Palladium and platinum complexes containing the linear tetraphosphine bis[((diphenylphosphino)ethyl)phenylphosphino]methane

Article abstract of DOI:10.1021/om0209069

The linear tetraphosphine bis [((diphenylphosphino)ethyl)phenylphosphino] methane (DPPEPM) has been prepared and separated into its meso and racemic forms. Each has been reacted with elemental sulfur, and the structure of the meso compound DPPEPM-S₄ has been determined crystallographically. The meso or racemic form of DPPEPM reacts with 2 equiv of [MCl₂(cod)] (M = Pd, Pt) or [PtR₂(cod)] (R = Me, Ph, CH₂Ph, C₆H₄Me-4) to give complexes of the form [M₂X₄(μ-DPPEPM)], in which DPPEPM acts as both a chelating and a bridging ligand. Complexes containing additional chloride bridges, [M₂R₂(μ-Cl)(μDPPEPM)]PF₆, have been prepared from DPPEPM and [PtClR(cod)] (R = Me, Ph, CH₂Ph), [PdClR(cod)] (R = Me, CH₂Ph), or [Pd₂R₂(μ-Cl)₂(AsPh₃)₂] (R = Ph, COMe), followed by TlPF₆. Chloride-bridged compounds could also be prepared by treatment of [M₂Cl₄(μ-DPPEPM)] with 1 equiv of TlPF₆. Addition of Bu₄NI to [M₂Me₂(μ-Cl)(μ-DPPEPM)]PF₆ resulted in bridge opening, and further treatment with TlPF₆ gave the corresponding iodide-bridged species. The compounds have been characterized by NMR spectroscopy and by elemental analysis or high-resolution mass spectrometry. The solid-state structures of [Pd₂Cl₄(μ-DPPEPM)] and [Pt₂Ph₄(μ-DPPEPM)] are also reported.

Full text of DOI:10.1021/om0209069

1494
Organometallics 2003, 22, 1494-1502
P a lla d iu m a n d P la tin u m Com p lexes Con ta in in g th e
Lin ea r Tetr a p h osp h in e
Bis[((d ip h en ylp h osp h in o)eth yl)p h en ylp h osp h in o]m eth a n e
Padma Nair, Gordon K. Anderson,* and Nigam P. Rath
Department of Chemistry and Biochemistry, University of MissourisSt. Louis,
8001 Natural Bridge Road, St. Louis, Missouri 63121
Received November 1, 2002
The linear tetraphosphine bis[((diphenylphosphino)ethyl)phenylphosphino]methane
(DPPEPM) has been prepared and separated into its meso and racemic forms. Each has
been reacted with elemental sulfur, and the structure of the meso compound DPPEPM-S4
has been determined crystallographically. The meso or racemic form of DPPEPM reacts
with 2 equiv of [MCl2(cod)] (M ) Pd, Pt) or [PtR2(cod)] (R ) Me, Ph, CH2Ph, C6H4Me-4) to
give complexes of the form [M2X4(µ-DPPEPM)], in which DPPEPM acts as both a chelating
and a bridging ligand. Complexes containing additional chloride bridges, [M2R2(µ-Cl)(µ-
DPPEPM)]PF6, have been prepared from DPPEPM and [PtClR(cod)] (R ) Me, Ph, CH2Ph),
[PdClR(cod)] (R ) Me, CH2Ph), or [Pd2R2(µ-Cl)2(AsPh3)2] (R ) Ph, COMe), followed by TlPF6.
Chloride-bridged compounds could also be prepared by treatment of [M2Cl4(µ-DPPEPM)]
with 1 equiv of TlPF6. Addition of Bu4NI to [M2Me2(µ-Cl)(µ-DPPEPM)]PF6 resulted in bridge
opening, and further treatment with TlPF6 gave the corresponding iodide-bridged species.
The compounds have been characterized by NMR spectroscopy and by elemental analysis
or high-resolution mass spectrometry. The solid-state structures of [Pd2Cl4(µ-DPPEPM)] and
[Pt2Ph4(µ-DPPEPM)] are also reported.
In tr od u ction
plexes.5 Indeed, we have used the [PtR(dppm-PP)-
(dppm-P)]+ cations as precursors to a range of hetero-
bimetallic derivatives.6
Bis(diphenylphosphino)methane (dppm) and related
ligands have been used extensively in the construction
of homobimetallic complexes.1 In certain cases R2PCH2-
PR2 (R ) Me, OR) ligands form bimetallic complexes of
the form [M2X4(µ-R2PCH2PR2)2], in which the bridging
phosphino groups lie cis to one another,2 but, most
commonly, the phosphino groups occupy mutually trans
sites. This is found for the side-by-side dimers [M2X2-
(µ-dppm)2] (M ) Pd, Pt)3 and the many A-frame
structures involving rhodium, iridium, palladium, and
platinum.4 One or two dppm ligands have been em-
ployed also in the synthesis of heterobimetallic com-
We have made extensive studies of A-frame complexes
of palladium and platinum. These include symmetrical
and unsymmetrical species, with bridging halides7 or
hydrides.8 The hydride-bridged species [M2R2(µ-H)(µ-
dppm)2]PF6 are stable at ambient temperature in the
solid state and in solution, and they undergo reductive
elimination of RH in solution only at elevated temper-
atures.9 It is likely that the thermal stability of these
complexes is due to the favored trans orientation of the
phosphino groups, which prevents the R and H groups
from occupying the adjacent sites needed for elimina-
tion, except perhaps transiently at high temperatures.
To increase the potential catalytic activity of the bime-
tallic systems, we sought to maintain the M2P4 unit but
to constrain the phosphino groups in mutually cis
* To whom correspondence should be addressed. E-mail:
ganderson@umsl.edu. Fax: 314-516-5342.
(1) (a) Puddephatt, R. J . Chem. Soc. Rev. 1983, 12, 99. (b) Balch, A.
L. In Homogeneous Catalysis with Metal Phosphine Complexes; Pigno-
let, L. H., Ed.; Plenum: New York, 1983; pp 167-213. (c) Balch, A. L.
Comments Inorg. Chem. 1984, 3, 51. (d) Chaudret, B.; Delavaux, B.;
Poilblanc, R. Coord. Chem. Rev. 1988, 86, 191. (e) Puddephatt, R. J .;
Manojlovic-Muir, L.; Muir, K. W. Polyhedron 1990, 9, 2767. (f)
Anderson, G. K. Adv. Organomet. Chem. 1993, 35, 1.
(2) (a) Manojlovic-Muir, L.; Muir, K. W.; Frew, A. A.; Ling, S. S. M.;
Thomson, M. A.; Puddephatt, R. J . Organometallics 1984, 3, 1637. (b)
Azam, K. A.; Ferguson, G.; Ling, S. S. M.; Parvez, M.; Puddephatt, R.
J .; Srokowski, D. Inorg. Chem. 1985, 24, 2799. (c) Manojlovic-Muir,
L.; J obe, I. R.; Maya, B. J .; Puddephatt, R. J . J . Chem. Soc., Dalton
Trans. 1987, 2117. (d) Radecka-Paryzek, W.; McLennan, A. J .; Pud-
dephatt, R. J . Inorg. Chem. 1986, 25, 3097.
(3) (a) Brown, M. P.; Puddephatt, R. J .; Rashidi, M.; Seddon, K. R.
J . Chem. Soc., Dalton Trans. 1977, 951. (b) Manojlovic-Muir, L.; Muir,
K. W.; Solomun, T. Acta Crystallogr., Sect. B 1979, 35, 1237. (c) Hunt,
C. T.; Balch, A. L. Inorg. Chem. 1982, 21, 1641.
(4) (a) Kubiak, C. P.; Eisenberg, R. J . Am. Chem. Soc. 1977, 99, 6129.
(b) Anderson, G. K.; Clark, H. C.; Davies, J . A. J . Organomet. Chem.
1981, 210, l35. (c) Cooper, S. J .; Brown, M. P.; Puddephatt, R. J . Inorg.
Chem. 1981, 20, 1374. (d) Anderson, D. J .; Kramarz, K. W.; Eisenberg,
R. Inorg. Chem. 1996, 35, 2688 and references therein.
(5) Braunstein, P.; Clerc, G.; Morise, X. Organometallics 2001, 20,
5036.
(6) (a) Xu, C.; Anderson, G. K. Inorg. Chim. Acta 1995, 228, 73. (b)
Xu, C.; Anderson, G. K.; Rath, N. P. Inorg. Chim. Acta 1997, 265, 241.
(c) Xu, C.; Anderson, G. K.; Brammer, L.; Braddock-Wilking, J .; Rath,
N. P. Organometallics 1996, 15, 3972.
(7) (a) Fallis, K. A.; Xu, C.; Anderson, G. K. Organometallics 1993,
12, 2243. (b) Stockland, R. A., J r.; Anderson, G. K.; Rath, N. P.
Organometallics 1997, 16, 5096. (c) J anka, M.; Anderson, G. K.; Rath,
N. P. Organometallics 2000, 19, 5071. (d) Stockland, R. A., J r.; J anka,
M.; Hoel, G. R.; Rath, N. P.; Anderson, G. K. Organometallics 2001,
20, 5212.
