Enolphosphato-Phosphines: A New Class of P,O Ligands

Article abstract of DOI:10.1021/ic030032y

The new bifunctional ligands Ph₂PCH=CPh[OP(O)(OR)₂] (1) (1a, R = Et; 1b, R = Ph) represent the first examples of P,O derivatives resulting from the association of a phosphine moiety and an enolphosphate group. The Z stereochemistry a

Full text of DOI:10.1021/ic030032y

Inorg. Chem. 2003, 42, 7752−7765
Enolphosphato−Phosphines: A New Class of P,O Ligands
,†
,†
Xavier Morise,* Pierre Braunstein,* and Richard Welter‡
Laboratoire de Chimie de Coordination and Laboratoire DECMET, UMR 7513 CNRS,
UniVersite´ Louis Pasteur, 4 rue Blaise Pascal, F-67070 Strasbourg Cedex, France
Received January 27, 2003
The new bifunctional ligands Ph2PCHdCPh[OP(O)(OR)2] (1) (1a, R) Et; 1b, R) Ph) represent the first examples
of P,O derivatives resulting from the association of a phosphine moiety and an enolphosphate group. The Z
stereochemistry about the double bond provides a favorable situation for these ligands to act as P,O-chelates.
Neutral and cationic Pd(II) complexes have been synthesized and characterized, in which 1a or 1b acts either as
a P-monodentate ligand or a P,O-chelate, via coordination of the oxygen atom of the PdO group. In the latter
case, it has been observed that phosphines 1a and 1b can display a hemilabile behavior, owing to successive
dissociation and recoordination of the O atom. Competition experiments revealed that phosphine 1a presents a
higher chelating ability than 1b, a feature ascribed to the more electrodonating properties of the ethoxy groups in
1a compared to the phenoxy groups in 1b. P,O-Chelation affords seven-membered metallocycles, which is unusual
for P,O-chelates. Complexes trans-[PdCl2{Ph PCHdC(Ph)OP(O)(OPh)2}2] (2b), [PdCl{Ph PCHdC(Ph)OP(O)(OEt)2}-
2
2
(µ-Cl)]2 (3a), [Pd(dmba){Ph2PCHdC(Ph)OP(O)(OEt)2}][PF ] (8a′), and cis-[Pd{Ph2PCHdC(Ph)OP(O)OEt)2}][BF ]
6
4 2
(10a) have been structurally characterized. Interestingly, the seven-membered rings in 8a′ and 10a adopt a sofa
conformation with the double bond lying almost perpendicular to the plane containing the Pd, the two P, and the
two O atoms.
Introduction
Surprisingly, phosphine ligands containing a phosphoryl
function, i.e., phosphonate, phosphinate or phosphate, have
received relatively little attention, although it is established
that the PdO group can coordinate to a metal center via the
oxygen atom.8-11 Thus, such ligands may be considered as
potential P,O-chelates or assembling ligands in the formation
of bi- or polynuclear species. They could also represent
valuable precursors to supported catalysts12 and hybrid
organic-inorganic or layered metal-phosphonate materi-
als.12-14 Recent advances in this area include the synthesis
Recent review articles have illustrated the considerable
current interest in organometallic complexes containing
functional phosphine ligands, in particular for catalytic
processes.1-3 Numerous P,O-ligands in which a phosphine
moiety is associated with carboxylate, ketone, alcohol, ether,
ester, sulfoxide, or phosphine oxide functions have been
prepared. Many of their metal complexes display catalytic
properties often related to the electronic properties of the
P,O-chelating ligand1,4,5 and/or the possible occurrence of
hemilabile behavior of these ligands.1,2,6,7
(7) Braunstein, P.; Chauvin, Y.; Na¨hring, J.; DeCian, A.; Fischer, J.;
Tiripicchio, A.; Ugozzoli, F. Organometallics 1996, 15, 5551.
(8) DeBolster, M. W. G.; Goeneveld, W. L. In Topics in Phosphorus
Chemistry; Griffith, E. J., Grayson, M., Eds.; Wiley: New York, 1976;
Vol. 8, p 273 and references therein.
(9) Gahagan, M.; Mackie, R. K.; Cole-Hamilton, D. J.; Cupertino, D. C.;
Harman, M.; Hursthouse, M. B. J. Chem. Soc., Dalton Trans. 1990.
(10) Weis, K.; Rombach, M.; Vahrenkamp, H. Inorg. Chem. 1993, 32, 2470.
(11) (a) Morise, X.; Braunstein, P.; Welter, R. C. R. Chimie 2003, 6, 91.
(b) Kingsley, S.; Chandrasekhar, V.; Incarvito, C. D.; Lam, M. K.;
Rheingold, A. L. Inorg. Chem. 2001, 40, 5890.
* To whom correspondence should be addressed. E-mail: morise@
chimie.u-strasbg.fr (X.M.); braunst@chimie.u-strasbg.fr (P.B.).
† Laboratoire de Chimie de Coordination.
‡ Laboratoire DECMET.
(1) Bader, A.; Lindner, E. Coord. Chem. ReV. 1991, 108, 27.
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1999, 48, 233. (b) Lindner, E.; Pautz, S.; Haustein, M. Coord. Chem.
ReV. 1996, 15, 145 and references therein.
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(5) Hoberg, H.; Ballesteros, A.; Sigan, A.; Jegat, C.; Milchereit, A.
Synthesis 1991, 395.
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585, 162.
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B. Chem. Mater. 1995, 7, 995.
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7752 Inorganic Chemistry, Vol. 42, No. 24, 2003
10.1021/ic030032y CCC: $25.00 © 2003 American Chemical Society
Published on Web 10/25/2003

New Class of P,O Ligands
1
of water soluble tertiary phosphines,15-19 and rhodium
complexes of phosphino-phosphonate ligands have been
used in the catalytic carbonylation of methanol20-22 or in
styrene hydroformylation.23,24 PtCl2-SnCl2 hydroformylation
catalysts with phosphonated triarylphosphines have also been
reported recently.25
The H NMR chemical shifts of the aromatic protons have been
omitted for clarity, since they are unexceptional.
The chlorophosphates ClP(O)(OR)2 (Aldrich) were degassed
before use. AgBF4 (Avocado) and TlPF6 (Strem) were dried
overnight in vacuo before use. The compounds Ph2PCH2C(O)Ph,35a
[PdCl2(COD)],36 [Pd(Me)Cl(COD)],37 [Pd(dmba)(µ-Cl)]2,38 [Pd(η3-
C3H5)(µ-Cl)]2,39 [Pd(NCMe)4](BF4)2,40 and Ph2PN(Me)PPh2
35b,c
As part of our ongoing interest in the chemistry of
multifunctional phosphine ligands containing hard and soft
donor functions,26-34 we describe here the preparation of the
first enolphosphato-phosphine ligands, Ph2PCHdCPh-
[OP(O)(OR)2] [1a (R ) Et)] and [1b (R) Ph)], and their
palladium complexes.
were prepared according to the literature.
Syntheses. Ph2PCHdC(Ph)OP(O)(OEt)2 (1a). A THF suspen-
sion (30 mL) of KH (0.600 g, 15.0 mmol) was prepared in a Schlenk
flask connected to a bubbler. Solid Ph2PCH2C(O)Ph (3.04 g, 10.0
mmol) was then added, at room temperature. This resulted in gas
(H2) evolution, whereas the solution progressively turned yellow-
orange. After the evolution of H2 had ceased (ca. 10 min), the
reaction mixture was stirred for 20 min. Meanwhile, dry and
degassed ClP(O)(OEt)2 (1.725 g, 1.44 mL, 10.0 mmol) was placed
in a Schlenk flask, equipped with a filter frit containing a 1 cm
pad of dry Celite, and was cooled to -60 °C. The filtered THF
solution was then added, and after 2 min, the cold bath was removed
and the reaction mixture stirred for 2 h, during which its color
progressively turned beige. The solvent was then removed in vacuo.
The residue was extracted with CH2Cl2, and the volatiles were
evaporated, affording a beige solid, which was washed with Et2O
(20 mL) and pentane (20 mL) and dried in vacuo. The phosphine
1a was obtained as a beige (slightly sticky) powder (3.700 g, 84%
yield). In order to obtain analytically pure material, 1a (ca. 0.200
g) was dissolved in 3 mL and precipitated upon addition of pentane
(15 mL). The beige precipitate was filtered and dried overnight in
vacuo. Anal. Calcd for C24H26O4P2 (M ) 440.420): C, 65.45; H,
5.95. Found: C, 65.58; H, 5.82.
Experimental Section
General. All the reactions and manipulations were carried out
under an inert atmosphere of purified nitrogen using standard
Schlenk tube techniques. Solvents were dried and distilled under
nitrogen before use: hexane, pentane, and toluene over sodium,
tetrahydrofuran and diethyl ether over sodium-benzophenone, and
dichloromethane over calcium hydride. Nitrogen (Air liquide,
R-grade) was passed through BASF R3-11 catalyst and molecular
sieves columns to remove residual oxygen and water. Elemental
C, H, and N analyses were performed by the Service de Mi-
croanalyses (Universite´ Louis Pasteur, Strasbourg). Infrared spectra
1
were recorded on an IFS 66 Bruker FT-IR spectrometer. The H,
31P{1H}, and 13C{1H} NMR spectra were recorded at 300.1, 121.5,
and 75.5 MHz, respectively, on a Bruker AC300 instrument.
Phosphorus chemical shifts were externally referenced to 85% H3-
PO4 in H2O with downfield chemical shifts reported as positive.
Ph2PCHdC(Ph)P(O)(OPh)2 (1b). This compound was obtained
as a white powder, in a manner similar to 1a from Ph2PCH2C(O)-
Ph (3.04 g, 10.0 mmol) and ClP(O)(OPh)2 (2.07 mL, 10.0 mmol).
Yield: 4.400 g (82%). The same procedure as that described for
1a was applied to obtain analytically pure 1b. Anal. Calcd for
C32H26O4P2 (M ) 536.509): C, 71.64; H, 4.88. Found: C, 71.82;
H, 4.96.
(15) Ganguly, S.; Mague, J. T.; Roundhill, D. M. Inorg. Chem. 1992, 31,
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1983.
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G.; deVries, J. G.; Oevering, H. J. Chem. Soc., Dalton Trans. 2000,
671.
[PdCl2{Ph2PCHdC(Ph)OP(O)(OEt)2}2] (2a). Solid [PdCl2-
(COD)] (0.285 g, 1.0 mmol) and 1a (0.880 g, 2.0 mmol) were
placed in a Schlenk flask and degassed in vacuo for 5 min. Then,
20 mL of freshly distilled CH2Cl2 was added, and the mixture was
stirred for 15 min at room temperature, after which the volatiles
were removed in vacuo. The yellow residue was washed with Et2O
(2 × 15 mL) and pentane (2 × 15 mL) and dried under reduced
pressure. Complex 2a was obtained as a yellow powder (0.855 g,
81% yield). Both cis and trans isomers were formed (see text, Table
1). Anal. Calcd for C48H52Cl2O8P4Pd (M ) 1058.146): C, 54.49;
H, 4.95. Found: C, 54.32; H, 4.82.
[PdCl2{Ph2PCHdC(Ph)OP(O)(OPh)2}2] (2b). This complex
was obtained as a yellow-orange solid, in a manner similar to 2a
from [PdCl2(COD)] (0.055 g, 0.19 mmol) and 1b (0.203 g, 0.38
mmol). Yield: 0.205 g (86%). Both cis and trans isomers were
formed. Anal. Calcd for C64H52Cl2O8P4Pd (M ) 1250.32): C, 61.48;
(26) Braunstein, P.; Gomes-Carneiro, T. M.; Matt, D.; Balegroune, F.;
Grandjean, D. J. Organomet. Chem. 1989, 367, 117.
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Chem. 2000, 601, 43.
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Toronto, D. V. New J. Chem. 2000, 24, 437.
(35) (a) Bouaoud, S.-E.; Braunstein, P.; Grandjean, D.; Matt, D.; Nobel,
D. Inorg. Chem. 1986, 25, 3765. (b) Wang, F. T.; Najdzionek, J.;
Leneker, K. L.; Wasserman, H.; Braitsch, D. M. Synth. React. Inorg.
Metal-Org. Chem. 1978, 8, 119. (c) Sekabunga, E. J.; Smith, M. L.;
Webb, T. R.; Hill, W. E. Inorg. Chem. 2002, 41, 1205.
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(37) Lapido, F. T.; Anderson, G. K. Organometallics 1994, 13, 303.
(38) Cope, A. C.; Friedrich, E. C. J. Am. Chem. Soc. 1968, 90, 909.
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(40) Sen, A.; Lai, T.-W. Inorg. Chem. 1984, 23, 3257.
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Braunstein, P.; Naud, F. J. Chem. Soc., Dalton Trans. 2000, 2577.
Inorganic Chemistry, Vol. 42, No. 24, 2003 7753

