New tertiary phosphines from cinnamaldehydes and diphenylphosphine

Article abstract of DOI:10.1021/ic701597g

A 1:1 hydrophosphination of the olefinic bond of cinnamaldehyde (and substituted ones) with Ph₂PH, under argon using neat reagents, gives quantitative formation of the new tertiary phosphines Ph₂PCH(Ar) CH₂CHO (2) as racemic mixtures (Ar = Ph, p-tol, and p-OMe-C ₆H₄). α-Methylcinnamaldehyde similarly affords Ph₂PCH(Ph)CH(Me)CHO, but as a mixture of diastereomers with predominantly S,S- and R,R-chirality [diastereomeric ratio (dr) ～20]. In a 2:1 reaction of Ph₂PH with cinnamaldehyde, hydrophosphination of both the C=C and C=O bonds takes place to give the diphosphine derivative Ph ₂PCH(Ph)CH₂CH(OH)PPh₂ (3) as a diastereomeric mixture with dr ～2.3. In most organic solvents, the hydrophosphination of the C=O group is reversible, leading to a dynamic equilibrium between 3 and 2, but 3 is stable in coordinating solvents such as DMSO, DMF, and pyridine. X-ray analysis of a P,P-chelated PdCl₂(3) complex, formed from trans-PdCl₂(PhCN)₂ and 3 in MeOH, reveals that the S,S/R,R-enantiomers are favored.

Full text of DOI:10.1021/ic701597g

Inorg. Chem. 2007, 46, 11467−11474
New Tertiary Phosphines from Cinnamaldehydes and
Diphenylphosphine
Dmitry V. Moiseev, Brian O. Patrick, and Brian R. James*
Department of Chemistry, UniVersity of British Columbia,
VancouVer, British Columbia, Canada V6T 1Z1
Received August 10, 2007
A 1:1 hydrophosphination of the olefinic bond of cinnamaldehyde (and substituted ones) with Ph2PH, under argon
using neat reagents, gives quantitative formation of the new tertiary phosphines Ph2PCH(Ar)CH2CHO (2) as racemic
mixtures (Ar
but as a mixture of diastereomers with predominantly S,S- and R,R-chirality [diastereomeric ratio (dr)
2:1 reaction of Ph2PH with cinnamaldehyde, hydrophosphination of both the C C and C O bonds takes place to
give the diphosphine derivative Ph2PCH(Ph)CH2CH(OH)PPh2 (3) as a diastereomeric mixture with dr 2.3. In
most organic solvents, the hydrophosphination of the C O group is reversible, leading to a dynamic equilibrium
)
Ph, p-tol, and p-OMe−C6H4).
R
-Methylcinnamaldehyde similarly affords Ph2PCH(Ph)CH(Me)CHO,
∼
20]. In a
d
d
∼
d
between 3 and 2, but 3 is stable in coordinating solvents such as DMSO, DMF, and pyridine. X-ray analysis of a
P,P-chelated PdCl2(3) complex, formed from trans-PdCl2(PhCN)2 and 3 in MeOH, reveals that the S,S/R,R-enantiomers
are favored.
Introduction
[(HOCH2)2PH], sodium (hydroxymethane)sulfonate [HOCH2
S(O)2ONa], and sodium (hydroxymethane)sulfinite HOCH2
S(O)ONa.4
Our group has been involved in a collaborative project
dealing with development of water-soluble phosphines,
particularly tris(hydroxymethyl)phosphine, (HOCH2)3P, as
bleaching and brightness stabilization agents for wood pulps,
and interaction of such phosphines with conjugated carbonyl
components of lignin is involved in the bleaching process.1
A commonly used bleaching agent in the pulp industry is
the so-called “hydrosulfite”, which is in fact sodium dithion-
ite (Na2S2O4), the bleaching involving a reasonably well
understood reduction process by the dithionite,2 and notably
the collaborative studies have recently revealed a remarkable
synergistic effect of the use of a combination of (HOCH2)3P
and Na2S2O4 for the bleaching.3 This led us to study the
complex interaction between these two chemicals, where
reactions at ambient conditions in aqueous solution under
Ar can lead to formation of bis(hydroxymethyl)phosphine
The generation of the (HOCH2)2PH encouraged us to
investigate the reaction of such secondary phosphines with
lignin model compounds, and as cinnamaldehyde possesses
the conjugated phenyl-propanoid backbone similar to that
present in lignin chromophores,1b one such system studied
was the reaction of this aldehyde (and substituted ones) with
diphenylphosphine. This current paper describes this study,
and although there is literature on the interaction of Ph2PH
with R,â-unsaturated carbonyl compounds (including cin-
namaldehyde),5 our findings are very different and have led
to the synthesis of new tertiary phosphines and a diphosphine,
which result from sequential hydrophosphination of the Cd
C bond and the CdO bonds of the aldehyde, the respective
products being formed at Ph2PH:cinnamaldehyde ratios of
1 or 2. There is, of course, extensive literature on the
hydrophosphination of such moieties by Ph2PH and other
secondary phosphines, including Michael-type addition reac-
tions to activated olefinic substrates, and such studies have
been widely used for synthesis of new functionalized
* Author to whom correspondence should be addressed. E-mail: brj@
chem.ubc.ca.
(1) (a) Moiseev, D. V.; Patrick, B. O.; James, B. R.; Hu, T. Q. Inorg.
Chem. 2007, 46, 8998, and references therein. (b) Moiseev, D. V.;
James, B. R.; Hu, T. Q. Inorg. Chem. 2007, 46, 4704, and references
therein. (c) Chandra, R.; Hu, T. Q.; James, B. R.; Ezhova, M. B. J.
Pulp Paper Sci. 2007, 33, 15.
(2) Ellis, M. E. In Pulp BleachingsPrinciples and Practice; Dence, C.
W., Reeve, D. W., Eds.; Tappi Press: Atlanta, GA, 1996; Chapter 2.
(3) Hu, T. Q.; James, B. R.; Williams, T.; Schmidt, J. A.; Moiseev, D.
PCT Int. Appl. 2007, WO 2007016769 A1 20070215.
(4) Moiseev, D. V.; James, B. R. Hu, T. Q. Unpublished work.
(5) Hashimoto, T.; Maeta, H.; Matsumoto, T.; Morooka, M.; Ohba, S.;
Suzuki, K. Synlett 1992, 340.
10.1021/ic701597g CCC: $37.00
Published on Web 11/09/2007
© 2007 American Chemical Society
Inorganic Chemistry, Vol. 46, No. 26, 2007 11467

Moiseev et al.
200.5 (d, 3JPC ) 12.3, CHO), 139.9 (d, 2JPC ) 8.5, Cipso-CH), 135.9
phosphines.6-10 An example of the use of the new diphos-
phine as a ligand at a PdII center is also presented.