(8) (a) Xu, C.; Anderson, G. K. Organometallics 1994, 13, 3981. (b)
Xu, C.; Anderson, G. K. Organometallics 1996, 15, 1760. (c) Stockland,
R. A., J r.; Anderson, G. K.; Rath, N. P. Inorg. Chim. Acta 1997, 259,
173. (d) Stockland, R. A., J r.; Anderson, G. K.; Rath, N. P. Inorg. Chim.
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10.1021/om0209069 CCC: $25.00 © 2003 American Chemical Society
Publication on Web 03/06/2003

Pd and Pt Complexes Containing a Tetraphosphine
Organometallics, Vol. 22, No. 7, 2003 1495
dissolved in ether (20 mL) and kept at -40 °C overnight. The
ether was evaporated to give a sticky solid. This was washed
several times with small amounts of cold methanol to give
DPPEPM (4.89 g, 75%) as a 1:1 mixture of meso and rac
diastereomers.
Sep a r a t ion of t h e m eso a n d r a c Dia st er eom er s of
DP P EP M. A 1:1 mixture of the meso and rac diastereomers
of DPPEPM (3.0 g) was stirred in benzene/MeOH (1:4) for
several hours, leading to the exclusive extraction of the rac
diastereomer. The less soluble meso diastereomer was filtered
off and dried under vacuum (1.32 g, 88%). The rac form was
isolated by removal of the solvents and crystallized from
CH2Cl2/EtOH (0.97 g, 65%).
positions. We decided to investigate the chemistry of
palladium and platinum complexes of the linear tetra-
phosphine ligands reported by Stanley,10 in which a pair
of phosphino groups can form a five-membered chelate
ring with each metal center and the two square-planar
units are held together by a single methylene bridge.
This is in contrast to the all-ethylene-bridged tetra-
phosphine reported by Bru¨ggeller, which is capable of
wrapping round a square-planar platinum(II) center.11
Whereas much of Stanley’s work has focused on the
ethyl-substituted derivative Et2PCH2CH2PPhCH2-
PPhCH2CH2PEt2, eLTTP, we chose to make use of the
all-phenyl analogue, Ph2PCH2CH2PPhCH2PPhCH2CH2-
PPh2 (bis[((diphenylphosphino)ethyl)phenylphosphino]-
methane, DPPEPM). A preliminary report of the syn-
thesis and structures of a series of platinum complexes
of this ligand has appeared.12
meso form: 31P{1H} NMR (CDCl3) δ(P) -25.5 (dd, J PP ) 13,
18 Hz, 2P, internal), -12.0 (dd, J PP ) 13, 18 Hz, 2P, external);
1H NMR (CDCl3): δ(H) 1.80-2.11 (br m, PCH2CH2P), 2.32 (br,
PCH2P), 7.25-7.40 (m, C6H5).
rac form: 31P{1H} NMR (CDCl3): δ(P) -24.8 (dd, J PP ) 13,
17 Hz, 2P, internal), -11.9 (dd, J PP ) 13, 17 Hz, 2P, external);
1H NMR (CDCl3): δ(H) 1.63-1.84 (br m, PCH2CH2P), 2.04 (t,
2J PH ) 12 Hz, PCH2P), 7.25-7.34 (m, C6H5).
Exp er im en ta l Section
Syn th esis of m eso-DP P EP M-S4. A solution of meso-
DPPEPM (0.22 g, 0.34 mmol) in CH2Cl2 (10 mL) was treated
with elemental sulfur (0.44 g, 0.17 mmol), and the mixture
was allowed to react for 1 h. It was then passed through a
silica gel column, and the column was eluted with more CH2-
Cl2. The fractions were combined, and the solvent was removed
in vacuo. The product was redissolved in CH2Cl2, and addition
of pentane gave the product as a white powder. Crystals
suitable for X-ray diffraction were grown by slow evaporation
of a CDCl3 solution. 31P{1H} NMR (CDCl3): δ(P) 41.5 (m, 2P,
internal), 44.7 (m, 2P, external). The spectrum was simulated
All reactions were carried out under an atmosphere of argon.
All the solvents were distilled prior to use. Neutral alumina
and Hyflo Supercel were obtained from Fisher and Fluka,
respectively. [PtCl2(cod)],13 [PdCl2(cod)],14 [PtR2(cod)] (R ) Me,
Ph, CH2Ph, 2-tolyl), [PtClR(cod)] (R ) Me, Ph, CH2Ph),15,16 and
[PdClMe(cod)]17 were prepared as reported previously. 1H and
31P{1H} NMR spectra were recorded on a Bruker ARX-500 or
Avance 300 instrument or a Varian Unity Plus 300 or XL-300
spectrometer. Infrared spectra were recorded on a Perkin-
Elmer 1600 series FT-IR spectrometer. High-resolution mass
spectra were obtained in FAB mode, on a J EOL M Station-
J MS700 instrument, using nitrobenzyl alcohol (NBA) as
solvent. Microanalyses were performed by Atlantic Microlab,
Inc., Norcross, GA.
Syn th esis of P h HP CH2P HP h .18 Phenylphosphine (5.0 g,
0.045 mol) and CH2Cl2 (1.95 g, 0.023 mol) were added to a
flask containing DMF (55 mL). The mixture was cooled in an
ice bath. Then 7 mL of aqueous KOH (9.35 g in 7.5 mL of
water) was added dropwise over a period of 1 h. As the addition
proceeded, the solution gradually turned deep yellow. The
solution was stirred for 7-12 h. During this time the solution
became colorless, with a white solid sticking to the sides of
the flask. Water (36.5 mL) was added, and a cloud of hydrogen
gas was produced. The resulting mixture was then washed
with pentane (3 × 50 mL). The solvent was evaporated under
reduced pressure to give the product as a clear, viscous liquid
(2.55 g, 48%). The product consisted of a mixture of meso and
rac diastereomers. 31P{1H} NMR (C6D6): δ(P) -54.8, -53.9.
Syn th esis of DP P EP M. Bis(phenylphosphino)methane
(2.3 g, 0.010 mol), vinyldiphenylphosphine (4.26 g, 0.020 mol),
and cyclohexane (40 mL) were added to a flask fitted with a
bent tube containing 2,2′-azobis(isobutyronitrile) (AIBN; 0.03
g). A reflux condenser was attached to the flask, and the AIBN
was tipped into the solution. The reaction mixture was refluxed
overnight and then cooled. The solvent was evaporated under
reduced pressure to leave a viscous, colorless liquid. This was
successfully using the following coupling constants: 3J P1-P2
)
5
5
2
3J P3-P4 ) 65.4 Hz, J P1-P3 ) J P2-P4 ) 0.5 Hz, J P2-P3 ) 13.2
1
Hz. H NMR (CDCl3): δ(H) 2.00-2.06, 2.32-2.38, 2.63-2.69,
2.83-2.89 (br m, 8H, PCH2CH2P), 2.99-3.08 (two overlapping
pseudoquartets, J HH ) 2J PH ) 13 Hz, PCH2P), 7.30-7.72 (m,
2
C6H5).
Syn th esis of r a c-DP P EP M-S4. This complex was prepared
similarly and obtained in 92% yield. 31P{1H} NMR (CDCl3):
δ(P) 41.8 (m, 2P, internal), 44.8 (m, 2P, external). The
spectrum was simulated successfully using the following
3
5
coupling constants: J P1-P2
) )
3J P3-P4 ) 65.4 Hz, J P1-P3
5J P2-P4 ) 0.5 Hz, J P2-P3 ) 14.2 Hz. 1H NMR (CDCl3): δ(H)
2.07-2.13, 2.70-2.75, 2.82-2.87 (br m, 8H, PCH2CH2P), 2.97-
3.08 (t, J PH ) 13 Hz, 2H, PCH2P), 7.37-7.80 (m, C6H5).
2
2
Syn th esis of [P d 2Cl4(µ-m eso-DP P EP M)]. meso-DPPEPM
(0.12 g, 0.18 mmol) was dissolved in CH2Cl2 (15 mL), and
[PdCl2(cod)] (0.10 g, 0.36 mmol) was added. The solution was
stirred for 15 min, and then the solvent was removed under
reduced pressure. The residue was washed several times with
pentane and dried in vacuo. The product was isolated as a light
yellow powder (0.122 g, 67%). Anal. Calcd for C41H40Cl4P4Pd2:
C, 48.69; H, 3.98. Found: C, 48.72; H, 4.15. 31P{1H} NMR
(CDCl3): δ(P) 61.8 (internal P), 62.6 (external P). 1H NMR
(CDCl3): δ(H) 1.67-2.02, 2.49-2.70, 3.17-3.37 (PCH2CH2P),
2
2
3.87 (q, J HH
) )
2J PH ) 14 Hz, 1H, PCH2P), 4.33 (q, J HH
2J PH ) 12 Hz, 1H, PCH2P), 7.31-8.34 (m, C6H5). Crystals
suitable for an X-ray diffraction study were grown by slow
evaporation of a CDCl3 solution.
(10) Broussard, M. E.; J uma, B.; Train, S. G.; Peng, W.-J .; Laneman,
S. A.; Stanley, G. G. Science 1993, 260, 1784.
(11) (a) Bru¨ggeller, P. Inorg. Chim. Acta 1989, 155, 45. (b) Bru¨ggeller,
P.; Hu¨bner, T. Acta Crystallogr., Sect. C 1990, 46, 388.
