Stereospecific diphosphination of activated acetylenes: A general route to backbone-functionalized, chelating 1,2-diphosphinoethenes

Article abstract of DOI:10.1021/om060716o

The symmetrical diphosphanes R₂P-PR₂ {where R = Ph (1a), Cy (1b), or Bu^t (1c)} are made by the reaction of R ₂PLi with R₂PCl. The unsymmetrical diphosphanes R ₂P-PR′₂ {where R = Bu^t and R′ = Ph (2a); R = Bu^t and R′ = o-Tol (2b); R′ = Cy and R′ = Ph (2c); R = Cy and R′ = o-Tol (2d); R = Cy and R′ = Bu^t (2e)} are made by the reaction of R₂P(BH₃)Li with R′₂PCl followed by deprotection with Et₂NH. Diphosphanes 1a,b and 2a-d react with ZC≡CZ (Z = CO₂Me) to give the corresponding R₂-PCZ=CZPR₂ (3a,b) or R ₂PCZ=CZPR′₂ (4a-d). The reaction of 2a,b with HC≡CZ give the corresponding R₂PCH=CZPR₂ (5a,b). A mechanism is proposed that accounts for the cis stereospecificity and the regioselectivity of these diphosphinations. Treatment of [PtCl ₂(1,5-cod)] or [PdCl₂(NCPh)₂] with a selection of the diphosphines (3-5) gave the expected chelate complexes, four of which, [PtCl₂(3b)], [PtCl₂(4a)], [PtCl₂(4c)], and (PdCl₂(4a)], have had their crystal structures determined.

Full text of DOI:10.1021/om060716o

Organometallics 2006, 25, 5937-5945
5937
Stereospecific Diphosphination of Activated Acetylenes: A General
Route to Backbone-Functionalized, Chelating
1,2-Diphosphinoethenes
Deborah L. Dodds,† Mairi F. Haddow,† A. Guy Orpen,† Paul G. Pringle,*,† and
Gary Woodward§
School of Chemistry, UniVersity of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K., and Rhodia Inc.,
350 George Patterson BouleVard, Bristol, PennsylVania 19007
ReceiVed August 7, 2006
The symmetrical diphosphanes R2P-PR2 {where R ) Ph (1a), Cy (1b), or But (1c)} are made by the
reaction of R2PLi with R2PCl. The unsymmetrical diphosphanes R2P-PR′2 {where R ) But and R′ ) Ph
(2a); R ) But and R′ ) o-Tol (2b); R ) Cy and R′ ) Ph (2c); R ) Cy and R′ ) o-Tol (2d); R ) Cy
and R′ ) But (2e)} are made by the reaction of R2P(BH3)Li with R′2PCl followed by deprotection with
Et2NH. Diphosphanes 1a,b and 2a-d react with ZCtCZ (Z ) CO2Me) to give the corresponding R2-
PCZdCZPR2 (3a,b) or R2PCZdCZPR′2 (4a-d). The reaction of 2a,b with HCtCZ give the corresponding
R2PCHdCZPR2 (5a,b). A mechanism is proposed that accounts for the cis stereospecificity and the
regioselectivity of these diphosphinations. Treatment of [PtCl2(1,5-cod)] or [PdCl2(NCPh)2] with a selection
of the diphosphines (3-5) gave the expected chelate complexes, four of which, [PtCl2(3b)], [PtCl2(4a)],
[PtCl2(4c)], and [PdCl2(4a)], have had their crystal structures determined.
Introduction
Chelating diphosphines have been at the heart of organome-
tallic chemistry and catalysis since the invention of dppe over
Unsymmetrical diphosphanes have been made similarly; for
example, 2a was made11 in 37% yield via the route shown in
eq 2, although the product was contaminated with the sym-
metrical diphosphanes 1a and P2Cy4 (1b).
40 years ago.1 The ready synthesis of chelating PCCP ligands
having a 1,2-ethane backbone has led to the legion of variations
on the structure with the substituents at P and C being used to
control stereoelectronic effects (including chirality)2 and solubil-
ity.3 Much less elaboration of diphosphines with 1,2-phenylene
or 1,2-ethylene backbones has been reported despite the potential
usefulness of backbone rigidity.4 Part of the reason for this is
undoubtedly that the synthetic routes to diphos ligands with sp2-
carbon backbones are not readily adaptable to the introduction
of functionality. Here we report a general route to 1,2-ethylene
diphosphines from readily accessible diphosphanes.
Unsymmetrical diphosphanes are known to undergo metath-
esis reactions, e.g., the process shown in eq 3, which involves
P-P bond cleavage.12
Diphosphanes have been known for over 100 years,5 but their
applications in synthesis have been little explored.6,7 Tetraphe-
nyldiphosphane 1a is the most studied diphosphane and has been
made by several methods8-10 from Ph2PCl or Ph2PH including
catalytic dehydrogenative coupling of Ph2PH.10 The route shown
in eq 1 gave 1a in 80% yield.8
We report here the addition of P-P bonds across activated
CtC bonds (diphosphination) as an efficient route to chelating
diphosphinoethenes with ester-substituted backbones. Though
P-P additions to alkynes have been previously reported,13,14
they are rare compared to the addition of other E-E bonds to
alkynes.15
* Corresponding author. E-mail: paul.pringle@bristol.ac.uk.
† University of Bristol.
§ Rhodia Inc.
(1) Aguiar, A. M.; Daigle D. J. Am. Chem. Soc. 1964, 86, 2299.
(2) For leading references see: (a) Wada, Y.; Imamoto, T.; Tsurutu, H.;
Yamaguchi, K.; Gridnev, I. D. AdV. Synth. Catal. 2004, 346, 777. (b) Fries,
G.; Wolf, J.; Ilg, K.; Walfort, B.; Stalk, D.; Werner, H. Dalton Trans. 2004,
1873.
(3) (a) For, leading references see: Amrani, Y.; Lecomte; Sinou, D.;
Bakos, J.; Toth, I.; Hell, B. Organometallics 1989, 8, 542. (b) Hanson, B.
E. Coord. Chem. ReV. 1999, 185-186. 795. (c) Pinault, N.; Bruce, D. W.
Coord. Chem. ReV. 2003, 241, 1.
(4) Freixa, Z.; van Leeuwen, P. W. N. M. Dalton Trans. 2003, 1890,
and references therein.
(9) (a) Spanier, E. J.; Caropreso, F. E. Tetrahedron Lett. 1969, 3, 199.
(b) Goldwhite, H.; Kaminski, J.; Millhauser, G.; Ortiz, J. E.; Bargas, M.;
Vertal, L.; Lappert, M. F.; Smith, S. J. Organometallic Chem. 1986, 310,
21. (c) Calderazzo, F.; Pampaloni, G. Polyhedron 1998, 7, 2039. (d) Dick
D. G.; Rousseau, R.; Stephan, D. W. Can. J. Chem. 1991, 69 357.
(10) Bo¨hm, V. P. W.; Brookhart, M. Angew. Chem. Int. Ed. 2001,
40, 4694.
(11) Issleib, K.; Krech, K. Chem. Ber. 1965, 98, 1093.
(12) (a) McFarlane, H. C. E.; McFarlane, W. J. J. Chem. Soc., Chem.
Commun. 1972, 1189. (b) Harris, R. K.; Norval, E. M. J. Chem. Soc., Dalton
Trans. 1979, 826.
(5) Kosolopoff, G. M.; Maier L. In Organic Phosphorus Compounds;
Wiley: New York, 1972; Vol. 1.
(6) Cowley, A. H. Chem. ReV. 1965, 65, 617.
(13) Cullen, W. R.; Dawson, D. S. Can. J. Chem. 1967, 45, 2887.
(14) Sato, A.; Yorimitsu, H.; Oshima, K. Angew. Chem. Int. Ed. 2005,
44, 1694.
(7) Caminade, A-M.; Majoral, J.-P.; Mathieu, R. Chem. ReV. 1991, 91,
575.
(8) Kuchen, W.; Buchwald, H. Chem. Ber. 1959, 227.
(15) Beletskaya, I.; Moberg, C. Chem. ReV. 2006, 106, 2320.