Morise et al.
1
Table 1. Selected IR and H and 31P{1H} NMR Data of 1-18
1H NMR, δ a
31P{1H} NMR, δa
IR,
cm-1b
compd
H enolate of P ligand
other
P
PO
ν(PdO)
Ph2PCHdC(Ph)OP(O)(OEt)2
1a 6.20 (dd, 2J(PH) ) 3.1, 1.18 (dt, 6H, CH2CH3, 3J(HH) ) 7.0,
-29.8
-7.0
-18.0
1277s
1313s
1269sc
4J(PH) ) 1.4)
4J(PH) ) 1.0); 4.08 (m, 4H, OCH2)
Ph2PCHdC(Ph)OP(O)(OPh)2
1b 6.33 (dd, 2J(PH) ) 3.5,
-28.4
4J(PH) ) 1.1)
[PdCl2{PPh2CHdC(Ph)OP(O)-
(OEt)2}2]
2a 6.24 (dt, 2J(PH) ) 7.3, 0.97 (t, 12H, CH2CH3, 3J(HH) ) 7.1);
4.6 (trans) -8.1 (trans)
12.1 (cis) -8.0 (cis)
4J(PH) ) 1.6)
(trans isomer)
5.62 (dd, 2J(PH) )
11.0, 4J(PH) ) 2.1)
(cis isomer)
3.69 (m, 8H, OCH2)
1.03 (t, 12H, CH2CH3, 3J(HH) ) 7.1);
3.69 (m, 8H, OCH2)
[PdCl2{PPh2CHdC(Ph)OP(O)-
(OPh)2}2]
2b 6.54 (dt, 2J(PH) ) 7.6,
4.8 (trans) -19.6 (trans) 1302s
12.1 (cis) -19.6 (cis)
4J(PH) ) 1.7)
(trans isomer)
5.87 (dd, 2J(PH) )
11.4, 4J(PH) ) 1.9)
(cis isomer)
[PdCl{PPh2CHdC(Ph)OP(O)-
(OEt)2}(µ-Cl)]2
3a 5.92 (d br, 2J(PH) )
1.11 (t, 12H, CH2CH3, 3J(HH) ) 7.0);
13.7
13.8
19.9
21.1
20.9
-8.6
-20.1
-5.3
-19.5
-7.5
1272s
1294sd
1276sc
1299s
1272s
10.2, 4J(PH)
3.86 (m, 8H, OCH2)
not resolved)
[PdCl{PPh2CHdC(Ph)OP(O)-
(OPh)2}(µ-Cl)]2
3b 6.18 (d br, 2J(PH) )
10.9, 4J(PH)
not resolved)
[PdMe{PPh2CHdC(Ph)OP(O)-
(OEt)2}(µ-Cl)]2
4a 6.33 (br, 2J(PH)
0.75 (d, 6H, PdMe, 3J(PH) ) 3.0); 1.11
(t, 12H, CH2CH3, 3J(HH) ) 7.0);
4.15 (m br, 8H, OCH2)
0.77 (d, 6H, PdMe, 3J(PH) ) 2.3)
and 4J(PH)
not resolved)
[PdMe{PPh2CHdC(Ph)OP(O)-
(OPh)2}(µ-Cl)]2
4b 5.97 (d br, 2J(PH) )
8.5, 4J(PH) )
not resolved)
[Pd(dmba)Cl{PPh2CHdC(Ph)-
OP(O)(OEt)2}]
5a 6.02 (dd, 2J(PH) ) 6.2, 1.04 (t, 6H, CH2CH3, 3J(HH) ) 7.1);
4J(PH) ) 1.3)
2.84 (d, 6H, NMe2, 4J(PH) ) 3); 3.77
(m, 4H, OCH2); 4.08 (d, 2H, NCH2,
4J(PH) ) 1.4)
[Pd(dmba)Cl{PPh2CHdC(Ph)-
OP(O)(OPh)2}]
5b 6.32 (dd, 2J(PH) ) 6.4, 2.77 (d, 6H, NMe2, 4J(PH) ) 2.3); 4.08
20.8
4.0
-19.4
-7.7
1304s
1281s
4J(PH) ) 1.7) (d, 2H, NCH2, 4J(PH) ) 1.7)
[Pd(η3-allyl)Cl{PPh2CHdC(Ph)-
6a 6.02 (dd, 2J(PH) ) 5.4, 1.06 (dt, 6H, CH2CH3, 3J(HH) ) 7.0,
OP(O)(OEt)2}]e
4J(PH) ) 1.2)
4J(PH) ) 0.8); 3.11 (d, 1H, allyl Hb,
3J(HbHc) ) 11.0); 3.43-3.86
(overlapping signals, 6H, OCH2 and
allyl Ha and He); 4.72 (apparent t, 1H,
3
allyl Hd, 3J(PHd) ≈ J(HcHd) ≈ 7.2);
5.66 (m, 1H, allyl Hc)
[Pd(η3-allyl)Cl{PPh2CHdC(Ph)-
OP(O)(OPh)2}]e
6b 6.21 (dd, 2J(PH) ) 5.8, 2.99 (d, 1H, allyl Hb, 3J(HbHc) ) 12.0);
5.3
-19.2
-6.1
1304s
1227s
4J(PH) ) 1.2)
3.58 (d, 1H, allyl Ha, 3J(HaHc) ) 5.8);
3.60 (dd, 1H, allyl He, 3J(PHe) ) 13.7,
3J(HcHe) ) 10.4); 4.62 (apparent t, 1H,
3
allyl Hd, 3J(PHd) ≈ J(HcHd) ≈ 7.0);
5.41 (m, 1H, allyl Hc)
7a 6.29 (dd, 2J(PH) ) 6.0, 0.58 (d, 3H, PdMe, 3J(PH) ) 2.5); 1.11
22.9
[PdMe(NCMe){Ph2PCHdC(Ph)OP(O)-
(OEt)2}][BF4]
4J(PH) ) 2.4)
(dt, 6H, CH2CH3, 3J(HH) ) 7.0,
4J(PH) ) 1.3); 2.32 (s, 3H, MeCN);
4.08 (m, 4H, OCH2)
7b 6.37 (dd, 2J(PH) ) 5.2, 0.59 (d, 3H, PdMe, 3J(PH) ) 2.4); 2.24
21.5
21.4
24.0
-16.1
-16.1
-7.7
1240s
1241s
1228s
[PdMe(NCMe){Ph2PCHdC(Ph)OP(O)-
(OPh)2}][BF4]
4J(PH) ) 2.3)
(s, 3H, MeCN)
7b′ 6.37 (dd, 2J(PH) ) 4.9, 0.59 (d, 3H, PdMe, 3J(PH) ) 2.3); 2.23
4J(PH) ) 2.3)
(s, 3H, MeCN)
[PdMe(NCMe){Ph2PCHdC(Ph)OP(O)-
(OPh)2}][PF6]
8a 6.32 (dd, 2J(PH) ) 7.6, 1.07 (dt, 6H, CH2CH3, 3J(HH) ) 7.1,
[Pd(dmba){PPh2CHdC(Ph)OP(O)-
(OEt)2}][BF4]
4J(PH) ) 2.7)
4J(PH) ) 1.4); 2.82 (d, 6H, NMe2,
4J(PH) ) 2.6); 4.01 (m, 4H, OCH2);
4.10 (d, 2H, NCH2, 4J(PH) ) 1.2)
8a′ 6.37 (dd, 2J(PH) ) 7.5, 1.09 (dt, 6H, CH2CH3, 3J(HH) ) 7.0,
24.2
23.5
-7.5
1240s
1240s
[Pd(dmba){PPh2CHdC(Ph)OP(O)-
(OEt)2}][PF6]
4J(PH) ) 2.7)
4J(PH) ) 1.4); 2.79 (d, 6H, NMe2,
4J(PH) ) 2.5); 3.94 (m, 4H, OCH2);
4.09 (d, 2H, NCH2, 4J(PH) ) 1.2)
8b 6.50 (dd, 2J(PH) ) 6.9, 2.47 (d, 6H, NMe2, 4J(PH) ) 1.9); 4.02
-17.3
[Pd(dmba){PPh2CHdC(Ph)OP(O)-
(OPh)2}][BF4]
4J(PH) ) 2.4) (s, 2H, NCH2, 4J(PH) not resolved)
7754 Inorganic Chemistry, Vol. 42, No. 24, 2003