(12) Nair, P.; Anderson, G. K.; Rath, N. P. Inorg. Chem. Commun.
2002, 5, 563.
(13) Chatt, J .; Vallarino, L. M.; Venanzi, M. J . Chem. Soc. 1957,
2496.
(14) Bailey, C. T.; Lisenskey, G. C. J . Chem. Educ. 1985, 62, 896.
(15) J anka, M.; Anderson. G. K.; Rath, N. P.; Organometallics 2000,
19, 5071.
Syn th esis of [P d 2Cl4(µ-r a c-DP P EP M)]. This complex was
prepared similarly and obtained in 63% yield. Anal. Calcd for
C
41H40Cl4P4Pd2: C, 48.69; H, 3.98. Found: C, 48.04; H, 4.11.
31P{1H} NMR (CDCl3): δ(P) 64.3 (internal P), 67.4 (external
P). 1H NMR (CDCl3): δ(H) 2.79, 3.20, 3.29, 3.46 (PCH2CH2P),
4.02 (t, J PH ) 14 Hz, PCH2P), 7.16-8.13 (m, C6H5).
2
Syn th esis of [P t2Cl4(µ-m eso-DP P EP M)]. meso-DPPEPM
(0.26 g, 0.40 mmol) was dissolved in CH2Cl2 (25 mL), and
[PtCl2(cod)] (0.30 g, 0.80 mmol) was added. The solution was
stirred for 15 min, and the solvent was removed under reduced
pressure. The residue was washed several times with pentane,
(16) Clark, H. C.; Manzer, L. E. J . Organomet. Chem. 1973, 59, 411.
(17) Ladipo, F. T.; Anderson, G. K. Organometallics 1994, 13, 303.
(18) Laneman, S. A.; Fronczek, F. R.; Stanley. G. G. Inorg. Chem.
1989, 28, 1872.

1496 Organometallics, Vol. 22, No. 7, 2003
Nair et al.
and the product was isolated as a colorless powder (0.301 g,
63%). Anal. Calcd for C41H40Cl4P4Pt2: C, 41.42; H, 3.92.
Found: C, 41.67; H, 3.52. 31P{1H} NMR (CDCl3): δ(P) 37.6 (s,
CH2P, PtCH2Ph), 2.65-2.88 (br m, PCH2P), 6.22-6.82 (m,
C6H5), 7.08-7.31 (m, PPh2).
Syn th esis of [P t2(CH2P h )4(µ-r a c-DP P EP M)]. This com-
2
1
1J PtP ) 3575 Hz, J PP ) 22 Hz, internal P), 38.7 (s, J PtP
)
plex was prepared similarly and obtained in 51% yield. 31P-
3680 Hz, external P). 1H NMR (CDCl3): δ(H) 2.06-3.08 (m,
2
1
{1H} NMR (CDCl3): δ(P) 34.9 (d, J PP ) 10 Hz, J PtP ) 1855
Hz, internal P), 43.5 (d, 2J PP ) 10 Hz, 1J PtP ) 1869 Hz, external
P). 1H NMR (CDCl3): δ(H) 1.42-1.50, 1.60-1.65, 2.36-2.91
2
2
PCH2CH2P), 3.92 (q, J HH ) J PH ) 14 Hz, PCH2P), 4.45 (q,
2
2J HH ) J PH ) 13 Hz, PCH2P), 7.31-8.34 (m, C6H5).
2
Syn th esis of [P t2Cl4(µ-r a c-DP P EP M)]. This complex was
prepared similarly and obtained in 61% yield. Anal. Calcd for
(br m, PCH2CH2P, PtCH2Ph), 3.24 (t, J PH ) 12 Hz, PCH2P),
6.56-6.93 (m, C6H5) 7.05-7.40 (PPh2).
C
41H40Cl4P4Pt2: C, 41.42; H, 3.92. Found: C, 42.41; H, 3.58.
Syn th esis of [P t2(C6H4CH3-4)4(µ-m eso-DP P EP M)]. meso-
DPPEPM (0.080 g, 0.12 mmol) was dissolved in CH2Cl2 (15
mL), and [Pt(C6H5CH3-4)2(cod)] (0.118 g, 0.24 mmol) was
added. The solution was stirred for 30 min, and then the
solvent was removed under reduced pressure. The residue was
washed several times with pentane, and the product was
isolated as a yellow powder (0.101 g, 59%). 31P{1H} NMR
31P{1H} NMR (CDCl3): δ(P) 40.0 (1J PtP ) 3556 Hz, internal
P), 41.9 (1J PtP ) 3558 Hz, external P). H NMR (CDCl3): δ(H)
2.06-3.08 (m, PCH2CH2P), 4.14 (t, J PH ) 14 Hz, PCH2P),
7.36-8.64 (m, C6H5).
1
2
Syn th esis of [P t2Me4(µ-m eso-DP P EP M)]. meso-DPPEPM
(0.11 g, 0.17 mmol) was dissolved in CH2Cl2 (15 mL), and
[PtMe2(cod)] (0.11 g, 0.33 mmol) was added. The solution was
stirred for 15 min, and then the solvent was removed under
reduced pressure. The residue was washed several times with
pentane, and the product was isolated as an off-white powder
(0.10 g, 55%). Anal. Calcd for C45H52P4Pt2: C, 48.86; H, 4.74.
Found: C, 48.95; H, 4.66. 31P{1H} NMR (CDCl3): δ(P) 37.9
1
3
2
(CDCl3): δ(P) 36.9 (br s, J PtP ) 1703 Hz, J PtP ) 37 Hz, J PP
2
1
) 24 Hz, internal P), 40.0 (d, J PP ) 7 Hz, J PtP ) 1690 Hz,
external P). H NMR (CDCl3): δ(H) 2.09 (s, 6H, CH3), 2.15 (s,
1
6H, CH3), 1.58-1.73, 1.81-1.87, 2.03-2.08 (br m, PCH2CH2P),
3
2.58, 3.45 (br m, PCH2P), 6.61 (d, J HH ) 7 Hz, 4H, CH-2,6),
3
3
6.83, (d, J HH ) 7 Hz, 4H, CH-2,6), 7.01 (d, J HH ) 7 Hz, 4H,
1
3
2
3
(br s, J PtP ) 1737 Hz, J PtP ) 44 Hz, J PP ) 24 Hz, internal
CH-3,5), 7.07 (d, J HH ) 7 Hz, 4H, CH-3,5), 7.18-7.41 (m,
P), 46.8 (d, 2J PP ) 6 Hz, 1J PtP ) 1806 Hz, external P). 1H NMR
(CDCl3): δ(H) 0.64 (d, J PH ) 8 Hz, J PtH ) 70 Hz, CH3), 0.76
C6H5). HRMS (CsI added): exact mass calcd for
C H68P4-
69
12
3
1
Cs195Pt2+, 1543.2622; obsd, 1543.2593.
3
1
(d, J PH ) 8 Hz, J PtH ) 70 Hz, CH3), 1.40-1.45, 1.55-1.75,
1.77-2.06 (br m, PCH2CH2P), 2.95 (br m, PCH2P), 3.41 (br m,
PCH2P), 6.87-7.86 (m, C6H5).1H{31P} NMR (CDCl3): δ(H) 0.55
(s, J PtH ) 70 Hz, CH3), 0.67 (s, J PtH ) 70 Hz, CH3), 1.47-
1.53, 1.60-1.65, 2.00-2.06, 2.19-2.25 (br m, PCH2CH2P), 2.89
(d, 2J HH ) 15 Hz, PCH2P), 3.37 (d, 2J HH ) 15 Hz, PCH2P), 6.90-
7.58 (m, C6H5).
Syn t h esis of [P t2(C6H4CH3-4)4(µ-r a c-DP P E P M)]. This
complex was prepared similarly and obtained in 51% yield.
31P{1H} NMR (CDCl3): δ(P) 40.1 (d, 2J PP ) 7 Hz, 1J PtP ) 1721
Hz, internal P), 41.8 (d, 2J PP ) 7 Hz, 1J PtP ) 1699 Hz, external
P). 1H NMR (CDCl3): δ(H) 2.12 (s, 6H, CH3), 2.20 (s, 6H, CH3),
2.03-2.08, 3.47-3.54, 3.73-3.75 (br m, PCH2CH2P), 3.14 (t,
2J PH ) 10 Hz), 6.65-7.47 (m, C6H5).