10.1021/om060716o CCC: $33.50 © 2006 American Chemical Society
Publication on Web 11/01/2006

5938 Organometallics, Vol. 25, No. 25, 2006
Dodds et al.
Scheme 2. Borane-Assisted Synthesis of Unsymmetrical
Diphosphanes
Results and Discussion
Diphosphane Synthesis. The symmetrical diphosphanes
1a-c were made according to eq 4 and fully characterized (see
Experimental Section).
Attempts to extend this method to the synthesis of unsym-
metrical diphosphanes 2a-e gave the desired products in 40-
75% yield (according to 31P NMR) but contaminated with
significant amounts of symmetrical diphosphanes and other
byproducts. For example, treatment of But2PH with BuLi
followed by (o-Tol)2PCl gave a mixture of the desired But2P-
P(o-Tol)2 2b (40%), the symmetrical diphosphanes 1c (11%)
and P2(o-Tol)4 (1d) (30%), But2PH (16%), and But2PCl (3%).
We know from subsequent experiments (see below) that 2b is
stable to metathesis, and therefore 1c and 1d are likely formed
by the comproportionation shown in Scheme 1.
synthesis of diphosphine 3a in three steps from 2,3-dichloro-
maleic acid anhydride has been previously reported.16
Scheme 1. Comproportionation of Unsymmetrical
Diphosphanes
The very bulky diphosphane 1c did not react with DMAD
under ambient conditions or upon heating the reaction mixture
for 3 days at 60 °C in the presence of the radical initiator AIBN.
The unsymmetrical diphosphanes 2a-d all added smoothly
to DMAD to give diphosphines 4a-d according to eq 7 (see
Experimental Section for the characterizing data).
An efficient general route to pure unsymmetrical diphos-
phanes was found to be via the borane adducts of the secondary
phosphines (eq 5). For example 2b was formed almost
exclusively (by 31P NMR), and when the product was stirred at
ambient temperatures in THF for 72 h or refluxed in toluene
for 1 h, there was no sign of metathesis to 1c and 1d.
The symmetrical diphosphanes 1a and 1b did not react with
the terminal acetylene methyl propiolate under the conditions
in which they added rapidly to DMAD. However the unsym-
metrical 2a and 2b did react with methyl propiolate to give 5a
and 5b according to eq 8 (see Experimental Section for the
characterizing data). Remarkably only one product was observed
(i.e., the isomers 5a′ and 5b′ were not detected).
A mechanistic explanation for the high chemoselectivity of
the reactions in eq 5 is given for 2b in Scheme 2. In the
intermediate diphosphane monoborane 2b‚BH3, one of the
P-centers is more crowded and therefore less susceptible to
nucleophilic attack. Attack at the other phosphorus generates
only the desired product.
Diphosphinations of Activated Alkynes. The symmetrical
diphosphanes 1a and 1b were added to dimethylacetylene
dicarboxylate (DMAD) in toluene at ambient temperatures. The
reactions were followed by 31P NMR spectroscopy, which
showed that the additions were rapid and gave the diphosphines
3a and 3b as the cis isomers exclusively (eq 6) (see Experi-
mental Section for the characterizing data). The crystal structure
of diphosphine 3b has been determined (see below). The
The proposed mechanism for the diphosphinations (eqs 6-8)
is shown in Scheme 3. A contribution from a mechanism
involving radicals cannot be ruled out but is considered unlikely
because of the high cis stereoselectivity observed; radical-
initiated P-P additions to terminal alkynes has recently been
reported to give mainly trans alkenes.14
(16) Becher, H. J.; Bensmann, W.; Fenske, D.; Pfennig, B. Monatsh.
Chem. 1978, 109, 1023, and references therein.

Stereospecific Diphosphination of ActiVated Acetylenes
Organometallics, Vol. 25, No. 25, 2006 5939
Scheme 3. Proposed Mechanism of Diphosphination of
Activated Alkynes
Scheme 4. Platinum and Palladium Complexes of
Diphosphinoethenes
Nucleophilic attack by the diphosphane on the Michael
activated alkyne would give zwitterionic intermediate A. A
zwitterionic intermediate has been proposed as an intermediate
in the reaction of tertiary phosphines with DMAD to give
phosphorus ylides.17 The intact P-P bond in A ensures that
the subsequent intramolecular rearrangement gives the observed
cis alkene product. The lability of the P-P bond in A is
consistent with the propensity of cationic species of the type
X-ray Crystallography. Crystals of 3b suitable for X-ray
crystallography were obtained from a diethyl ether solution in
the space group P1h (see Figure 1 and Table 1 for selected bond
lengths and angles). One of the cyclohexyl substituents on P2
was disordered over two positions with occupancies of about
74% and 26%. The structure was refined with a suitable restraint
on the P-C bond length, and refinement proceeded smoothly
to give the structure shown.
R2P-PR3 to undergo P-P cleavage reactions.6 The rate of
+
the first step in Scheme 3 would depend on the electrophilicity
of the alkyne, which explains the greater reactivity of DMAD
than methyl propiolate. It would also depend on the nucleo-
philicity of the diphosphane, which explains why the nonpolar
and very bulky 1c is unreactive and why the isomer formed in
the reaction of the unsymmetrical diphosphanes with methyl-
propiolate (eq 8) is derived from the attack of the more electron
rich (PBut2) end of the diphosphane. The rate of the reaction
between 2b and DMAD was faster at higher concentrations of
DMAD and was faster in MeCN and CH2Cl2 than in toluene;
these observations are consistent with the rate-limiting formation
of the polar intermediate A.
Platinum(II) and Palladium(II) Chelates. The coordination
chemistry of none of the ligands discussed here has been previ-
ously reported.18 Treatment of [PtCl2(1,5-cod)] or [PdCl2(NC-
Ph)2] with diphosphinoethenes 3a,b, 4a,c,d, and 5a in dichloro-
methane gave the expected chelates 8a-f and 9a-f (see
Scheme 4).
The complexes were characterized by a combination of 31P,
1H, and 13C NMR spectroscopy, IR spectroscopy, mass spectrom-
etry, and X-ray crystallography. The 31P NMR spectra were par-
ticularly characteristic: the large coordination chemical shifts
(∆δ 55-75 ppm for 8a-f and 80-100 ppm for 9a-f) are
typical for five-membered chelates;19 the values of ∆δ (e.g.,
[PtCl2(dppe)] 58.5 Hz, [PdCl2(dppe)] 81.5 Hz) and 1J(PtP) (ca.
3500 Hz) are consistent with cis phosphines which are trans to
Cl ligands. In addition, the crystal structures of the platinum
complexes 8b, 8c, and 8d and palladium complex 9c have been
determined.
Figure 1. X-ray crystal structure of diphosphinoethene 3b. Only
the major component shown as the structure is disordered. Picture
is shown with 50% ellipsoids. Hydrogen atoms are omitted for
clarity.
(17) Tebby, J. C.; Wilson, I. F.; Griffiths, D. V. J. Chem. Soc., Perkin
Trans. 1 1979, 2133, and references therein.
Table 1. Selected Bond Lengths (Å) and Angles (deg) for
Diphosphinoethene 3b
(18) Complexes of the type [MCl2(Ph2PCHdCRPR′2)] (M ) Pt, Pd; R
) CF3, Ph, But; R′ ) Ph, CH2CH2CN) have been made by the reaction of
PHR′2 to [MCl2(Ph2PCtCR)2]; see: Carty, A. J.; Johnson, D. K.; Jacobson,
S. E. J. Am. Chem. Soc. 1979, 101, 5612. A platinum(II) complex of the
maleic anhydride derivative Ph2PCH(CO)(O)dCH(CO)PPh2 has been
described; see: Ravindar, V.; Schumann, H.; Hemling, H.; Blum, J. Inorg.
Chim. Acta 1995, 240, 145. A dicobalt complex containing a bridging η4-
Me2PCH(CO2Me)dCH(CO2Me)PMe2 ligand has also been reported; see:
Zolk, R.; Werner, H. J. Organomet. Chem. 1987, 331, 95.