New Class of P,O Ligands
Table 1. (Continued)
1H NMR, δ a
31P{1H} NMR, δa
IR,
cm-1b
ν(PdO)
compd
H enolate of P ligand
other
P
PO
-6.5
9a 6.41 (dd, 2J(PH) ) 3.6, 1.08 (dt, 6H, CH2CH3, 3J(HH) ) 11.3
1208sd
[Pd(η3-allyl){PPh2CHdC(Ph)OP(O)-
(OEt)2}][BF4]e
4J(PH) ) 1.8)
7.0, 4J(PH) ) 1.3); 3.10 (br,
overlapping signals, 2H, allyl
Hb and Ha); 4.00 (m, 4H,
OCH2); 4.26 (br, 1H, allyl Hd
or He); 5.01 (br, 1H, allyl Hd
or He); 6.01 (apparent quint,
1H, allyl Hc)
9b 6.56 (br, 2J(PH)
and 4J(PH)
2.87 (br, 1H, allyl Ha or Hb); 3.29 11.3
(br, 1H, allyl Ha or Hb); 3.75
(m, 1H, allyl Hd or He); 4.59
(br, 1H, allyl Hd or He); 5.75
(m, 1H, allyl Hc)
-16.0
1226s
[Pd(η3-allyl){PPh2CHdC(Ph)OP(O)-
(OPh)2}][BF4]e
not observed)
10a 6.79 (dd, 2J(PH) )
10.5, 4J(PH) ) 2.5)
1.13 (dt, 12H, CH2CH3, 3J(HH) ) 28.4 (d,
-11.0 (d) 1221s
-21.0 (d) 1244sc
cis-[Pd{PPh2CHdC(Ph)OP(O)-
(OEt)2}2][BF4]2
7.1, 4J(PH) ) 1.3); 4.05
J(PP) ) 16)
(m, 8H, OCH2)
10b 6.99 (dd, 2J(PH) )
10.0, 4J(PH) ) 2.5)
29.4 (d,
J(PP) ) 16)
cis-[Pd{PPh2CHdC(Ph)OP(O)-
(OPh)2}2][BF4]2
11a 6.31 (m br)
0.28 (m br, 3H, Pd-Me); 0.99
(m, 12H, CH2CH3); 3.66
(m, 4H, OCH2), 4.09
(m, 4H, OCH2)
13.3
-6.6
1272s, 1225s
[PdMe{PPh2CHdC(Ph)OP(O)-
(OEt)2}{PPh2CHdC(Ph)OP(O)-
(OEt)2}][BF4]
11b 6.28 (m)
0.56 (apparent t, 3H, Pd-Me
13.9
-18.3
-20.0
1310s, 1243s
1271s
[PdMe{PPh2CHdC(Ph)OP(O)-
(OPh)2}{PPh2CHdC(Ph)OP(O)-
(OPh)2}][BF4]
3J(PH) ) 6.4)
12 6.30 (dd, 2J(PH) )
12.0, 4J(PH) ) 3.0)
2.56 (dd, 2J(PH) ) 11.6 and 11)
2.3 (d,2J(PP) )
480, P of 1b);
[PdCl{PPh2N(Me)PPh2}-
{PPh2CHdC(Ph)OP(O)-
(OPh)2}][CF3SO3]
32.5 (dd, 2J(PP) )
480 and 46,
PNP trans to 1b);
37.6 (d, 2J(PP) )
46, PNP cis to 1b)
13a 5.84 (dd, 2J(PH) ) 4.0, 0.80 (dd, 3H, Pd-Me, 3J(PH) )
8.8 (d, P of 1a,
2J(PP) ) 401);
70.8 (d, PNH)
-6.1
1271s
[1608s,
ν(CO)]
[PdMe{PPh2NHC(O)Me}-
{PPh2CHdC(Ph)OP(O)-
(OEt)2}][BF4]
4J(PH) ) 3.7)
6.4 and 5.8); 0.93 (m, 6H,
CH2CH3); 2.40 (s, 3H,
C(O)CH3); 3.66 (m, 4H,
OCH2); 9.56 (br, 1H, NH)
13b 6.08 (m)
0.85 (m, 3H, Pd-Me); 2.14
(s, C(O)CH3); 9.57
(br, 1H, NH)
8.5 (d, P of 1b,
2J(PP) ) 412);
71.0 (d, PN)
-17.8
-6.8
1301s
[1608s,
ν(CO)]
[PdMe{PPh2NHC(O)Me}-
{PPh2CHdC(Ph)OP(O)-
(OPh)2}][BF4]
14a 6.43 (m)
14b 6.30 (m)
0.33 (dd, 3H, Pd-Me, 3J(PH) )
6.4 and 6.2); 0.75 (m, 6H,
CH2CH3); 3.53 (m, 4H,
15.0 (P of 1a,
J(PP) ) 408);f
18.3 (PCH2)g
1223s
[1672s,
ν(CO)]
[PdMe{PPh2CHdC(Ph)OP(O)-
(OEt)2}{PPh2CH2C(O)Ph}]-
[BF4]
OCH2); 4.36 (m, 2H, PCH2)
0.63 (dd, 3H, Pd-Me, 3J(PH) )
6.7 and 5.9); 4.31 (dd, 2H,
PCH2, 2J(PH) ) 10.2,
4J(PH) ) 1.6)
12.5 (P of 1b,
J(PP) ) 401);f
23.2 (PCH2)g
-17.9
1241s
[1672,
ν(CO)]
[PdMe{PPh2CHdC(Ph)OP(O)-
(OPh)2}{PPh2CH2C(O)Ph}]-
[BF4]
17 6.10 (m, P-CHdCPh 0.50 (m, 3H, Pd-Me); 0.84
12.1 (P of 1b,
2J(PP) ) 404);f
16.6 (P of 1a)g
-7.6 (1a) 1310s (1b)
-18.1 (1b) 1226vs (1a)
[PdMe{PPh2CHdC(Ph)OP(O)-
(OEt)2}{PPh2CHdC(Ph)OP(O)-
(OPh)2}][BF4]
of 1b); 6.40 (m,
(m, 6H, CH2CH3); 3.55
P-CHdCPh of 1a)
(m, 4H, OCH2)
a Recorded in CDCl3 unless otherwise stated, coupling constants in Hz, aromatic protons are omitted for clarity since their chemical shifts are totally
unexceptional. b Recorded in Nujol unless otherwise stated. c In KBr. d In CDCl3. e Numbering of the allylic protons as pictured:
f Part A of an AB spin system. g Part B of an AB spin system.
H, 4.19. Found: C, 61.34; H, 4.26. Yellow crystals, suitable for
X-ray analysis, were obtained by slow diffusion of hexane into a
CH2Cl2 solution of 2b.
[PdCl{Ph2PCHdC(Ph)OP(O)(OEt)2}(µ-Cl)]2 (3a). This com-
plex was obtained as an orange solid, in a manner similar to 2a
from [PdCl2(COD)] (0.285 g, 1.0 mmol) and 1a (0.440 g, 1.0
Inorganic Chemistry, Vol. 42, No. 24, 2003 7755