1
1
(d, JPC ) 14.7, Cipso-P), 135.6 (d, JPC ) 16.2, C′ipso-P), 134.1
2
(d, 2JPC ) 20.9, o-C of PhP), 133.1 (d, JPC ) 18.3, o-C of Ph′P),
3
129.7 (s, p-C of PhP), 128.9 (d, JPC ) 7.4, m-C of PhP), 128.8
Experimental Section
(d, 3JPC ) 7.4, m-C of Ph′P), 128.6 (s, p-C of Ph′P), 128.5 (s, m-C
of PhC), 128.0 (d, 3JPC ) 6.8, o-C PhC), 126.6 (d, 5JPC ) 2.1, p-C
of PhC), 47.2 (d, 2JPC ) 20.1, CH2), 38.8 (d, 1JPC ) 13.9, PhCH).
APCI (MeOH): m/z 319.2 (100%) [M + H]+, calcd 319.1.
Ph2PCH(p-tol)CH2CHO (2b). The procedure used follows that
given for 2a, except that the mixture with 4-Me-cinnamaldehyde
generated a red amorphous substance. After the treatment with Et2O,
a pale pink solid was obtained (0.95 g, 57%). The elemental analysis
General. Cinnamaldehyde and R-methylcinnamaldehyde (Ald-
rich products) were distilled under reduced pressure before use.
4-Methyl- and 4-methoxycinnamaldehyde were prepared by base-
catalyzed condensation of acetaldehyde (Aldrich) with p-tolualde-
hyde (Eastman) or 4-methoxybenzaldehyde, respectively (Aldrich).
Ph2PH (Strem Chemicals) was used as received. trans-PdCl2-
(PhCN)2 was made by a literature procedure11 from PdCl2 purchased
from Colonial Metals, Inc. Organic solvents were dried over the
appropriate agents and were distilled under Ar, while CDCl3, CD3-
OD, and DMSO-d6 (Cambridge Isotope Laboratory) were used as
received. Syntheses were carried out under Ar either using standard
Schlenk glassware or a glovebox. 31P{1H} NMR spectra were
recorded on a Bruker AV300 spectrometer (121 MHz), at 300 K
1
1
and NMR data (31P{1H}, H, H{31P}, 13C{1H}) for 2b are given
in the Supporting Information (Table S1).
Ph2PCH(p-OMe-C6H4)CH2CHO (2c). The procedure used was
as for 2b but using 4-MeO-cinnamaldehyde (yield 0.82 g, 47%).
The elemental analysis and NMR data (31P{1H}, 1H, 1H{31P}, 13C-
{1H}) for 2c are given in the Supporting Information (Table S1).
Ph2PCH(Ph)CH(Me)CHO (2d). A mixture of Ph2PH (0.88 mL,
0.50 mmol) and R-methylcinnamaldehyde (1.40 mL, 1.0 mmol)
was heated at 60 °C for 72 h; excess aldehyde was then distilled
off at ∼90 °C under reduced pressure (∼0.1 Torr). The resulting
colorless, viscous residue was analyzed by 1H NMR spectroscopy,
which revealed a mixture of diastereomers of 2d in a diastereomeric
ratio (dr) of ∼10, along with some remaining aldehyde (15 mol
%). The aldehyde was removed by dissolving the residue in Et2O
(5 mL) and keeping the solution for 2 days at -20 °C; the resulting
white solid was filtered off and dried under vacuum (0.95 g, 57%).
The 31P{1H} NMR spectrum revealed two diastereomers with dr
∼20. Anal. Calcd for C22H21OP: C, 79.50; H, 6.37. Found: C,
79.71; H, 6.57.
1
unless otherwise stated; H and 13C NMR spectra were recorded
1
on an AV400 instrument (400 MHz for H, 100 Hz for 13C{1H}).
All NMR spectra were measured in CDCl3 unless otherwise stated.
A residual deuterated solvent proton (relative to external SiMe4)
and external 85% aqueous H3PO4 were used as references: br )
broad, s ) singlet, d ) doublet, t ) triplet, p ) pentet, and m )
multiplet. J values are given in Hertz. When necessary, atom
assignments were made by means of 1H-1H, 1H-13C{1H} (HSQC
1
and HMBC), and H-31P{1H} NMR correlation spectroscopies.
Elemental analyses were performed on a Carlo Erba 1108 analyzer.
Mass spectrometry was performed on a Bruker Esquire electrospray
(APCI) ion trap spectrometer with samples dissolved in MeOH,
with positive ion polarity, scanning from 60 to 1000 m/z.
2d-r (major diastereomer; S,S- and R,R-enantiomers). 31P-
Ph2PCH(Ph)CH2CHO (2a). In a glovebox, Ph2PH (0.88 mL,
0.50 mmol) was added dropwise to stirred cinnamaldehyde (0.66
mL, 0.53 mmol) at room temperature (rt, ∼20 °C). After 15 min,
the mixture was heated briefly at 50 °C to yield a pink solid that
was triturated with Et2O (∼6 mL), filtered off, washed once with
Et2O, and dried under vacuum (1.30 g, 82% yield). Anal. Calcd
for C21H19OP: C, 79.23; H, 6.02. Found: C, 79.44; H, 6.25. 31P-
{1H} NMR: δ -8.6 s. 1H NMR: δ 9.97 (br s, 1H, CHO; 1H{31P}:
3
d, JHH ) 1.1), 7.75-7.68 (m, 2H), 7.46-7.40 (m, 3H), 7.23-
7.08 (m, 10H), 3.84 (dd, 2JPH ) 4.7, 1H, PCH; 1H{31P}, d, 3JHH
)
1
3
3
5.7), 2.79 (m, 1H, MeCH; H{31P}, dp, JHH ) 6.9, JHH ) 1.1),
1.07 (d, 3JHH ) 6.9, 3H, CH3). 13C{1H} NMR: δ 203.6 (d, 3JPC
10.9, CHO), 138.2 (d, 2JPC ) 8.5, Cipso-CH), 136.3 (d, 1JPC ) 14.9,
ipso-P), 135.9 (d, 1JPC ) 13.5, C′ipso-P), 134.2 (d, 2JPC ) 21.2, o-C
of PhP), 133.2 (d, 2JPC ) 19.1, o-C of Ph′P), 129.7 (s, p-C of PhP),
)
1
{1H} NMR: δ 0.50 s. H NMR: δ 9.57 (br s, 1H, CHO), 7.67-
C
7.62 (m, 2H), 7.46-7.41 (m, 3H), 7.23-7.10 (m, 10H), 4.10 (ddd,
2JPH ) 5.4, 3JHH ) 11.1, 3JHH ) 3.4, 1H, PCH; 1H{31P}, dd), 3.04
3
3
129.6 (d, JPC ) 8.4, m-C of PhP), 128.8 (d, JPC ) 7.4, m-C of
Ph′P), 128.5 (s, p-C of Ph′P), 128.4 (s, m-C of PhC), 127.9 (d,
3
2
3
3
(dddd, JPH ) 5.4, JHH ) 17.4, JHH ) 11.1, JHH ) 1.9, 1H,
CHAHB; 1H{31P}, ddd), 2.69 (dddd, 3JPH ) 7.3, 2JHH ) 17.4, 3JHH
3JPC ) 7.1, o-C of PhC), 126.8 (d, JPC ) 1.4, p-C of PhC), 49.1
5
) 3.3, 3JHH ) 0.9, 1H, CHAHB; H{31P}, ddd). 13C{1H} NMR: δ
1
(d, 2JPC ) 13.9, MeCH), 48.0 (d, 1JPC ) 17.0, PCH), 13.5 (d, 3JPC
) 7.6, CH3).