P1-C1
1.8555(16)
1.8704(17)
1.8735(15)
1.817(4)
C1-P1-C7
C13-P1-C7
99.36(6)
104.52(7)
113.2(3)
105.4(2)
100.49(7)
94.99(10)
103.97(8)
1.98(18)
P1-C13
P1-C7
C25B-P2-C2
C25B-P2-C19
C2-P2-C19
C2-P2-C25A
C19-P2-C25A
P1-C1-C2-P2
P2-C25B
P2-C2
1.8481(16)
1.8706(15)
1.915(2)
P2-C19
P2-C25A
C1-P1-C13
97.39(7)
(19) Garrou, P. E. Chem. ReV. 1981, 81, 229.

5940 Organometallics, Vol. 25, No. 25, 2006
Dodds et al.
Crystals of 8b, as a chloroform solvate, suitable for X-ray
crystallography were obtained from a chloroform solution in
the space group P21/n (see Figure 2 and Table 2 for selected
bond lengths and angles).
left quadrant). However, in other respects the diphosphine 3b
shows a high degree of preorganization for complexation to a
metal; thus the phosphorus atoms are syn to each other, and
the C1-C2-P2-CCy and C2-C1-P2-CCy torsions are such
that the phosphorus lone pairs are ideally placed to chelate a
metal, and even the CO2Me groups on the backbone adopt a
very similar conformation in the free phosphine and the
complex. On complexation the P-CCy bond shortens (lengths
in 3b, 1.870(2)-1.874(2) and in 8b, 1.826(5)-1.848(5)),
although the change in the P-Cbackbone bond lengths is not
significant. There is a simultaneous increase in the CPC angles
(ignoring parameters for disordered atoms).
Crystals of 8c, as a chloroform solvate, suitable for X-ray
crystallography were obtained from a chloroform solution in
the space group P1h (see Figure 5 and Table 3 for selected bond
lengths and angles).
Figure 2. X-ray crystal structure of [PtCl2(3b)] (8b)‚CHCl3. Picture
is shown with 50% ellipsoids. Hydrogen atoms are omitted for
clarity.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for
[PtCl2(3b)] (8b)‚CHCl3
Pt1-P1
Pt1-P2
Pt1-Cl2
Pt1-Cl1
P1-C1
P1-C13
P1-C7
P2-C25
P2-C2
2.2151(12)
2.2182(12)
2.3568(12)
2.3581(12)
1.826(5)
1.830(5)
1.848(5)
1.839(5)
1.844(5)
P2-C19
1.855(5)
89.04(4)
107.7(2)
103.2(2)
106.6(2)
106.9(2)
107.0(2)
103.7(2)
2.1(5)
P1-Pt1-P2
C1-P1-C13
C1-P1-C7
C13-P1-C7
C25-P2-C2
C25-P2-C19
C2-P2-C19
P1-C1-C2-P2
The orientation of the cyclohexyl groups may be described
in terms of a quadrant diagram, where each of the cyclohexyl
rings lies in a quadrant, with a torsion angle Cbackbone-P-
Ccyclohexyl-H describing the rotation of the cyclohexyl around
the P-C bond. Values ca. (60° correspond to gauche confor-
mations (g+ or g-) and values close to (180° to anti (a). This
is shown in Figure 3 for the free diphosphine (3b) and in Figure
4 for its complex 8b. It is notable that in most cases (except
the minor orientation of the disordered cyclohexyl in 3b) diagon-
ally opposite cyclohexyl groups adopt the same conformation.
Figure 5. X-ray crystal structure of [PtCl2(4a)] (8c)‚CHCl3. Picture
is shown with 50% ellipsoids. Hydrogen atoms are omitted for
clarity.
Table 3. Selected Bond Lengths (Å) and Angles (deg) for
[PtCl2(4a)] (8c)‚CHCl3
Pt1-P1
Pt1-P2
Pt1-Cl1
Pt1-Cl2
P1-C13
P1-C7
P1-C1
P2-C2
P2-C23
2.1980(10)
2.2654(11)
2.3549(11)
2.3743(10)
1.814(4)
1.817(4)
1.834(4)
1.865(4)
1.879(4)
P2-C19
1.895(4)
88.70(4)
107.7(2)
104.89(19)
104.06(18)
104.44(19)
105.94(18)
113.6(2)
2.5(5)
P1-Pt1-P2
C13-P1-C7
C13-P1-C1
C7-P1-C1
C2-P2-C23
C2-P2-C19
C23-P2-C19
P1-C1-C2-P2
Crystals of 8d, as a dichloromethane solvate, suitable for
X-ray crystallography were obtained from a CH2Cl2 solution
in the space group P21/n (see Figure 6 and Table 4 for selected
bond lengths and angles). The two cyclohexyl groups in 8d
mimic the g+/a pattern of orientation seen in 8b. In 8d, there is
no significant difference in the metal phosphorus bond lengths,
despite the difference in substituents.
Figure 3. Quadrant diagram for 3b.
Crystals of 9c, as a chloroform solvate, suitable for X-ray
crystallography were obtained from a chloroform solution in
the space group P1h (see Figure 7 and Table 5 for selected bond
lengths and angles).
Figure 4. Quadrant diagram for 8b.
Thus complexation of the ligand involves rotation of at least
one of the cyclohexyl groups (that represented by the bottom

Stereospecific Diphosphination of ActiVated Acetylenes
Organometallics, Vol. 25, No. 25, 2006 5941
Figure 6. X-ray crystal structure of [PtCl2(4c)] (8d)‚CH2Cl2.
Picture is shown with 50% ellipsoids. Hydrogen atoms are omitted
for clarity.
Table 4. Selected Bond Lengths (Å) and Angles (deg) for
Figure 7. X-ray crystal structure of [PdCl2(4a)] (9c)‚CHCl3. Picture
is shown with 50% ellipsoids. Hydrogen atoms are omitted
for clarity.
[PtCl2(4c)] (8d)‚CH2Cl2
Pt1-P2
Pt1-P1
Pt1-Cl1
Pt1-Cl2
P1-C13
P1-C7
2.2074(15)
2.2087(16)
2.3563(15)
2.3592(15)
1.835(5)
1.831(5)
1.846(6)
1.804(6)
1.819(5)
P2-C2
1.842(6)
88.46(6)
107.6(2)
108.5(3)
101.5(3)
109.0(2)
107.1(3)
105.0(3)
-10.4(6)
P2-Pt1-P1
C13-P1-C7
C13-P1-C1
C7-P1-C1
C19-P2-C25
C19-P2-C2
C25-P2-C2
P1-C1-C2-P2
Table 5. Selected Bond Lengths (Å) and Angles (deg) for
[PdCl2(4a)] (9c)‚CHCl3
Pd1-P2
Pd1-P1
Pd1-Cl2
Pd1-Cl1
P1-C1
2.1933(9)
2.2843(9)
2.3417(9)
2.3672(9)
1.855(3)
1.881(3)
1.887(3)
1.799(3)
1.806(3)
P2-C2
1.826(3)
88.06(4)
P2-Pd1-P1
C1-P1-C7
C1-P1-C11
C7-P1-C11
C21-P2-C15
C21-P2-C2
C15-P2-C2
P1-C1-C2-P2
P1-C1
104.80(12)
105.91(11)
113.62(12)
108.70(13)
104.42(12)
103.98(12)
3.1(3)
P2-C19
P2-C25
P1-C7
The crystal structures of [MCl2(4a)]‚CHCl3, 8c (M ) Pt) and
9c (M ) Pd), are isostructural. Both show distortion of
coordination at the d8 M(II) center from the square planar ideal;
the chlorine (Cl1) cis to the phosphine with two tert-butyl groups
(on P2) is positioned such that the angle P2-M-Cl1 is 98.17-
(4)° for 8c and 98.34(4)° for 9c. The Cl1 is also displaced from
the mean plane formed by M, P1, P2, and Cl2 by about 3° in
each case.
P1-C11
P2-C21
P2-C15
regioselective diphosphination is a general method to a range
of symmetrical and unsymmetrical chelating diphosphines
featuring a rigid backbone bearing functional groups that should
be amenable to further elaboration.
The bond length M-P2 is longer than M-P1 in both 8c and
9c, probably due to the steric requirements of the bulky tert-
butyl substituents. Counterintuitively, the M-Cl2 bond trans
to M-P2 is longer than the M-Cl1 by about 0.02 Å. This
implies that the higher trans influence of P1 than P2 (as
indicated by the M-Cl bond lengths) is not reflected in their
M-P bond lengths. The M-P1 bond length is comparable to
the metal-phosphorus bond lengths in 8b and 8d.