1
1
Syn th esis of [P t2Me4(µ-r a c-DP P EP M)]. This complex
was prepared similarly and obtained in 55% yield. 31P{1H}
NMR (CDCl3): δ(P) 39.3 (m, 1J PtP ) 1795 Hz, internal P), 46.6
Syn th esis of [P t2Me2(µ-Cl)(µ-m eso-DP P EP M)]P F 6. [Pt-
ClMe(cod)] (0.105 g, 0.29 mmol) and meso-DPPEPM (0.097 g,
0.15 mmol) were dissolved in acetone (10 mL). To this stirred
solution was added dropwise TlPF6 (0.052 g, 0.14 mmol) in
acetone (1 mL). A white precipitate began to form, and the
reaction was allowed to run overnight. The solvent was
removed under vacuum, and the resulting solid was washed
with pentane. The solid was then extracted with acetone and
passed down a short column of alumina. The column was
washed with small portions of acetone. The total effluent was
collected, and the solvent was removed to leave the product
as a white powder (0.104 g, 56%). 31P{1H} NMR (acetone-d6):
δ(P) 44.0 (s, 1J PtP ) 4643 Hz, external P), 47.0 (s, 1J PtP ) 1773
Hz, 2J PP ) 37 Hz, internal P). 1H NMR (acetone-d6): δ(H) 0.63
(2J PtH ) 40 Hz, CH3), 1.68-1.78, 2.51-2.60, 2.87-3.17 (br m,
PCH2CH2P), 4.42, 4.46 (pseudoquartets, 2J HH ) 2J PH ) 13 Hz,
1
1
(m, J PtP ) 1799 Hz, external P). H NMR (CDCl3): δ(H) 0.67
3
2
3
(d, J PH ) 6 Hz, J PtH ) 66 Hz, CH3), 0.81 (d, J PH ) 6 Hz,
2J PtH ) 64 Hz, CH3), 1.68-1.81, 2.09-2.41, 2.84 (br m,
PCH2CH2P), 3.27 (t, J PH ) 11 Hz, PCH2P), 6.67-7.76 (m,
C6H5).
2
Syn th esis of [P t2P h 4(µ-m eso-DP P EP M)]. meso-DPPEPM
(0.11 g, 0.17 mmol) was dissolved in CH2Cl2 (20 mL), and
[PtPh2(cod)] (0.159 g, 0.34 mmol) was added. The solution was
stirred for 15 min, and then the solvent was removed under
reduced pressure. The residue was washed several times with
pentane, and the product was isolated as a light yellow powder
1
(0.13 g, 54%). 31P{1H} NMR (CDCl3): δ(P) 36.1 (br s, J PtP
)
1712 Hz, 3J PtP ) 41 Hz, 2J PP ) 23 Hz, internal P), 39.7 (d, 2J PP
1
1
) 6 Hz, J PtP ) 1705 Hz, external P). H NMR (CDCl3): δ(H)
1.64-1.81, 1.94-2.06 (br, m, PCH2CH2P), 3.46, 3.60 (br m,
PCH2P), 6.42-7.97 (m, C6H5). Crystals suitable for an X-ray
diffraction study were grown by slow evaporation of a CDCl3/
Et2O solution.
PCH2P), 6.69-7.59 (m, C6H5). HRMS: exact mass calcd for
12
C
H4635ClP4195Pt2+, 1111.1534; obsd, 1111.1472.
43
Syn th esis of [P t2P h 2(µ-Cl)(µ-m eso-DP P EP M)]P F 6. [Pt-
ClPh(cod)] (0.080 g, 0.19 mmol) and meso-DPPEPM (0.0634
g, 0.097 mmol) were dissolved in THF (10 mL). To this stirred
solution was added dropwise TlPF6 (0.052 g, 0.14 mmol) in
THF (1 mL). A white precipitate started to form, and the
reaction was allowed to run overnight. The solvent was
removed under vacuum, and the resulting solid was washed
with pentane several times. The solid was then extracted with
THF and passed down a short column of alumina, with small
portions of THF as eluent. The total effluent was collected,
and the solvent was removed to give the product as an off-
white solid (0.060 g, 55%). 31P{1H} NMR (acetone-d6): δ(P) 39.0
Syn th esis of [P t2P h 4(µ-r a c-DP P EP M)]. This complex
was prepared similarly and obtained in 55% yield. Anal. Calcd
for C65H60P4Pt2: C, 57.60; H, 4.43. Found: C, 57.03; H, 4.75.
31P{1H} NMR (CDCl3): δ(P) 39.8 (d, 2J PP ) 7 Hz, 1J PtP ) 1712
Hz, internal P), 41.5 (d, 2J PP ) 7 Hz, 1J PtP ) 1687 Hz, external
1
P). H NMR (CDCl3): δ(H) 1.68-1.81, 2.09-2.41, 2.84 (br m,
2
PCH2CH2P), 3.04 (t, J PH ) 12 Hz, PCH2P), 6.67-7.76 (m,
C6H5).
Syn th esis of [P t2(CH2P h )4(µ-m eso-DP P EP M)]. meso-
DPPEPM (0.086 g, 0.13 mmol) was dissolved in CH2Cl2 (15
mL) and [Pt(CH2Ph)2(cod)] (0.127 g, 0.26 mmol) was added.
The solution was stirred for 15 min, then the solvent was
removed under reduced pressure. The residue was washed
several times with pentane, and the product was isolated as a
light yellow powder (0.105 g, 57%). 31P{1H} NMR (CDCl3): δ(P)
33.1 (br s, 1J PtP ) 1842 Hz, 3J PtP ) 36 Hz, 2J PP ) 24 Hz, internal
P), 44.7 (d, 2J PP ) 4 Hz, 1J PtP ) 1879 Hz, external P). 1H NMR
(CDCl3): δ(H) 1.43-1.50, 1.60-1.74, 2.10-2.21 (br m, PCH2-
1
1
2
(s, J PtP ) 4525 Hz, external P), 42.2 (s, J PtP ) 1724 Hz, J PP
1
) 24 Hz, internal P). H NMR (acetone-d6): δ(H) 1.83-1.85,
2.16-2.31, 2.99-3.03 (br m, PCH2CH2P), 3.57, 4.67 (pseudo-
quartets, J HH ) 2J PH ) 14 Hz, PCH2P), 6.69-7.59 (m, C6H5).
2
12
HRMS: exact mass calcd for
obsd, 1236.1815.
C
H5035ClP4195Pt2+, 1236.1851;
53
Syn th esis of [P t2(CH2P h )2(µ-Cl)(µ-m eso-DP P EP M)]P F 6.
[PtCl(CH2Ph)(cod)] (0.060 g, 0.092 mmol) and meso-DPPEPM
(0.079 g, 0.18 mmol) were dissolved in acetone (7 mL). To this

Pd and Pt Complexes Containing a Tetraphosphine
Organometallics, Vol. 22, No. 7, 2003 1497
stirred solution was added dropwise TlPF6 (0.032 g, 0.092
mmol) in MeOH (1 mL). The reaction was allowed to run
overnight, and the solvent was removed under vacuum. The
resulting solid was washed with pentane, extracted with
acetone, and passed down a short column of alumina, with
small portions of acetone as eluent. The total effluent was
collected, and the solvent was removed, giving the product as
a light yellow solid (0.077 g, 59%). 31P{1H} NMR (acetone-d6):
δ(P) 42.1 (s, 1J PtP ) 4732 Hz, external P), 43.3 (s, 1J PtP ) 1809
Hz, 2J PP ) 26 Hz, internal P). 1H NMR (acetone-d6): δ(H) 2.72-
2.97, 3.15-3.21, 3.60-3.66 (br m, PCH2CH2P, PtCH2Ph),
(0.060 g, 0.057 mmol) and meso-DPPEPM (0.036 g, 0.057
mmol), and isolated as an orange powder (0.045 g, 65%). 31P-
{1H} NMR (acetone-d6): δ(P) 33.8 (dd, J PP ) 17, 10 Hz,
external P), 58.7 (dd, J PP ) 17, 10 Hz, internal P). 1H NMR
(acetone-d6): δ(H) 2.17-2.50, 2.71-2.74, 2.94-2.98 (br m,
PCH2CH2P), 3.18 (br m, 1H, PCH2P), 3.56 (br m, 1H, PCH2P),
12
6.23-7.80 (m, C6H5). HRMS: exact mass calcd. for
C H50-
53
35ClP4106Pd2+, 1057.0621; observed, 1057.0588.
Syn th esis of [P d 2(COMe)2(µ-Cl)(µ-m eso-DP P EP M)]P F 6.
[Pd2Me2(µ-Cl)2(AsPh3)2] (0.070 g, 0.075 mmol) was dissolved
in CH2Cl2 (10 mL). Carbon monoxide was bubbled through the
solution for 2 h, then meso-DPPEPM (0.049 g, 0.075 mmol),
methanol (1 mL), and TlPF6 (0.026 g, 0.075 mmol) were added,
and the mixture was stirred overnight. The solvent was
removed under vacuum. The resulting solid was washed
several times with pentane and then extracted with CH2Cl2.
The solution was passed through a column of neutral alumina,
with CH2Cl2 as eluent. The solvent was evaporated to give a
dark yellow solid (0.040 g, 47%). 31P{1H} NMR (CDCl3): δ(P)
22.9 (dd, J PP ) 21, 22 Hz, external P), 40.3 (dd, J PP ) 21, 22
Hz, internal P). 1H NMR (CDCl3): δ(H) 2.19 (s, COCH3), 1.92-
2.09, 2.19-2.29, 2.61-2.75 (br m, PCH2CH2P), 3.34-3.40 (br
m, PCH2P), 7.00-7.53 (m, C6H5). IR (neat solid): 1684 cm-1
3.98-4.11, 4.42-4.47 (br m, PCH2P), 6.65-7.75 (m, C6H5).
12
HRMS: exact mass calcd for
obsd, 1263.2159.