2d-â (minor diastereomer; S,R- and R,S-enantiomers). 31P-
(6) Delacroix, O.; Gaumont, A. C. Curr. Org. Chem. 2005, 9, 1851, and
references therein.
{1H} NMR: δ -8.2 s. H NMR: δ 9.51 (m, 1H, CHO; H{31P}:
1
1
(7) (a) Kuhl, O.; Blaurock, S.; Sieler, J.; Hey-Hawkins, E. Polyhedron
2001, 20, 2171. (b) Lavenot, L.; Bortoletto, A.; Roucoux, C.; Larpent,
C.; Patin, H. J. Organomet. Chem. 1996, 509, 9. (c) Blinn, D. A.;
Button, R. S.; Farazi, V.; Neeb, M. K.; Tapley, C. L.; Trehearne, T.
E.; West, S. D.; Kruger, T. L.; Storhoff, B. N. J. Organomet. Chem.
1990, 393, 143. (d) Van Doorn, J. A.; Wife, R. L. Phosphorus 1990,
47, 253. (e) Pudovik, A. N.; Konovalova, I. V.; Romanov, G. V.;
Pozhidaev, V. M.; Anoshina, N. P.; Lapin, A. A. Zh. Obshch. Khim.
1978, 48, 1001. (f) Evangelidou-Tsolis, E.; Ramirez, F.; Pilot, J. F.;
Smith, C. P. Phosphorus Relat. Group V Elem. 1974, 4, 109.
(8) Bradaric-Baus, C. J.; Zhou, Y. PCT Int. Appl. 2004, WO 2004094440
A2 20041104.
(9) Muller, G.; Sainz, D. J. Organomet. Chem. 1995, 495, 103.
(10) (a) Carlone, A.; Bartoli, G.; Bosco, M.; Sambri, L.; Melchiorre, P.
Angew. Chem. Int. Ed. 2007, 46, 4504. (b) Ibraham, I.; Rios, R.;
Vesley, J.; Hammar, P.; Eriksonn, L.; Himo, F.; Co´rdova, A. Angew.
Chem. Int. Ed. 2007, 46, 4507. (c) Chikkali, S.; Gudat, D. Eur. J.
Inorg. Chem. 2006, 3005. (d) Burck, S.; Gudat, D.; Nieger, M.; Du,
Mont, W. W. J. Am. Chem. Soc. 2006, 128, 3946.
3
d, JHH ) 1.0), 7.68-7.64 (m, 2H), 7.52-7.46 (m, 3H), 7.38-
7.23 (m, 10H), 4.25 (pseudo t, JPH ≈ 4.9, 1H, PCH; H{31P}, d,
2
1
3JHH ) 4.5), 2.54 (m, 1H, MeCH), 1.20 (d, 3JHH ) 6.9, 3H, CH3).
13C{1H} NMR: δ 203.6 (d, JPC ) 10.9, CHO, overlapped with
3
CHO of 2d-R), 48.1 (d, 2JPC ) 15.8, MeCH), 44.7 (d, 1JPC ) 14.2,
PCH), 10.8 (d, 3JPC ) 9.6, CH3). Other 13C{1H} signals could not
be assigned.
Ph2PCH(Ph)CH2CH(OH)PPh2 (3). Dropwise addition of cin-
namaldehyde (0.38 mL, 0.30 mmol) to stirred Ph2PH (1.10 mL,
0.63 mmol) generated a viscous mixture, which was then heated at
60 °C and stirred for 15 min to give a pink glasslike residue. The
31P{1H} spectra of the residue in various solvents show mainly two
sets of two singlets (corresponding to two diastereomers, 3a and
3b), and small amounts (∼7 mol %) of 2a and Ph2PH; the 31P{1H}
data are listed in Table 1. 1H and 13C{1H} NMR data given below
pertain to DMSO-d6 solution.
(11) (a) Hartley, F. R. Organometal. ReV. A 1976, 6, 119. (b) Kharasch,
M. S.; Seyler, R. C.; Mayo, F. R. J. Am. Chem. Soc. 1938, 60, 882.
11468 Inorganic Chemistry, Vol. 46, No. 26, 2007

New Tertiary Phosphines
Table 1. 31P{1H} Singlet Resonances (δ) for Ph2PH, 3a, 3b, and 4 in
Decomposition of 3 and 4. In a glovebox, the compound (0.05
mmol) was dissolved in 1 mL of a selected solvent, and ∼0.7 mL
of the solution was placed under Ar in a J-Young NMR tube;
31P{1H} NMR spectral changes were then monitored.
Various Solventsa
3a
3b
solvent
Ph2PH
R-P
γ-P
R-P
γ-P
4
PdCl2[Ph2PCH(Ph)CH2CH(OH)PPh2] (5). The diphosphine 3
(39 mg, 0.077 mmol, based on 95% purity) in MeOH (1 mL) was
added to a 1 mL MeOH solution of PdCl2(PhCN)2 (28 mg, 0.073
mmol) under Ar. The immediately formed pale yellow solid
subsequently dissolved within 1 min, and the solution was kept
for 4 h at rt. Deposited crystals of 5 were filtered off, washed once
with MeOH (∼1 mL), and dried overnight under vacuum (25 mg,
50%, dr ∼20). Anal. Calcd for C33H30Cl2OP2Pd: C, 58.13; H, 4.43.
Found: C, 58.26; H, 4.64. Leaving the MeOH solution for 16 h
afforded 5 in 80% yield, with dr ∼ 3.3 as estimated by 31P{1H}
NMR.
DMSO
DMF
pyridine
acetone
CH3CN
Et2O
-39.7
-39.7
-39.6
-39.1
-39.0
-39.7
-39.6
-39.8
-40.1
-39.6
-39.8
-39.8
-39.9
-7.5
-6.0
-5.2
-4.8
-4.5
-3.6
-3.0
-2.4
-1.8
-1.0
-6.6
-6.6
-6.5
-0.8
-0.4
0.4
0.3
-0.5
0.4
-0.8
0.3
0.1
-0.3
0.3
-5.7
-4.6
-4.0
-3.8
-4.2
-3.6
-4.1
-3.9
-3.7
-3.4
-4.5
-4.5
-4.7
1.5
2.1
2.2
2.5
1.5
2.4
1.0
1.8
1.6
2.0
2.6
2.7
2.5
-6.8
-
-4.5
-4.0
-4.4
-3.0
-2.4b
-1.6
-1.7
-
CH2Cl2
CHCl3
benzene
hexane
MeOH
EtOH
-5.7
-5.8
-6.1
0.4
0.4
iPrOH
5a (S,S/R,R-enantiomers). 31P{1H} NMR (161 MHz on the
a Spectra measured using 0.05 M solution of the phosphines. b The
reported value (ref 9) is -6.5 ppm.