The five-membered MPCdCP ring may also be characterized
by a fold angle, i.e., the dihedral angle between the PMP and
PCCP planes. In the crystal structures of the complexes reported
here (8b, 8c, 8d, and 9c) the MPCdCP ring is effectively planar;
none has a fold angle of more than 4°.
Experimental Section
Unless otherwise stated, all work was carried out under a dry
nitrogen atmosphere, using standard Schlenk line techniques. Dry
N2-saturated solvents were collected from a Grubbs system20 in
flame- and vacuum-dried glassware. NMR spectra were measured
on a Jeol Eclipse 300 or a Jeol GX 400 spectrometer. Unless
otherwise stated H, 13C, and 31P NMR spectra were recorded at
1
400, 100, and 121 MHz, respectively at +23 °C. Mass spectra were
recorded on a VG Analytical Autospec (EI) or VG Analytical
Quattro (ESI). Elemental analyses were carried out by the Mi-
croanalytical Laboratory of the School of Chemistry, University
of Bristol. [PtCl2(1,5-cod)]21 and [PdCl2(NCPh)2]22 starting materials
and (o-Tol)2PCl23 were made by literature methods, but all other
phosphines were purchased from Strem. The compounds generally
crystallized with chlorinated solvents (as shown by 1H NMR
Finally, unlike dppe chelates, where the λ/δ ring conforma-
tions render the P-substituents inequivalent (pseudoaxial and
pseudoequatorial), the rigid backbones in 8b-d and 9c make
the P-substituents isoclinal.
(20) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;
Timmers, F. J. Organometallics 1996, 15, 1518.
(21) McDermott, J. X.; White, J. F.; Whitesides, G. M. J. Am. Chem.
Soc. 1976, 98, 6521.
(22) Doyle, J. R.; Slade, P. E.; Jonassen, H. B. Inorg. Synth. 1960, 6,
218.
Conclusion
Symmetrical and unsymmetrical diphosphanes have been
shown to be readily accessible and show no evidence of
metathesis under ambient conditions. The stereospecific and
(23) Clark, P. W.; Mulraney, B. J. J. Organomet. Chem. 1981, 217, 51.

5942 Organometallics, Vol. 25, No. 25, 2006
Dodds et al.
spectroscopy), which sometimes made elemental analyses for these
compounds variable (see below).
Hz, CCH3); 13C (CDCl3) with the aid of DEPT-135 δ 142.5 (d,
1J(PC) 29 Hz, ipso-C), 137.1 (d, J(PC) 15 Hz, CH), 130.0 (d, J(PC)
5 Hz, CH), 128.3 (s, CH), 125.4 (d, J(PC) 4 Hz, CH), 34.3 (dd,
1J(PC) 29 Hz, 2J(PC) 10 Hz, CCH3), 31.9 (dd, 2J(PC) 13 Hz, 3J(PC)
1,1,2,2-Tetraphenyldiphosphane (1a).24 To a solution of dis-
tilled Ph2PH (0.93 cm3, 5.37 mmol) in THF (20 cm3) was added
dropwise n -BuLi (1.6 M solution in hexanes, 4.4 cm3, 6.98 mmol)
at -78 °C. After 30 min, the resulting solution was warmed to
room temperature and stirred for 2 h. The solution was then cooled
to -78 °C, Ph2PCl (0.96 cm3, 5.37 mmol) was added, and the
solution was stirred for 16 h. The solvent was removed under
reduced pressure to leave the white solid product, which was then
washed with methanol (2 × 20 cm3) and dried in vacuo to give 1a
as a white powder (1.62 g, 4.37 mmol, 81%). NMR data: 31P
(CDCl3) δ -14.6 (s); 1H (300 MHz, CDCl3) δ 7.45-7.32 (8H, m,
CH), 7.32-7.14 (12H, m, CH); MS (ESI) m/z 371 (MH+); HRMS
(ESI) calcd for C24H21P2 371.1124, found 371.1113.
3
5 Hz, CCH3), 21.7 (d, J(PC) 23 Hz, CCH3); MS (ESI) m/z 375
((M + O) H+); HRMS (ESI) calcd for the monoxide of 2b, C22H33-
OP2, 375.2009, found 375.2001.
1,1-Dicyclohexyl-2,2-diphenyldiphosphane (2c). 2c was pre-
pared from Cy2PH‚BH3 and Ph2PCl using the method described
for 2a. White solid 2c was obtained from methanol and dried in
vacuo (2.29 g, 6.00 mmol, 75%). NMR data: 31P (CDCl3) δ -6.4
1
1
1
(d, J(PP) 221 Hz, PCy2), -28.2 (d, J(PP) 221 Hz, PPh2); H
(CDCl3) δ 8.03-6.97 (10H, m, CH), 2.13-0.81 (22H, m, CH/CH2);
13C (CDCl3) with the aid of DEPT-135 δ 136.7 (dd, 1J(PC) 20 Hz,
2J(PC) 7 Hz, ipso-C), 134.5 (dd, J(PC) 19 Hz, J(PC) 8 Hz, CH),
128.1 (m, CH), 32.9 (dd, J(PC) 20 Hz, J(PC) 9 Hz, CH), 32.0 (dd,
J(PC) 12 Hz, J(PC) 8 Hz, CH2), 31.0 (dd, J(PC) 10 Hz, J(PC) 6
Hz, CH2), 27.4 (m, CH2), 26.2 (m, CH2); MS (ESI) m/z 399 ((M +
O) H+); HRMS (ESI) calcd for the monoxide of 2c, C24H33OP2,
399.2009, found 399.2001.
1,1,2,2-Tetracyclohexyldiphosphane (1b).25 1b was prepared
from Cy2PH and Cy2PCl using the method described for 1a, and re-
crystallization from methanol gave white crystalline solid 1b, which
was dried in vacuo (4.00 g, 10.14 mmol, 98%). NMR data: 31P
1
(CDCl3) δ -21.0 (s); H (300 MHz, CDCl3) δ 2.02-0.90 (44H,
m, CH /CH2); MS (ESI) m/z 411 ((M + O) H+); HRMS (ESI)
calcd for the monoxide of 1b, C24H45OP2, 411.2947, found
411.2940.
1,1-Dicyclohexyl-2,2-di-o-tolyldiphosphane (2d). 2d was pre-
pared from Cy2PH‚BH3 and (o-Tol)2PCl using the method described
for 2a. Recrystallization from methanol gave white crystalline solid
2d, which was dried in vacuo (2.42 g, 5.90 mmol, 84%). NMR
1,1,2,2-Tetra-tert-butyldiphosphane (1c).26 1c was prepared
from But2PH and But2PCl using the method described for 1a.
Recrystallization from methanol gave white crystalline solid 1c,
which was dried in vacuo (0.30 g, 1.03 mmol, 30%). NMR data:
31P (CDCl3) δ 40.6 (s); 1H (300 MHz, CDCl3) δ 1.31 (36H, t, J(PH)
6.2 Hz, CCH3); 13C (CDCl3) δ 34. 8 (s, CCH3), 33.0 (t, J(PC) 9
Hz, CCH3); MS (ESI) m/z 291 (MH+); HRMS (ESI) calcd for
C16H37P2 291.2376, found 291.2365.