Morise et al.
mmol). Yield: 0.585 g (91%). Anal. Calcd for C48H52Cl4O8P4Pd2
(M ) 1235.45): C, 46.67; H, 4.24. Found: C, 46.66; H, 4.31.
Orange crystals, suitable for X-ray analysis, were obtained by slow
diffusion of Et2O into a CH2Cl2 solution of 2b.
[PdMe(NCMe){Ph2PCHdC(Ph)OP(O)(OPh)2}](PF6) (7b′).
This complex was obtained as a pale yellow powder, in a manner
similar to 7b from 4b (0.245 g, 0.177 mmol) and TlPF6 (0.123 g,
0.354 mmol). Yield: 0.256 g (86%). Anal. Calcd for C35H32F6-
NO4P3Pd (M ) 843.96): C, 49.81; H, 3.82; N, 1.66. Found: C,
49.72; H, 3.66; N, 1.80.
[PdCl{Ph2PCHdC(Ph)OP(O)(OPh)2}(µ-Cl)]2 (3b). This com-
plex was obtained as an orange solid, in a manner similar to 2a
from [PdCl2(COD)] (0.345 g, 1.2 mmol) and 1b (0.648 g, 1.2
mmol). Yield: 0.760 g (88%). Anal. Calcd for C64H52Cl2O8P4Pd2
(M ) 1427.63): C, 53.85; H, 3.67. Found: C, 54.17; H, 3.81.
[PdMe{Ph2PCHdC(Ph)OP(O)(OEt)2}(µ-Cl)]2 (4a). This com-
plex was obtained as a beige solid, in a manner similar to 2a from
[Pd(Me)Cl(COD)] (0.265 g, 1.0 mmol) and 1a (0.440 g, 1.0 mmol).
Yield: 0.512 g (86%). Anal. Calcd for C50H58Cl2O8P4Pd2 (M )
1194.62): C, 50.27; H, 4.89. Found: C, 50.17; H, 4.84.
[PdMe{Ph2PCHdC(Ph)OP(O)(OPh)2}(µ-Cl)]2 (4b). This com-
plex was obtained as a beige solid, in a manner similar to 2a from
[Pd(Me)Cl(COD)] (0.211 g, 0.8 mmol) and 1b (0.429 g, 0.8 mmol).
Yield: 0.493 g (89%). Anal. Calcd for C66H58Cl2O8P4Pd2 (M )
1386.82): C, 57.16; H, 4.22. Found: C, 56.98; H, 4.11.
[Pd(dmba)Cl{Ph2PCHdC(Ph)OP(O)(OEt)2}] (5a). Solid [Pd-
(dmba)(µ-Cl)]2 (0.276 g, 0.5 mmol) and 1a (0.440 g, 1.0 mmol)
were placed in a Schlenk flask and degassed in vacuo for 5 min.
Then, CH2Cl2 (25 mL) was added, and the reaction mixture was
stirred for 0.5 h at room temperature. The volatiles were removed
under vacuum, and the residue was washed with Et2O (2 × 15
mL) and pentane (20 mL). Complex 5a was obtained as a green-
yellow solid (0.645 g, 89%). Anal. Calcd for C33H38ClNO4P2Pd
(M ) 716.48): C, 55.32; H, 5.35; N, 1.95. Found: C, 55.60; H,
5.22; N, 1.97.
[Pd(dmba)Cl{Ph2PCHdC(Ph)OP(O)(OPh)2}] (5b). This com-
plex was obtained as a pale green-yellow solid, in a manner similar
to 5a from [Pd(dmba)(µ-Cl)]2 (0.331 g, 0.6 mmol) and 1b (0.643
g, 1.2 mmol). Yield: 0.853 g (87%). Anal. Calcd for C41H38-
ClNO4P2Pd (M ) 812.56): C, 60.61; H, 4.71; N, 1.72. Found: C,
60.81; H, 4.86; N, 1.71.
[Pd(η3-C3H5)Cl{Ph2PCHdC(Ph)OP(O)(OEt)2}] (6a). This
complex was obtained as a yellow solid, in a manner similar to 5a
from [Pd(η3-C3H5)(µ-Cl)]2 (0.205 g, 0.56 mmol) and 1a (0.493 g,
1.12 mmol). Yield: 0.635 g (91%). Anal. Calcd for C27H31ClO4P2-
Pd (M ) 623.34): C, 52.03; H, 5.01. Found: C, 51.72; H, 4.94.
[Pd(η3-C3H5)Cl{Ph2PCHdC(Ph)OP(O)(OPh)2}] (6b). This
complex was obtained as a yellow solid, in a manner similar to 5a
from [Pd(η3-C3H5)(µ-Cl)]2 (0.165 g, 0.43 mmol) and 1b (0.461 g,
0.86 mmol). Yield: 0.590 g (94%). Anal. Calcd for C35H31ClO4P2-
Pd (M ) 719.44): C, 58.43; H, 4.34. Found: C, 58.04; H, 4.30.
[Pd(dmba){Ph2PCHdC(Ph)OP(O)(OEt)2}](BF4) (8a). This
complex was obtained as a yellow powder, in a manner similar to
7b, using CH2Cl2 as solvent, from 5a (0.094 g, 0.13 mmol) and
AgBF4 (0.025 g, 0.13 mmol). Yield: 0.072 g (72%). Anal. Calcd
for C33H38BF4NO4P2Pd (M ) 767.83): C, 51.62; H, 4.99; N, 1.82.
Found: C, 51.76; H, 4.94; N, 1.90.
[Pd(dmba){Ph2PCHdC(Ph)OP(O)(OEt)2}](PF6) (8a′). This
complex was obtained as a yellow-orange powder, in a manner
similar to 8a from 5a (0.143 g, 0.199 mmol) and TlPF6 (0.070 g,
0.2 mmol). Yield: 0.135 g (82%). Anal. Calcd for C33H38F6NO4P3-
Pd (M ) 825.99): C, 47.99; H, 4.64; N, 1.70. Found: C, 47.64;
H, 4.48; N, 1.56. Orange crystals, suitable for X-ray analysis, were
obtained by slow diffusion of Et2O into a CH2Cl2 solution of 8a′.
[Pd(dmba){Ph2PCHdC(Ph)OP(O)(OPh)2}](BF4) (8b). This
complex was obtained as a pale-orange powder, in a manner similar
to 8a from 5b (0.406 g, 0.499 mmol) and AgBF4 (0.098 g, 0.5
mmol). Yield: 0.376 g (87%). Anal. Calcd for C41H38BF4NO4P2-
Pd (M ) 863.92): C, 57.00; H, 4.43; N, 1.62. Found: C, 57.17;
H, 4.48; N, 1.71.
[Pd(η3-C3H5){Ph2PCHdC(Ph)OP(O)(OEt)2}](BF4) (9a). To
a CH2Cl2 (20 mL) solution of 6a (0.150 g, 0.24 mmol) was added
in one portion solid AgBF4 in excess (0.070 g, 0.35 mmol). The
reaction mixture was stirred overnight. After filtration over a Celite
pad and evaporation of the volatiles under reduced pressure, the
residue was washed with Et2O (2 × 15 mL). Compound 9a was
obtained as a pale green-brown powder (0.120 g, 75% yield). Anal.
Calcd for C27H31BF4O4P2Pd (M ) 674.70): C, 48.07; H, 4.63.
Found: C, 47.85; H, 4.77.
[Pd(η3-C3H5){Ph2PCHdC(Ph)OP(O)(OPh)2}](BF4) (9b). This
complex was obtained as a yellow-brown solid, in a manner similar
to 9a from 6b (0.138 g, 0.19 mmol) and AgBF4 (0.050 g, 0.25
mmol, excess). Yield: 0.118 g (81%). Anal. Calcd for C35H31-
BF4O4P2Pd (M ) 770.79): C, 54.54; H, 4.05. Found: C, 54.17;
H, 3.69.
cis-[Pd{Ph2PCHdC(Ph)OP(O)(OEt)2}2](BF4)2 (10a). Solid
[Pd(NCMe)4](BF4)2 (0.071 g, 0.16 mmol) and 1a (0.141 g, 0.32
mmol) were placed in a Schlenk flask and degassed in vacuo, before
CH2Cl2 (20 mL) was added at room temperature. The reaction
mixture turned pale yellow and was stirred for 1 h. The volatiles
were removed under reduced pressure, and the residue was washed
with Et2O (2 × 10 mL) and pentane (2 × 10 mL). Complex 10a
was obtained as a yellow-orange powder (0.154 g, 83% yield). Anal.
Calcd for C48H52B2F8O8P4Pd (M ) 1160.85): C, 49.66; H, 4.52.
Found: C, 49.74; H, 4.30. Orange crystals, suitable for X-ray
analysis, were obtained by slow diffusion of Et2O into a CH2Cl2
solution of 10a.
[PdMe(NCMe){Ph2PCHdC(Ph)OP(O)(OEt)2}](BF4) (7a). To
a MeCN (20 mL) solution of 4a (0.109 g, 0.18 mmol) was added
in one portion solid AgBF4 (0.036 g, 0.09 mmol). The reaction
mixture was stirred for 2 h, during which it became almost colorless
and a pale gray precipitate was formed. After filtration over a Celite
pad and evaporation of the volatiles under reduced pressure, the
residue was washed with Et2O (2 × 15 mL). Compound 7a was
obtained as a pale brown powder (0.132 g, 84% yield). Anal. Calcd
for C27H32BF4NO4P2Pd (M ) 689.71): C, 47.02; H, 4.68; N, 2.03.
Found: C, 46.68; H, 4.33; N, 1.66.
[PdMe(NCMe){Ph2PCHdC(Ph)OP(O)(OPh)2}](BF4) (7b). This
complex was obtained as a beige powder, in a manner similar to
7a from 4b (0.094 g, 0.067 mmol) and AgBF4 (0.026 g, 0.136
mmol). A 1/1 mixture of MeCN and CH2Cl2 was used, owing to
the poor solubility of 4b in pure MeCN. Yield: 0.084 g (79%).
Anal. Calcd for C35H32BF4NO4P2Pd (M ) 785.80): C, 53.50; H,
4.10; N, 1.78. Found: C, 53.56; H, 4.18; N, 1.80.
cis-[Pd{Ph2PCHdC(Ph)OP(O)(OPh)2}2](BF4)2 (10b). This
complex was obtained as a yellow solid, in a manner similar to
10a from [Pd(NCMe)4](BF4)2 (0.098 g, 0.22 mmol) and 1b (0.236
g, 0.44 mmol). Yield: 0.262 g (88%). Anal. Calcd for C64H52B2F8-
O8P4Pd (M ) 1353.03): C, 56.81; H, 3.87. Found: C, 57.12; H,
3.67.
7756 Inorganic Chemistry, Vol. 42, No. 24, 2003

