Palladium coordination compounds of σ3λ5-phosphoranes: First examples of phosphonio-methylene(imino)metallophosphorane [(R3P)(Me3Si)C=P(MLn)=NSiMe3] and phosphonio-methylene(oxo)phosphorane [(R3P)(Me3Si)C=P(=O)NSiMe3] ligands

Article abstract of DOI:10.1021/om9801913

The oxidative addition reaction of Pd(PPh₃)₄ with Cl₂C=PN(SiMe₃)₂ forms the phosphavinyl phosphonium complex Cl(Ph₃P)Pd[η²-C(Cl)(PPh₃)=PN(SiMe ₃)₂] (IIIa), which results from PPh₃ migration from Pd to carbon in the η¹-phosphavinyl intermediate trans-Cl(Ph₃P)₂Pd-[C(Cl)=PN(SiMe₃)₂] (IIa). The reaction of Pd(dba)(dppe) with Cl₂C=PN(SiMe₃)₂ forms the η¹-phosphavinyl complex cis-Cl(dppe)Pd[C(Cl)=PN(SiMe₃)₂] (VI), which does not undergo phosphine migration. Compound IIIa undergoes substitution of the chloride ligand by PPh₃ or MeCN in the presence of KPF₆ to generate [(Ph₃P)₂Pd(η₂-C(Cl)(PPh ₃)=PN(SiMe₃)₂)](PF₆) (IV) or [(Ph₃P)(MeCN)Pd(η²-C(Cl)(PPh₃)=PN(SiMe ₃)₂)](PF₆) (V), respectively; the structure of V was determined by X-ray diffraction studies. The reaction of Pd(PEt₃)₄ with Cl₂C= PN(SiMe₃)₂ forms the η¹-phosphavinyl complex trans-Cl(Et₃P)₂Pd[C(Cl)=PN(SiMe₃)₂] (IIb), which does not undergo PEt₃ migration. When 2 equiv of Pd(PEt₃)₄ are reacted with Cl₂C= PN(SiMe₃)₂ the phosphonio-methylene(imino)metallophosphorane complex Pd(PEt₃)(Cl)[μ-η¹:η²-C(SiMe ₃)(PEt₃)=P=N(SiMe₃)]Pd(PEt₃)Cl (VIIa-b) forms as a 1:1 isomeric mixture. Compound VIIa-b reacts with MeI or NaI to generate Pd(PEt₃)(I)[μ-η¹:η²-C(SiMe ₃)(PEt₃)= P=N(SiMe₃)]Pd(PEt₃)I (VIIIa-b) and reacts with traces of water to generate Cl(Et₃P)Pd-[η²-C(SiMe₃)(PEt ₃)=P(=O)NH(SiMe₃)] (IX). The structure of VIIIb was partially determined, and the structure of IX was determined by X-ray diffraction studies. Compounds VIIa-b, VIIIa-b, and IX exhibit the first examples of coordinated methylene(imino, oxo)phosphorane ligands.

Full text of DOI:10.1021/om9801913

Organometallics 1998, 17, 5275-5286
5275
P a lla d iu m Coor d in a tion Com p ou n d s of
σ3λ5-P h osp h or a n es: F ir st Exa m p les of
P h osp h on io-Meth ylen e(im in o)m eta llop h osp h or a n e
[(R3P )(Me3Si)CdP (MLn )dNSiMe3] a n d
P h osp h on io-Meth ylen e(oxo)p h osp h or a n e
[(R3P )(Me3Si)CdP (dO)NSiMe3] Liga n d s
Wayde V. Konze, Victor G. Young, J r.,† and Robert J . Angelici*
Department of Chemistry, Iowa State University, Ames, Iowa 50011
Received March 16, 1998
The oxidative addition reaction of Pd(PPh3)4 with Cl2CdPN(SiMe3)2 forms the phosphavinyl
phosphonium complex Cl(Ph3P)Pd[η2-C(Cl)(PPh3)dPN(SiMe3)2] (IIIa ), which results from
PPh3 migration from Pd to carbon in the η1-phosphavinyl intermediate trans-Cl(Ph3P)2Pd-
[C(Cl)dPN(SiMe3)2] (IIa ). The reaction of Pd(dba)(dppe) with Cl2CdPN(SiMe3)2 forms the
η1-phosphavinyl complex cis-Cl(dppe)Pd[C(Cl)dPN(SiMe3)2] (VI), which does not undergo
phosphine migration. Compound IIIa undergoes substitution of the chloride ligand by PPh3
or MeCN in the presence of KPF6 to generate [(Ph3P)2Pd(η2-C(Cl)(PPh3)dPN(SiMe3)2)](PF6)
(IV) or [(Ph3P)(MeCN)Pd(η2-C(Cl)(PPh3)dPN(SiMe3)2)](PF6) (V), respectively; the structure
of V was determined by X-ray diffraction studies. The reaction of Pd(PEt3)4 with Cl2Cd
PN(SiMe3)2 forms the η1-phosphavinyl complex trans-Cl(Et3P)2Pd[C(Cl)dPN(SiMe3)2] (IIb),
which does not undergo PEt3 migration. When 2 equiv of Pd(PEt3)4 are reacted with Cl2Cd
PN(SiMe3)2 the phosphonio-methylene(imino)metallophosphorane complex Pd(PEt3)(Cl)[µ-
η1:η2-C(SiMe3)(PEt3)dPdN(SiMe3)]Pd(PEt3)Cl (VIIa -b) forms as a 1:1 isomeric mixture.
Compound VIIa -b reacts with MeI or NaI to generate Pd(PEt3)(I)[µ-η1:η2-C(SiMe3)(PEt3)d
PdN(SiMe3)]Pd(PEt3)I (VIIIa -b) and reacts with traces of water to generate Cl(Et3P)Pd-
[η2-C(SiMe3)(PEt3)dP(dO)NH(SiMe3)] (IX). The structure of VIIIb was partially determined,
and the structure of IX was determined by X-ray diffraction studies. Compounds VIIa -b,
VIIIa -b, and IX exhibit the first examples of coordinated methylene(imino, oxo)phosphorane
ligands.
In tr od u ction
CdP double-bond character are coordinated; in addition,
a few examples of η2-coordinated diphosphaallenes have
been reported.9 There are also examples of cyclic
phosphorus-substituted ligands including η4-phosphacy-
clobutadienes, η5-phosphacyclopentadienyls, and η6-
phosphabenzenes in which delocalized rings containing
CdP double bonds are coordinated to transition metal
complexes.10 The propensity for η2-coordination of Cd
P double bonds is especially evident in phosphallenes
(A) which coordinate through the CdP double bond in
preference to the CdC double bond.11,12 In view of the
many different coordination compounds with ligands
containing CdP double bonds, it is interesting that there
are none of methylene(oxo)phosphoranes R2CdP(dO)R
(B) or methylene(imino)phosphoranes R2CdP(dNR)R
(C). These compounds are included in a recent review13
of three-coordinate pentavalent phosphorus compounds
Carbon-phosphorus multiply bonded ligands have
received much attention recently because of the rich
coordination chemistry that they afford. In particular,
the CdP double bonds in several different types of
ligands have been found to exhibit a preferential η2-
coordination mode in many transition metal complexes.