1
data: 31P (CDCl3) δ -6.2 (d, J(PP) 197 Hz, PCy2), -46.5 (d,
1J(PP) 197 Hz, P(o-Tol)2); 1H (CDCl3) δ 7.77-7.69 (2H, m, CH),
7.20-7.28 (6H, m, CH), 2.45 (6H, s, CCH3), 1.82 (2H, d, CH,
2J(PH) 8.0 Hz), 1.74-1.54 (10H, m, CH2), 1.32-1.03 (10H, m,
CH2); 13C (CDCl3) with the aid of DEPT 135 δ 142.4 (dd, 2J(PC)
26 Hz, 3J(PC) 2 Hz, CCH3), 136.1 (dd, 1J(PC) 21 Hz, J(PC) 7 Hz,
ipso-C), 135.0 (d, J(PC) 17 Hz, CH), 129.9 (d, J(PC) 5 Hz, CH),
128.2 (s, CH), 125.7 (s, CH), 33.3 (dd, J(PC) 20 Hz, J(PC) 11 Hz,
CH), 32.6 (dd, J(PC) 15 Hz, J(PC) 8 Hz, CH2), 31.8 (dd, J(PC) 10
Hz, J(PC) 5 Hz, CH2), 27.8 (d, J(PC) 11 Hz, CH2), 27.5 (d, J(PC)
9 Hz, CH2), 26.3 (s, CH2), 21.6 (d, 3J(PC) 21 Hz, CCH3); MS (ESI)
m/z 427 ((M + O) H+); HRMS (ESI) calcd for the monoxide 2d,
C26H37OP2, 427.2323, found 427.2314.
1,1-Di-tert-butyl-2,2-diphenyldiphosphane (2a). To a solution
of But2PH‚BH3 (1.53 g, 9.55 mmol) (prepared from But2PH and
1.1 equiv of BH3‚THF) in THF (20 cm3) was added dropwise
n-BuLi (1.6 M solution in hexanes, 6.56 cm3, 10.50 mmol) at
-78 °C. After 30 min, the solution was allowed to warm to room
temperature, and the solution was then stirred for a further 2 h.
The resulting solution was then added dropwise to a cooled
(-78 °C) solution of Ph2PCl (1.77 cm3, 2.11 g, 9.55 mmol) in THF
(10 cm3), and then the mixture was allowed to warm to room
temperature and stirred for 16 h. Et2NH (4.93 cm3, 3.49 g, 47.73
mmol) was then added and the solution stirred for a further 16 h.
The solvent was removed in vacuo, leaving an oily, white solid.
Recrystallization from hot methanol (20 cm3) gave white solid 2a,
which was dried in vacuo (1.36 g, 4.13 mmol, 43%). NMR data:
1,1-Dicyclohexyl-2,2-di-tert-butyl-diphosphane (2e). 2e was
prepared from But2PH‚BH3 and Cy2PCl using the method described
for 2a. Recrystallization from methanol gave white crystalline solid
2e, which was dried in vacuo (0.96 g, 2.80 mmol, 65%). NMR
data: 31P (CDCl3) δ 22.9 (d, 1J(PP) 395 Hz, PBut2), -2.2 (d, 1J(PP)
395 Hz, PCy2); 1H (CDCl3) δ 2.10 (1H, s, CH), 1.95 (1H, s, CH),
1.89-1.56 (8H, m, CH2), 1.47-1.11 (12H, m, CH2), 1.26 (18H, d,
J(PH) 11.72 Hz, CCH3); 13C (CDCl3) with the aid of DEPT 135 δ
34.7 (dd, J(PC) 5 Hz, 1J(PC) 29 Hz, CCH3), 33.9 (dd, J(PC) 7 Hz,
1
1
31P (CDCl3) δ 34.3 (d, J(PP) 250 Hz, PBut2), -25.7 (d, J(PP)
1
250 Hz, PPh2); H (CDCl3) δ 7.81 (4H, s, CH), 7.26 (6H, s, CH),
3
2
J(PC) 14 Hz, CH2), 32.5 (dd, J(PC) 5 Hz, J(PC) 13 Hz, CCH3),
32.2 (dd, J(PC) 5 Hz, J(PC) 22 Hz, CH), 27.7 (d, J(PC) 11 Hz,
CH2), 26.4 (s, CH2); MS (ESI) m/z 359 ((M + O) H+); HRMS
(ESI) calcd for C20H41OP2 359.2643, found 359.2627.
1.15 (18H, d, J(PH) 10.3 Hz, CCH3); 13C (CDCl3) with the aid of
DEPT-135 δ 138.0 (dd, 1J(PC) 20 Hz, 2J(PC) 6 Hz, ipso-C), 135.4
(dd, J(PC) 21 Hz, J(PC) 7 Hz, CH,), 128.4 (s, CH), 128.1 (d, J(PC)
8 Hz, CH), 34.5 (dd, 1J(PC) 28 Hz, 2J(PC) 8 Hz, CCH3), 31.8 (dd,
2J(PC) 12 Hz,3J(PC) 5 Hz, CCH3); MS (ESI) m/z 347 ((M + O)
H+); HRMS (ESI) calcd for the monoxide of 2a, C20H29OP2,
347.1698, found 347.1688.
(Z)-2,3-Bis(diphenylphosphino)but-2-enedioic Acid Dimethyl
Ester (3a). To a solution of P2Ph4 (1a) (1.00 g, 2.70 mmol) in
toluene (10 cm3) was added dimethylacetylene dicarboxylate
(DMAD) (0.33 cm3, 0.38 g, 2.70 mmol), and this rapidly produced
a deep red solution. 31P NMR indicated that the P-P bonded species
had cleanly and selectively added to the alkyne. The solvent was
removed under reduced pressure, and the resulting oil was dissolved
in Et2O. Yellow crystals of 3a formed upon cooling the solution to
-10 °C in a freezer, and these were filtered off, washed in Et2O,
and dried in vacuo to give a yellow crystalline powder of 3a (0.50
1,1-Di-tert-butyl-2,2-di-o-tolyldiphosphane (2b). 2b was pre-
pared from But2PH‚BH3 and (o-Tol)2PCl using the method described
for 2a. Recrystallization from methanol gave white crystalline solid
2b, which was dried in vacuo (5.24 g, 14.61 mmol, 91%). NMR
data: 31P (CDCl3) δ 32.4 (d, 1J(PP) 203 Hz, PBut2), -50.6 (d, 1J(PP)
203 Hz, P(o-Tol)2); 1H (CDCl3) δ 8.08-7.98 (2H, m, CH), 7.19-
3
6.95 (6H, m, CH), 2.54 (6H, s, CCH3), 1.12 (18H, d, J(PH) 10.6
1
g, 0.97 mmol, 36%). NMR data: 31P (CDCl3) δ -11.9 (s); H
(CDCl3) δ 7.38 (8H, m, CH), 7.26 (12H, m, CH) 3.22 (6H, s, CH3);
13C (CDCl3) with the aid of DEPT 135 δ 166.4 (m, CdO), 150.3
(s, CdC), 134.3 (t, J(PC) 2 Hz, ipso-C), 133.8 (t, J(PC) 11 Hz,
CH), 129.0 (s, CH), 128.2 (t, J(PC) 4 Hz, CH), 51.6 (s, OCH3);
MS (ESI) m/z 513 (MH+); HRMS (ESI) calcd for C30H27O4P2
513.1389, found 513.1379.
(24) Dashti-Mommertz, A.; Neumuller, B. Z. Anorg. Allg. Chem. 1999,
625, 954.
(25) Richter, R.; Kaiser, J.; Sieler, J.; Hartung, H.; Peter, C. Acta
Crystallogr. 1977, B33, 1887.
(26) (a) Aime, S.; Harris, R. K.; McVicker, E. M. J. Chem. Soc., Chem.
Commun. 1974, 251, 426. (b) Harlan, C. J.; Jones, R. A.; Koschmieder, S.
U.; Nunn, C. M. Polyhedron. 1990, 9, 669.

Stereospecific Diphosphination of ActiVated Acetylenes
Organometallics, Vol. 25, No. 25, 2006 5943
(Z)-2,3-Bis(dicyclohexylphosphino)but-2-enedioic Acid Dim-
ethyl Ester (3b). 3b was prepared from P2Cy4 (1b) and DMAD
using the method described for 3a. Isolated, crystalline 3b was
obtained in only 16% yield, but 3b can be generated quantitatively
in situ (as shown by 31P NMR) and used for further reactions. NMR
CDCl3) δ 3.85 (s, 6H, CH3), 1.98-1.58 (24H, m, CH/CH2), 1.45-
1.12 (20H, m, CH/CH2); 13C (75 MHz, CDCl3) δ 164.5 (m, Cd
O), 151.6 (m, CdC), 53.5 (s, OCH3), 35. 2 (d, J(PC) 31 Hz, CH2),
31.1 (s, CH2), 29.0 (m, CH), 27.1 (m, CH2), 25.9 (s, CH2); MS
(EI) m/z 802 (M+), 684 (M+ - 2 CO2Me); IR ν(CdO) 1736 cm-1
.