C
H5435ClP4195Pt2+, 1263.2160;
55
Syn th esis of [P t2Cl2(µ-Cl)(µ-m eso-DP P EP M)]P F 6. [Pt2-
Cl4(µ-meso-DPPEPM)] (0.075 g, 0.063 mmol) was dissolved in
THF (7 mL), and TlPF6 (0.022 g, 0.063 mmol) was added. A
white precipitate started to form, and the reaction was allowed
to proceed overnight. The mixture was passed through a short
column of Hyflo Supercel to remove TlCl. The solvent was
removed under vacuum, and the product was obtained as a
light yellow powder (0.044 g, 54%).31P{1H} NMR (acetone-d6):
1
1
δ(P) 44.0 (br, J PtP ) 3557 Hz, internal P), 46.5 (br, J PtP
)
3896 Hz, external P). 1H NMR (acetone-d6): δ(H) 2.21-2.70,
2.85-3.17, 3.65-3.75 (br m, PCH2CH2P), 3.88-4.12 (br m,
12
+
(νCO). HRMS: exact mass calcd for
C
H4635ClP4O2106Pd2
45
989.0206; obsd, 989.0232.
PCH2P), 7.01-7.83 (m, C6H5). HRMS: exact mass calcd for
Syn th esis of [P d 2Cl2(µ-Cl)(µ-m eso-DP P EP M)]P F 6. [Pd2-
Cl4(µ-meso-DPPEPM)] (0.080 g, 0.079 mmol) was dissolved in
THF (7 mL), and TlPF6 (0.027 g, 0.079 mmol) was added. A
yellow precipitate started to form, and the reaction was
allowed to proceed overnight. The mixture was passed through
a short column of Hyflo Supercel to remove TlCl. The solvent
was removed under vacuum, and the product was obtained
as a yellow powder (0.060 g, 68%). 31P{1H} NMR (acetone-d6):
δ(P) 68.5 (s, internal P), 72.3 (s, external P). 1H NMR (acetone-
d6): δ(H) 2.35-2.56, 2.86-3.00, 3.05-3.21 (br m, PCH2CH2P),
3.23-3.34, (br m, PCH2P), 7.28-7.71 (m, C6H5). Anal. Calcd
for C41H40Cl3P5Pd2‚0.5THF: C, 44.64; H, 3.83. Found: C, 44.75;
C
H4035Cl3P4195Pt2+, 1151.0442; obsd, 1151.0482.
12
41
Syn th esis of [P d 2Me2(µ-Cl)(µ-m eso-DP P EP M)]P F 6. [Pd-
ClMe(cod)] (0.088 g, 0.33 mmol) and meso-DPPEPM (0.108 g,
0.17 mmol) were dissolved in CH2Cl2 (10 mL). To this stirred
solution was introduced TlPF6 (0.058 g, 0.17 mmol) in metha-
nol (1 mL). A yellow precipitate started to form, and the
reaction mixture was stirred for 15 min. The solvent was
removed under vacuum. The resulting solid was washed with
pentane and then extracted with CH2Cl2 and passed down a
short column of alumina. The column was washed with small
portions of CH2Cl2. The total effluent was collected, and the
solvent was removed to leave the product as a yellow solid
(0.112 g, 63%). Anal. Calcd for C43H46P5Pd2ClF6: C, 47.81; H,
4.29. Found: C, 47.24; H, 4.39. 31P{1H} NMR (CDCl3): δ(P)
33.1 (dd, J PP ) 16, 11 Hz, external P), 62.2 (dd, J PP ) 16, 11
12
+
H, 4.40. HRMS: exact mass calcd for
972.9216; obsd, 972.9222.
C ,
H4035Cl3P4106Pd2
41
Syn th esis of [P t2Me2(µ-I)(µ-m eso-DP P EP M)]P F 6. [Pt2-
Me2(µ-Cl)(µ-meso-DPPEPM)]PF6 (0.040 g, 0.031 mmol) was
dissolved in acetone (8 mL), and Bu4NI (0.012 g, 0.031 mmol)
in acetone (1 mL) was added by syringe. The mixture turned
dark red. To this stirred solution was introduced TlPF6 (0.011
g, 0.031 mmol) in acetone (1 mL). A precipitate started to form,
and the reaction mixture was stirred overnight. The solvent
was removed under vacuum. The resulting solid was washed
several times with water and sec-butyl alcohol and then
extracted with acetone and passed down a short column of
alumina. The column was washed with small portions of
acetone. The total effluent was collected, and the solvent was
removed to leave the product as a light yellow solid (0.030 g,
71%). 31P{1H} NMR (CDCl3): δ(P) 47.2 (1J PtP ) 4297 Hz,
external P), 48.9 (1J PtP ) 1808 Hz, internal P). 1H NMR
1
Hz, internal P). H NMR (CDCl3): δ(H) 0.63 (s, CH3), 1.98-
2.21, 2.73-2.80, 2.82-2.93 (br m, PCH2CH2P), 3.70 (pseudo-
2
2
quartet, J HH ) 14 Hz, J PH ) 14 Hz, 1H, PCH2P), 3.51 (br m,
1H, PCH2P), 6.84-7.63 (m, C6H5). HRMS: exact mass calcd
12
for
C
H4635ClP4106Pd2+, 933.0308; obsd, 933.0320.
43
Syn th esis of [P d 2Me2(µ-Cl)(µ-r a c-DP P EP M)]P F 6. This
complex was prepared similarly and obtained in 55% yield.
31P{1H} NMR (CDCl3): δ(P) 36.3 (dd, J PP ) 16, 11 Hz, external
P), 61.5 (dd, J PP ) 16, 11 Hz, internal P). 1H NMR (CDCl3):
δ(H) 0.46 (s, CH3), 1.81-2.21, 2.73-2.80 (br m, PCH2CH2P),
2
3.10 (t, J PH ) 9 Hz, PCH2P), 6.71-7.63 (m, C6H5).
Syn th esis of [P d 2(CH2P h )2(µ-Cl)(µ-m eso-DP P EP M)]-
P F 6. [Pd2(CH2Ph)2(µ-Cl)2(AsPh3)2] (0.068 g, 0.063 mmol) and
meso-DPPEPM (0.041 g, 0.063 mmol) were dissolved in THF
(7 mL). To this stirred solution was added dropwise TlPF6
(0.022 g, 0.063 mmol) in THF (1 mL). A precipitate began to
form, and the reaction was allowed to run for 1 h. The solvent
was removed under vacuum. The resulting solid was washed
several times with pentane, and then extracted with THF and
passed down a short column of Hyflo Supercel. The column
was washed with small portions of THF. The total effluent
was collected, and the solvent was removed, leaving the
product as a yellow powder (0.045 g, 59%). 31P{1H} NMR
(C6D6): δ(P) 34.8 (dd, J PP ) 29, 12 Hz, external P), 58.7 (dd,
2
(acetone-d6): δ(H) 0.71 (s, J PtH ) 47 Hz, CH3), 1.55-1.85,
2.29-2.36, 2.47-2.51 (br m, PCH2CH2P), 3.80-4.01 (br m,
PCH2P), 6.93-7.77 (m, C6H5). HRMS: exact mass calcd for
12
C
H46127IP4195Pt2+, 1203.0891; obsd, 1203.0842.
43
Syn th esis of [P d 2Me2(µ-I)(µ-m eso-DP P EP M)]P F 6. [Pd2-
Me2(µ-Cl)(µ-meso-DPPEPM)]PF6 (0.080 g, 0.074 mmol) was
dissolved in acetone (8 mL). To this solution was added Bu4-
NI (0.027 g, 0.074 mmol) in acetone (1 mL), and the mixture
turned dark red. An acetone solution (1 mL) of TlPF6 (0.026
g, 0.074 mmol) was introduced, and a precipitate started to
form. The reaction mixture was stirred overnight, and the
solution turned olive green. The solvent was removed under
vacuum. The resulting solid was washed several times with
water and sec-butyl alcohol and then extracted with acetone
and passed down a short column of alumina. The column was
washed with small portions of acetone. The total effluent was
collected, and the solvent was removed to leave the product
1
J PP ) 29, 12 Hz, internal P). H NMR (C6D6): δ(H) 1.88-2.24
(br m, PCH2CH2P, PdCH2Ph), 2.84, 3.18 (br m, PCH2P), 6.61-
12
7.73 (m, C6H5). HRMS: exact mass calcd for
C
H5435Cl-
55
P4106Pd2+, 1085.0934; obsd, 1085.0945.
Syn th esis of [P d 2P h 2(µ-Cl)(µ-m eso-DP P EP M)]P F 6. This
complex was prepared analogously from [Pd2Ph2(µ-Cl)2(AsPh3)2]

1498 Organometallics, Vol. 22, No. 7, 2003
Nair et al.