New Class of P,O Ligands
[PdMe{Ph2PCHdC(Ph)OP(O)(OEt)2}{Ph2PCHdC(Ph)OP-
(O)(OEt)2}][BF4] (11a). Solid 7a (0.050 g, 0.072 mmol) and 1a
(0.032 g, 0.072 mmol) were placed in a Schlenk flask and degassed
in vacuo, before CH2Cl2 (5 mL) was added at room temperature.
The reaction mixture was stirred for 15 min, and the volatiles were
removed under reduced pressure. The residue was washed with Et2O
(10 mL) and pentane (10 mL). Complex 11a was obtained as a
pale brown solid (0.075 g, 95% yield). Anal. Calcd for C49H55-
BF4O8P4Pd (M ) 1089.08): C, 54.04; H, 5.09. Found: C, 54.44;
H, 5.38.
[PdMe{Ph2PCHdC(Ph)OP(O)(OPh)2}{Ph2PCH2C(O)Ph}]-
[BF4] (14b). This complex was obtained as a pale yellow-brown
solid, in a manner similar to 11a, from 7b (0.039 g, 0.049 mmol)
and Ph2PCH2C(O)Ph (0.015 g, 0.049 mmol) in 97% yield (0.050
g), or from 16 (0.055 g, 0.099 mmol) and 1b (0.053 g, 0.099 mmol)
in 92% yield (0.097 g). It could not be separated from 11b and 15.
The relative ratio 14b/11b/15, determined by 31P{1H} NMR
spectroscopy, is 4:1:1. Yield: 0.050 g (97%). Anal. Calcd for
C53H46BF4O5P3Pd‚0.5CH2Cl2 (M ) 1049.08 - 42.47): C, 58.87;
H, 4.34. Found: C, 58.62; H, 4.26.
[PdMe{Ph2PCHdC(Ph)OP(O)(OPh)2}{Ph2PCHdC(Ph)OP-
(O)(OPh)2}][BF4] (11b). This complex was obtained as a yellow
solid, in a manner similar to 11a, from 7b (0.108 g, 0.137 mmol)
and 1b (0.074 g, 0.137 mmol). Yield: 0.165 g (94%). Anal. Calcd
for C65H55BF4O8P4Pd‚0.5 CH2Cl2 (M ) 11281.26 + 42.47): C,
59.43; H, 4.26. Found: C, 59.55; H, 4.36.
[PdMe{Ph2PCHdC(Ph)OP(O)(OEt)2}{Ph2PCHdC(Ph)OP-
(O)(OPh)2}][BF4] (17). This complex was obtained as a yellow
solid, in a manner similar to 11a, from 7a (0.060 g, 0.087 mmol)
and 1b (0.046 g, 0.087 mmol) in 93% yield (0.096 g), or from 7b
(0.075 g, 0.095 mmol) and 1a in 96% yield (0.105 g). It could not
be separated from 11a and 11b. The ratio 17/11a/11b, determined
by 31P{1H} NMR spectroscopy, is 4:1:1. Anal. Calcd for C57H55-
BF4O8P4Pd (M ) 1185.17): C, 57.77; H, 4.68. Found: C, 58.01;
H, 4.83.
[PdCl{Ph2PN(Me)PPh2}{Ph2PCHdC(Ph)OP(O)(OPh)2}][CF3-
SO3] (12). [PdCl2(COD)] (0.365 g, 1.278 mmol) and Ph2PN(Me)-
PPh2 (0.510 g, 1.278 mmol) were placed in a Schlenk flask and
degassed in vacuo, before CH2Cl2 (15 mL) was added at room
temperature. The reaction mixture was stirred for 30 min, and the
volatiles were removed under reduced pressure. The residue was
washed with Et2O (2 × 10 mL) and hexane (15 mL), which afforded
[PdCl2{Ph2PN(Me)PPh2}] as a pale yellow solid (0.665 g, 90%
yield,31P{1H} NMR: δ 31 ppm). The latter was suspended in a
CH2Cl2/acetonitrile mixture (ratio: 1/1, 25 mL), before AgSO3-
CF3 (0.296 g, 1.152 mmol) was added. The reaction mixture was
stirred for 3 h at room temperature, filtered over a pad of dried
Celite, and 1b (0.617 g, 1.150 mmol) was added. After stirring for
30 min, the volatiles were removed under reduced pressure. The
residue was washed with Et2O (15 mL) and pentane (15 mL), which
afforded 12 as a red-orange solid. Yield: 1.326 g (94% based on
1b, 84% overall). Anal. Calcd for C58H49ClF3NO7P4PdS (M )
1226.84): C, 56.78; H, 4.03; N, 1.14. Found: C, 56.39; H, 4.08;
N, 1.21.
X-ray Collection and Structure Determinations. The X-ray
data were collected on an Enraf-Nonius KappaCCD diffractometer
(graphite monochromated Mo KR radiation λ ) 0.71073 Å) (trans-
2b, 3a, and 18), an Enraf-Nonius CAD4 diffractometer (graphite
monochromated Mo KR radiation λ ) 0.71073 Å) (8a′), and a
Philips PW1100 diffractometer (graphite monochromated Cu KR
radiation λ ) 1.54184 Å) (10a). The structures were solved using
the direct-methods program SIR,41 except for 18, for which the
SHELXS-97 was used.42 Subsequent full-matrix least-squares
refinements were carried out using the SHELXL-97 program.42 All
non-hydrogen atoms were refined with anisotropic parameters. The
hydrogen atoms were included in their calculated positions and
refined with a riding model.
Results and Discussion
Synthesis of the Phosphine-Phosphate Ligands Ph2-
PCHdC(Ph)OP(O)(OR)2 (1). Deprotonation of Ph2PCH2C-
(O)Ph35a with KH, in THF at room temperature, yielded the
corresponding enolate K[Ph2PCH-C(-O)Ph] A,43 which
was reacted in situ with ClP(O)(OR)2 to afford the new
phosphine-phosphates Ph2PCHdC(Ph)OP(O)(OR)2 (1a)
(R ) Et) and (1b) (R ) Ph) in high yields (>80%) (Scheme
1). Although this selective P-O bond formation was
anticipated, owing to the known oxophilicity of phosphorus,
it contrasts with the selective P-C coupling observed when
the lithium salts Li[CH2-C(-O)Ph] or Li[Ph2PCH-
C(-O)NPh2] were reacted with Ph2PCl, to give the keto-
phosphine Ph2PCH2C(O)Ph35a and the bisphosphine (Ph2P)2-
CHC(O)NPh2,30 respectively. The 31P{1H} NMR spectra of
1a,b consisted in a single phosphine resonance at ca. δ -29,
accompanied by a signal at lower field, δ -7.0 (1a) or
-18.0 (1b), which was ascribed to the phosphate moiety
[PdMe{Ph2PNHC(O)Me}{Ph2PCHdC(Ph)OP(O)(OEt)2}]-
[BF4] (13a). This complex was obtained as a pale brown solid, in
a manner similar to 11a, from 7a (0.053 g, 0.077 mmol) and Ph2-
PNHC(O)Me (0.018 g, 0.077 mmol). Yield: 0.063 g (92%). Anal.
Calcd for C39H43BF4NO5P3Pd (M ) 891.91): C, 52.52; H, 4.86;
N, 1.57. Found: C, 52.28; H, 4.91; N, 1.69.
[PdMe{Ph2PNHC(O)Me}{Ph2PCHdC(Ph)OP(O)(OPh)2}]-
[BF4] (13b). This complex was obtained as an off-white solid, in
a manner similar to 11a, from 7b (0.044 g, 0.056 mmol) and Ph2-
PNHC(O)Me (0.013 g, 0.056 mmol). Yield: 0.048 g (88%). Anal.
Calcd for C47H43BF4NO5P3Pd (M ) 988.00): C, 57.14; H, 4.39;
N, 1.42. Found: C, 57.38; H, 4.51; N, 1.31.
[PdMe{Ph2PCHdC(Ph)OP(O)(OEt)2}{Ph2PCH2C(O)Ph}]-
[BF4] (14a). This complex was obtained as a pale brown solid, in
a manner similar to 11a, from 7a (0.046 g, 0.067 mmol) and Ph2-
PCH2C(O)Ph (0.020 g, 0.067 mmol) in 90% yield (0.058 g), or
1
(Table 1). In addition, both H NMR spectra showed only
one enolate resonance (Table 1). The absence of any J(PP)
from [PdMe{Ph2PCH2C(O)Ph}(NCMe)][BF4] (16) (0.055 g, 0.099
mmol) and 1a (0.043 g, 0.099 mmol) in 92% yield (0.087 g). It
(41) Burla, M. C.; Camalli, M.; Cascarano, G.; Giacovazzo, C.; Polidori,
G.; Spagna, R.; Viterbo, D. SIR Program. J. Appl. Crystallogr. 1989,
22, 389.
(42) Sheldrick, G. M. SHELXL97, Program for the Refinement of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(43) Veya, P.; Floriani, C.; Chiesi-Villa, A.; Guastini, C.; Dedieu, A.;
Ingold, F.; Braunstein, P. Organometallics 1993, 12, 4359.
could not be separated from 11a and [PdMe{Ph2PCH2C(O)Ph}{Ph2-
PCH2C(O)Ph}][BF4] (15). The relative ratio 14a/11a/15, determined
by 31P{1H} NMR spectroscopy, is 9:1:1. Anal. Calcd for C45H46-
BF4O5P3Pd‚0.5CH2Cl2 (M ) 952.99 + 42.47): C, 54.90; H, 4.76.
Found: C, 55.29; H, 4.63.
Inorganic Chemistry, Vol. 42, No. 24, 2003 7757

Morise et al.
Scheme 1
Scheme 2
coupling in the 31P{1H} NMR spectra and the magnitude of
2
the J(PH) for the enolate protons (3.1 and 3.5 Hz for 1a
and 1b, respectively) suggested that only the Z-isomers were
obtained in this reaction. This was confirmed by the X-ray
structures of some of the Pd complexes obtained with 1 (vide
infra) since no isomerization about the CdC double bond is
anticipated upon metal coordination. We propose that the
stereoselectivity of the reaction results from the formation
of the five-membered intermediate A (Scheme 1).43 Then,
subsequent reactions with chlorophosphates would lead to
the Z-isomers of 1. Similar intermediates have been reported
for the deprotonated form of methylenediphosphonates,
â-ketophosphonates, or phosphine oxides.44-46
the enolate proton resonances (Table 1). Interestingly, in the
latter case, the signals for the cis and trans isomers showed
not only different intensities, but also different patterns.
Indeed, in contrast to the doublet of doublets observed for
the cis isomer, the enolate protons of the trans isomer gave
a doublet of virtual triplets, as a result of the existence of a
strong trans-J(PP′) coupling between the P atoms of the two
phosphines moieties.51,52
Neutral Complexes. Reactions of 1a,b with neutral Pd-
(II) precursors led to the formation of complexes 2-6a,b,
as a result of either substitution of a cyclooctadiene (COD)
ligand (2-4a,b) or cleavage of chloro-bridged dimers
(5,6a,b) (Scheme 2). Their spectroscopic data clearly indicate
that the enolphosphato-phosphines (1) behave as monoden-
tate-P ligands (Table 1). Thus, the ν(PdO) vibrations of
2-6a,b occurred in the same region as those of the free
ligands 1. In the 31P{1H} NMR spectra, P-coordination was
reflected in the low field shift (∆δ ) +34 to 51 ppm)
observed for the phosphine resonances by comparison with
those of 1, whereas the phosphate signals remain unaffected
(Table 1). Complexes [PdCl2{Ph2PCHdC(Ph)OP(O)(OR)2}2]
(2) (a, R ) Et; b, R ) Ph) were obtained as mixtures of
trans/cis isomers, with a predominance of the trans isomer.47
Yet, this was more pronounced in 2b, for which the structure
of the trans isomer was confirmed by X-ray diffraction, with
a trans/cis ratio of 90/10, as compared to the 83/17 ratio
found for 2a. Note that the 31P resonances of the phosphine
moieties of the trans isomers occurred at higher field than
those of the cis isomer (δ ca. 4.7 vs 12.1),48-50 whereas in
The reaction of [Pd(X)Cl(COD)] (X ) Cl, Me) with 1
mol equiv of 1 led, exclusively, to the chloride-bridged
dimers 3a,b and 4a,b, respectively. Mononuclear species,
in which 1 would act as a P,O-chelate, have not been
detected. The X-ray structure of [PdCl{Ph2PCHdC(Ph)OP-
(O)(OEt)2}(µ-Cl)]2 (3a) has been determined (vide infra).
The dmba (N,N-dimethylbenzylamine) complexes 5-6
presented spectroscopic characteristics similar to those of
1
4
2-4. In the H NMR spectra of 5a,b, the J(PH) couplings
observed for the NMe2 and CH2 protons of the dmba ligand,
which range from 1.4 to 3 Hz, are in accordance with a trans
arrangement of P and N atoms around the Pd center (Table
1, Scheme 2).53,54 The 31P resonances of the η3-allyl
complexes 6a,b were observed at higher field (δ ca. 5) than
those of 5a,b (δ ca. 20.8). Both the chemical shifts and the
patterns of the 1H allylic resonances of 6a,b resemble those
reported for other [(η3-allyl)PdCl(PR3)] complexes (Table
1).55,56
1
the H NMR spectra, the opposite trend was observed for
(44) Iorga, B.; Savignac, P. J. Organomet. Chem. 2001, 624, 203 and
references therein.
(45) Evreinov, V. I.; Antoshin, A. E.; Safronova, Z. V.; Kharitonov, A.
V.; Tsvetkov, E. N. IzV. Akad. Nauk SSSR, Ser. Khim. 1990, 873.
(46) Truter, M. R.; Lestas, C. N. J. Chem. Soc. A 1971, 738.
(47) trans and cis isomers refer to the arrangement of the P atoms around
the Pd center.
(51) Verstuyft, A. W.; Nelson, J. H.; Redfield, D. A.; Cary, L. W. Inorg.
Chem. 1976, 15, 1128.
(52) Verstuyft, A. W.; Redfield, D. A.; Cary, L. W.; Nelson, J. H. Inorg.
Chem. 1977, 16, 2776.
(53) Bouaoud, S.-E.; Braunstein, P.; Grandjean, D.; Matt, D.; Nobel, D.
Inorg. Chem. 1986, 25, 3765.
(48) Verstuyft, A. W.; Lewis, W. C.; Nelson, J. H. Inorg. Chem. 1975, 14,
1495.
(49) Nelson, J. H.; Rahn, J. A.; Bearden, W. H. Inorg. Chem. 1987, 26,
2193.
(54) Braunstein, P.; Frison, C.; Morise, X.; Adams, R. D. J. Chem. Soc.,
Dalton Trans. 2000, 2205.
(55) Faller, J. W.; Blankenship, C.; Whitmore, B.; Sena, S. Inorg. Chem.
1985, 24, 4483.
(50) Burrows, A. D.; Mahon, M. F.; Palmer, M. T. J. Chem. Soc., Dalton
Trans. 2000, 1669.
(56) Braunstein, P.; Naud, F.; Dedieu, A.; Rohmer, M.-M.; DeCian, A.;
Rettig, S. J. Organometallics 2001, 20, 2966.
7758 Inorganic Chemistry, Vol. 42, No. 24, 2003