1
data: 31P (CDCl3) δ -5.6 (s); H (300 MHz, CDCl3) δ 3.72 (6H,
Anal. (calc for 8b‚1/3CHCl3): C, 43.28 (43.25); H, 5.97 (6.02).
This complex was also characterized by X-ray crystallography as
a chloroform solvate.
s, CH3), 1.94-1.56 (24H, m, CH/CH2) 1.41-1.08 (20H, m, CH/
CH2); 13C (75 MHz, CDCl3) δ 168.4 (s, CdO), 153.2 (s, CdC),
52.0 (s, OCH3), 36.0 (t, J(PC) 6 Hz, CH2), 30.9 (dt, J(PC) 12 Hz,
CH), 27.3 (dt, J(PC) 21 Hz, CH2), 26.4 (s, CH2); MS (ESI) m/z
537(MH+); HRMS (ESI) calcd for C30H51O4P2 537.3262, found
537.3257. Anal. (calc): C, 69.87 (67.14); H, 9.44 (9.39).
[PtCl2(4a)] (8c). 8c was prepared from ligand 4a and [PtCl2-
(1,5-cod)] using the method described for 8a, giving an off-white
solid (0.147 g, 0.168 mmol, 55%). NMR data: 31P (CDCl3) δ 97.9
1
1
1
(s, J(PtP) 3704 Hz, PBut2), 43.1 (s, J(PtP) 3534 Hz, PPh2); H
(CDCl3) δ 7.81 (4H, m, CH), 7.55 (2H, m, CH), 7.46 (4H, m, CH),
3.80 (3H, s, CH3), 3.53 (3H, s, CH3), 1.63 (18H, d, CH3); 13C
(CDCl3) δ 134.3 (d, J(PC) 11 Hz, CH), 132.6 (s, CH), 128.7 (d,
J(PC) 12 Hz, CH), 125.6 (d, 1J(PC) 70 Hz, ipso-C), 53.8 (s, OCH3),
(Z)-2-(Di-tert-butylphosphino)-3-(diphenylphosphino)but-2-
enedioic Acid Dimethyl Ester (4a). To a solution of But2P-PPh2
(2a) (0.10 g, 0.30 mmol) in toluene (5 cm3) was added DMAD
(0.0 4 cm3, 0.045 g, 0. 30 mmol), and this rapidly resulted in a
deep red solution. 31P NMR indicated that the P-P bonded species
had cleanly and selectively added to the alkyne by the presence of
one pair of doublets. The product 4a thus generated was used in
1
53.3 (s, OCH3) 40.6 (d, J(PC) 21 Hz, CCH3), 30.4 (m, CCH3);
MS (EI) m/z 738 (M+), 701 (M+ - Cl), 644 (M+ - Cl - CO2-
Me), 608 (M+ - 2Cl - CO2Me); IR ν(CdO) 1744 cm-1. Anal.
(calc for 8c‚CH2Cl2): C, 38.58 (39.37); H, 3.80 (4.37).
3
situ. NMR data: 31P (CDCl3) δ 30.4 (d, J(PP) 182 Hz, PBut2),
3
-11.3 (d, J(PP) 182 Hz, PPh2).
[PtCl2(4c)] (8d). 8d was prepared from ligand 4c and [PtCl2-
(1,5-cod)] using the method described for 8a, giving a white solid
(0.164 g, 0.207 mmol, 77%). NMR data: 31P (CDCl3) δ 71.3 (s,
1J(PtP) 3544 Hz, PCy2), 47.5 (s, 1J(PtP) 3652 Hz, PPh2); 1H
(CDCl3): δ 7.84-7.73 (4H, m, CH), 7.58-7.51 (2H, m, CH),
7.50-7.42 (4H, m, CH), 3.88 (3H, s, CH3), 3.53 (3H, s, CH3),
(Z)-2-(Di-tert-butylphosphino)-3-(di-o-tolylphosphino)but-2-
enedioic Acid Dimethyl Ester (4b). 4b was prepared from But2P-
P(o-Tol)2 (2b) and DMAD by the same method described for 4a
3
and used in situ. NMR data: 31P (CDCl3) δ 31.8 (d, J(PP) 181
3
Hz, PBut2), -27.1 (d, J(PP) 181 Hz, P(o-Tol)2).
1.94-1.65 (12H, m, CH/CH2), 1.45-1.17 (10H, m, CH/CH2); 13
C
(Z)-2-(Dicyclohexylphosphino)-3-(diphenylphosphino)but-2-
enedioic Acid Dimethyl Ester (4c). 4c was prepared from Cy2P-
PPh2 (2c) and DMAD by the method described for 4a and used in
(CDCl3) δ 134.1 (d, J(PC) 12 Hz, CH), 132.6 (s, CH), 128.7 (d,
J(PC) 12 Hz, CH), 125.7 (d, 1J(PC) 68 Hz, ipso-C), 53.7 (s, OCH3),
53.2 (s, OCH3), 34.8 (d, 1J(PC) 30 Hz, CH), 31.0 (s, CH2), 28.4 (s,
CH2), 26.9 (dd, J(PC) 8.5 Hz, J(PC) 13 Hz), 25.9 (s); MS (ESI)
m/z 813 ((M + Na) H+), 755 ((M - Cl) H+). Anal. (calc for 8d‚0.5
CH2Cl2) (calc): C, 43.68 (43.98); H, 4.94 (4.72). This complex
was also characterized by X-ray crystallography as the dichlo-
romethane solvate.
3
situ. NMR data: 31P (CDCl3) δ -3.7 (d, J(PP) 167 Hz, PCy2),
3
-10.7 (d, J(PP) 167 Hz, PPh2).
(Z)-2-(Dicyclohexylphosphino)-3-(di-o-tolylphosphino)but-2-
enedioic Acid Dimethyl Ester (4d). 4d was prepared from Cy2P-
P(o-Tol)2 (2d) and DMAD by the method described for 4a and
3
used in situ. NMR data: 31P (CDCl3) δ -2.7 (d, J(PP) 172 Hz,
3
PCy2), -25.3 (d, J(PP) 172 Hz, P(o-Tol)2).
[PtCl2(4d)] (8e). 8e was prepared from ligand 4d and [PtCl2-
(1,5-cod)] using the method described for 8a, giving a white solid
(0.077 g, 0.094 mmol, 40%). NMR data: 31P (CDCl3): δ 67.0 (s,
(Z)-3-(Di-tert-butylphosphino)-2-(diphenylphosphino)acryl-
ic Acid Methyl Ester (5a). To a solution of But2P-PPh2 (2a) (0.308
g, 0. 93 mmol) in toluene (5 cm3) was added methyl propiolate
(0.08 cm3, 0.078 g, 0.67 mmol), which resulted in a deep brown
solution. 31P NMR indicated that the P-P bonded species had
cleanly and selectively added to the alkyne by the presence of two
doublets. The product 5a thus generated was used in situ. NMR
data: 31P (CDCl3) δ 8.5 (d, 3J(PP) 129 Hz, PBut2), -11.6 (d, 3J(PP)
129 Hz, PPh2).
1J(PtP) 3504 Hz, PCy2), 44.3 (s, J(PtP) 3721 Hz, P(o-Tol)2); H
(CDCl3): δ 7.63 (1H, q, J(HH) 7.7 Hz, CH), 7.52-7.38 (3H, m,
CH), 7.34-7.16 (4H, m, CH), 3.86 (3H, s, OCH3), 3.46 (3H, s,
OCH3), 2.67 (6H, d, J(PH) 10.3 Hz, CCH3,), 2.22 (1H, s, CH),
2.11 (1H, s, CH), 1.96-0.90 (20H, m, CH2); 13C (CDCl3) δ 143.4
(dd, 4J(PC) 10 Hz, 1J(PC) 40 Hz, ipso-C), 136.2 (d, J(PC) 14 Hz,
CH), 134.6 (d, J(PC) 18 Hz, CH), 132.5 (t, J(PC) 34 Hz, CH),
125.7 (t, J(PC) 12 Hz, CH), 53.6 (s, OCH3), 53.3 (s, OCH3), 35.2
(d, J(PC) 24 Hz, CH), 28.4 (m, CH2), 26.8 (m, CH2), 25.9 (d, J(PC)
1
1
(Z)-3-(Di-tert-butylphosphino)-2-(di-o-tolylphosphino)acryl-
ic Acid Methyl Ester (5b). 5b was prepared from But2P-PTol2
(2b) and methyl propiolate by the method described for 5a and
used in situ. 31P (CDCl3): δ 9.3 (d, 3J(PP) 124 Hz, PBut2), -26.9
3
3
18 Hz, CH2), 24.5 (d, J(PC) 6 Hz, CCH3), 23.5 (d, J(PC) 6 Hz,
CCH3); MS (EI) m/z 781 (M+ - Cl); IR ν(CdO) 1737 cm-1. Anal.