AV400, CD2Cl2): δ 24.1 [d, 2JPP ) 16.0, PCH(OH)] and 23.6 [d,
1
2JPP ) 16.0, PCH(Ph)]. H NMR (resonances in the δ 8.30-6.30
region overlap with corresponding signals of 5b; see below): δ
8.29-8.22 (m, 2H, o-H of PhPCH(OH)), 7.93-7.85 (m, 2H, o-H
of PhPCH(Ph)), 7.85-7.78 (m, 2H, o-H of Ph′PCH(OH)), 7.70-
7.35 (m, 10H, p-H and m-H of Ph2PCH(OH), p-H of Ph2PCH(Ph),
and m-H of PhPCH(Ph)), 7.32-7.25 (m, 2H, o-H of Ph’PCH(Ph)),
7.19-7.07 (m, 3H, p-H of PhCH, m-H of Ph′PCH(Ph)), 6.94 (t,
1
3a (S,S/R,R-enantiomers). H NMR: δ 7.60-7.01 (m, 23H,
Ph), 6.92 (d, 3JHH ) 7.7, 2H, o-H of PhC), 5.45 (pseudo t, 3JPH
)
6.7, JHH ) 6.8, 1H, OH; H{31P}, d), 4.07-3.94 (m, 2H, CHPh
and CH(OH)), 1.91-1.68 (m, 2H, CH2). 13C{1H} NMR: δ 138.9
(d, 2JPC ) 9.0, Cipso-CH), 137.1 (d, 1JPC ) 16.0, Cipso-P), 136.9 (d,
1JPC ) 15.4, Cipso-P), 136.4 (d, 1JPC ) 16.9, Cipso-P), 136.3 (d, 1JPC
) 13.7, Cipso-P), 133.7 (d, 2JPC ) 19.2, o-C of PhP), 133.5 (d, 2JPC
) 20.0, o-C of PhP), 132.9 (d, 2JPC ) 21.2, o-C of PhP), 132.7 (d,
2JPC ) 19.1, o-C of PhP), 129.2 (d, 3JPC ) 7.6, o-C of PhC), 129.0
3
1
3
3JHH ) 7.8, m-H of PhCH), 6.35 (d, JHH ) 7.8, o-H of PhCH),
5.02 (d, 3JHH ) 6.8, CH(OH); 1H{31P}, same), 4.58 (pseudo t, 2JPH
1
3
3
) 10.3, 1H, CH(Ph); H{31P}, dd, JHH ) 12.3, JHH ) 1.6), 2.77
(br s, 1H, OH), 2.71-2.20 (m, 2H, CH2, overlapped with CH2
2
signals of 5b). 13C{1H} NMR: δ 138.0 (d, JPC ) 9.0, Cipso of
4
5
(d, JPC ) 7.6, m-C of PhC), 126.1 (d, JPC ) 1.8, p-C of PhC),
PhCH), 136.9 (d, 2JPC ) 11.1, o-C of Ph′PCH(Ph)), 135.8 (d, 2JPC
) 9.5, o-C of PhPCH(OH)), 134.6 (d, 2JPC ) 9.8, o-C of Ph′PCH-
1
3
68.2 (dd, JPC ) 11.2, JPC ) 3.8, CH(OH)), 39.3 (dd, PCH,
overlapped with intense resonance of (CD3)2SO), 37.7 (dd, 2JPC
)
(OH)), 133.8 (d, 2JPC ) 9.1, o-C of PhPCH(Ph)), 132.6 (d, 4JPC
)
20.5, JPC ) 26.1, CH2). Other 13C{1H} resonances (and for 3b,
see below) could not be assigned (even using HMQC and HMBC
data) because of overlapping signals.
2
4
2.5, p-C of PhPCH(OH)), 132.0 (d, JPC ) 2.6, p-C of Ph′PCH-
(Ph)), 131.8 (d, 4JPC ) 2.1, p-C of Ph′PCH(OH)), 131.2 (d, 4JPC
)
1
3
1
2.8, p-C of PhPCH(Ph)), 65.3 (dd, JPC ) 38.2, JPC ) 7.0, CH-
(OH)), 35.5 (dd, 1JPC ) 22.7, 3JPC ) 9.0, CH(Ph)), 34.2 (overlapping
dd, seen as pseudo t, 2JPC ) 7.4, 3JPC ) 6.8, CH2). Other 13C{1H}
resonances (and for 5b, see below) could not be assigned because
of overlapping signals.
3b (S,R/R,S-enantiomers). H NMR: δ 7.60-7.01 (m, 25H,
Ph, overlapped with Ph-proton signals of 3a), 5.04 (pseudo t, 3JPH
) 5.0, JHH ) 6.1, 1H, OH; H{31P}, d), 4.14 (m, 1H, CH(OH)),
3
1
3.88 (m, 1H, CHPh; H{31P}, dd, JHH ) 10.7, JHH ) 4.1), 2.08
1
3
3
(m, 1H, CHAHB; H{31P}, ddd, JHH ) 5.6, JHH ) 11.1, JHH
)
1
3
3
2
5b (S,R/R,S-enantiomers). 31P{1H} NMR (CD2Cl2): δ 39.1 [d,
14.1), 1.84 (m, 1H, CHAHB, overlapped with CH2 proton signals
of 3a). 13C{1H} NMR: δ 140.9 (d, JPC ) 8.1, Cipso-CH), 134.6
(d, JPC ) 19.0, o-C of PhP), 133.6 (d, JPC ) 16.5, o-C of PhP),
133.1 (d, JPC ) 19.4, o-C of PhP), 133.0 (d, JPC ) 17.5, o-C of
PhP), 126.1 (p-C of Ph2PCH(OH),overlapped with p-C signal of
3a), 69.1 (dd, JPC ) 12.1, JPC ) 11.4, CH(OH)), 40.7 (dd, JPC
) 13.5, 3JPC ) 11.0, CHPh), 39.0 (dd, CH2, overlapped with intense
resonance of (CD3)2SO).