New Class of P,O Ligands
Table 2. Selected Crystallographic Data for Complexes trans-2b, 3a‚2Et2O, 8a′, 10a‚CH2Cl2, and 18
trans-2b
3a‚2Et2O
8a′
10a‚CH2Cl2
18
a
formula
fw
color
cryst syst
space group
T/K
C64H52Cl2O8P4Pd
1250.32
yellow
triclinic
P1h
C48H52Cl4O8P4Pd2‚C4H10O
C33H38F6NO4P3Pd
825.99
orange
monoclinic
P21/c
C48H32B2F8O8P4Pd‚CH2Cl2
C23H26BF4N2OPPd
570.64
yellow
triclinic
P1h
173
1309.58
orange
monoclinic
C2/c
1225.62
orange
orthorhombic
Pnna
293
173
293
173
a/Å
b/Å
c/Å
12.402(2)
13.622(2)
18.275(4)
71.93(5)
86.04(5)
77.52(5)
2865.7(9)
2
24.9753(4)
9.8367(3)
23.6794(4)
90
96.923(3)
90
10.3847(5)
21.2069(5)
16.9638(5)
90
100.346(5)
90
17.133(3)
22.051(5)
14.681(3)
90
90
90
10.172(5)
11.129(5)
11.190(5)
99.023(5)
104.466(5)
95.540(5)
1199.2(10)
2
R/deg
â/deg
γ/deg
V/Å3
5775.0(2)
4
3675.1(2)
4
5546.5(8)
4
Z
F(000)
1280
0.585
10981
2664
0.970
6593
1680
0.702
7444
2464
5.346
3368
576
0.890
14964
µ/mm-1
data measured
data with I > 2σ(I)
8675
0.0385
0.1054
5492
0.0501
0.1599
5361
0.0497
0.1233
2610
0.0582
0.1615
13091
0.0436
0.1171
R
Rw
a The 20 OEt protons have not been included owing to the significant disorder oberved for these groups.
Figure 1. ATOMS view of the molecular structure of trans-2b; for better
clarity, only the ipso carbon atoms of the phenyl groups of the phosphate
moieties have been represented.
Figure 2. ATOMS view of the molecular structure of 3a‚2Et2O.
Crystal Structures of trans-2b and 3a. Views of the
crystal structures of trans-[PdCl2{Ph2PCHdC(Ph)OP(O)-
(OPh)2}2] (2b) and [PdCl{Ph2PCHdC(Ph)OP(O)(OEt)2}(µ-
Cl)]2 (3a) are shown in Figures 1 and 2, respectively, with
crystallographic data in Table 2 and selected bond lengths
and angles in Table 3. There is an effective center of
symmetry in complex 2b, at the Pd center, which is not
crystallographically imposed. In both complexes, the Pd
center adopts a square planar geometry. Bond lengths and
angles involving the Pd, P, and Cl atoms are within the same
range as those reported for other trans-[PdCl2(L)2]50,57,58 and
[PdCl(L)(µ-Cl)]2 complexes (L ) phosphine).59,60 Bond
distances and angles within the phosphate moieties are
nonexceptional. The C(13)-C(14) (2b and 3a) and C(45)-
C(46) (2b) bond distances, which range from 1.323(3) to
1.330(6) Å (Table 3), are in agreement with the presence of
a double bond between these atoms. The cis arrangement of
the Ph2P and phosphate groups about these double bonds
confirms the formation of 1 as the Z-isomer. In both
complexes, the phosphate groups bend toward the Pd center,
thus leading the enolate O atoms of the phosphate moieties
to occupy almost an apical position above (or below) the
metal. However, it seems reasonable to assume that this
results from the favorable cis geometry of ligand 1, rather
than from an inclination toward the formation of penta-
coordinated species. Indeed, the O(1)-Pd and O(5)-Pd
distances in 2b (3.549 and 3.460 Å, respectively) and the
O(1)-Pd distance in 3a (3.272 Å) only suggest weak, if not
negligeable, O‚‚‚Pd interactions. Another feature of note is
the fact that, in 3a, the C(1)-C(6), P(1), Pd, and Cl(2′) atoms
(57) Leznoff, D. B.; Rancurel, C.; Sutter, J. P.; Rettig, S. J.; Pink, M.;
Kahn, O. Organometallics 1999, 18, 5097.
(58) Pitter, S.; Dinjus, E.; Jung, B.; Gorls, H. Z. Naturforsch., B 1996, 51,
934.
(59) Coles, S. J.; Faulds, P.; Hurthouse, M. B.; Kelly, D. G.; Ranger, G.
C.; Toner, A. J.; Walker, N. M. J. Organomet. Chem. 1999, 586, 234.
(60) Newkome, G. M.; Evans, D. W.; Fronczek, F. R. Inorg. Chem. 1987,
26, 3500.
Inorganic Chemistry, Vol. 42, No. 24, 2003 7759

Morise et al.
Table 3. Selected Bond Lengths (Å) and Angles (deg) for trans-2b
and 3a
are within the same plane, which is almost perpendicular to
that containing the Pd, Cl, and P atoms.
trans-2b
3a
Cationic Complexes. The cationic complexes 7-9a,b
have been prepared by reaction of the corresponding chloro-
derivatives 4-6 with AgBF4 (or TlPF6 in the case of 7b′
and 8a′) (eqs 1-3). Halide abstraction occurs under mild
conditions, and 7-9 have been isolated in high yields after
purification (see Experimental Section). These new com-
plexes are stabilized by coordination of the phosphate
function of 1 via the oxygen atom of the PdO groups, which
leads to the formation of seven-membered ring metallocycles.
The latter represent, to the best of our knowledge (SciFinder
search), the first examples of metallocycles of this size
involving a P,O-chelate. Selected spectroscopic data of 7-9
are given in Table 1. As a result of the O-coordination, the
ν(PdO) vibrations of 7-9 occurred at shorter wavenumbers
(ca. 60 cm-1) than those of 4-6. A slight low field shift of
the 1H and 31P resonances of the P,O-ligands was observed,
by comparison with those of the corresponding neutral
complexes 4-6 (Table 1). Note that there is no observable
3+4J(PP) coupling.
Pd-Cl1
2.2924(6)
2.2926(6)
2.3432(6)
2.3570(6)
1.811(2)
1.323(3)
1.408(3)
1.578(2)
1.443(2)
1.576(2)
1.570(2)
1.801(2)
1.323(3)
1.403(3)
1.586(2)
1.449(2)
1.563(2)
1.567(2)
178.94(3)
87.48(2)
91.94(2)
91.95(2)
88.65(2)
178.72(2)
129.8(2)
125.2(2)
119.7(2)
126.6(2)
124.2(2)
127.0(2)
117.4(2)
125.4(2)
Pd-Cl1
Pd-Cl2
Pd-Cl2′
Pd-P1
P1-C13
C13-C14
C14-O1
O1-P2
O2-P2
O3-P2
O4-P2
2.288(2)
2.334(2)
2.438(2)
2.244(2)
1.805(4)
1.330(6)
1.395(5)
1.603(3)
1.462(4)
1.557(4)
1.554(3)
Pd-Cl2
Pd-P1
Pd-P3
P1-C13
C13-C14
C14-O1
O1-P2
O2-P2
O3-P2
O4-P2
P3-C45
C45-C46
C46-O5
O5-P4
O6-P4
O7-P4
O8-P4
Cl1-Pd-Cl2
Cl1-Pd-P1
Cl1-Pd-Cl2
Cl1-Pd-Cl2′
Cl1-Pd-P1
Cl2-Pd-Cl2′
Cl2-Pd-P1
Cl2′-Pd-P1
P1-C13-C14
176.71(5)
92.19(4)
88.39(4)
84.76(4)
94.60(4)
177.31(4)
124.9(3)
124.1(4)
116.4(4)
128.0(3)
Cl1-Pd-P3
Cl2-Pd-P3
Cl2-Pd-P3
P1-Pd-P3
P1-C13-C14
C13-C14-C15
C13-C14-O1
C14-O1-P2
P3-C45-C46
C45-C46-C47
C45-C46-O5
C46-O5-P4
C13-C14-C15
C13-C14-O1
C14-O1-P2
Table 4. Selected Bond Lengths (Å) and Angles (deg) for 8a′ and
10a‚CH2Cl2
8a′
10a‚CH2Cl2
Pd-P1
2.249(2)
2.178(4)
2.127(4)
1.983(5)
1.803(5)
1.321(7)
1.478(4)
1.583(4)
1.540(4)
1.543(4)
1.411(6)
1.492(8)
1.474(8)
1.487(7)
95.3(2)
170.7(2)
95.1(2)
88.6(2)
167.7(2)
82.1(2)
126.4(4)
112.6(2)
118.4(4)
Pd-P1
Pd-O4
P1-C13
C13-C14
C14-O1
O1-P2
P2-O2
P2-O3
P2-O4
2.225(2)
2.108(6)
1.792(6)
1.321(8)
1.417(7)
1.558(5)
1.526(5)
1.557(7)
1.448(7)
Pd-O1
Pd-N
Pd-C33
P1-C13
C13-C14
O1-P2
P2-O2
P2-O3
P2-O4
O2-C14
N-C25
N-C26
N-C27
P1-Pd-O1
P1-Pd-N
P1-Pd-C33
O1-Pd-N
O1-Pd-C33
N-Pd-C33
P1-Pd-P1′
P1-Pd-O4
P1-Pd- O4′
O4-Pd-O4′
Pd-P1-C13
P1-C13-C14
C13-C14-O1
O1-P2-O4
99.6(2)
90.6(2)
165.0(2)
81.9(4)
103.2(2)
128.6(4)
119.4(6)
112.5(3)
P1-C13-C14
O1-P2-O2
C13-C14-O2
167.7(2)° and 170.7(2)°, respectively. Chelation of the Pd
center by the dmba ligand is reflected in the Pd-N and Pd-
C(33) distances of 2.127(4) and 1.983(5) Å, respectively,
and in the N-Pd-C(33) angle of 82.1(2)°. These values are
similar to those reported for other complexes containing this
ligand.61-66 Coordination of the P(1) atom [Pd-P(1) )
2.249(2) Å] occurs in cis position to the aryl group of the
dmba ligand (antisymbiotic effect), as already observed in
The crystal structure of [Pd(dmba){Ph2PCHdC(Ph)OP-
(O)(OEt)2}][PF6] (8a′) has been determined. Crystallographic
data and selected bond lengths and angles are given in Tables
2 and 4, respectively. A view of the molecular structure of
the cation in 8a′ is shown in Figure 3. The coordination
around the Pd center is best described as distorted square
planar, with O(1)-Pd-C(33) and P(1)-Pd-N angles of
7760 Inorganic Chemistry, Vol. 42, No. 24, 2003