Several examples of η2-coordinated phosphaalkenes are
known,1-4 and there are examples of η3-coordinated
diphosphaallyl complexes,5-8 in which two bonds having
† X-ray Crystallographic Laboratory, Chemistry Department, Uni-
versity of Minnesota, Minneapolis, Minnesota 55455.
(1) van der Knaap, T. A.; J anneskens, L. W.; Meeuwissen, H. J .;
Bickelhaupt, F.; Walther, D.; Dinjus, E.; Uhlig, E.; Spek, A. L. J .
Organomet. Chem. 1983, 254, C33.
(2) van der Knaap, T. A.; Bickelhaupt, F.; Kraaykamp, J . G.; Koten,
G. V.; Bernards, J . P. C.; Edzes, H. T.; Veeman, W. S.; Boer, E. D.;
Baerends, E. J . Organometallics 1984, 3, 1804-1811.
(3) Al-Resayes, S. I.; Klein, S. I.; Kroto, H. W.; Meidine, M. F.; Nixon,
J . F. J . Chem. Soc., Chem. Commun. 1983, 930.
(4) Cowley, A. H.; J ones, R. A.; Stewart, C. A.; Stuart, A. L.; Atwood,
J . L.; Hunter, W. E.; Zhang, H. M. J . Am. Chem. Soc. 1983, 105, 3737-
3738.
(5) Appel, R.; Schuhn, W.; Knoch, F. Angew. Chem., Int. Ed. Engl.
1985, 24, 420.
(8) El-Ouatib, R.; Ballivet-Tkatchenko, D.; Etemad-Moghadam, G.;
Koenig, M. J . Organomet. Chem. 1993, 453, 77-84.
(9) Bickelhaupt, F. Multiple Bonds and Low Coordination in
Phosphorus Chemistry; Regitz, M., Scherer, O. J ., Ed.; Thieme:
Stuttgart, 1990; pp 195-199.
(10) Mathey, F. New J . Chem. 1987, 11, 585-593.
(11) Nixon, J . F. Phosphorus Sulfur 1987, 30, 471.
(12) Nixon, J . F. Chem. Rev. 1988, 88, 1327.
(6) Appel, R.; Schuhn, W.; Knoch, F. J . Organomet. Chem. 1987,
319, 345.
(7) Appel, R.; Schuhn, W. J . Organomet. Chem. 1987, 329, 179.
(13) Romanenko, V. D.; Sanchez, M. Coord. Chem. Rev. 1997, 158,
275-324.
10.1021/om9801913 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 10/29/1998

5276 Organometallics, Vol. 17, No. 24, 1998
Konze et al.
(σ3λ5-phosphoranes) and constitute an area of recently
increased study. In these methylene(oxo, imino)phos-
phoranes, the CdP double bond should allow for η2-
coordination to a transition metal, although such com-
plexes have not been previously discussed.
We recently succeeded in preparing the first example
of a coordinated isocyaphide (CtPR) ligand by oxidative
addition of the C-X bond in the phosphavinyl complex
(1) (eq 1) to generate a diplatinum complex [(Cl)(Et3P)-
characterize the first example of a complex 5, containing
a phosphavinyl phosphonium ligand. In these reactions,
the R-group migration from phosphorus to carbon was
avoided and an interesting PPh3 migration to the CdP
carbon afforded the new ligands. The reactions in eqs
3 and 4 were postulated to involve η1-phosphavinyl
intermediates similar to that (1) in eq 1, which then
rearranged to η2-phosphavinyl complexes having car-
bene-like character, which facilitated the attack of PPh3
on the CdP carbon atoms.17
In our continuing studies of oxidative addition reac-
tions of dihalophosphaalkenes with low-valent transi-
tion metal complexes, we explore in the present paper
reactions of Cl2CdPN(SiMe3)2 with Pd(0) complexes.
During the course of these studies, we isolated a stable
phosphavinyl phosphonium complex that is the pal-
ladium analogue of the unstable nickel complex 3 (eq
3) and explored ligand substitution reactions to generate
a series of these complexes with η2-(R3P)(Cl)CdPR
ligands acting as three-electron donors (D). We have
also isolated the first example of a complex with a
phosphonio-methylene(imino)metallophosphorane ligand
η2-coordinated to one palladium center and η1-coordi-
nated to another in a dinuclear complex (E). This new
ligand results from a 1,3-SiMe3 migration from nitrogen
to carbon and was further functionalized by a hydrolysis
reaction into the first example of a phosphonio-meth-
ylene(oxo)phosphorane ligand, which is η2-coordinated
to a palladium atom with the (R3P)(Me3Si)CdP(dO)-
NSiMe3 ligand acting as a three-electron donor (F ). The
Pt(µ-CdPR)Pt(PEt3)2(Cl)] (2) containing a semibridging
CtPR group.14 A series of phosphavinyl compounds
X(R′3P)2M[C(dPR)X] (M ) Pt, Pd; X ) Cl, Br; R′ ) Ph,
Et; R ) 2,4,6-tri-tert-butylbenzene) analogous to 1 were
prepared and in all cases exhibited a novel R-group
migration from phosphorus to carbon to generate
Mes*CtP and M(PR′3)2X2.15 Romanenko and co-work-
ers16 reported the reaction of Pd(PPh3)4 with Cl2CdP-
Mes*, which resulted in the formation of Mes*CtP and
Pd(PPh3)2Cl2 with no observable intermediates (eq 2).
The Mes* group rearrangement in these reactions
prompted us to attempt similar oxidative addition
reactions between dihalophosphaalkenes containing
nonaromatic R-groups and low-valent transition metals.
In the course of these studies, we have prepared17 (eq
3) and structurally characterized the first example of a
ligands in E and F represent the first examples of
transition metal-coordinated methylene(imino)phospho-
ranes and methylene(oxo)phosphoranes, respectively.
Although these ligands contain phosphonio substituents
on the CdP carbon atoms, their η2-coordination through
the CdP double bond opens up the possibility of
coordinating other members of this well-known class of
σ3λ5-phosphoranes.
The preparations of complexes of types D, E, and F
are discussed, along with substitution reactions, likely
pathways of formation, and chemical reactivity. Struc-
ture and bonding in the complexes containing these new
ligands are also examined.
complex 4, containing a phosphavinylidene phosphorane
(Ph3PdCdPR) ligand, which forms from an intermedi-
ate phosphavinyl phosphonium complex (3), which was
not isolated. In a similar reaction17 (eq 4) with Mes*
as the R-group, we were able to isolate and structurally
(14) J un, H.; Angelici, R. J . Organometallics 1994, 13, 2454-60.
(15) J un, H.; Young, V. G., J r.; Angelici, R. J . Organometallics 1994,
13, 2444-53.
Exp er im en ta l Section
(16) Romanenko, V. D.; Sanchez, M.; Sarina, T. V.; Mazie`res, M.
R.; Wolf, R. Tetrahedron Lett. 1992, 21, 2981.
(17) Konze, W. V.; Young, V. G., J r.; Angelici, R. J . Organometallics
1998, 17, 1569-1581.