2
1
2JPP ) 16.8, PCH(Ph)] and 28.0 [d, JPP ) 16.8, PCH(OH)]. H
NMR: δ 8.32-8.29 (m, 2H, o-H of PhPCH(OH)), 7.78-7.71 (m,
2H, o-H of PhPCH(Ph)), 7.27-7.21 (m, 2H, o-H of Ph′PCH(Ph)),
2
2
2
2
2
4.98 (ddd, 2JPH ) 5.1, CH(OH); 1H{31P}, dd, 3JHH ) 11.6, 3JHH
)
2
1
3
2.2), 4.12 (ddd, JPH ) 8.3, CH(Ph); H{31P}, dd, JHH ) 11.8,
1
3
1
3JHH ) 2.3). 13C{1H} NMR: δ 137.9 (d, 2JPC ) 9.6, Cipso of PhCH),
137.0 (d, JPC ) 10.7, o-C of Ph′PCH(OH)), 136.7 (d, JPC ) 9.9,
o-C of PhPCH(OH)), 134.4 (d, JPC ) 9.4, o-C of PhPCH(Ph)),
2
2
Ph2PCH(OH)Et (4). The synthesis was a modification of a
literature procedure.9 Freshly distilled, oxygen-free propionaldehyde
(0.36 mL, 0.50 mmol) was added to stirred Ph2PH (0.88 mL, 0.50
mmol) under Ar at rt, and after 15 min a pure, white solid product
was formed quantitatively. Anal. Calcd for C15H17OP: C, 73.76;
H, 7.01. Found: C, 73.51; H, 7.03. 31P NMR shifts in different
solvents are listed in Table 1. 1H NMR (DMSO-d6): δ 7.61-7.27
(m, 10H, Ph), 5.09 (br s, 1H, OH), 4.36 (t, 3JHH ) 6.0, 1H, CH(OH);
2
4
133.9 (d, JPC ) 9.4, o-C of Ph′PCH(Ph)), 132.5 (d, JPC ) 2.5,
4
p-C), 132.1 (d, JPC ) 2.5, p-C), 131.8 (presumably d, p-C of
PhPCH(Ph), overlapped with p-C signal of Ph′PCH(OH)), 131.4
4
1
3
(d, JPC ) 2.9, p-C), 71.4 (dd, JPC ) 31.1, JPC ) 7.5, CH(OH)),
1
2
47.6 (br d, JPC ) 23.3, CH(Ph)), 37.2 (br d, JPC ≈ 8).
X-ray Crystallographic Analysis of 5. X-ray-quality, pale
yellow crystals of 5‚3MeOH were obtained as described above in
the synthesis reaction, the 31P{1H} NMR revealing two diastere-
omers (dr ∼ 20). Selected crystallographic data are shown in Table
2, and more details are provided in the Supporting Information.
Measurements were made at 173 ((0.1) K on a Bruker X8 APEX
diffractometer using graphite-monochromated Mo KR radiation
(0.710 73 Å). Data were collected to a maximum 2θ value of 55.8°,
in a series of φ and ω scans in 0.50° oscillations with 25.0 s
exposures; the crystal-to-detector distance was 36.00 mm. Of the
1H{31P}, same), 1.45 (dp, JHH ) JPH ) 7.2, 2H, CH2; H{31P},
3
3
1
p), 0.95 (t, JHH ) 7.2, 3H, CH3). 13C{1H} NMR (DMSO-d6): δ
3
1
1
137.5 (d, JPC ) 13.9, Cipso of PhP), 137.2 (d, JPC ) 15.2, C′ipso
-
P), 133.6 (d, 2JPC ) 18.9, o-C of PhP), 133.3 (d, 2JPC ) 17.2, o-C
of Ph′P), 128.6 (s, p-C of PhP), 128.3 (d, 3JPC ) 6.8, m-C of PhP),
128.2 (s, p-C of Ph′P), 128.0 (d, 3JPC ) 6.3, m-C of Ph′P), 72.4 (d,
1JPC ) 4.6, CHOH), 27.7 (d, JPC ) 23.5, CH2), 10.7 (d, JPC
)
2
3
12.3, CH3).
Inorganic Chemistry, Vol. 46, No. 26, 2007 11469

Moiseev et al.
resonances also show coupling to the P-atom in the 31P
spectrum, the H signals are readily assigned (see Experi-
Table 2. Crystallographic Data for 5‚3MeOH
1
empirical formula
cryst color, habit
cryst size, mm3
cryst syst
space group
a, Å
C36H42O4P2PdCl2
mental Section); the 13C{1H} spectrum (which delineates the
diastereotopic PPh2 phenyl groups), MS data, and elemental
analysis support the formulation. The p-tolyl and anisole
derivatives, 2b and 2c, were obtained likewise as pink solids
in more moderate yields, because of better solubility in Et2O
than 2a, and were characterized similarly by elemental
analysis and NMR spectroscopy (Table S1).
colorless, blade
0.05 × 0.13 × 0.40
primitive
Pbca (#14)
14.7439(6)
21.8538(9)
21.9153(9)
7061.3(5)
8
b, Å
c, Å
V, Å3
Z
F(000)
3200.00
8.05
46556
8420
The reaction of Ph2PH with R-methylcinnamaldehyde to
generate 2d required prolonged heating (see Scheme 2) and
a 2:1 excess of the aldehyde, which was largely removed
by distillation under vacuum. Further workup from Et2O
yielded 2d as a white solid in 57% yield; the solution 31P-
{1H} spectrum, which shows just two singlets, means that
2d (a molecule with two chiral centers) is isolated as a
mixture of diastereomers in about a 20:1 ratio as judged by
the signal intensities. There is no direct evidence for which
diastereomer is favored, but based on reasoning discussed
in our earlier paper on attack of PR3 [R ) (CH2)3OH] on
cinnamaldehyde, which is thought to generate the phospho-
nium cation [PhCH(PR3)CH(D)CHO]+ as S,S and R,R
enantiomers,1b the same S,S/R,R-diastereomer (labeled 2d-
R) is favored. Its aldehydic proton is downfield-shifted (δH
9.97) from that of the S,R/R,S-diastereomer (2d-â) (δH 9.51)
µ, cm-1
total reflns
unique reflns
Rint
0.066
no. variables
R1 (I > 2σ(I))
wR2
450
0.055 (5943 obsd reflns)
0.113 (all data)a
1.12 (all data)
gof
2
2
2
a w ) 1/[σ2(Fo ) + (0.00P)2 + 36.2447P], where P ) (Fo + 2Fc )/3.
46 556 reflections collected, 8420 were unique (Rint ) 0.066);
equivalent reflections were merged. Data were collected and
integrated using the Bruker SAINT software package12 and were
corrected for absorption effects using the multiscan technique
(SADABS),13 with minimum and maximum transmission coef-
ficients of 0.703 and 0.961, respectively. Data were corrected for
Lorentz and polarization effects, and the structures were solved by
direct methods.14 The material appears to be a mixture of diaster-
eomers, with predominantly S,S (or R,R) at C(1) and C(3),
respectively, and a small (∼5%) fraction of the S,R (or R,S) isomer
(see Figure 2 for atom labeling). This manifests itself as apparent
minor disorder at C(3) as well as minor disorder of the PdP2Cl2
fragment. There may be disorder in the positions of the other atoms;
however, the minimal disorder and the very small shifts in positions
between the major and minor fragments make it impossible to see
these fragments. All non-hydrogen atoms except the disordered
minor fragments were refined anisotropically, and all disordered
fragments were refined isotropically. The hydroxyl hydrogen (H1o)
was located in a difference map and refined isotropically, while
all other H atoms were placed in calculated positions. Of the three
molecules of MeOH found in the asymmetric unit, one is disordered
in two orientations.