(calc for 8e‚0.5CH2Cl2): C, 45.84 (45.33); H, 5.10 (5.03).
3
(d, J(PP) 124 Hz, PTol2).
[PtCl2(5a)] (8f). 8f was prepared from ligand 5a and [PtCl2-
(1,5-cod)] using the method described for 8a, giving a gray solid
(0.101 g, 0.149 mmol, 48%). NMR data: 31P (CDCl3) δ 70.0 (s,
1J(PtP) 3619 Hz, PBut2), 45.2 (s, 1J(PtP) 3650 Hz, PPh2); 1H
(CDCl3) δ 7.77 (4H, m, CH), 7.35 (6H, m, CH), 5.22 (1H, s, Cd
CH), 3.60 (3H, s, OCH3), 1.47 (18H, dd, J(HH) 2.3 Hz, J(PH)
15.5 Hz, CCH3); 13C (CDCl3) δ 161.3 (d, J(PC) 23 Hz, CdO),
155.2 (dd, J(PC) 25 Hz, J(PC) 40 Hz, CdC) 134.5 (d, J(PC) 12
Hz, CH), 132.2 (s, CH), 128.5 (d, J(PC) 12 Hz, CH), 53.3 (s,
OCH3), 38.4 (d, J(PC) 26 Hz, CCH3), 30.4 (s, CCH3); MS (EI)
m/z 680 (M+), 645 (M+ - Cl); IR ν(CdO) 1727 cm-1. Anal. (calc
for 8f‚CH2Cl2): C, 38.42 (39.23); H, 4.40 (4.48).
[PdCl2(3b)] (9b). A solution of ligand 3b (0.054 g, 0.101 mmol)
in CH2Cl2 (2 cm3) was added dropwise to a solution of [PdCl2-
(NCPh)2] (0.039 g, 0.101 mmol) in CH2Cl2 (2 cm3). After 1 h the
brown solution was reduced in volume by half and Et2O (10 cm3)
added dropwise. The resulting pale orange solid 9b was washed
[PtCl2(3a)] (8a). A solution of ligand 3a (0.10 g, 0.199 mmol)
in CH2Cl2 (2 cm3) was added dropwise to a solution of [PtCl2(1,5-
cod)] (0.071 g, 0.119 mmol) in CH2Cl2 (6 cm3). After 1 h the
volume of the solution was reduced by half under vacuum. Et2O
(20 cm3) was added dropwise, and 8a precipitated out of solution
as a white solid. The solid 8a was filtered off, washed with Et2O
(3 × 10 cm3), and dried in vacuo (0.075 g, 0.096 mmol, 48%).
NMR data: 31P (CDCl3) δ 49.5 (s, 1J(PtP) 3637 Hz); MS (EI) m/z
778 (M+), 743 (M+ - Cl); IR ν(CdO) 1737 cm-1
.
[PtCl2(3b)] (8b). A solution of ligand 3b (0.035 g, 0.066 mmol)
in CH2Cl2 (2 cm3) was added dropwise to a solution of [PtCl2(1,5-
cod)] (0.025 g, 0.067 mmol) in CH2Cl2 (2 cm3). After 1 h the
volume of the solution was reduced by half under vacuum. Et2O
(10 cm3) was added dropwise, and 8b precipitated out of solution
as a white solid. The solid 8b was filtered off, washed with Et2O
(3 × 5 cm3), and dried in vacuo (0.052 g, 0.065 mmol, 70%). NMR
1
1
data: 31P (CDCl3) δ 68.4 (s, J(PtP) 3587 Hz); H (300 MHz,

5944 Organometallics, Vol. 25, No. 25, 2006
Dodds et al.
Table 6. Crystal Data
3b
8b‚CHCl3
8c‚CHCl3
8d‚CH2Cl2
9c‚CHCl3
color, habit
size/mm
empirical formula
M
yellow block
0.35 × 0.28 × 0.12
C30H50O4P2
536.64
colorless block
0.50 × 0.25 × 0.10
C31H51Cl5O4P2Pt
922
colorless plate
0.16 × 0.15 × 0.04
C27H35Cl5O4P2Pt
857.83
colorless block
0.08 × 0.08 × 0.08
C31H40Cl4O4P2Pt
875.46
colorless block
0.26 × 0.20 × 0.20
C27H35Cl5O4P2Pd
769.14
cryst syst
space group
a/Å
b/Å
triclinic
P1h
11.359(2)
11.784(2)
12.843(3)
100.44(3)
94.37(3)
115.06(3)
1508.7(7)
2
0.176
100
monoclinic
P21/n
13.2422(10)
19.2312(19)
14.6945(11)
90
94.133(8)
90
3732.4(5)
4
triclinic
P1h
monoclinic
P21/n
12.271(3)
14.619(3)
18.508(4)
90
93.40(3)
90
3314.3(12)
4
4.688
triclinic
P1h
8.844(3)
11.587(5)
17.470(7)
90.783(9)
104.471(8)
109.036(9)
1637.8(11)
2
8.8712(5)
11.6350(7)
17.5707(10)
90.801(1)
104.334(1)
108.685(1)
1655.89(17)
2
c/Å
R/deg
â/deg
γ/deg
V/Å3
Z
µ/mm-1
4.236
173
4.768
173
1.108
173
T
100
no. of reflns: total/
indep/Rint
17 343/6908/0.0223
24 867/6245/0.0560
17 698/7554/0.0572
22 940/7577/0.0618
17 320/7465/0.0316
final R1
0.0425
0.615, -0.365
0.0320
1.167, -1.084
0.0339
2.643, -1.648
0.0378
1.217, -1.239
0.0334
1.147, -0.892
largest peak, hole/e Å-3
and dried in vacuo (0.048 g, 0.067 mmol, 72%). NMR data: 31P
(CDCl3) δ 7.59-7.39 (4H, m, CH), 7.37-7.13 (4H, m, CH), 3.85
(3H, s, OCH3), 3.43 (3H, s, OCH3), 2.70 (6H, d, CCH3, J(PH) 15.7
Hz), 2.29 (1H, s, CH), 2.08 (1H, s, CH), 1.91-1.47 (12H, m, CH2),
1.42-1.03 (8H, m, CH2); 13C NMR (CDCl3) δ 164.9 (dd, J(PC) 3
Hz, J(PC) 30 Hz, CdO), 163.4 (dd, J(PC) 3 Hz, J(PC) 25 Hz,
CdO), 154.1 (dd, J(PC) 28 Hz, J(PC) 35 Hz, CdC), 148.9 (dd,
J(PC) 23 Hz, J(PC) 34 Hz, CdC), 143.6 (dd, J(PC) 11 Hz, J(PC)
60 Hz, CCH3), 135.7 (d, J(PC) 13 Hz, CH), 134.4 (d, J(PC) 9 Hz,
CH), 133.0 (s, CH), 132.6 (m, CH), 132.0 (d, J(PC) 9 Hz, CH),
125.9 (t, J(PC) 11 Hz, CH), 124.9 (dd, J(PC) 53 Hz, J(PC) 124
Hz, ipso-C), 53.6 (d, CCH3, J(PC) 46 Hz), 36.8 (t, CH), 28.8 (dd,
CH2), 27.0 (m, CH2), 25.8 (d, CH2, J(PC) 19 Hz), 25.0 (d, CH2,
J(PC) 7 Hz), 23.8 (d, CH2, J(PC) 9 Hz); MS (ESI) m/z 753 ((M +
Na) H+), 695 ((M - Cl) H+). Anal. (calc for 9e‚2CH2Cl2): C,
45.69 (45.38); H, 5.07 (5.15).