Gen er a l P r oced u r e. All manipulations were carried out
under a dry, oxygen-free argon atmosphere, using standard
Schlenk techniques. Solvents were reagent grade and dried

Pd Coordination Compounds of σ3λ5-Phosphoranes
Organometallics, Vol. 17, No. 24, 1998 5277
Sch em e 1
Sch em e 2
by refluxing over appropriate drying agents under nitrogen.
Tetrahydrofuran (THF) and diethyl ether (Et2O) were distilled
over sodium benzophenone ketyl, while hexanes, toluene, and
dichloromethane were distilled over CaH2. Acetonitrile was
distilled over anhydrous MgSO4.
For IIa , 0 °C: δ(P(x)) 213.9 (t, 3J P(x)P(a) ) 50.1 Hz), δ(P(a)) 22.3
3
(d, J P(a)P(x) ) 50.1 Hz). For IIIa , 25 °C: δ(P(x)) 124.4 (d,
2J P(x)P(a) ) 91.4 Hz), δ(P(a)) 25.8 (dd, 2J P(a)P(x) ) 91.4 Hz, 3J P(a)P(b)
3
) 10.1 Hz), δ(P(b)) 21.3 (d, J P(b)P(a) ) 10.1 Hz). Electrospray
The 1H NMR spectra of compounds were recorded on a
Varian VXR 300 MHz spectrometer with TMS (δ 0.00 ppm)
as the internal standard. The 31P{1H} and 31P NMR spectra
were recorded on a Bruker AC 200 MHz spectrometer using
85% H3PO4 (δ 0.00 ppm) as the external standard. The 13C-
{1H} and 13C NMR spectra were recorded on a Bruker DRX
400 MHz spectrometer using CDCl3 as the internal standard.
Electrospray mass spectra were recorded on a Finnigan TSQ
700 spectrometer using CH2Cl2 as solvent. FAB mass spectra
were recorded on a Kratos MS 50 spectrometer using THF as
solvent. The compounds Pd(dppe)(dba),18 Pd(PPh3)2(dba),18
MS (for IIIa ): m/e 870 (M+ - Cl), 608 (M+ - (Cl + PPh3)).
Anal. Calcd for C43H48Cl2N1P3Pd1Si2 (IIIa ): C, 57.05; H, 5.34;
N, 1.55. Found: C, 56.75; H, 5.46; N, 1.68.
P r epar ation of [(P h 3P )2P d(η2-C(Cl)(P P h 3)dP N(SiMe3)2)]-
(P F 6) (IV). Meth od A. To a cooled (-50 °C), stirred slurry
of Pd(PPh3)4 (1.00 g, 0.865 mmol) in CH2Cl2 (20 mL) was added
Cl2CdPN(SiMe3)2 (0.261 g, 0.952 mmol) and KPF6 (0.319 g,
1.73 mmol). The initially light yellow solution turned red upon
warming slowly to room temperature with stirring over a
period of about 1 h. The solution was filtered, the filtrate was
reduced to 5 mL, and 25 mL of hexanes was added to form a
yellow precipitate, which was collected on a medium-porosity
fritted glass filter and washed with 3 × 10 mL portions of Et2O
Pd(PPh3)4,19 Pd(PEt3)3,20 and Cl2CdPN(SiMe3)2 were pre-
21
pared by literature methods. Phosphine ligands were pur-
chased from Strem and used without further purification, with
the exception of PPh3, which was recrystallized from MeOH.
P r epar ation of Cl(P h 3P )P d[η2-C(Cl)(P P h 3)dP N(SiMe3)2]
(IIIa ) th r ou gh In ter m ed ia tes (P h 3P )2P d [η2-C(Cl)2dP N-
(SiMe3)2] (Ia ) a n d tr a n s-Cl(P h 3P )2P d [C(Cl)dP N(SiMe3)2]
(IIa ). To a cooled (-50 °C) slurry of Pd(PPh3)4 (1.00 g, 0.865
mmol) in CH2Cl2 (20 mL) was added Cl2CdPN(SiMe3)2 (0.261
g, 0.952 mmol). The initially light yellow solution was warmed
to yield 0.715 g of crude product.
A
31P NMR spectrum (in
CH2Cl2) showed that this precipitate contained almost pure
IV, with a small amount (≈5%) of [Pd(PPh3)3Cl](PF6) (char-
acterized by comparison of its 31P NMR spectrum with
literature values).23 Further attempts to purify compound IV
resulted in decomposition with formation of [Pd(PPh3)3Cl](PF6)
and unidentifiable products.
Met h od B. To
a
solution of Cl(Ph3P)Pd[η2-C(Cl)-
slowly with stirring.
A
31P{1H} NMR spectrum taken after
(PPh3)dPN(SiMe3)2] (IIIa ) (0.100 g, 0.110 mmol) in CH2Cl2
(5 mL) was added PPh3 (0.0318 g, 0.121 mmol) and KPF6
(0.0223 g, 0.121 mmol). After stirring for 30 min the solution
was filtered, the filtrate was reduced to 5 mL, and 25 mL of
hexanes was added to form a yellow precipitate, which was
collected on a medium-porosity fritted glass filter and washed
the initial addition (-50 °C) showed Ia as the only intermedi-
ate. After the solution was allowed to warm slowly to 0 °C,
the color turned dark red.
A
31P{1H} NMR spectrum was
taken (0 °C) and showed traces of Ia along with IIa as the
main product. When the solution reached room temperature
after about 1 h, IIa had converted almost completely to IIIa ,
along with formation of Pd(PPh3)2Cl2 (characterized by com-
parison of its 31P NMR spectrum with that of an authentic
sample).22 The solution was filtered and the solvent was
removed under vacuum from the filtrate to yield a red oily
solid. The residue was treated with 25 mL of THF, the red
solution was filtered to remove Pd(PPh3)2Cl2, and the filtrate
was reduced to 2 mL. After adding 20 mL of hexanes and
cooling to 0 °C, a light yellow precipitate formed, which was
collected on a medium-porosity fritted glass filter, washed with
3 × 5 mL portions of hexanes, and dried under vacuum to give
analytically pure IIIa (0.580 g, 74% based on Pd). 31P{1H}
NMR (CH2Cl2) (see Scheme 1 for atom labels) for Ia , -50 °C:
δ(P(x)) 41.8 (dd, 2J P(x)P(b) ) 35.3 Hz, 2J P(x)P(a) ) 23.4 Hz), δ(P(a))
25.8 (d, 2J P(a)P(x) ) 23.4 Hz), δ(P(b)) 21.3 (d, 2J P(b)P(x) ) 35.3 Hz).
with 3 × 10 mL portions of Et2O.
A
31P NMR spectrum in
CH2Cl2 showed that this precipitate contained IV with a small
amount of [Pd(PPh3)3Cl](PF6) impurity, which could not be
separated. 31P{1H} NMR (CD2Cl2, 0 °C) (see Scheme 2 for
2
2
atom labels): δ(P(x)) 118.2 (ddd, J P(x)P(a) ) 123.6 Hz, J P(x)P(c)
) 32.5 Hz, 2J P(x)P(b) ) 5.1 Hz), δ(P(a)) 25.1 (ddd, 2J P(a)P(x) ) 123.6
3
3
Hz, J P(a)P(b) ) 20.1 Hz, J P(a)P(c) ) 20.6 Hz), δ(P(b)) 17.4 (ddd,
3J P(b)P(a) ) 20.1 Hz, J P(b)P(c) ) 11.9 Hz, J P(b)P(x) ) 5.1 Hz),
δ(P(c)) 13.8 (ddd, 2J P(c)P(x) ) 32.5 Hz, 3J P(c)P(a) ) 20.6 Hz, 2J P(c)P(b)
) 11.9 Hz), δ(PF6) -144 (sept., 1J PF ) 709.1 Hz). Electrospray
MS: m/e 870 (M+ - PPh3), 608 (M+ - (Cl + PPh3)).