Ta ble 1. Cr ysta llogr a p h ic Da ta for m eso-DP P EP M-S4, [P d 2Cl4(µ-m eso-DP P EP M)], a n d
[P t2P h 4(µ-m eso-DP P EP M)
meso-DPPEPM-S4 [Pd2Cl4(µ-meso-DPPEPM)]
[Pt2Ph4(µ-meso-DPPEPM)]
cryst syst
space group, Z
a, Å
b, Å
c, Å
orthorhombic
Pna21, 4
12.1988(11)
8.9786(8)
35.885(3)
90
monoclinic
P21/c, 8
20.0126(2)
30.1998(3)
16.5381(2)
90
91.039(1)
90
9993.60(19)
1.662
213(2)
1.414
1.40-26.00
183 477
19 651
empirical
1126
0.0365, 0.0749
0.0555, 0.817
1.057
monoclinic
P21/c, 4
29.1088(8)
12.3862(3)
17.8170(5)
90
96.055(2)
90
6388.0(3)
1.609
223(2)
4.643
1.79-25.68
87 744
12 111
empirical
730
0.0712, 0.1198
0.1153, 0.1319
1.108
R, deg
â, deg
90
90
γ, deg
cell vol, Å3
3930.4(6)
1.326
223(2)
0.434
2.27-27.61
50 037
8999
none
442
0.0663, 0.1171
0.0735, 0.1201
1.272
D(calcd), Mg/m3
temp, K
abs coeff, mm-1
θ range, deg
no. of rflns collected
no. of indep rflns
abs cor
no. of params refined
R(F), Rw(F2) (F2 >2.0σ(F2))
R(F), Rw(F2) (all data)
goodness of fit
largest diff peak and hole, e Å-3
0.418 and -0.377
0.832 and -0.937
2.402 and -2.328
as a pale green solid (0.065 g, 75%). 31P{1H} NMR (acetone-
NMR spectroscopy. The meso form exhibits two doublets
of doublets in its 31P{1H} NMR spectrum, the internal
P atoms producing a resonance at -25.5 ppm and the
external P atoms at -12.0 ppm. The rac isomer gives
rise to an almost identical spectrum, with doublets of
doublets at -24.8 and -11.9 ppm. Both isomers have
broad resonances in their 1H NMR spectra due to the
ethylene and aromatic hydrogens. The meso form shows
a broad signal due to the nonequivalent hydrogens of
the central CH2 group, whereas the rac isomer may be
distinguished by its magnetically equivalent CH2 hy-
drogens that give rise to a triplet at 2.04 ppm.
d6): δ(P) 38.8 (dd, J PP ) 16, 9 Hz, external P), 64.1 (dd, J PP
)
16, 9 Hz, internal P). 1H NMR (acetone-d6): δ(H) 0.78 (s, CH3),
1.97-2.08, 2.36-2.52, 2.82-3.00 (br m, PCH2CH2P), 3.11 (br
m, 1H, PCH2P), 3.77 (br m, 1H, PCH2P), 7.15-7.69 (m, C6H5).
12
HRMS: exact mass calcd for
obsd, 1024.9637.
C
H46127IP4106Pd2+, 1024.9664;
43
X-r a y Str u ctu r e Deter m in a tion s. Preliminary examina-
tion and data collection were performed using a Siemens
SMART CCD detector system single-crystal X-ray diffracto-
meter equipped with a sealed-tube X-ray source (50 kV × 40
mA) using graphite-monochromated Mo KR radiation (λ )
0.710 73 Å). Preliminary unit cell constants were determined
with a set of 45 narrow-frame (0.3° in ω) scans. The double-
pass method of scanning was used to exclude any noise. The
collected frames were integrated using an orientation matrix
determined from the narrow-frame scans. The SMART soft-
ware package19 was used for data collection, and SAINT19 was
used for frame integration. Final cell constants were deter-
mined by a global refinement of xyz centroids of 8192 reflec-
tions. An empirical absorption correction was applied using
SADABS.20 Structure solution and refinement were carried out
using the SHELXTL-PLUS (5.03) software package.21 Crystal-
lographic data are collected in Table 1.
When a CH2Cl2 solution of meso- or rac-DPPEPM was
stirred with elemental sulfur, the corresponding tetra-
sulfide was formed in high yield (eq 1). In each case,
Resu lts a n d Discu ssion
the product was characterized by NMR spectroscopy,
and the structure of the meso isomer was determined
by X-ray crystallography. The 31P{1H} NMR spectra are
second order, but they appear as two approximate
doublets of triplets. The spectra have been simulated
We have prepared the linear tetraphosphine ligand
bis[((diphenylphosphino)ethyl)phenylphosphino]meth-
ane (DPPEPM) as reported previously, by addition of
KPHPh to CH2Cl2, followed by reaction of the resulting
bis(phenylphosphino)methane with Ph2PCHdCH2 in
the presence of AIBN.18 The ligand was obtained as an
approximately 1:1 ratio of meso and rac diastereomers.
These could be separated by extraction with a 4:1
methanol/benzene solvent mixture; the rac form dis-
solved, and the meso diastereomer could be separated
by filtration. The latter was obtained as a colorless solid,
and after solvent removal, the rac form was isolated as
an oily solid. Both compounds were characterized by
1
successfully (see Experimental Section). The H NMR
spectrum of the meso form shows two overlapping
pseudoquartets for the central CH2 group, whereas the
magnetically equivalent hydrogens of the central me-
thylene group in the rac isomer appear as a simple
triplet at 3.0 ppm.
The solid-state structure of meso-DPPEPM-S4 is
shown in Figure 1, and selected bond distances and
angles are given in Table 2. The figure illustrates the
linear nature of the ligand backbone. The pair of sulfur
atoms on P(1) and P(2), and those on P(3) and P(4), point
in opposite directions. Such an arrangement of substit-
uents on phosphorus is evidently preferred here, but if
it were maintained in solution, it would preclude che-
lation to a metal through these pairs of P atoms. The
(19) SMART and SAINT; Siemens Analytical X-ray Division, Madi-
son, WI.
(20) SADABS: Blessing, R. H. Acta Crystallogr., Sect. A 1995, 51,
33.
(21) Sheldrick, G. M. SHELXTL-PLUS (5.03) Software Package;
Siemens Analytical X-ray Division, Madison, WI, 1995.

Pd and Pt Complexes Containing a Tetraphosphine
Organometallics, Vol. 22, No. 7, 2003 1499
F igu r e 1. Molecular structure of meso-DPPEPM-S4, with
atoms represented by thermal ellipsoids at the 50% level.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for DP P EP M-S4
F igu r e 2. Molecular structure of [Pd2Cl4(µ-meso-
DPPEPM)], with atoms represented by thermal ellipsoids
at the 50% level. Hydrogen atoms have been omitted for
clarity.
P(1)-S(1)
P(3)-S(3)
P(1)-C(1)
P(1)-C(13)
P(1)-C(15)
P(3)-C(21)
P(3)-C(28)
P(4)-C(30)
1.9369(17)
1.9364(13)
1.801(4)
1.818(4)
1.805(3)
1.821(4)
1.808(4)
1.806(4)
P(2)-S(2)
P(4)-S(4)
P(1)-C(7)
P(2)-C(14)
P(2)-C(21)
P(3)-C(22)
P(4)-C(29)
P(4)-C(36)
1.9293(13)
1.9402(16)
1.802(4)
1.812(4)
1.831(4)
1.803(4)
1.795(4)
1.804(5)
tion to the metal, there is very little difference in the
electronic environment of the internal and external P
atoms. Its 1H NMR spectrum contains two broad
pseudoquartets at 3.87 and 4.33 ppm due to the central
CH2 group. The platinum complex exhibits signals at
δ(P) 37.6 (1J PtP ) 3575 Hz) and 38.7 ppm (1J PtP ) 3680
Hz), due to the internal and terminal P atoms, respec-
tively. The 195Pt satellites for the resonance due to the
C(1)-P(1)-C(7)
C(7)-P(1)-C(13)
C(7)-P(1)-S(1)
107.0(2)
104.77(19) C(1)-P(1)-S(1)
113.03(17) C(13)-P(1)-S(1)
C(1)-P(1)-C(13)
104.7(2)
114.40(16)
112.08(15)
C(15)-P(2)-C(14) 105.59(18) C(15)-P(2)-C(21) 106.57(17)
C(14)-P(2)-C(21) 102.72(17) C(15)-P(2)-S(2)
C(14)-P(2)-S(2) 111.76(13) C(21)-P(2)-S(2)
113.31(13)
115.88(12)
2
internal P atoms exhibit a J PP value of 22 Hz, and
3
observation of this coupling (and in other cases, J PtP
C(22)-P(3)-C(28) 106.02(18) C(22)-P(3)-C(21) 105.58(17)
(vide infra)) allows identification of the signals due to
the internal P atoms. The central CH2 group again gives
rise to two pseudoquartets, at 3.92 and 4.45 ppm. The
complexes are air-stable, either as solids or in solution.
The coordination behavior of the rac ligand is similar.
The palladium complex gives rise to 31P resonances at
C(28)-P(3)-C(21) 103.75(17) C(22)-P(3)-S(3)
C(28)-P(3)-S(3) 110.82(14) C(21)-P(3)-S(3)
116.18(13)
113.48(13)
C(29)-P(4)-C(36) 106.50(19) C(29)-P(4)-C(30) 105.2(2)
C(36)-P(4)-C(30) 106.0(2)
C(36)-P(4)-S(4)
P(2)-C(21)-P(3)
C(29)-P(4)-S(4)
111.65(15)
114.49(17)
112.40(16) C(30)-P(4)-S(4)
116.56(18)
1
64.3 and 67.4 ppm and a H resonance at 4.02 ppm, due
P-S bond distances are all 1.93-1.94 Å, which is typical
of such bonds in P(V) compounds.23 The P-C bond
distances all lie between 1.79 and 1.83 Å, the longest
bonds being to the central CH2 group. The P atoms
exhibit pseudo-tetrahedral geometry, the larger angles
being those involving the S atom. The P-C-P angle,
involving the central methylene carbon, is 116.6(2) Å.