[PdCl2(5a)] (9f). 9f was prepared from ligand 5a and [PdCl2-
(NCPh)2] using the method described for 9b, giving a green solid
(0.108 g, 0.183 mmol, 59%). NMR data: 31P (CDCl3) δ 96.3 (d,
2J(PP) 21 Hz, PBut2), 67.8 (d, 2J(PP) 21 Hz, PPh2); 1H (CDCl3) δ
7.88 (4H, m, CH), 7.46 (6H, m, CH), 3.68 (3H, s, OCH3), 1.58
(18H, d, J(PH) 15.7 Hz, CCH3); 13C (CDCl3) δ 154.6 (s, CdC)
134.5 (d, J(PC) 12 Hz, CH), 132.3 (d, J(PC) 2 Hz, CH), 128.6 (d,
J(PC) 12 Hz, CH), 127.1 (d, J(PC) 60 Hz, ipso-C), 53.4 (s, OCH3),
39.5 (d, J(PC) 18 Hz, CCH3), 30.3 (d, J(PC) 4 Hz, CCH3); MS
(EI) m/z 557 (M+ - Cl); IR ν(CdO) 1728 cm-1. Analysis (calc
for 9f‚2CH2Cl2): C, 41.89 (41.00); H, 3.87 (4.73).
1
(CDCl3) δ 95.8 (s); H (CDCl3) δ 3.85 (6H, s, CH3), 2.22-1.02
(44H, m, CH /CH2); 13C (75 MHz, CDCl3) δ 164.4 (t, J(PC) 15
Hz, CdO), 151.0 (t, J(PC) 26 Hz, CdC), 53.7 (s, OCH3), 36.2 (t,
J(PC) 12 Hz, CH), 29.2 (d, J(PC) 17 Hz, CH2), 27.1 (s, CH2), 25.8
(s, CH2); MS (EI) m/z 679 (M+ - Cl), 596 (M+ - 2 CO2Me); IR
ν(CdO) 1736 cm-1
.
[PdCl2(3a)] (9a). 9a as a pale orange solid (0.067 g, 0.097 mmol,
52%) was prepared in a fashion similar to 9b from ligand 3a and
[PdCl2(NCPh)2]. NMR data: 31P (CDCl3) δ 71.8 (s); 1H (300 MHz,
CDCl3) δ 7.93-7.84 (8H, m, CH), 7.67-7.59 (4H, m, CH), 7.57-
7.49 (8H, m, CH), 3.56 (6H, s, CH3); MS (ESI) m/z 713 (M +
Na).
[PdCl2(4a)] (9c). 9c was prepared from ligand 4a and [PdCl2-
(NCPh)2] using the method described for 9b, giving a pale orange
solid (0.175 g, 0.269 mmol, 88%). NMR data: 31P NMR (CDCl3)
δ 126.6 (d, 2J(PP) 15 Hz, PBut2), 65.0 (d, 2J(PP) 15 Hz, PPh2); 1H
(CDCl3) δ 7.77 (4H, dd, J(HH) 7.0 Hz, J(PH) 13.0 Hz, CH), 7.50
(2H, m, CH), 7.40 (4H, m, CH), 3.74 (3H, s, OCH3), 3.45 (3H, s,
OCH3) 1.60 (18H, d, J(PH) 16.8 Hz, CH3); 13C (CDCl3) δ 165.6
(d, J(PC) 29 Hz, CdO), 163.1 (d, J(PC) 24 Hz, CdO), 153.6 (d,
J(PC) 62 Hz, CdC), 152.0 (d, J(PC) 50 Hz, CdC), 134.4 (d, J(PC)
12 Hz, CH), 132.8 (d, J(PC) 3 Hz, CH), 128.8 (d, J(PC) 13 Hz,
CH), 126.2 (d, J(PC) 54 Hz, ipso-C), 53.9 (s, OCH3), 53.3 (s,
OCH3), 41.3 (d, J(PC) 12 Hz, CCH3), 30.7 (d, J(PC) 4 Hz, CCH3);
MS (EI) m/z 615 (M+ - Cl), 599 (M+ - Cl - Me); IR ν(CdO)
1744 cm-1. Anal. (calc for 9c‚1.5(CH2Cl2)): C, 42.69 (42.50); H,
4.83 (4.80). This complex was also characterized by X-ray
crystallography.
[PdCl2(4c)] (9d). 9d was prepared from ligand 4c and [PdCl2-
(NCPh)2] using the method described for 9b, giving a pale green
solid (0.156 g, 0.223 mmol, 78%). NMR data: 31P (CDCl3) δ 98.0
(d, 2J(PP) 19 Hz, PCy2), 69.9 (d, 2J(PP) 19 Hz, PPh2); 1H (CDCl3)
δ 7.82 (4H, m, CH), 7.58 (2H, m, CH), 7.48 (4H, m, CH), 3.91
(3H, s, OCH3), 3.55 (3H, s, OCH3), 2.21 (2H, s, CH), 1.97-1.59
(12H, m, CH2), 1.53 - 1.19 (8H, m, CH2). 13C (CDCl3) δ 134.2
(d, J(PC) 12 Hz, CH), 132.7 (d, J(PC) 3 Hz, CH), 128.9 (d, J(PC)
12 Hz, CH), 126.1 (d, 1J(PC) 59 Hz, ipso-C), 53.8 (s, OCH3), 53.3
(s, OCH3), 36.0 (d, 1J(PC) 22 Hz, CH), 28.8 (d, J(PC) 12 Hz, CH2),
26.9 (d, J(PC) 13 Hz, CH2), 25.7 (s, CH2); MS (EI) m/z 665 (M+
- Cl), 584 (M+ - 2 CO2Me); IR: ν(CdO) 1736 cm-1. Anal. (calc
for 9d‚1.5(CH2Cl2)): C, 45.36 (45.62); H, 5.27 (4.98).
Crystal Structure Determinations. X-ray diffraction experi-
ments on 8d (as its dichloromethane solvate) and 3b were carried
out at 100 K on a Bruker SMART APEX diffractometer; experi-
ments on 8b, 8c, and 9c (all three as their chloroform solvates)
were carried out at 173 K on a Bruker SMART diffractometer,
using Mo KR X-radiation (λ ) 0.71073 Å). All data collections
were performed using a CCD area detector, from a single crystal
coated in paraffin oil mounted on a glass fiber. Intensities were
integrated from several series of exposures, each exposure covering
0.3° in ω. Absorption corrections were based on equivalent
reflections using SADABS V2.10,27 and structures were refined
2
against all Fo data with hydrogen atoms riding in calculated
positions using SHELXTL.28 Crystal and refinement data are given
in Table 6.
Except for 3b (described earlier), no disorder was present in the
other crystal structures, and refinements proceeded smoothly to give
the structures shown.
[PdCl2(4d)] (9e). 9e was prepared from ligand 4d and [PdCl2-
(NCPh)2] using the method described for 9b, giving a pale green
solid (0.068 g, 0.093 mmol, 39%). NMR data: 31P (CDCl3) δ 92.8
(27) Sheldrick, G. M. SADABS, Bruker-Nonius area detector scaling and
absorption correction (V2.10); University of Goettingen: Germany, 2003.
(28) Shelxtl Version 6.14; Bruker AXS, 2000-2003.
2
2
1
(d, J(PP) 17 Hz, PCy2), 63.6 (d, J(PP) 17 Hz, P(o-Tol)2); H

Stereospecific Diphosphination of ActiVated Acetylenes
Organometallics, Vol. 25, No. 25, 2006 5945
Supporting Information Available: X-ray crystal data in CIF
format for complexes 3b, 8b, 8c, 8d, and 9c are available free of
charge via the Internet at http://pubs.acs.org.
Acknowledgment. We thank Gordon Docherty (Rhodia) for
useful discussions, Rhodia for a studentship (to D.L.D.), EPSRC
for financial support, Johnson Matthey for a loan of precious
metal compounds, and The Leverhulme Trust for a Research
Fellowship (to P.G.P.).
OM060716O