2
2
P r ep a r a tion of [(P h 3P )(MeCN)P d (η2-C(Cl)(P P h 3)dP N-
(SiMe3)2)](P F 6) (V). Meth od A. To a cooled (-30 °C), stirred
slurry of Pd(PPh3)4 (1.00 g, 0.865 mmol) in MeCN (30 mL) was
added Cl2CdPN(SiMe3)2 (0.261 g, 0.952 mmol) and KPF6
(0.319 g, 1.73 mmol). The initially light yellow solution turned
red upon warming slowly to room temperature with stirring
over a period of about 1 h. The solution was filtered, filtrate
was reduced to 5 mL, and a mixture of 15 mL of hexanes and
15 mL of Et2O was added with stirring. The resulting red
(18) Herrmann, W. A.; Thiel, W. R.; Brossmer, C.; Oefele, K.;
Priermeier, T.; Scherer, W. J . Organomet. Chem. 1993, 461, 51-60.
(19) Powell, J .; Shaw, B. L. J . Chem. Soc. A 1968, 774.
(20) Kuran, W.; Musco, A. Inorg. Chim. Acta 1975, 12, 187-193.
(21) Prishchenko, A. A.; Gromov, A. V.; Luzikov, Y. N.; Borisenko,
A. A.; Lazhko, E. I.; Klaus, K.; Lutsenko, I. F. Zh. Obshch. Khim. 1985,
54, 1520.
(22) Grim, S. O.; Keiter, R. L. Inorg. Chim. Acta 1970, 4, 56.
(23) Yamazaki, S. Polyhedron 1985, 4, 1915.

5278 Organometallics, Vol. 17, No. 24, 1998
Konze et al.
precipitate was collected by filter cannula, redissolved in
minimal MeCN, filtered, and cooled slowly to -30 °C. After
approximately 3 days at -30 °C, compound V separated from
the solution as clear crystals (0.445 g, 49%).
Sch em e 3
Meth od B. To a stirred solution of Cl(Ph3P)Pd[η2-C(Cl)-
(PPh3)dPN(SiMe3)2] (IIIa ) (0.500 g, 0.552 mmol) in MeCN (20
mL) at room temperature was added KPF6 (0.112 g, 0.608
mmol). The solution was stirred for 15 min and filtered over
Celite to remove KCl. The filtrate was reduced to 3 mL, and
a mixture of 15 mL of hexanes and 15 mL of Et2O was added
with stirring. The resulting red precipitate was collected by
filter cannula and redissolved in minimal MeCN; the solution
was then filtered and cooled slowly to -30 °C. After ap-
proximately 3 days at -30 °C, compound V was separated from
the solution as light yellow crystals (0.357 g, 61%). 1H NMR
(CD2Cl2, 25 °C): δ 7.1-7.7 (30H, PPh3), 1.66 (s, 3H, MeCN),
0.15 (s, 18H, N(SiMe3)2). 31P{1H} NMR (CD2Cl2, 25 °C) (see
2
Scheme 2 for atom labels): δ(P(x)) 132.8 (d, J P(x)P(a) ) 97.0
2
3
Hz), δ(P(a)) 28.0 (dd, J P(a)P(x) ) 97.0 Hz, J P(a)P(b) ) 6.4 Hz),
Sch em e 4
3
1
δ(P(b)) 21.1 (d, J P(b)P(a) ) 6.4 Hz), δ(PF6) -144 (sept., J PF
)
709.5 Hz). Electrospray MS: m/e 870 (M+ - MeCN), 608 (M+
- (MeCN + PPh3)). Anal. Calcd for C45H51Cl1F6N2P4Pd1Si2:
C, 51.19; H, 4.87; N, 2.65. Found: C, 50.90; H, 4.85; N, 2.66.
Con ver sion of [(P h 3P )(MeCN)P d (η2-C(Cl)(P P h 3)dP N-
(SiMe3)2)](P F 6) (V) to Cl(P h 3P )P d [η2-C(Cl)(P P h 3)dP N-
(SiMe3)2] (IIIa ). To a stirred solution of [(Ph3P)(MeCN)Pd(η2-
C(Cl)(PPh3)dPN(SiMe3)2)](PF6) (V) (0.100 g, 0.0947 mmol) in
CH2Cl2 (10 mL) at 25 °C was added (Ph3P)2N+Cl- (PPNCl)
(0.109 g, 0.189 mmol). After stirring for 5 min, a 31P NMR
spectrum showed quantitative conversion to Cl(Ph3P)Pd[η2-
C(Cl)(PPh3)dPN(SiMe3)2] (IIIa ).
Syn th esis of P d (P Et3)(Cl)[µ-η1:η2-C(SiMe3)(P Et3)dP d
N(SiMe3)]P d (P E t 3)Cl (VIIa -b ) t h r ou gh In t er m ed ia t e
(Et3P )2P d [η2-C(Cl)2dP N(SiMe3)2] (Ib). To a stirred solution
of Pd(PEt3)3 (1.58 g, 3.43 mmol) in hexanes (25 mL) at 0 °C
was added dropwise Cl2CdPN(SiMe3)2 (0.470 g, 1.71 mmol).
The color remained orange during the addition. A 31P NMR
spectrum taken after 5 min of stirring at 0 °C showed a
mixture of (Et3P)2Pd[η2-C(Cl)2dPN(SiMe3)2] (Ib ) and un-
reacted Pd(0). The solution was warmed quickly to room
temperature and stirred for 15 min, during which time the
color turned red. Stirring was then stopped, and the flask was
allowed to sit at room temperature overnight to form crystals
of Pd(PEt3)(Cl)[µ-η1:η2-C(SiMe3)(PEt3)dPdN(SiMe3)]Pd(PEt3)-
Cl (VIIa -b). The filtrate was removed by cannula, and the
crystals were washed with 3 × 5 mL of hexanes and dried
under vacuum to give pure VIIa -b (0.824 g, 57%). 31P{1H}
NMR (THF) (see Scheme 3 for atom labels), for VIIa : δ(P(x))
P r epar ation of cis-Cl(dppe)P d[C(Cl)dP N(SiMe3)2] (VI).