1
and from that of 2a (δH 9.57), appearing in the H{31P}
3
spectrum as a doublet with a JHH vicinal coupling of 1.1
Hz. On the contrary, the benzyl proton of 2d-R (δH 3.84) is
upfield-shifted from that of 2a (δH 4.10), whereas the
corresponding signal of 2d-â (δH 4.25) is downfield-shifted.
The P-atoms of 2d-R and 2d-â appear in the 31P{1H}
spectrum as singlets at δP -8.6 and -8.2, respectively.
The reaction of 1a with 2 equiv of Ph2PH affords a pinkish,
glasslike residue which, according to a 31P{1H} spectrum in
DMSO-d6, consists of the diphosphine 3 (as a mixture of
diastereomers, Scheme 3), some 2a (∼2%), and Ph2PH
(∼5%). Attempts to purify 3 revealed its instability in
common organic solvents by decomposing into 2a and Ph2-
PH (Scheme 4); such reversibility of the addition of
secondary phosphines to carbonyl functions has long been
known,7d,f but we are unaware of any reports on the solvent
dependence (see below). Table 1 summarizes the im-
mediately measured 31P{1H} data for 3 in various solvents,
while the NMR data given in the Experimental Section are
measured in DMSO-d6, in which 3 is stable (see below).
Like compound 2d, the diphosphine contains two chiral
centers, and the 31P{1H} spectra reveal two sets of two
singlets, each set being attributed to one of two diastereomers
(3a and 3b); on the basis of data from a Pd(II) complex
containing 3 (see below), the major diastereomer (3a) is
considered to be the S,S/R,R mixture; in DMSO-d6 the
measured dr ) 2.3.
Results and Discussion
All the reactions involving Ph2PH were exothermic, as
judged by handling of the reaction vessel. Diphenylphosphine
reacts with cinnamaldehyde (1a) in the absence of solvent
at room temperature to afford the tertiary phosphine 2a
(Scheme 1). A pink-colored viscous liquid is first formed
rapidly and, to avoid formation of the diphosphine 3 (see
below), the reaction mixture was briefly stirred at 50 °C to
give a pink solid. After workup, 2a was obtained in good
yield as a racemate; the compound is soluble in acetone,
benzene, and CHCl3, but poorly soluble in Et2O, and in
CDCl3 gives a singlet at δP 0.50 in the 31P{1H} spectrum.
The four nonaromatic protons form an X-AB-Y spin
system in the 1H{31P} spectrum and, as the CH and CHAHB
The data in Table 1 show that the 31P{1H} shift for the
R-P atom of 3a and 3b (adjacent to the OH group) is
markedly solvent-dependent (e.g., a difference of 6.5 ppm
between values for 3a in DMSO and in hexane), while shift
values for the γ-P atom vary by only 1.2 ppm. A few
examples of the 31P{1H} spectra of 3 in different solvents
(12) SAINT, Version 7.03A; Bruker AXS Inc., Madison, WI, 1997-2003.
(13) SADABS. Bruker Nonius area detector scaling and absorption correc-
tion-V2.10; Bruker AXS Inc., Madison, WI, 2003.
(14) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.; Giaco-
vazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna,
R. J. Appl. Crystallogr. 1999, 32, 115.
11470 Inorganic Chemistry, Vol. 46, No. 26, 2007

New Tertiary Phosphines
Figure 1. The experimental 1H{31P} spectra for the CH- and CH2-protons of Ph2PCH(OH)Et (4) recorded in (A) DMSO-d6, (B) CD3OD, and (C) CDCl3.
1
1H NMR spectra for the CH-proton are shown to the right of the H{31P} spectra.
Scheme 1
Scheme 2
Scheme 3
Figure 2. ORTEP diagram of PdCl2[S,S-Ph2PCH(Ph)CH2CH(OH)PPh2]
(5) showing 50% probability thermal ellipsoids; H-atoms are omitted for
clarity.
are given in the Supporting Information (Figure S1). In
DMSO, the R-P atoms of 3a and 3b are the most upfield-
shifted, while in hexane they are the most downfield-shifted.
For 3a, the R- and γ-protons appear in the 1H{31P} spectrum
in DMSO-d6 as overlapping multiplets centered at δH 4.0,
and the diastereotopic â-protons appear as a multiplet
centered at δH 1.8. The corresponding spectrum for 3b is
better resolved. The R-H appears as a multiplet at δH 4.14
(due to coupling to CH2 and OH protons), and the γ-H
appears as a doublet of doublets at δH 3.88 (3JHH ) 10.7,
3JHH ) 4.1 Hz); one of the CH2 protons appears at δH 2.08
Inorganic Chemistry, Vol. 46, No. 26, 2007 11471

Moiseev et al.
Scheme 4
Scheme 5
those seen for the R-P atom of 3a and 3b; our δP value of
-2.4 in CH2Cl2 is 4.1 ppm to higher field than the reported
value.9 Similar to 3, 4 is stable in DMSO, and the 1H NMR
data for 4 given in the Experimental are measured in DMSO-
d6; the 1H data generally agree with those previously reported
in CDCl3,9 but our data are more detailed and there is the
complication of rapid decomposition of 4 in CHCl3/CDCl3.16
The solvent also affects the pattern of the 1H and 1H{31P}
NMR spectra of 4. In the latter in DMSO-d6, the alkyl
protons form an XABY3 spin system (Figure 1A), which is
well-simulated using JXA ) 3.6, JXB ) 9.0, JAB ) 14.6, JYA
) JYB ) 7.4 Hz, and the low value of ∆δAB ) 1.5 Hz; in
as a doublet of doublets of doublets with two vicinal and
3
one geminal coupling constant (3JHH ) 5.6, JHH ) 11.1,
2
and JHH ) 14.1 Hz), while the signal for other proton
overlaps with the CH2 proton signals of 3a. The individual
JPH constants for these protons could not be evaluated, but
the JPH and JHH values for the OH resonances of 3a and 3b
(δH 5.45 and 5.04, respectively) were readily determined.
The 13C{1H} resonances for the R-, â-, and γ-carbon atoms
of both diastereomers, including JPC values for both P-atoms,
were generally readily measured, although the γ-C signal
for 3a (a presumed doublet of doublets) was buried under
the DMSO-d6 resonance and required detection using an
HMQC experiment.
We then studied semiquantitatively the decomposition
process, which involves loss of Ph2PH to form the phosphine-
substituted aldehyde 2aspresumably the reverse of the
second step of the synthesis of 3 (Scheme 4). The decom-
position rate at room temperature was studied in several
solvents. Data in Figure S2 show that the rates of, and the
degree of, decomposition decrease in the order CHCl3 [donor
number (DN) ) 4.0] ∼ CH2Cl2 (1.0) > C6H6 (0.1) > MeCN
(14.1) > Me2CO (17.0) > Et2O (19.2),15 the trend generally
implying increased stability with DN and, as mentioned
above, no decomposition was seen in DMSO (DN ) 29.8);
similarly, solutions of 3 in DMF (DN ) 26.6) and pyridine
(33.1) are stable. In CHCl3/CH2Cl2, an equilibrium showing
∼65% conversion to 2a and Ph2PH is established with t1/2
∼30 min; in acetone, an equilibrium with ∼25% conversion
occurs with t1/2 ∼ 20 h, while in Et2O there is only ∼20%
conversion after 1 week. Decomposition of 3 in alcohols
follows the trend MeOH > EtOH > iPrOH (see Figure S3)
and is faster (e.g., t1/2 ∼20 h for ∼65% conversion in MeOH)
than expected from the respective donor numbers (30, 32
and 36),15 and this might result from the presence of trace
water (see below).
