd (724.00): calcd C 54.75, H 6.13, N
(w), 960 (w), 933 (w), 838 (m), 736 (s), 688 (s), 618 (w), 511 (m),
488 (w) cm-1; (-)-ESI-MS: m/e (%): 812.1 [M - H]-;
C38H43Cl2N3O2P2Pd (813.05): C 56.14, H 5.33, N 5.17, found C
56.32, H 5.09, N 4.56.
3.87, found C 54.31, H 6.18, N 3.72.
2-(1-Diphenylphosphino-pent-2-ene-3-oxy)-(1,3-dineopentyl-1,2-
dihydro-benzo[c][1,3,2]diazaphosphole) (5). Ethyl(vinyl)ketone (30
mg, 0.36 mmol) and 4 (157 mg, 0.34 mmol) were dissolved in
[Diethyl 2-(1,3-Dineopentyl-1,2-dihydro-benzo[c][1,3,2]diazaphosphol-
2-yl)-3-(diphenylphosphino)succinate] Dichloro-palladium (II) (10). A
solution of diethyl maleate (180 mg, 1.05 mmol) were added
dropwise to a stirred solution of 4 (500 mg, 1.08 mmol) in THF (8
mL). The mixture was then refluxed for 5 h, allowed to cool to rt,
and evaporated to dryness. The residue was again dissolved in THF,
and a solution of (cod)PdCl2 (150 mg, 0.53 mmol) in CH2Cl2 (5
mL) was added. The mixture was stirred for 30 min, and again
evaporated to dryness. The residue was dissolved in 1:1 CH2Cl2/
Et2O (1 mL) and stored at -20 °C for crystallization. Orange
crystals formed which were collected by filtration and dried in
1
THF-d8 (0.6 mL). Monitoring the reaction by H and 31P NMR
allowed to detect the formation of 5 as only addition product. The
constitution of 5 was elucidated by analysis of multinuclear (1H,
13C, 31P) NMR one- and two-dimensional NMR spectra recorded
directly from the reaction mixture. No attempts toward isolation
of the product were made. Conducting the reaction by replacing 4
by an approximately equimolar mixture of 2-chloro-1,3-dineopentyl-
1,2-dihydro-benzo[c][1,3,2]diazaphosphole and diphenyl(trimeth-
ylsilyl)phosphine allowed to detect the formation of both 4 (via
coupling of the chlorophosphine and the silylphosphine) and 5
beside a further species resulting from 1,4-addition of the P-Si-
bond of the silylphosphine to ethyl(vinyl)ketone. Formation of this
product was obviously faster than the P-P coupling reaction, and
further condensation of this product with the chlorophosphine
provides a second pathway to 5. Spectroscopic data of 5: 1H NMR
(Toluene-d8): δ ) 7.40 (m, 4 H, o-C6H5), 7.10-7.00 (m, 6 H, m/p-
C6H5), 6.85 (m, 2 H, C6H4), 6.73 (m, 2 H, C6H4), 4.58 (m, 1 H,
)CH), 3.6 - 3.4 (m, 4 H, NCH2), 2.95 (m, 2 H, PCH2), 2.00 (m,
2 H, CH2), 0.90 (s, 18 H, CH3), 0.82 (t, 3 H, 3JHH ) 7.0 Hz, CH3);
13C{1H}-NMR (Toluene-d8): δ ) 152.7 (dd, JPC ) 10.6 Hz, 2.0
1
vacuum (yield 140 mg, 32%); mp 224 °C; H NMR (CD2Cl2): δ
) 8.11 (m, 2 H, o-C6H5), 7.74 (m, 2 H, o-C6H5), 7.60 (m, 1 H,
p-C6H5), 7.57-7.47 (m, 3 H, m/p-C6H5), 7.44 (m, 2 H, m-C6H5),
6.96 (m, 1 H, C6H4), 6.90-6.78 (m, 3 H, C6H4), 4.39 (dd, 1 H,
3JHH ) 13.8 Hz, 3JPH ) 11.2 Hz, PCH), 4.29 (dd, 1 H, 3JHH ) 13.8
Hz, 3JPH ) 11.1 Hz, PCH), 4.19 (dd, 1 H, 2JHH ) 3JPH ) 16.0 Hz,
2
3
NCH2), 3.69 (t, 1 H, JHH ) JPH ) 17 Hz, NCH2), 3.66 (t, 1 H,