To a solution of Pd(dppe)(dba) (1.00 g, 1.35 mmol) in CH2Cl2
(30 mL) was added Cl2CdPN(SiMe3)2 (0.371 g, 1.35 mmol). The
color turned from dark orange to light yellow immediately after
the addition. After stirring for 5 min, the solution was filtered,
and the solvent was removed from the filtrate under vacuum
to yield a light yellow oily solid residue. The residue was
stirred vigorously with 20 mL of Et2O to produce a yellow
precipitate, which was collected on a medium-porosity fritted
glass filter. The precipitate was washed with 2 × 10 mL of
Et2O, followed by 3 × 5 mL of MeCN to give VI (0.745 g, 71%)
that was pure by 31P NMR spectroscopy. 31P{1H} NMR (CD2-
Cl2, 25 °C) (see eq 5 for atom labels): δ(P(x)) 230.1 (dd, 3J P(x)P(b)
) 41.8 Hz, 3J P(x)P(a) ) 29.9 Hz), δ(P(a)) 55.8 (dd, 3J P(a)P(x) ) 29.9
2
3
Hz, J P(a)P(b) ) 22.1 Hz), δ(P(b)) 41.9 (dd, J P(b)P(x) ) 41.8 Hz,
2J P(b)P(a) ) 22.1 Hz).
2
2
194.9 (dd, J P(x)P(a) ) 18.0 Hz, J P(x)P(b) ) 8.3 Hz), δ(P(a)) 38.2
2
3
P r ep a r a tion of tr a n s-Cl(Et3P )2P d [C(Cl)dP N(SiMe3)2]
(IIb ) t h r ou gh In t er m ed ia t e (E t 3P )2P d [η2-C(Cl)2dP N-
(SiMe3)2] (Ib). To a stirred solution of Pd(PEt3)3 (1.35 g, 2.93
mmol) in hexanes (20 mL) at 0 °C was added dropwise Cl2-
CdPN(SiMe3)2 (0.803 g, 2.93 mmol). The color changed from
(dd, J P(a)P(x) ) 18.0 Hz, J P(a)P(b) ) 5.5 Hz), δ(P(b)) 27.2 (ddd,
2 3
3J P(b)P(c) ) 63.3 Hz, J P(b)P(x) ) 8.3 Hz, J P(b)P(a) ) 5.5 Hz),
δ(P(c)) 16.2 (d, J P(c)P(b) ) 63.3 Hz). For VIIb: δ(P(x)) 182.2
3
2
2
2
(ddd, J P(x)P(a) ) 16.8 Hz, J P(x)P(b) ) 5.5 Hz, J P(x)P(c) ) 5.5 Hz),
δ(P(a)) 31.3 (dd, 2J P(a)P(x) ) 16.8 Hz, 3J P(a)P(b) ) 16.5 Hz), δ(P(b))
26.0 (ddd, 3J P(b)P(c) ) 55.0 Hz, 3J P(b)P(a) ) 16.5 Hz, 2J P(b)P(x) ) 5.5
Hz), δ(P(c)) 14.0 (dd, J P(c)P(b) ) 55.0 Hz, J P(c)P(x) ) 5.5 Hz).
Anal. Calcd for C25H63Cl2N1P4Pd2Si2 (mixture of VIIa and
VIIb): C, 35.68; H, 7.55; N, 1.66. Found: C, 35.20; H, 7.31;
N, 1.49.
orange to almost colorless during the addition.
A
31P NMR
3
2
spectrum taken after 5 min of stirring at 0 °C showed
quantitative formation of (Et3P)2Pd[η2-C(Cl)2dPN(SiMe3)2]
(Ib). The solution was allowed to warm slowly to room
temperature and stirred for 1 h. A 31P NMR spectrum showed
that all of Ib had converted to trans-Cl(Et3P)2Pd[C(Cl)dPN-
(SiMe3)2] (IIb). The solution was reduced to 5 mL under
vacuum, filtered, and cooled slowly to -78 °C to form colorless
crystals of IIb. Compound IIb melts at ≈10 °C and could not
be isolated in pure form, as it contains small amounts of Pd-
(PEt3)2Cl2 (characterized by comparison of its 31P NMR spec-
trum with an authentic sample). 31P{1H} NMR (hexanes) (see
Scheme 3 for atom labels), for Ib, 0 °C: δ(P(x)) 38.0 (dd, 2J P(x)P(b)
Syn th esis of P d (P Et3)(I)[µ-η1:η2-C(SiMe3)(P Et3)dP dN-
(SiMe3)]P d (P Et3)I (VIIIa -b). To a stirred solution of Pd-
(PEt3)(Cl)[µ-η1:η2-C(SiMe3)(PEt3)dPdN(SiMe3)]Pd(PEt3)Cl-
(VIIa -b) (0.200 g, 0.238 mmol) in THF (10 mL) was added
MeI (0.101 g, 0.713 mmol). After stirring for 24 h at room
temperature, the color had changed from orange to deep red.
The solvent was removed under vacuum, and the red, oily
residue was taken up in 35 mL of Et2O. The solution was
filtered quickly, and the filtrate was cooled slowly to -30 °C
2
2
) 38.5 Hz, J P(x)P(a) ) 24.8 Hz), δ(P(a)) 5.5 (dd, J P(a)P(x) ) 24.8
Hz, J P(a)P(b) ) 5.5 Hz), δ(P(b)) 4.0 (dd, J P(b)P(x) ) 38.5 Hz,
to form red crystals. A
31P NMR spectrum showed the red
2
2
2J P(b)P(a) ) 5.5 Hz). For IIb, 25 °C: δ(P(x)) 223.8 (t, J P(x)P(a)
)
crystals to be composed of approximately 90% VIIIb and 10%
VIIIa . Yield: 0.0635 g, 24%. 31P{1H} NMR (THF) (see
Scheme 4 for atom labels), for VIIIa : δ(P(x)) 196.8 (d, 2J P(x)P(a)
3
33.4 Hz), δ(P(a)) 16.1 (d, J P(a)P(x) ) 33.4 Hz). 13C{1H} NMR
3
1
(hexanes), for IIb, 25 °C: δ(CdPR) 191.0 (dt, J CP(x) ) 135.1
Hz, J CP(a) ) 9.6 Hz).
2
2
3
) 18.3 Hz), δ(P(a)) 37.2 (dd, J P(a)P(x) ) 18.3 Hz, J P(a)P(b) ) 7.0

Pd Coordination Compounds of σ3λ5-Phosphoranes
Organometallics, Vol. 17, No. 24, 1998 5279
Ta ble 1. Cr ysta l a n d Da ta Collection P a r a m eter s for [(P h 3P )(MeCN)P d (η2-C(Cl)(P P h 3)dP N(SiMe3)2)](P F 6)
(V) a n d Cl(Et3P )P d [η2-C(SiMe3)(P Et3)dP (dO)NH(SiMe3)] (IX)
V
IX
formula
space group
a, Å
C
C2/c
45.7520(3)
51H60ClF6N5P4PdSi2
C42H108Cl2N2O3P6Pd2Si4
Fdd2
24.7392(4)
b, Å
12.1002(2)
46.7039(6)
c, Å
25.1991(4)
11.2593(1)
R, deg
â, deg
γ, deg
V, Å3
Z
90
90
90
90
123.146(1)
90
11680.4(3)
8
13009.2(3)
8
1.298
d
calc, g/cm3
1.341
crystal size, mm
0.45 × 0.36 × 0.09
0.22 × 0.19 × 0.09
µ, mm-1
0.570
0.889
data collection instrument
radiation (monochromated in incident beam)
temp, K
Siemens SMART
Mo KR (γ ) 0.710 73 Å)
173(2)
Siemens SMART
Mo KR (γ ) 0.710 73 Å)
173(2)
scan method
area detector, ω-frames
1.06-25.03
28 232
10 122
7618
660
1.000/0.811
0.0529
0.1043
1.063
area detector, ω-frames
data collection range, θ, deg
no. of data collected
no. of unique data total
with I g 2σ(I)
1.74-25.03
16 542
5542
4860
324
1.000/0.840
0.0417
0.0967
1.087
no. of parameters refined
trans factors, max/min
Ra (I > 2σ(I))
b
Rw (I > 2σ(I))
quality of fit indicatorsc
largest peak, e/Å-3
0.584
0.839
a
b
2
R ) ∑||Fo| - |Fc||/∑|Fo|. Rw ) [∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2; w ) 1/σ2(|Fo|). c Quality-of-fit ) [∑w(|Fo| - |Fc|)2/(Nobs - Nparameters)]1/2
.