In order to test the generality of decomposition of (R-
hydroxy)monophosphines, we synthesized Ph2PCH(OH)Et
(4) via a room temperature reaction between propionaldehyde
and Ph2PH, a process of the type shown in the reverse
reaction of Scheme 4, that is, hydrophosphination of the
carbonyl. Phosphine 4 has been synthesized previously by
the same reaction carried out at -20 °C but, not mentioned
in this report,9 4 in solution reversibly decomposes back to
its synthetic components (cf. Scheme 4); of note, however,
the reversible nature of such a reaction (between benzalde-
hyde and Ph2PH) has long been known.7f The behavior of 3
in solution is similar to that of 4, although 3 shows less
decomposition at equilibrium than does 4 (Figures S4 and
S5 show decomposition data for 4 in the same solvents used
in the study of 3). The variation with solvent of the 31P{1H}
shifts for 4 is also shown in Table 1 and is very similar to
1
the H spectrum, the R-H shows the same broad triplet,
implying immeasurable 2JPH coupling (Figure 1A). In CD3-
1
OD (where δP ) -5.7), the H{31P} spectrum shows the
same spin system, but the â-protons are now anisochronous
by 14.8 Hz (Figure 1B), and the spectrum is simulated using
JXA ) 3.4, JXB ) 9.2, JAB ) 14.0, JYA ) JYB ) 7.4; in the
2
1H spectrum, the R-H resonance now shows JPH coupling
of 1.3 Hz (Figure 1B). In CDCl3 (where δP ) -1.6, the most
downfield-shifted; see Table 1), the â-protons are now
1
anisochronous by 51.2 Hz (Figure 1C) and the H{31P}
spectrum is simulated using JXA ) 4.7, JXB ) 8.9, JAB
)
2
14.1, JYA ) JYB ) 7.4); the R-H shows the largest JPH
coupling of ) 5.2 Hz (Figure 1C). A similar analysis of the
1
1H and H{31P} data for the alkyl-chain protons of 3a and
3b is more complicated, since there is coupling of the
diastereotopic CH2 protons to both P atoms that cannot be
assessed quantitatively.
The decomposition of (R-hydroxy)phosphines could occur
via an acid-base interaction between the OH proton and
phosphine lone pair to give a phosphonium intermediate,
which rearranges to give its component reagents; Scheme 5
shows this as an intramolecular process, while an intermo-
lecular process has been suggested for other rearrangements
of (R-hydroxy)phosphines.17 The better donor solvents likely
prevent the OH‚‚‚P atom interaction by stabilization of the
proton; as well as pyridinium, protonated DMSO and DMF
cations have been characterized in the solid state.18 It should
be noted that the various solvents were purified by standard
procedures, with no special attempts to remove trace water
and/or acid, which would be important in the decomposition
process; e.g. trace HCl in CHCl3 would certainly promote
the decomposition and indeed could account for the faster
decomposition in this solvent, but the general observed
correlation with DN is nevertheless likely valid, especially
(16) Although not mentioned in ref 9, Muller confirmed via a private
communication that his group had observed decomposition of 4 in
CHCl3.
(17) Evanelidou-Tsolis, E.; Ramirez, F. Phosphorus Relat. Group V Elem.
1974, 4, 123.
(18) (a) James, B. R.; Morris, R. H.; Einstein, F. W. B.; Willis, A. J. Chem.
Soc., Chem. Commun. 1980, 31. (b) BenedettiMorelli, E.; Di Blasio,
B.; Blaine. P. J. Chem. Soc. Perkin Trans. 2 1980, 500.
(15) Marcus, Y. J. Sol. Chem. 1984, 13, 599.
11472 Inorganic Chemistry, Vol. 46, No. 26, 2007

New Tertiary Phosphines
Scheme 6
Table 3. Selected Bond Distances and Angles for 5 (Estimated
Standard Deviations in Parentheses)
fully characterized complex 5, PdCl2(P,P-3) (see Scheme 6).
A solution 31P{1H} spectrum reveals two sets of resonances,
one for each diastereomer pair, the relative intensities being
determined by the dr value, which decreases if the crystal-
yielding reaction solution is kept for a longer period,
presumably because of differences in the solubilities of the
diastereomers. Figure S6 shows the spectrum of a CD2Cl2
solution of 5 obtained in 80% yield with dr ∼ 3 after a 16
h reaction; the P1 and P2 atoms of the more favorable
diastereomer appear at δP 23.6 and 24.1, respectively (2JPP
) 16.0 Hz), while the corresponding data for the minor
isomer are δP 39.1 and 28.0 (2JPP ) 16.8 Hz). A 4 h reaction
gave 5 in 50% yield with dr ∼ 20, and an X-ray-quality
crystal of 5 with this dr value was analyzed crystallographi-
cally (Figure 2, Tables 2 and 3). The compound crystallizes
as a mixture of diastereomers, with predominantly S,S- and
R,R-chirality at C(1) and C(3), respectively, and a small
fraction (∼5%) of the S,R- and R,S-isomers. The Pd atom
shows the expected square-planar coordination, the Pd-P
and Pd-Cl distances being close to those reported for the
analogous 1,3-bis(diphenylphosphino)propane complex, PdCl2-
(dppp),20 although the P-Pd-P bite angle of 5 (96.43°) is
some 6° larger than that of the dppp complex. The C(1)-
P(1)-Pd(1) and C(3)-P(2)-Pd(1) angles are similarly about
5° greater than those found for PdCl2(dppp).20
length (Å)
angle (deg)
P(1)-Pd(1)
P(2)-Pd(1)
Cl(1)-Pd(1)
Cl(2)-Pd(1)
C(1)-P(1)
C(3)-P(2)
C(3)-O(1)
2.2599(14)
2.2423(14)
2.3519(16)
2.3625(13)
1.862(5)
P(1)-Pd(1)-P(2)
P(1)-Pd(1)-Cl(1)
P(2)-Pd(1)-Cl(2)
Cl(1)-Pd(1)-Cl(2)
C(1)-P(1)-Pd(1)
C(3)-P(2)-Pd(1)
C(1)-P(1)-C(10)
C(1)-P(1)-C(16)
O(1)-C(3)-P(2)
96.43(5)
87.35(5)
86.24(5)
90.15(5)
120.15(15)
117.41(15)
103.6(2)
104.5(2)
111.0(3)
1.845(5)
1.408(6)
as the measured decomposition rates were reproducible. The
downfield-shifted 31P NMR resonances in nondonor solvents
(Table 1) are also consistent with favored formation of the
phosphonium intermediates, and thus more rapid decomposi-
tion (and vice versa). That the relative stability of 3 is greater
than that of 4 (Figures S2-S5) perhaps indicates that the
γ-P of 3 might interact with the OH proton via an intramo-
lecular interaction and impede protonation of the R-P atom.