3
2JHH ) JPH ) 15.9 Hz, NCH2), 3.80-3.70 (m, 2 H, OCH2), 3.46
(m, 1 H, OCH2), 3.44 (m, 1 H, OCH2), 3.26 (dd, 1 H, 3JPH ) 12.1
Hz, 2JHH ) 15.3 Hz, NCH2), 1.14 (s, 9 H, CH3), 1.00 (s, 9 H, CH3),
2
3
3
Hz, OC)), 137.9 (m, C6H4), 132.3 (d, JPC ) 18.2 Hz, m-C6H5),
0.84 (t, 3 H, JHH ) 7.2 Hz, CH3), 0.54 (t, 3 H, JHH ) 7.2 Hz,
128.4 (d, 4JPC ) 2.9 Hz, p-C6H5), 128.3 (d, 2JPC ) 10.8 Hz, o-C6H5),
118.6 (s, C6H4), 109.2 (s, C6H4), 104.6 (dd, JPC ) 3.5 Hz, 8.9 Hz,
)CH), 54.0 (d, 2JPC ) 16 Hz, CH2), 34.0 (d, 3JPC ) 1.8 Hz, CCH3),
CH3); 13C{1H} NMR (CD2Cl2) δ ) 166.9 (m, CdO), 166.7 (m,
2
2
CdO), 141.3 (d, JPC ) 4.2 Hz, C6H4), 140.4 (d, JPC ) 3.4 Hz,
C6H4), 135.6 (d, 2JPC ) 12 Hz, o-C6H5), 134.9 (d, 2JPC ) 10.9 Hz,
1
3
4
4
29.0 (s, CCH3), 25.3 (d, JPC ) 12.9 Hz, CH2P), 15.6 (d, JPC
)
o-C6H5), 133.6 (d, JPC ) 3.1 Hz, p-C6H5), 133.0 (d, JPC ) 3.6
3 3
12.7 Hz, CH2CH3), 11.5 (d, JPC ) 1 Hz, CH2CH3); 31P{1H} NMR
Hz, p-C6H5), 129.3 (d, JPC ) 11.0 Hz, m-C6H5), 129.2 (d, JPC )
1
(Toluene-d8) δ ) 116.2 (d, 5JPP ) 3.1 Hz, N2P), -15.2 (d, 5JPP
)
10.8 Hz, m-C6H5), 127.0 (d, JPC ) 56.5 Hz, i-C6H5), 126.2 (d,
1JPC ) 56 Hz, i-C6H5), 121.1 (s, C6H4), 120.8 (s, C6H4), 111.2 (d,
3.1 Hz, PPh2).
3JPC ) 5.4 Hz, C6H4), 111.1 (d, JPC ) 4.7 Hz, C6H4), 68.2 (s,
3
[3-(1,3-Dineopentyl-1,2-dihydro-benzo[d][1,3,2]diazaphospholyl)-
4-(diphenylphosphino)-1-phenylpyrrolidine-2,5-dione] Dichloro Pal-
ladium (8). A solution of maleic N-phenylimide (180 mg, 1.04
mmol) in THF (5 mL) were added to a solution of 4 (460 mg, 0.99
mmol) in THF (5 mL). The mixture was stirred for 1 h, a solution
of (cod)PdCl2 (280 mg, 0.98 mmol) in CH2Cl2 (20 mL) was added
dropwise, and stirring was continued for one more hour. Volatiles
were then removed in vacuum, the residue dissolved in CH2Cl2 (3
mL) and stored at 4 °C for crystallization. A yellow crystalline
precipitate formed which was collected by filtration and dried in
vacuum, yield 200 mg (26%), mp 202 °C; 1H NMR (CD2Cl2) δ )
8.35 (m, 2 H, o-C6H5), 7.65-7.56 (m, 6 H), 7.46 (m, 2 H),
7.40-7.33 (m, 3 H), 6.97 (m, 1 H, C6H4), 6.94-6.84 (m, 5 H),
4.40 (dd, 1 H, 2JHH ) 15.6 Hz, 3JPH ) 14.0 Hz, NCH2), 4.39 (ddd,
1 H, 3JHH ) 11.2 Hz, 2JPH ) 10.9 Hz, 3JPH ) 17.2 Hz, PCH), 4.00
(ddd, 1 H, 3JHH ) 11.3 Hz, 2JPH ) 9.4 Hz, 3JPH ) 14.1 Hz, PCH),
OCH2), 66.1 (s, OCH2), 63.2 (br s, NCH2), 63.1 (br s, NCH2), 34.6
(d, 3JPC ) 1.2 Hz, CCH3), 34.3 (d, 3JPC ) 2.0 Hz, CCH3), 30.2 (s,
CCH3), 29.9 (s, CCH3), 15.5 (s, CH3), 13.3 (s, CH3); 31P{1H} NMR
3
(C6D6): δ ) 134.1 (broad, N2P), 68.1 (d, JPP ) 15.3 Hz, PPh2);
IR νi ) 2950 (m), 1732 (s), 1484 (m), 1434 (s), 1262 (m), 838 (m),
813 (m), 746 (m), 689 (m), 505 (m), 492 (m) cm-1; (+)-ESI MS:
m/e (%) ) 1647.31 (16) [2M + Na]+, 1589.31 (15) [2M - Cl]+,
1551.37 (12) [2M - HCl2]+, 835.14 (100) [M + Na]+, 775.18 (59)
[M - Cl]+; C36H48Cl2N2O4P2Pd (812.06): calcd C 53.25, H 6.45,
N 3.73, found C 53.87, H 6.45, N 3.15.