When meso-DPPEPM was allowed to react with
2 equiv of [MCl2(cod)] (M ) Pd, Pt) in CH2Cl2 solu-
tion, bimetallic complexes of the form [M2Cl4(µ-meso-
DPPEPM)] were produced (eq 2). After solvent removal
to the magnetically equivalent methylene hydrogens.
[Pt2Cl4(µ-rac-DPPEPM)] exhibits 31P resonances at 40.0
(1J PtP ) 3556 Hz, internal P) and 41.9 ppm (1J PtP ) 3558
Hz, terminal P).
The solid-state structure of [Pd2Cl4(µ-meso-DPPEPM)]
has been determined by X-ray crystallography. Its
molecular structure is shown in Figure 2, and selected
bond distances and angles are given in Table 3. The
structure reveals that it is a bimetallic complex, in
which each palladium is coordinated by two P atoms
and two chlorides. The cis-PdCl2P2 unit is almost
perfectly planar (the sums of the angles about Pd(1) and
Pd(2) being 359.96 and 360.22°), although the angles
deviate slightly from the ideal 90°. The largest angle in
each molecule is that between the two chlorides, whereas
the smallest angle is between the two P atoms of the
five-membered chelate ring, as expected. The chelating
nature of the coordinated diphosphine unit imposes a
cis geometry at each metal center and the “halves” of
the molecule are held together by the single PCH2P
bridging group. The molecule is free to rotate about this
and washing with pentane, the palladium or platinum
complex was isolated in good yield as a yellow or
colorless solid, respectively. The 31P{1H} NMR spectrum
of [Pd2Cl4(µ-meso-DPPEPM)] exhibits signals at δ(P)
61.8 and 62.6, corresponding to 4δ(P) values of 87.3 and
74.6 ppm, respectively. This indicates that, on coordina-
(23) (a) Codding, P. W.; Kerr, K. A. Acta Crystallogr., Sect. B 1978,
34, 3785. (b) Tkachev, V. V.; Shvets, A. A.; Tokina, L. M.; Osipov, O.
A. Zh. Strukt. Khim. 1987, 28, 1496. (c) Lobana, T. S.; Sandhu, M. K.;
Tiekink, E. R. T. J . Chem. Soc., Dalton Trans. 1988, 1401. (d)
Weichmann, H.; Meunier-Piret, J . Organometallics 1993, 12, 4097. (e)
Apperley, D. C.; Bricklebank, N.; Hursthouse, M. B.; Light, M. E.;
Coles, S. J . Polyhedron 2001, 20, 1907.
(22) Laneman, S. A.; Fronczek, F. R.; Stanley, G. G. J . Am. Chem.
Soc. 1988, 110, 5585.

1500 Organometallics, Vol. 22, No. 7, 2003
Nair et al.
Ta ble 3. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for On e of th e Molecu les of
[P d 2Cl4(µ-m eso-DP P EP M)]
Pd(1)-P(1)
Pd(1)-Cl(1)
Pd(2)-P(3)
Pd(2)-Cl(3)
P(2)-C(3)
2.2364(10)
2.3606(10)
2.2331(10)
2.3675(10)
1.827(4)
Pd(1)-P(2)
Pd(1)-Cl(2)
Pd(2)-P(4)
Pd(2)-Cl(4)
P(3)-C(3)
2.2272(9)
2.3604(9)
2.2349(9)
2.3568(11)
1.830(3)
P(1)-Pd(1)-P(2)
85.38(4)
P(1)-Pd(1)-Cl(1)
90.13(4)
P(1)-Pd(1)-Cl(2) 173.96(4)
P(2)-Pd(1)-Cl(1) 174.43(4)
P(2)-Pd(1)-Cl(2)
P(3)-Pd(2)-P(4)
P(3)-Pd(2)-Cl(4) 173.54(4)
P(4)-Pd(2)-Cl(4)
Pd(1)-P(2)-C(3) 114.53(11) Pd(2)-P(3)-C(3)
P(2)-C(3)-P(3) 120.99(19)
90.04(3)
85.75(3)
Cl(2)-Pd(1)-Cl(1)
P(3)-Pd(2)-Cl(3)
94.67(4)
91.33(4)
P(4)-Pd(2)-Cl(3) 176.82(4)
88.06(4)
Cl(3)-Pd(2)-Cl(4)
94.82(4)
116.66(12)
F igu r e 3. Molecular structure of [Pt2Ph4(µ-meso-
DPPEPM)], with atoms represented by thermal ellipsoids
at the 50% level. Hydrogen atoms have been omitted for
clarity.
single bridge in solution, but in the solid state the two
PdCl2P2 planes are rotated away from each other such
that the Pd-Pd distance is 6.08 Å. This metal-metal
distance is comparable to those found in the platinum
analogue (5.931 Å),12 [Ni2Cl4(meso-eLTTP)] (6.272(1)
Å),18 and [Rh2Cl2(CO)2(rac-eLTTP)] (5.813(2) Å).22 It is
slightly shorter than the Pt-Pt distance of 6.338(1) Å
found in [Pt2Cl4(rac-1,2-DPPEPE)] (DPPEPE ) bis-
[((diphenylphosphino)ethyl)phenylphosphino]ethane), in
which the internal P atoms are connected by a two-
carbon unit.24 The central P-C-P angles in the
palladium and platinum complexes [M2Cl4(µ-meso-
DPPEPM)] are 120.99(19) and 118.0(4)°, respectively,
increased from 116.6(2)° in the sulfide, and the opening
of this angle may contribute to the large M-M dis-
tances. The P-C-P angles in [Ni2Cl4(eLTTP)] are
121.7(4) and 119.3(3)° for the meso and rac forms,18
although the angle is only 113(1)° in [Rh2Cl2(CO)2-
(rac-eLTTP)].22
Ta ble 4. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for [P t2P h 4(µ-m eso-DP P EP M)]
Pt(1)-P(1)
Pt(1)-C(42)
Pt(2)-P(3)
Pt(2)-C(54)
P(2)-C(3)
2.284(3)
2.077(11)
2.273(3)
2.077(11)
1.837(11)
Pt(1)-P(2)
Pt(1)-C(48)
Pt(2)-P(4)
Pt(2)-C(60)
P(3)-C(3)
2.274(3)
2.082(10)
2.296(3)
2.060(11)
1.836(11)
P(1)-Pt(1)-P(2)
83.92(10) P(1)-Pt(1)-C(42)
93.5(3)
175.6(3)
86.9(4)
177.8(3)
96.4(3)
P(1)-Pt(1)-C(48) 177.9(3)
P(2)-Pt(1)-C(42)
C(42)-Pt(1)-C(48)
P(2)-Pt(1)-C(48)
P(3)-Pt(2)-P(4)
P(3)-Pt(2)-C(60)
P(4)-Pt(2)-C(60) 177.4(3)
Pt(1)-P(2)-C(3)
P(2)-C(3)-P(3)
95.6(3)
83.88(11) P(3)-Pt(2)-C(54)
94.5(3)
P(4)-Pt(2)-C(54)
C(54)-Pt(2)-C(60)
Pt(2)-P(3)-C(3)
85.1(4)
119.7(4)
124.0(4)
123.3(6)
tained in the presence of CsI, shows the parent species
complexed by one Cs+ ion; presumably the Cs+ ion
interacts with one of the aryl rings in the complex.
Reactions of the rac form of the ligand proceed analo-
gously, and the NMR spectra of the [Pt2R4(µ-rac-
DPPEPM)] complexes are qualitatively similar to those
of the meso derivatives.