New Class of P,O Ligands
Figure 4. CrystalMaker view of the ligand environment at the Pd center
in the cation of 8a′, showing the puckering of the seven-membered ring.
consequence of the obtuse P(1)-Pd-O(1) angle, the P(1)-
Pd-C(33) angle [95.1(2)°] is more acute (by 2-5°) than
those found in other complexes containing both dmba and
P,O-chelates.61-63,65,66,69 The most striking feature is the
distortion observed in the seven-membered chelate resulting
in a puckered sofa conformation (Figure 4). Thus, whereas
the Pd, P(1), O(2), P(2), and O(1) atoms are almost coplanar
within 0.106(5) Å, C(13) and C(14) deviate from the plane
by 1.245(5) and 1.166(5) Å, respectively. A dihedral angle
of 120.2(5)° is observed between the best plane passing
through Pd, P(1), O(2), P(2), and O(1) and that containing
C(13), C(14), and C(15) (the ipso carbon atom of the phenyl
ring attached to the double bond). This contrasts with the
situation observed for the six-membered ring complex cis-
Figure 3. ATOMS view of the molecular structure of the cation in 8a′.
related systems.61,62,66,67 The Pd-O(1) distance of 2.178(4)
Å clearly indicates the presence of a dative bond between
these two atoms, thus confirming the chelation of the Pd by
the enolphosphato-phosphine ligand, 1a. To the best of our
knowledge, there is no other structurally characterized seven-
membered mononuclear metallocycle involving a P,O-chelate
(CSD search). The P,O-bite angle [P(1)-Pd-O(1) ) 95.1-
(1)°] is more obtuse than those reported for five- and six-
membered P,O-metallocycles, which range from 80° to
85°61-63,65,68-71 and 88° to 93.5°,64,72-77 respectively. In the
case of a Pd atom chelated with a BINAPO ligand (BINAPO
) 2-diphenylphosphino-2′-diphenylphosphinyl-1,1′-binaph-
thalene), the P,O-bite angle of the resulting eight-membered
ring [90.9(1)°]78 is also more acute than in 8a′. As a probable
[PdCl2{Ph2PCHdC(Ph)OPPh2}], in which the Pd, P, C, C,
O, and P atoms are almost coplanar.53 Thus, increasing the
ring size by one unit leads to a remarkable change of the
conformation of the metallocycle.
Treatment of the chloro-bridged dimers 4a,b with AgBF4
or TlPF6 afforded the mononuclear derivatives 7, for which
stabilization is achieved by coordination of a solvent
molecule (acetonitrile). Interestingly, this reaction was re-
gioselective, with formation, as sole product, of the isomer
in which the Me group is in a cis position to the P atom
[3J(PH) ) ca. 2.5 Hz] (eq 1). Although this arrangement is
consistent with the antisymbiotic effect, it contrasts with that
encountered in related complexes, of the type [PdMe-
(NCMe)(P,O)], for which mixtures of cis and trans isomers
were obtained.54 Reaction of [Pd(NCMe)4][BF4]2 with 2 mol
equiv of 1 led to the formation of complexes 10a,b (eq 4).
In the IR spectrum, the ν(PdO) vibrations are observed at
1221 and 1244 cm-1 for 10a and 10b, respectively (Table
1), which unambiguously establishes coordination of the
PdO groups to the Pd centers. By comparison with the 31P
resonances of 7-9, those of the Ph2P groups in 10 underwent
a low field shift of ca. 7 ppm, whereas those of the phosphate
functionalities were shifted toward higher field by ca. 5 ppm.
Both 31P{1H} NMR spectra consisted of only two signals,
indicating that only one geometric isomer was formed. The
magnitude of the J(PP) value (16 Hz) and other spectroscopic
data suggested the formation of the cis isomer.64,71,72,79 When
[Pd(NCMe)4][BF4]2 was reacted with only 1 mol equiv of
(61) Braunstein, P.; Matt, D.; Nobel, D.; Bouaoud, S.-E.; Grandjean, D. J.
Organomet. Chem. 1986, 301, 401.
(62) Braunstein, P.; Matt, D.; Dusausoy, Y.; Fischer, J.; Mitschler, A.;
Ricard, L. J. Am. Chem. Soc. 1981, 103, 5115.
(63) Andrieu, J.; Braunstein, P.; Dusausoy, Y.; Ghermani, N. E. Inorg.
Chem. 1996, 35, 7174.
(64) Coyle, R. J.; Slovokhotov, Y. L.; Antipin, M. Y.; Grushin, V. V.
Polyhedron 1998, 17, 3059.
(65) Ma, J.-F.; Kojima, Y.; Yamamoto, Y. J. Organomet. Chem. 2000,
616, 149.
(66) Mattheis, C.; Braunstein, P. J. Organomet. Chem. 2001, 621, 218.
(67) Bouaoud, S.-E.; Braunstein, P.; Grandjean, D.; Matt, D.; Nobel, D. J.
Chem. Soc., Chem. Commun. 1987, 489.
(68) Lindner, E.; Schmid, M.; Wegner, P.; Nachtigal, C.; Steimann, M.;
Fawzi, R. Inorg. Chim. Acta 1999, 296, 103.
(69) Slawin, A. M. Z.; Smith, M. B.; Woollins, J. D. J. Chem. Soc., Dalton
Trans. 1996, 1283.
(70) Matt, D.; Sutter-Beydoun, N.; Brunette, J. P.; Balegroune, F.;
Grandjean, D. Inorg. Chem. 1993, 32, 3488.
(71) Braunstein, P.; Douce, L.; Fischer, J.; Craig, N. C.; Goetz-Grandmont,
G.; Matt, D. Inorg. Chim. Acta 1992, 194, 151.
(72) Leung, P.-H.; He, G.; Lang, H.; Liu, A.; Loh, S.-K.; Selvaratnam, S.;
Mok, K. F.; White, A. J. P.; Williams, D. J. Tetrahedron 2000, 56, 7.
(73) Gu¨l, N.; Nelson, J. H. Tetrahedron 2000, 56, 71.
(74) Butts, C. P.; Crosby, J.; Lloyd-Jones, G. C.; Stephen, S. C. J. Chem.
Soc., Chem. Commun. 1999, 1707.
(75) Bei, X.; Uno, T.; Norris, J.; Turner, H. W.; Weinberg, W. H.; Guram,
A. S.; Petersen, J. L. Organometallics 1999, 18, 1840.
(76) Leung, P.-H.; Lang, H.; White, A. J. P.; Williams, D. J. Tetrahedron:
Asymmetry 1998, 9, 2961.
(78) Gladiali, S.; Pulacchini, S.; Fabbri, D.; Manassero, M.; Sansoni, M.
Tetrahedron: Asymmetry 1998, 9, 391.
(77) Leung, P.-H.; Loh, S.-K.; Vittal, J. J.; White, A. J. P.; Williams, D. J.
J. Chem. Soc., Chem. Commun. 1997.
(79) Redwine, K. D.; Wilson, W. L.; Moses, D. G.; Catalano, V. J.; Nelson,
J. H. Inorg. Chem. 2000, 39, 3392.
Inorganic Chemistry, Vol. 42, No. 24, 2003 7761

Morise et al.
Figure 6. CrystalMaker view of the ligand environment at the Pd center
in the cation of 10a‚CH2Cl2, showing the puckering of the seven-membered
rings.
Figure 5. ATOMS view of the molecular structure of the cation in
10a‚CH2Cl2.
atoms by 1.232(7) and 1.283(7) Å, respectively. A partial
view of the puckering of the chelate rings is depicted in
Figure 6. The dihedral angle between the latter plane and
that containing the C(13), C(14), and C(15) atoms is more
acute than in 8a′ [111.9(7)° vs 120.2(5)°].
1, complexes 10 were also formed and unreacted Pd starting
material was recovered. No other products were detected,
showing that the formation of the bis-P,O-chelates 10 is
thermodynamically favored.
Reaction of 7b with 1 mol equiv of 1b afforded the new
complex 11b (eq 5). The 31P{1H} NMR spectrum showed
only two singlets at δ 13.9 and -18.3 ppm, which were
ascribed to the phosphine and phosphate moieties, respec-
tively (Table 1). The former value is intermediate between
the chemical shifts observed for 1b in 7b (δ 21.5), where
this ligand behaves as a P,O-chelate, and in 12 (δ 2.3), in
which it is P-monocoordinated in trans position to another
phosphine moiety. This suggests the occurrence in solution
of a fast equilibrium on the NMR time scale 11b h 11b′,
resulting from the P,O-ligand acting alternatively as a
1
chelating or monodentate ligand (eq 5). The H NMR data
The proposed structure was confirmed by an X-ray
are consistent with the proposed structure. Thus, the reso-
3
nance for the methyl protons is a triplet [3J(PH) ≈ J(P′H)
determination of cis-[Pd{Ph2PCHdC(Ph)OP(O)(OEt)2}2]-
[BF4]2 (10a‚CH2Cl2). Crystallographic data and selected bond
lengths and angles are given in Tables 2 and 4, respectively.
A view of the molecular structure of the cation in 10a‚CH2Cl2
is shown in Figure 5, confirming that the Pd center is chelated
by two enolphosphato-phosphine ligands 1a. The phosphine
moieties occupy mutually cis positions [P(1)-Pd-P(1′) )
99.6(2)°], and a C2 axis passes through the Pd center. The
Pd-P(1) [2.225(2) Å] and Pd-O(4) [2.108(6) Å] bond
distances are within the expected range for bis-P,O-chelated
palladium complexes.64,71,72,79 The coordination environment
of the palladium atom is best described as distorted square
planar, with a P(1)-Pd-O(4′) angle of 165.0(2)°. Interatomic
bond lengths and angles within the P,O-ligand are in the
≈ 6.4 Hz], the two PPh2 groups appearing equivalent as a
result of the equilibrium already mentioned (Table 1). The
different coordination modes adopted by the two ligands 1b
in 11b were evidenced in the solid state IR spectrum (KBr
pellet). Two ν(PdO) vibrations at 1310 and 1243 cm-1 were
observed for the free and coordinated PdO function,
respectively. A similar hemilabile behavior has been observed
for the P,O-ligands Ph2PNRC(O)Me (R ) H, Me) and Ph2-
PCH2C(O)Ph in complexes analogous to 11b, i.e., [PdMe-
(P,O)2][PF6].54 Complex 11a, prepared from 7a and 1a,
showed in solution the same dynamic behavior as that
observed for 11b (eq 5). In particular, this was reflected in
the 31P NMR spectrum, which consisted of two singlets at δ
13.3 ppm (PPh2) and -6.6 ppm (phosphate) (Table 1). As
for 11b, the solid state IR spectrum revealed a static situation
with one ligand 1a acting as a P,O-chelate [ν(PdO): 1225
cm-1] while the other one is only P-coordinated [ν(PdO):
1272 cm-1].
expected range. As in [Pd(dmba){Ph2PCHdC(Ph)OP(O)-
(OEt)2}][PF6] (8a′), the seven-membered ring adopts a sofa
conformation, with C(13) and C(14) deviating from the mean
plane passing through the Pd-P(1)-O(1)-P(2) and O(4)
7762 Inorganic Chemistry, Vol. 42, No. 24, 2003