3
3
Hz), δ(P(b)) 21.5 (dd, J P(b)P(c) ) 71.1 Hz, J P(b)P(a) ) 7.0 Hz),
Fdd2 in IX by systematic absences and intensity statistics.24
Successful direct methods solutions were calculated, which
provided most non-hydrogen atoms from the E-maps. Several
full-matrix least-squares/difference Fourier cycles were per-
formed, which located the remainder of the non-hydrogen
atoms. All non-hydrogen atoms were refined with anisotropic
displacement parameters. Hydrogen atom positions were
generated with ideal geometries and refined as riding, isotropic
atoms. The structure of V contained three acetonitrile solvent
molecules, and the PF6 anion was split between two sites with
0.50:0.50 site occupancy, with one of the sites showing disorder.
A total of 102 restraints were used. The structure of IX
contained one Et2O solvent molecule which was disordered on
a 2-fold axis. Several ethyl groups were also disordered, and
260 total restraints were used. Selected bond distances and
bond angles for V and IX are given in Tables 2 and 3.
3
δ(P(c)) 17.4 (d, J P(c)P(b) ) 71.1 Hz). For VIIIb: δ(P(x)) 183.9
2
2
(d, J P(x)P(a) ) 17.2 Hz), δ(P(a)) 30.7 (dd, J P(a)P(x) ) 17.2 Hz,
3J P(a)P(b) ) 15.1 Hz), δ(P(b)) 19.8 (dd, 3J P(b)P(c) ) 61.0 Hz, 3J P(b)P(a)
3
) 15.1 Hz), δ(P(c)) 13.1 (d, J P(c)P(b) ) 61.0 Hz).
P r ep a r a tion of Cl(Et3P )P d [η2-C(SiMe3)(P Et3)dP (dO)-
NH(SiMe3)] (IX). To a stirred solution of Pd(PEt3)(Cl)[µ-η1:
η2-C(SiMe3)(PEt3)dPdN(SiMe3)]Pd(PEt3)Cl (VIIa -b) (0.100 g,
0.118 mmol) in THF (10 mL) was added deionized, degassed
H2O (4.28 µL, 0.238 mmol). After stirring for 5 min at room
temperature, the color had changed from orange to dark
orange. The solvent was reduced to 5 mL, and 25 mL of Et2O
was added with stirring. The solution was filtered, and the
filtrate was cooled slowly to -78 °C to form yellow crystals.
The crystals were isolated by removing the mother liquor with
a cannula and washing with 3 × 5 mL of hexanes at 0 °C to
yield IX (0.058 g, 82%). 31P{1H} NMR (THF) (see Scheme 4
2
for atom labels): δ(P(x)) 80.0 (d, J P(x)P(b) ) 11.0 Hz), δ(P(a))
Resu lts
2
2
37.1 (d, J P(a)P(b) ) 8.3 Hz), δ(P(b)) 24.2 (dd, J P(b)P(a) ) 8.3 Hz,
2J P(b)P(x) ) 11.0 Hz). FABMS: m/e 598 (M+ - H), 561 (M+
(H + Cl)), 338 (M+ - (H + Cl + Pd + PEt3)).
-
Rea ction s of P P h 3 or d p p e Com p lexes of P d (0)
w ith Cl2CdP N(SiMe3)2. The reaction (Scheme 1) of
Pd(PPh3)4 with 1.1 equiv of Cl2CdPN(SiMe3)2 at -50
°C in CH2Cl2 results in the formation of the phospha-
vinyl phosphonium compound Cl(Ph3P)Pd[η2-C(Cl)-
(PPh3)dPN(SiMe3)2] (IIIa ). Variable-temperature (-50
to 25 °C) 31P NMR monitoring of the reaction solution
shows two intermediates (Scheme 1). At -50 °C, the
only species present is the η2-phosphaalkene complex
(PPh3)2Pd[η2-C(Cl)2dPN(SiMe3)2] (Ia ) and free PPh3.
Upon warming to 0 °C, Ia undergoes oxidative addition
of one of the C-Cl bonds to form the phosphavinyl
compound trans-Cl(Ph3P)2Pd[C(Cl)dPN(SiMe3)2] (IIa ).
After the solution reaches room temperature and is
stirred for 3 h, compound IIIa is the only product, along
with a small amount of Pd(PPh3)2Cl2. When the reac-
tion is carried out with only 2 equiv of PPh3 using
X-r a y Cr ysta llogr a p h ic An a lyses of [(P h 3P )(MeCN)P d -
(η2-C(Cl)(P P h 3)dP N(SiMe3)2)](P F 6) (V) a n d Cl(Et3P )P d -
[η2-C(SiMe3)(P Et3)dP (dO)NH(SiMe3)] (IX). Diffraction-
quality crystals of V were obtained by recrystallization from
acetonitrile at -30 °C; crystals of IX were obtained from Et2O
at -30 °C. Data collection and reduction information are given
in Table 1. A colorless crystal of V and a yellow platelike
crystal of IX were mounted on glass fibers for data collection.
Initial sets of cell constants were calculated from reflections
taken from three sets of 20 frames, oriented such that
orthogonal wedges of reciprocal space were surveyed to
produce orientation matrixes determined from 91 reflections
in V and 114 in IX. Final cell constants were calculated from
a set of 6961 strong reflections in V and 5673 in IX taken
during the data collections. Hemisphere-type data collections
were employed in both structure determinations in which
randomly oriented regions of space were surveyed to the extent
of 1.3 hemispheres to a resolution of 0.84 Å. Three major
swaths of frames were collected with 0.30° steps in ω. The
space group C2/c was unambiguously determined in V, and
(24) SHELXTL-Plus V5.0; Siemens Industrial Automation Inc.:
Madison, WI, 1994.

5280 Organometallics, Vol. 17, No. 24, 1998
Konze et al.