[Dimethyl2-(1,3-Dineopentyl-1,2-dihydro-benzo[c][1,3,2]diazaphosphol-
2-yl)-3-(diphenylphosphino)succinate Dichloro Palladium(II) (11). A
solution of 4 (470 mg, 1.02 mmol) in THF (5 mL) was added
dropwise to a stirred solution of dimethyl fumarate (150 mg, 1.04
mmol) in DMF (10 mL). The solution was stirred for 11 h at 65
°C. The mixture was allowed to cool to rt, and a solution of
(cod)PdCl2 (200 mg, 0.70 mmol) in CH2Cl2 (10 mL) was added
dropwise. Stirring was continued for 1 h, and Et2O (40 mL) was
added. A yellow crystalline precipitate formed which was collected
by filtration and dried in vacuum (yield 170 mg, 31%); mp 220
2
3
3.60 (dd, 1 H, JHH ) 15.3 Hz, JPH ) 16.8 Hz, NCH2), 3.42 (dd,
2
1 H, 2JHH ) 15.6 Hz, 3JPH ) 22.4 Hz, NCH2), 3.07 (dd, 1 H, JHH
) 15.1 Hz, 3JPH ) 14.2 Hz, NCH2), 1.26 (s, 9 H, CH3), 1.01 (s, 9
2
H, CH3); 13C{1H} NMR (CD2Cl2): δ ) 139.28 (d, JPC ) 2.5 Hz,
C6H4), 139.24 (d, 2JPC ) 3.3 Hz, C6H4), 135.6 (d, 2JPC ) 11.1 Hz,
o-C6H5), 133.5 (d, 2JPC ) 11.8 Hz, o-C6H5), 132.92 (d, 4JPC ) 2.8
Hz, p-C6H5), 132.88 (d, 4JPC ) 2.7 Hz, p-C6H5), 131.2 (s, i-NC6H5),
1
°C; H NMR (CD2Cl2) δ ) 8.23 (m, 2 H, o-C6H5), 7.79 (m, 2 H,
o-C6H5), 7.73-7.43 (m, 6 H, m/p-C6H5), 7.05 (m, 1 H, C6H4),
4
129.4 (s, p-NC6H5), 129.37 (s, p-NC6H5), 129.3 (d, JPC ) 11.9
7.00-6.87 (m, 3 H, C6H4), 4.44 (m, 1 H, 3JHH ) 13.8 Hz Hz, 3JPH
Hz, m-C6H5), 128.9 (d, 4JPC ) 12.2 Hz, m-C6H5), 127.5 (d, 1JPC
)
) -1.0 Hz, JPH ) +11.2 Hz, PCH), 4.42 (m, 1 H, JHH ) 13.8
Hz Hz, 3JPH ) 10.5 Hz, PCH), 4.37 (dd, 1 H, 2JHH ) 15.6 Hz, 3JPH
) 14.8 Hz, CH2), 3.70 (dd, 1 H, 2JHH ) 15.6 Hz, 3JPH ) 18.1 Hz,
3
3
1
51.6 Hz, i-C6H5), 127.3 (d, JPC ) 59.0 Hz, i-C6H5), 125.8 (s,
2
m-NC6H5), 121.1 (s, C6H4), 120.5 (s, C6H4), 111.5 (d, JPC ) 5.6
2
2
3
Hz, C6H4), 110.4 (d, JPC ) 5.6 Hz, C6H4), 67.9 (dd, JPC ) 34.3
CH2), 3.60 (dd, 1 H, JHH ) 15.6 Hz, JPH ) 16.1 Hz, CH2), 3.37
2 3
Hz, 4.5 Hz, PCH), 63.2 (d, 3JPC ) 8.6 Hz, NCH2), 57.7 (d, 3JPC
)
(s, 3 H, OCH3), 3.22 (dd, 1 H, JHH ) 15.6 Hz, JPH ) 12.4 Hz,
CH2), 3.09 (s, 3 H, OCH3), 1.26 (s, 9 H, t-Bu), 1.08 (s, 9 H, t-Bu);
13C{1H} NMR (CD2Cl2) δ ) 166.8 (dd, JPC ) 30.7 Hz, 4.9 Hz,
6.8 Hz, NCH2), 49.3 (d, 2JPC ) 21.6 Hz, PCH), 34.5 (d, 3JPC ) 1.2
Hz, CCH3), 33.1 (s, CCH3), 29.7 (s, CCH3), 29.0 (s, CCH3). 31P{1H}
NMR (CD2Cl2): δ ) 139.4 (d, 3JPP ) 24.5 Hz, N2P), 96.0 (d, 3JPP
) 24.5 Hz, PPh2); IR νj ) 3057 (w), 2953 (w), 1781 (w), 1716 (s),
1597 (w), 1481 (m), 1435 (w), 1357 (m), 1262 (m), 1177 (w), 1098
CdO), 166.5 (dd, JPC ) 28.8 Hz, 6.3 Hz, CdO), 140.6 (d, 2JPC
)
)
2
2
3.7 Hz, C6H4), 138.9 (d, JPC ) 3.2 Hz, C6H4), 134.9 (d, JPC