New Class of P,O Ligands
product) and of 11a and 1554 (Scheme 3). This was clearly
evidenced in the 31P{1H} NMR spectrum, which showed the
signals of an AB spin system for 14a at δ 15.0 and 18.3
ppm, ascribed to the Ph2P moieties of 1a and the ketophos-
phine, respectively. In the latter case, the chemical shift is
characteristic for this ligand being P-monocoordinated to a
cationic Pd center.54 The magnitude of the 2J(PP) value (408
Hz) is indicative of a mutual trans arrangement of these
nuclei. The proposed structure of 14a is consistent with the
presence in the IR spectrum (KBr) of two strong vibrations
at 1672 and 1223 cm-1, corresponding to the free CdO and
coordinated PdO functions, respectively. Interestingly, when
complex 1654 was treated with 1 mol equiv of 1a, the same
reaction mixture was obtained (Scheme 3). This suggests the
existence of a thermodynamic equilibrium between 14a and
11a and 15 (Scheme 3), and in situ 31P{1H} NMR spectros-
copy gave a relative ratio of 9:1:1, respectively.
Similarly, a mixture of products consisting of 14b, 11b,
and 15 was obtained from 7b and Ph2PCH2C(O)Ph, or from
16 and 1b. The spectroscopic data are consistent with the
proposed structure for 14b (Table 1). However, the three
products are present in different proportions to the previous
mixture. Indeed, the ratio 14b and 11b and 15 was 4:1:1,
respectively.
Although ligand redistribution is observed, these experi-
ments indicate a higher chelating ability of 1a and 1b than
Ph2PCH2C(O)Ph. Not only was chelation of the latter not
observed in the presence of coordinated 1a or 1b (see 14a
and 14b), but the enolphosphatophosphine 1a or 1b displaces
the pre-existing P,O-chelate in 16. It is interesting that
chelation of 1a and 1b in 7a and 7b, respectively, gives rise
to more stable complexes than that of Ph2PCH2C(O)Ph in
16. Furthermore, the observed product ratios, with a stronger
predominance of 14a than 14b, suggest different chelating
abilities for the two enolphosphato-ligands 1a and 1b. Thus,
we set out to prepare a complex containing both ligands,
which could compete for chelation around the metal center.
Complexes 7a and 7b were treated with 1 mol equiv of 1b
and 1a, respectively. Both reactions led to the formation of
17, as the main product, accompanied with that of 11a and
11b, with similar relative ratios of 4:1:1, respectively
(eq 7).
The chelating ability of 1a and 1b was further compared
to that of other P,O-ligands. Reaction of complexes 7a and
7b with 1 mol equiv of the acetamidophosphine Ph2PNHC-
(O)Me54 led to the formation of a single product, 13a and
13b, respectively (eq 6). The 31P{1H} NMR spectrum of 13a
showed two doublets at δ 70.8 and 8.8 ppm, which were
ascribed to the Ph2P moieties of the acetamidophosphine and
1a, respectively. The 2J(PP) value of 401 Hz indicates a trans
arrangement of these two nuclei around the Pd center. The
range of 31P chemical shifts indicates that the pre-existing
P,O-chelate in 7a has been displaced by the incoming
acetamidophosphine ligand.54 This was confirmed by the IR
spectrum which showed two strong vibrations at 1608 and
1271 cm-1, ascribed to coordinated CdO of Ph2PNHC(O)-
Me (free ligand: 1715 cm-1)54 and free PdO of 1a, respec-
1
tively. In the H NMR spectrum, the enolate resonance
occurred at δ 5.84 ppm, whereas the NH proton was observed
at δ 9.56 ppm. The spectroscopic data of 13b are similar to
those of 13a and are consistent with the proposed structure.
1
The only noticeable difference concerns the H resonance
of the enolate proton, which resonated in 13b at lower field
than in 13a (δ 6.08 ppm).
If the acetamido phosphine Ph2PNHC(O)Me clearly
presents a higher chelating ability than 1a and 1b, a different
situation was observed when the complexes 7a and 7b were
reacted with the â-ketophosphine Ph2PCH2C(O)Ph. In both
cases, a mixture of products was obtained. The reaction with
7a led to the formation of the new complex 14a (main
Inorganic Chemistry, Vol. 42, No. 24, 2003 7763

Morise et al.
Scheme 3
which the two enolate resonances of 17 occur at δ 6.10 and
6.40. The former chemical shift value is very similar to that
observed for the enolate proton of 1b when this ligand acts
as a P-monodentate ligand in other cationic Pd complexes,
such as 12 or 13b, thus supporting the same coordination
mode for this ligand in 17. This indicates that 1a presents a
higher chelating ability than 1b. This is probably due to the
slightly enhanced electron-donating properties of the ethoxy
groups in 1a compared to that of the phenoxy groups in 1b,
resulting in the PdO function in 1a being more electron-
rich than that of 1b. In the free ligands, the lower electron-
donating properties of the OPh groups in 1b are also reflected
in the 31P phosphate resonance (δ -18.0) and in the
ν(PdO) vibration (1313 cm-1), which occurred at higher
field (δ -7.0) and higher wavenumbers (1277 cm-1) than
those of 1a, respectively.
When complexes 8 were reacted with 1 mol equiv of
Et4NCl, the coordinated phosphates were substituted by Cl-
and the neutral chloro-complexes 5 obtained (Scheme 4).
Interestingly, in the presence of PPh3 no reaction was
observed, the P,O-chelates in 8 being not displaced. How-
ever, treatment of these complexes with the functional
phosphine Ph2PNHC(O)Me54 resulted not only in the opening
of the P,O-chelate, as observed in 13a,b, but in the complete
The spectroscopic data are consistent with the proposed
structure of 17 (Table 1). In the 31P{1H} NMR spectrum,
the two phosphine moieties give rise to an AB system at δ
2
16.6 and 12.1 ppm, with a J(PP) value of 404 Hz. This
indicates a static situation in 17, with the two phosphine
groups being trans to each other, and evidences the fact that
one of the enolphosphatophosphine ligands acts as a P,O-
chelate while the other one is P-monocoordinated. The 31P
chemical shifts for both the phosphine and phosphate
moieties in 17 suggested the chelating ligand to be 1a.
displacement of 1. Thus, the known complex [Pd(dmba)-
{Ph2PNHC(O)Me}][BF4] (18),54 in which the incoming
1
Additional evidence came from the H NMR spectrum in
7764 Inorganic Chemistry, Vol. 42, No. 24, 2003

New Class of P,O Ligands
Scheme 4
Table 5. Selected Bond Lengths (Å) and Angles (deg) for 18
C1-Pd
C6-C7
C7-N1
C10-O
C10-N2
1.988(2)
1.502(3)
1.491(2)
1.246(2)
1.352(2)
C10-C11
N1-Pd
N2-P
1.500(3)
2.123(2)
1.722(2)
2.140(2)
2.217(2)
Figure 7. ATOMS view of the molecular structure of the cation in 18.
Pd-O
SCF3] [2.181(4) Å].54 In the latter, the Pd-P bond lengths
of 2.307(2) and 2.265(2) Å, for the monodentate and chelate
ligands, respectively,54 are also longer than that found in 18
[2.217(2) Å]. The other bond distances and angles involving
the dmba and P,O-ligands are within the expected range.
Pd-P
C1-Pd-O
N1-Pd-P
N1-Pd-O
C1-Pd-N1
C1-Pd-P
O-Pd-P
175.90(6)
175.63(4)
95.16(6)
83.10(7)
99.24(6)
82.75(5)
C7-N1-Pd
C10-O-Pd
N2-P -Pd
O-C10-N2
C10-N2-P
106.6(1)
117.0(2)
99.36(6)
121.6(2)
119.3(2)
Conclusion
We have prepared the first P,O-ligands combining a
phosphine moiety and an enolphosphate function. In their
palladium complexes, they can either monocoordinate the
metal center via their P atom or act as P,O-chelates, in which
case they may display a hemilabile behavior. The sofa
conformation observed for the seven-membered metallo-
cycles, obtained by P,O-chelation of these ligands, results
in an interesting face discrimation in square planar com-
plexes. This may be of future interest for regio/stereoselective
chemical transformations. The fact that the ethoxy ligand
1a appears to be a better chelate than its phenoxy analogue
1b suggests that fine-tuning of the electron-donating proper-
ties of this class of ligands, and hence the reactivity of their
metal complexes, could be achieved by changing the nature
of the substitutents of the phosphate functionality.
acetamidophosphine acts as P,O-chelate, was obtained in
almost quantitative yields (Scheme 4). This most likely
results from the formation of the entropically favored five-
membered metallocycle in 18, due to the known chelating
ability of Ph2PNHC(O)Me.54 It also reflects the importance
of keeping a relatively hard donor atom (oxygen) trans to
the σ-bonded carbon donor (antisymbiotic effect). This would
clearly not have been possible with PPh3 as a donor. Note
that treatment of 8 with the â-ketophosphine Ph2PCH2C-
(O)Ph led to untractable mixtures of products, which mainly
resulted from complex ligand redistribution reactions.
Crystal Structure of 18. During the course of this study,
X-ray quality crystals of [Pd(dmba){Ph2PNHC(O)Me}][BF4]
(18) have been obtained. Crystallographic data and selected
bond lengths and angles are given in Tables 2 and 5,
respectively. A view of the molecular structure of the cation
in 18 is shown in Figure 7. The geometry around the Pd
center is square planar, with C(1)-Pd-O and P-Pd-N(1)
angle values of 175.90(6)° and 175.63(4)°, respectively. The
Pd is chelated by the dmba moiety, and as expected,
coordination of the P atom occurs in trans position to the N
atom of the NMe2 group, as observed in 8a′ (vide supra).
The Pd-O distance of 2.140(2) Å is indicative of an effective
bond between these two atoms and of the P,O -chelation of
Ph2PNHC(O)Me. A slightly longer Pd-O bond length was
Acknowledgment. We are grateful to Dr. A. DeCian and
Mrs. N. Gruber for assistance with the crystal structure
determinations. This work was supported by the Centre
National de la Recherche Scientifique and the Ministe`re
De´le´gue´ a` la Recherche et aux Nouvelles Technologies.
Supporting Information Available: Crystallographic data in
CIF format and ORTEP plots. This material is available free of
charge via the Internet at http://pubs.acs.org. The crystallographic
material can also be obtained from the CCDC, the deposition
numbers being CCDC 215457-215461.
found in [PdMe{Ph2PNHC(O)Me}{Ph2PNHC(O)Me}][O3-
IC030032Y
Inorganic Chemistry, Vol. 42, No. 24, 2003 7765