Ta ble 2. Selected Bon d Dista n ces a n d An gles for [(P h 3P )(MeCN)P d (η2-C(Cl)(P P h 3)dP N(SiMe3)2)] (P F 6) (V)
Distances (Å)
Pd(1)-C(1)
Pd(1)-P(1)
Pd(1)-N(1)
Pd(1)-P(3)
2.161(4)
2.2688(11)
2.168(4)
C(1)-P(1)
C(1)-P(2)
P(1)-N(2)
N(1)-C(2)
1.803(4)
1.771(4)
1.704(3)
1.127(6)
C(1)-Cl(1)
N(2)-Si(1)
N(2)-Si(2)
1.793(4)
1.784(4)
1.788(4)
2.3451(11)
Angles (deg)
P(1)-C(1)-P(2)
115.8(2)
69.15(13)
110.0(2)
122.4(2)
109.2(2)
109.85(14)
157.80(10)
95.58(10)
C(1)-Pd(1)-P(1)
C(1)-Pd(1)-P(3)
P(1)-Pd(1)-P(3)
C(1)-P(1)-Pd(1)
N(2)-P(1)-Pd(1)
P(1)-N(2)-Si(1)
P(1)-N(2)-Si(2)
47.95(11)
P(1)-C(1)-Pd(1)
P(2)-C(1)-Pd(1)
P(1)-C(1)-Cl(1)
P(2)-C(1)-Cl(1)
C(1)-Pd(1)-N(1)
N(1)-Pd(1)-P(1)
N(1)-Pd(1)-P(3)
153.92(11)
106.48(4)
62.90(13)
114.90(13)
107.7(2)
129.2(2)
a
Numbers in parentheses are estimated standard deviations in the least significant digits.
Ta ble 3. Selected Bon d Dista n ces a n d An gles for Cl(Et3P )P d [η2-C(SiMe3)(P Et3)dP (dO)NH(SiMe3)] (IX)
Distances (Å)
C(1)-P(1)
C(1)-P(2)
Pd(1)-C(1)
Pd(1)-P(1)
1.787(6)
1.744(5)
2.228(5)
2.1696(13)
Pd(1)-Cl(1)
Pd(1)-P(3)
P(1)-N(1)
2.459(2)
2.270(2)
1.657(4)
P(1)-O(1)
C(1)-Si(2)
N(1)-Si(1)
1.489(4)
1.871(5)
1.748(4)
Angles (deg)
P(1)-Pd(1)-C(1)
47.92(14)
P(1)-C(1)-Si(2)
P(2)-C(1)-Si(2)
Pd(1)-C(1)-Si(2)
O(1)-P(1)-Pd(1)
O(1)-P(1)-N(1)
N(1)-P(1)-C(1)
O(1)-P(1)-C(1)
P(1)-N(1)-Si(1)
N(1)-P(1)-Pd(1)
119.1(3)
C(1)-Pd(1)-P(3)
C(1)-Pd(1)-Cl(1)
P(1)-Pd(1)-P(3)
P(1)-Pd(1)-Cl(1)
P(3)-Pd(1)-Cl(1)
P(2)-C(1)-P(1)
P(2)-C(1)-Pd(1)
P(1)-C(1)-Pd(1)
155.79(14)
108.07(14)
108.33(7)
155.67(7)
95.91(7)
117.5(3)
111.7(3)
64.3(2)
120.7(3)
107.1(2)
124.3(2)
109.7(2)
114.0(3)
118.6(2)
128.2(3)
116.6(2)
a
Numbers in parentheses are estimated standard deviations in the least significant digits.
Pd(dba)(PPh3)2 and 1.1 equiv of Cl2CdPN(SiMe3)2 in
CH2Cl2, compound IIIa forms at the same temperature
in the same amount of time. However, if less polar
solvents (e.g., THF, hexanes, toluene) are used, Ia still
forms but decomposes to unidentified products instead
of isomerizing to IIa and IIIa .
IIa and is quite similar to the 31P NMR spectra (δ 223-
3
243 ppm, J PP ) 25-43 Hz) of a series of trans-
phosphavinyl compounds of the type X(Et3P)2M[C(X)d
PMes*] (X ) Cl, Br; M ) Pd, Pt; Mes* ) tri-tert-
butylphenyl).15 In compound IIIa , where a PPh3 group
has migrated from palladium to the CdP carbon atom,
the chemical shift of P(x) is δ 124.4 ppm, which is far
upfield from P(x) in uncoordinated phosphavinyl phos-
phonium cations (e.g., in [(Ph3P)(H)CdPN(i-Pr)2](BF4),
δ 303.5),26 consistent with the η2-coordinated structure
in Scheme 1. The peak for P(x) in IIIa is split into a
doublet with a large coupling constant (2J P(x)P(a) ) 91.4
Hz) by the carbon-bound PPh3 group. This is analogous
Compounds Ia , IIa , and IIIa were characterized by
their 31P and 31P{1H} NMR spectra; compound IIIa was
further characterized by elemental analysis and elec-
trospray mass spectrometry. Compound IIIa is air
stable in the solid state, but air sensitive in solution.
The peaks corresponding to P(x) in the 31P NMR for
compounds Ia , IIa , and IIIa are conveniently assigned
by proton-coupled 31P NMR, in which the P(x) signal
remains sharp, while the PPh3 signals are broadened
dramatically by the phenyl protons. The assignment
of Ia as an η2-coordinated phosphaalkene is consistent
with the chemical shift for P(x) at δ 41.8, which is 210
ppm upfield from Cl2CdPN(SiMe3)2.21 This is similar
to the upfield shift of 266 ppm found for the P(x)
phosphorus atom in (Ph3P)2Pt[η2-Ph2CdPMes] relative
to free Ph2CdPMes.2 The peak for P(x) in Ia is split
2
to the large J PP coupling constants found in the
uncoordinated phosphavinyl phosphonium cations (e.g.,
2
in [(Ph3P)(H)CdPNi-Pr2] (BF4), J PP ) 124.6 Hz).26
Further evidence for the structure of IIIa is the similar-
ity of its 31P NMR spectrum (see Experimental Section)
to that of the cationic MeCN analogue [(Ph3P)(MeCN)-
Pd(η2-C(Cl)(PPh3)dPN(SiMe3)2)](PF6) (V), which was
characterized by X-ray diffraction.
The reaction (eq 5) of Pd(dppe)(dba) with 1 equiv of
Cl2CdPN(SiMe3)2 in CH2Cl2 at room temperature re-
sults in the formation of cis-Cl(dppe)Pd[C(Cl)dPN-
(SiMe3)2] (VI). This compound contains a chelating
phosphine and did not rearrange further to form a
phosphavinyl phosphonium compound, as in the forma-
tion of IIIa . The 31P NMR spectrum of VI exhibits a
signal for P(x) at δ ) 230.1 ppm, which is split into a
2
into a doublet of doublets (2J P(x)P(b) ) 35.3 Hz, J P(x)P(a)
) 23.4 Hz) by the two inequivalent PPh3 groups on Pd,
which is also consistent with the proposed η2-structure.
In IIa , the chemical shift (δ 213.9) for P(x) is 172 ppm
downfield from that in Ia in the region (200-350 ppm)25
typical of uncoordinated CdP double-bond compounds
and is now split into a triplet (3J P(x)P(a) ) 50.1 Hz) by
the two equivalent PPh3 groups on Pd. This is consis-
tent with the proposed trans-phosphavinyl structure of
3
doublet of doublets (3J P(x)P(b) ) 41.8 Hz, J P(x)P(a) ) 29.9
Hz) by the two inequivalent phosphorus atoms in the
(25) Lochschmidt, S.; Schmidpeter, A. Phosphorus Sulfur 1988, 29,
73.