12.8 Hz, o-C6H5), 134.2 (d, JPC ) 10.7 Hz, o-C6H5), 133.1 (d,
2

Alkene Diphosphination
4JPC ) 2.9 Hz, p-C6H5), 132.6 (d, JPC ) 3.1 Hz, p-C6H5), 128.8
Organometallics, Vol. 28, No. 6, 2009 1651
out using SHELXL-97 (full-matrix least-squares on F2).25 Hydrogen
atoms were refined using a riding model. One of the neopentyl
groups and the solvent molecule dmf in 11 were disordered over
two positions. The occupancy factors of the partially disordered
solvent molecules in the crystal structure of 8 were first refined
and, for a more convenient handling, eventually fixed to the values
obtained. CCDC-713241 (8), CCDC-713240 (10), and CCDC-
712825 (11) contain the supplementary crystallographic data for
this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
4
3
3
(d, JPC ) 11.8 Hz, m-C6H5), 128.8 (d, JPC ) 12 Hz, m-C6H5),
126.3 (d, 1JPC ) 56.0 Hz, i-C6H5), 125.7 (d, 1JPC ) 52.5 Hz, i-C6H5),
120.5 (s, C4H6), 120.2 (s, C6H4), 110.65 (d, 2JPC ) 5.1 Hz, C6H4),
110.63 (d, 2JPC ) 5.8 Hz, C6H4), 64.0 (dd, 1JPC ) 35.4 Hz, 2JPC
)
2
12.3 Hz, PCH), 61.3 (d, JPC ) 6.8 Hz, CH2), 59.5 (broad, CH2),
1
2
52.9 (s, OCH3), 52.4 (s, OCH3), 46.5 (dd, JPC ) 29.0 Hz, JPC
)
22.7 Hz, PCH), 34.6 (d, 3JPC ) 1.2 Hz, CCH3), 34.3 (d, 3JPC ) 1.2
Hz, CCH3), 30.2 (s, CCH3), 29.9 (s, CCH3); - 31P{1H} NMR (C6D6)
δ ) 130.9 (d, 1JPP ) 15.2 Hz, N2P), 69.9 (d, 1JPP ) 15.2 Hz, PPh2);
IR νi ) 2948 (m), 2871 (w), 1731 (s), 1481 (s), 1436 (m), 1364
(m), 1264 (m), 1178 (w), 1136 (m), 1096 (w), 1024 (m), 958 (m),
838 (s), 791 (w), 745 (s), 690 (m), 508 (m), 496 (m) cm-1; (+)-
ESI MS: m/e (%) ) 1591 (8) [2M + Na]+, 1495.30 (100) [2M -
HCl2]+, 807.11 (25) [M + Na]+, 747.15 (40) [M - Cl]+;
C34H44Cl2N2O4P2Pd (784.01): calcd C 52.09, H 5.66, N 3.17, found
C 52.11, H 5.66, N 3.65.
Acknowledgment. We thank Dr. J. Opitz, J. Trinkner, and
K. Wohlbold (Institut fu¨r Organische Chemie, Universita¨t
Stuttgart) for recording the mass spectra. The Deutsche
Forschungsgemeinschaft is acknowledged for financial support.
Supporting Information Available: CIF files giving X-ray
structural information on 8, 10, and 11. This material is available
free of charge via the Internet at http://pubs.acs.org.
Crystallography. The crystal structure determinations of 8, 10,
and 11 were performed on Nonius KappaCCD diffractometers at
100(2) K (8, 10), and 123(2) K (11) using Mo KR radiation (λ )
0.71073 Å). Crystal data, data collection parameters, and results
of the analyses are listed in Table 1. Direct Methods (SHELXS-
97)25 were used for structure solution, and refinement was carried
OM801179K
(25) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.