In a recent report, an analogous dynamic equilibrium between
(R-hydroxy)phosphines of the type ArCH(OH)PPh2 and its
precursor reagents (e.g, Ph2PH and benzaldehydes) was
mentioned in studies describing acid-catalyzed formation of
the phosphine oxides ArCH2P(O)Ph2from these reagents, and
for the 4-hydroxybenzaldehyde system, the intermediate (R-
hydroxy)phosphine was isolated;10c in the earlier work with
benzaldehyde itself, PhCH(OH)PPh2 had been detected in
solution.7f
As mentioned in the Introduction, there has been a report
on the interaction of Ph2PH with R,â-unsaturated carbonyl
compounds including cinnamaldehyde.5 These reactions,
which were catalyzed by Lewis acids in CH2Cl2 solution,
included schemes showing hydrophosphination of one or
both of the olefinic and carbonyl moieties.5,19 The schemes
incorporated (i) intermediate tertiary phosphines with an
aldehyde side chain (including Ph2PCH(Ph)CH2CHO, 2,
synthesized in our studies),5 (ii) phosphine intermediates with
a hydroxy-containing side chain,19 of the type exemplified
by 4 and formed by addition of a second mole of Ph2PH to
a phosphino-aldehyde (exemplified by 2f3). However, in
neither of these studies by Susuki’s group were the inter-
mediates isolated, and no 31P NMR data were presented: only
monophosphine oxides were isolated during the workup
procedures, or diphosphine dioxides when H2O2 was used
as an oxidant to give an isolable product.5,19
The X-AB-Y spin system of the propane-bridge protons
1
seen in the H{31P} spectrum of 5 (Figure S7) is simulated
using JXA ) 1.6, JXB ) 12.6, JYA ) 7.0, JYB e 1.0, and JAB
) 15.0 Hz (∆δAB ) 0.273 ppm) for 5a (Figure S8) and JXA
) 12.6, JXB ) 2.2, JYA ) 11.6, JYB ) 2.2, and JAB ) 14.0
Hz (∆δAB ) 0.273 ppm) for 5b (Figure S9). A distinctive
feature of 5a is that the HY proton does not couple to the P2
atom and appears as a doublet at δH 5.02 both in the 1H and
1
in H{31P} spectra (JYB is unresolved); in contrast, the HX
proton does show 2JPH coupling to the P1 atom and appears
in the 1H spectrum as a pseudotriplet at δH 4.58 (2JPH ) 10.3,
1
JXB ) 12.3 Hz; JXA 1.6 Hz, seen in the H{31P} but being
1
unresolved in the H spectrum). For 5b, however, the HY
1
proton couples to P2 (2JPH ) 5.1 Hz) and appears in the H
spectrum as a doublet of doublets of doublets at δH 4.98
(JYA ) 11.6 and JYB ) 2.2 Hz), overlapping with the
corresponding HY proton signal of 5a. The absence of two-
bond coupling between the CH proton and P within an PCH-
(OH) moiety has been noted previously.1b,21 The C(1) and
C(3) carbon atoms of 5a and 5b do show coupling to both
P atoms in the 13C{1H} spectrum, the signals being a doublet
of doublets at δC 35.5 and 65.3 (for 5a), and 47.6 and 71.4
(for 5b). The OH protons of 5a and 5b can be seen in a 1H
We have initiated studies on the coordination chemistry
of the new tertiary phosphines 2 and 3, using initially trans-
PdCl2(PhCN)2 as the metal source, and have isolated and
(19) Suzuki, K.; Hashimoto, T.; Maeta, H.; Matsumoto, T. Synlett 1992,
(20) Steffen, W. L.; Palenik, G. J. Inorg. Chem. 1976, 15, 2432.
(21) Lee, S. W.; Trogler, W. C. J. Org. Chem. 1990, 55, 2644.
125.
Inorganic Chemistry, Vol. 46, No. 26, 2007 11473

Moiseev et al.
spectrum, recorded in DMSO-d6: dd at δH 6.60 (3JPH ) 11.0,
phination of the CdO group is reversible in common organic
solvents and leads to an equilibrium between the diphosphine
and Ph2PCH(Ph)CH2CHO; however, the diphosphine is
stable in strong donor solvents such as DMSO, DMF, or
pyridine, likely due to stabilization of the phosphine-OH
proton. X-ray analysis of the complex PdCl2[Ph2PCH(Ph)-
CH2CH(OH)PPh2] (with dr ∼ 20) reveals that the S,S- and
R,R-enantiomers are favored.
3
3JHH ) 5.6 Hz) and 6.28 (3JPH ) 9.0, JHH ) 5.6 Hz),
respectively. Coordinated 3 shows no decomposition, con-
sistent with the unavailability of phosphorus lone pairs,
implying no semilabile character for the ligand (cf. Scheme
5).
Conclusions
New tertiary phosphines Ph2PCH(Ar)CH2CHO (Ar ) Ph,
p-tol, and p-OMe-C6H4), bearing an aliphatic aldehyde group
in the side chain, are prepared in good yield by hydrophos-
phination of the CdC bond of the corresponding cinnama-
ldehyde in a 1:1 reaction with Ph2PH at room temperature
in the absence of solvent. A similar reaction of Ph2PH with
R-methylcinnamaldehyde, but requiring more severe condi-
tions, affords Ph2PCH(Ph)CH(Me)CHO as a mixture of
diastereomers with predominantly S,S- and R,R-chirality,
which can be obtained with a dr of ∼20. In a 2:1 reaction of
Ph2PH with cinnamaldehyde, hydrophosphination of both the
CdC and CdO bonds gives the diphosphine Ph2PCH(Ph)-
CH2CH(OH)PPh2 as a mixture of diastereomers (dr ∼ 2.3)
in which the S,S/R,R mixture is dominant. The hydrophos-
Acknowledgment. We thank the Natural Sciences and
Engineering Research Council of Canada for financial
support via a Discovery Grant.
Supporting Information Available: Characterization data for
2b and 2c (Table S1); 31P{1H} spectra of 3 in various solvents
(Figure S1); decomposition of 3 and 4 in aprotic and alcohol
solvents (Figures S2-S5); 31P{1H} spectrum of 5, dr ∼ 3 (Figure
1
S6); experimental (Figure S7) and simulated H{31P} spectra of
5a (Figure S8) and 5b (Figure S9); and CIF file for 5‚3MeOH.
This material is available free of charge via the Internet at
http://pubs.acs.org.
IC701597G
11474 Inorganic Chemistry, Vol. 46, No. 26, 2007