Treatment of meso-DPPEPM with 2 equiv of [PtR2-
(cod)] (R ) Me, Ph, CH2Ph, C6H4Me-4) in CH2Cl2
solution also produced bimetallic complexes [Pt2R4(µ-
meso-DPPEPM)]. These were isolated as off-white to
yellow, air-stable solids. In each case, the 31P{1H} NMR
spectrum consists of two resonances with one-bond
couplings to platinum in the range 1700-1900 Hz, as
expected for P atoms lying trans to organic substitu-
ents.25 As noted above for [Pt2Cl4(µ-meso-DPPEPM)],
the 195Pt satellites for the internal P atoms exhibit
additional couplings, and this allows ready assignment
of resonances to these atoms. In each of the four
complexes [Pt2R4(µ-meso-DPPEPM)], the central reso-
nance for the internal P atoms is flanked by two sets of
Crystals of [Pt2R4(µ-meso-DPPEPM)] (R ) Me, Ph)
were isolated from CDCl3 or CDCl3/Et2O solution,
respectively. The structure of the methyl derivative has
been reported previously.11 The molecular structure of
the phenyl complex is shown in Figure 3, and selected
bond distances and angles are presented in Table 4. The
structure of [Pt2Ph4(µ-meso-DPPEPM)] consists of two
planar PtC2P2 units (the sums of the angles around Pt-
(1) and Pt(2) each being 359.9°) connected via the
PCH2P linkage. In this case, the smaller angles are
between the two P atoms and between the two phenyl
groups, whereas the P-Pt-C angles exceed 90°. The
average Pt-P distances in the methyl and phenyl
derivatives are greater than in the analogous chloride
complex (average 2.265 (Me) and 2.282 Å (Ph), compared
with 2.238 Å), as expected from the greater trans
influence of the organic groups.25 The average Pt-C
distance in [Pt2Ph4(µ-meso-DPPEPM)] is 2.074 Å. Again,
the two platinum centers are rotated away from one
another in the solid state, giving Pt-Pt distances of
6.732 and 6.632 Å in the methyl and phenyl derivatives,
respectively, slightly greater than in the chloride com-
plexes. The central P-C-P angles are 125.5(3) and
123.3(6)°, larger still than those found in the chloride
complexes. The Pt-P-C-P torsion angles in [Pt2Me4-
(µ-meso-DPPEPM)] are 58.9 and 137.9°, and the corre-
1
3
doublet satellites corresponding to J PtP and J PtP, due
to the isotopomer containing one 195Pt nucleus. In the
1H NMR spectrum of the methyl complex, two pseudot-
riplets (3J PH ) 8 Hz) are observed at 0.64 and 0.76 ppm,
due to the methyl groups lying trans to the internal and
external P atoms. The 4-tolyl complex similarly shows
two signals for the methyl substituents on the tolyl
rings. The coordinated CH2 groups in the benzyl com-
plex are obscured by the CH2 groups of the DPPEPM
ligand. In all four complexes, the central CH2 group of
the DPPEPM ligand gives rise to two pseudoquartets,
typical of the meso form of the ligand. The high-
resolution mass spectrum of the 4-tolyl complex, ob-
(24) Goller, H.; Bru¨ggeller, P. Inorg. Chim. Acta 1992, 197, 75.
(25) Appleton, T. G.; Clark, H. C.; Manzer, L. E. Coord. Chem. Rev.
1973, 10, 335.

Pd and Pt Complexes Containing a Tetraphosphine
Organometallics, Vol. 22, No. 7, 2003 1501
sponding angles in [Pt2Ph4(µ-meso-DPPEPM)] are 64.2
and 121.7°. If these angles are maintained in solution,
they might account for the significant values of 3J PtP in
these complexes. In contrast, the corresponding torsion
angles in [Pt2Cl4(µ-meso-DPPEPM)] are closer to 90°
complex exhibits resonances at 22.9 and 40.3 ppm. The
1H NMR spectra exhibit the expected signals. Similarly,
reaction of the rac ligand with [PdClMe(cod)], followed
by addition of TlPF6, gave [Pd2R2(µ-Cl)(µ-rac-DPPEPM)]-
PF6.
3
(73.7 and 82.1°), and the J PtP value is too small to be
measured in this complex.
We have been unable to obtain crystals of the chloride-
bridged complexes, and they have proved difficult to
obtain in analytically pure form because it is virtually
impossible to remove all traces of TlCl. They have been
characterized in each case by 1H and 31P{1H} NMR
spectroscopy, by high-resolution mass spectrometry,
and, in a small number of cases, by elemental analysis.
Although we do not have structural details, the presence
of the chloride bridge in these instances would force the
two metal centers into closer proximity than in the open
forms found for [M2X4(µ-DPPEPM)] derivatives.
Attempts to open the chloride bridges in the above
compounds with tertiary phosphines gave complicated
mixtures. Addition of iodide to [M2Me2(µ-Cl)(µ-meso-
DPPEPM)]PF6 (M ) Pd, Pt), however, did produce the
mixed halide derivative quite cleanly (eq 4). The bridge-
When meso-DPPEPM was added to a solution con-
taining 2 equiv of [PtClMe(cod)], the 31P{1H} NMR
spectrum of the resulting solution was complicated, but
the resonances could be assigned to the three possible
isomers of [ClMePt(µ-DPPEPM)PtClMe]. When 1 equiv
of TlPF6 was added, however, a white precipitate of TlCl
formed and, after filtration and purification, [Pt2Me2-
(µ-Cl)(µ-meso-DPPEPM)]PF6 was obtained as a yellow
solid in moderate yield (eq 3). Its 31P{1H} NMR spec-
trum contains resonances at 44.0 (1J PtP ) 4643 Hz) and
47.0 ppm (1J PtP ) 1773 Hz), due to the P atoms lying
trans to the bridging chloride and the terminal methyl
1
groups, respectively.25 Its H NMR spectrum contains
a single resonance at 0.55 ppm (2J PtH ) 44 Hz), due to
the two equivalent methyl groups, and the expected two
pseudoquartets due to the central CH2 group of the
DPPEPM ligand. The phenyl- and benzylplatinum
derivatives were formed similarly, by reaction of [PtClR-
(cod)] (R ) Ph, CH2Ph) with meso-DPPEPM and TlPF6.
In another bridge-forming reaction, treatment of
[Pt2Cl4(µ-meso-DPPEPM)] with 1 equiv of TlPF6 in THF
solution produced the trichlorodiplatinum complex
[Pt2Cl2(µ-Cl)(µ-meso-DPPEPM)]PF6 as a light yellow
solid. In this case, the 31P{1H} NMR spectrum consists
of two closely spaced resonances, each with a coupling
to platinum in excess of 3500 Hz. Similar 31P NMR
parameters were observed for the related complex
[Pt2Cl2(µ-Cl)(µ-DPPEPE)]Cl.24
opening reaction took place stereospecifically, with only
one isomer of the intermediate [MeClM(µ-DPPEPM)-
MIMe] being formed. In each case, a single species with
four nonequivalent P atoms was generated. Further
addition of TlPF6 gave the iodide-bridged complex in
good yield. The 31P{1H} NMR data for the iodide-bridged
complexes show slight shifts of both signals to higher
frequencies, and in the platinum complex the 1J PtP value
for the P atom lying trans to the bridging halide
decreases from 4643 to 4297 Hz, a consequence of the
greater trans influence of iodide compared to chloride.25
The chloride-bridged palladium complexes [Pd2R2(µ-
Cl)(µ-meso-DPPEPM)]PF6 (R ) Me, Ph, CH2Ph) could
also be prepared by reaction of 2 equiv of [PdClMe(cod)]
with 1 equiv of meso-DPPEPM in CH2Cl2 solution,
followed by addition of 1 equiv of TlPF6 in methanol, or
by reaction of equimolar amounts of [Pd2R2(µ-Cl)2-
(AsPh3)2], DPPEPM, and TlPF6 in THF solution. The
acetyl derivative [Pd2(COMe)2(µ-Cl)(µ-meso-DPPEPM)]-
PF6 could be generated by treating [Pd2R2(µ-Cl)2-
(AsPh3)2] with CO prior to the addition of DPPEPM and
TlPF6. The product was isolated as a yellow or orange
solid in each case. In contrast to the 31P{1H} NMR
spectra of the platinum complexes, which consist of two
resonances in the range 39-47 ppm, the spectra of the
palladium derivatives are characterized by two widely
separated resonances. In [Pd2R2(µ-Cl)(µ-meso-DPPEP-
M)]PF6 (R ) Me, Ph, CH2Ph) the resonance due to the
P atom lying trans to the bridging chloride appears at
33-35 ppm, whereas that due to the internal P atom
appears in the range 58-62 ppm. The acetylpalladium
Su m m a r y
We have shown that the meso and rac forms of the
linear tetraphosphine DPPEPM may be used to gener-
ate bimetallic palladium and platinum complexes of the
type [M2Cl4(µ-DPPEPM)] and organoplatinum deriva-
tives of the form [Pt2R4(µ-DPPEPM)]. Solid-state struc-
tures of both compound types reveal bimetallic struc-
tures in which the two metal square planes are rotated
away from each other about the single PCH2P bridge,
resulting in M-M distances of ca. 6 Å. Reactions of
“MClR” sources with DPPEPM give the analogous
complexes [M2Cl2R2(µ-DPPEPM)], but removal of one
chloride gives a chloride-bridged species of the form
[M2R2(µ-Cl)(µ-DPPEPM)]+. Although we have been un-
able to obtain a crystal structure of one of these
compounds, the presence of the bridging chloride would
necessitate a much shorter M-M distance. The ability
of these systems to move between open and closed,

1502 Organometallics, Vol. 22, No. 7, 2003
Nair et al.
bridged forms may have implications for their potential
use as bimetallic catalysts, and we are currently evalu-
ating their activity in a number of catalytic reactions.
University of Missouri Research Board for instrumenta-
tion grants.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data, atomic coordinates and displacement parameters, and
all bond distances and angles. This material is available free
of charge via the Internet at http://pubs.acs.org.
Ack n ow led gm en t. Thanks are expressed to the
National Science Foundation (Grant No. CHE-9508228)
for support of this work, and to NSF (Grant Nos. CHE-
9318696, 9309690, and 9974801), the U.S. Department
of Energy (Grant No. DE-FG02-92CH10499), and the
OM0209069