(26) Gru¨tzmacher, H.; Pritzkow, H. Angew. Chem., Int. Ed. Engl.
1989, 28, 740-741.

Pd Coordination Compounds of σ3λ5-Phosphoranes
Organometallics, Vol. 17, No. 24, 1998 5281
spectrum at 1.66 ppm, which is 0.28 ppm upfield of free
MeCN (δ 1.94) and similar to other N-coordinated
MeCN ligands.29
Rea ction s of P d (P Et 3)3 w ith Cl2CdP N(SiMe3)2.
The reaction (Scheme 3) of Pd(PEt3)3 with 1 equiv of
Cl2CdPN(SiMe3)2 in hexanes at 0 °C results in the
formation of the PEt3 analogue of IIa , trans-Cl(Et3P)2-
Pd[C(Cl)dPN(SiMe3)2] (IIb). Low-temperature (0 °C)
31P NMR monitoring of the reaction shows the PEt3
analogue of Ia , (Et3P)2Pd[η2-C(Cl)2dPN(SiMe3)2] (Ib),
as the only observable intermediate in the reaction.
When the solution reaches room temperature and is
allowed to stir for 1 h, one of the C-Cl bonds in
compound Ib undergoes oxidative addition to Pd to form
IIb along with a small amount of Pd(PEt3)2Cl2.
chelating dppe ligand. The chemical shifts and coupling
constants are quite similar to those in the previously
characterized cis-Cl(Ph3P)2Pt[C(Cl)dPMes*] (P(x):
δ
3
3
234.6 dd, J P(x)P(b) ) 45.4 Hz, J P(x)P(a) ) 22.5 Hz).15
Su bstitu tion Rea ction s of Cl(P h 3P )P d [η2-C(Cl)-
(P P h 3)dP N(SiMe3)2] (IIIa ). The reaction (Scheme 2)
of Cl(Ph3P)Pd[η2-C(Cl)(PPh3)dPN(SiMe3)2] (IIIa ) with
1.1 equiv of PPh3 and 2 equiv of KPF6 in CH2Cl2 at room
temperature results in the substitution of the Cl- ligand
by PPh3 to form the cationic complex [(Ph3P)2Pd(η2-
C(Cl)(PPh3)dPN(SiMe3)2)](PF6) (IV) along with a small
amount of [Pd(PPh3)3Cl](PF6),23 which could not be
separated. Compound IV was also prepared by the
addition of 1.1 equiv of Cl2CdPN(SiMe3)2 and 2 equiv
of KPF6 to a cooled (-50 °C) solution of Pd(PPh3)4 in
CH2Cl2. When compound IV is dissolved in MeCN at
room temperature, one of the PPh3 ligands is substi-
tuted by MeCN to form [(Ph3P)(MeCN)Pd(η2-C(Cl)-
(PPh3)dPN(SiMe3)2)](PF6) (V). Compound V was also
prepared by the addition of 1.1 equiv of Cl2CdPN-
(SiMe3)2 and 2 equiv of KPF6 to a cooled (-30 °C)
solution of Pd(PPh3)4 in MeCN, but is best prepared by
substitution of the Cl- ligand in Cl(Ph3P)Pd[η2-C(Cl)-
(PPh3)dPN(SiMe3)2] (IIIa ) with MeCN, in the presence
of KPF6. When compound V is isolated and dissolved
When Pd(PEt3)3 is reacted (Scheme 3) with 0.5 equiv
of Cl2CdPN(SiMe3)2 in hexanes at 0 °C, 31P NMR
monitoring of the reaction solution again shows Ib as
an intermediate along with free Pd(PEt3)3. However,
upon warming the solution to room temperature and
stirring for 30 min, orange crystals of the 1:1 isomeric
mixture of Pd(PEt3)(Cl)[µ-η1:η2-C(SiMe3)(PEt3)dPd
N(SiMe3)]Pd(PEt3)Cl (VIIa -b) begin to form. After
sitting overnight, the crystals of VIIa -b are isolated and
the remaining filtrate contains a small amount of
dissolved VIIa -b along with IIb, which forms as a
byproduct. To determine whether IIb is an intermedi-
ate that forms before VIIa -b, a sample of IIb was
dissolved in hexanes and 1 equiv of Pd(PEt3)3 was
added; no reaction was evident after several hours of
stirring at room temperature, which strongly suggests
that IIb is not a precursor to VIIa -b.
1
in CD2Cl2, its H NMR spectrum shows a signal for the
coordinated MeCN ligand. However, when V is dis-
solved in CD3CN, the signal for the coordinated MeCN
group disappears, indicating that the coordinated MeCN
ligand undergoes exchange with the CD3CN solvent.
When compound V is treated with PPNCl at room
temperature, the MeCN ligand is immediately displaced
by Cl- to form compound IIIa . Compound V is air
sensitive in solution, but only slightly air sensitive in
the solid state. These substitution reactions are sum-
marized in Scheme 2.
Compounds Ib and IIb were characterized by 31P
NMR spectroscopy; the spectra of these compounds were
quite similar to those of Ia and IIa (see Experimental
Section), and assignments of the peaks were made in a
similar manner (see results of IIIa ). The 1:1 mixture
of isomers VIIa -b was characterized by 31P NMR
spectroscopy and elemental analysis as well as by the
similarity of the spectra of VIIa -b to those of VIIIa -b
(see Experimental Section); the structure of VIIIb was
determined by a partially successful X-ray diffraction
study. The peaks corresponding to P(x) in the 31P NMR
of compounds VIIa -b are conveniently assigned by
proton-coupled 31P NMR spectroscopy, which shows that
the P(x) signal remains sharp, while the PEt3 signals
Compound IV was characterized by 31P NMR spec-
troscopy and electrospray mass spectrometry, while
compound V was characterized by 1H NMR and 31P
spectroscopy, electrospray mass spectroscopy, elemental
analysis, and X-ray diffraction studies. The peaks
corresponding to P(x) in the 31P NMR spectra of
compounds IV and V are conveniently assigned from
their proton-coupled 31P NMR, in which the P(x) signals
are sharp, but the PPh3 signals are broadened dramati-
cally by the phenyl protons. The chemical shifts of P(x)
in IV (δ 118.2) and V (δ 132.8) are similar to that for
P(x) in IIIa (δ 124.4), which is consistent with an η2-
coordinated phosphavinyl phosphonium ligand in all of
these complexes. As also found for IIIa , compounds IV
are broadened dramatically by the ethyl protons.
A
31P-31P COSY experiment was undertaken which
showed that the very complex 31P NMR spectrum of
VIIa -b results from the presence of two isomers as
opposed to a large palladium cluster; it also allowed for
the assignment of the P-P coupling constants. The
exact nature of the different isomers in VIIa -b could
not be determined but is likely due to E/Z isomers
around the PdN double bond. E/Z isomers are known
in iminophosphines (RNdPR)30 and imino(methylene)-
2
and V both show characteristically large J P(x)P(a) cou-
pling constants (123.6 Hz in IV and 97.0 Hz in V)
between the phosphonium substituent and the CdP
phosphorus atom. In IV, the signal for P(x) is also split
into a doublet of doublets by P(b) (2J P(x)P(b) ) 5.1 Hz)
(27) Regragui, R.; Dixneuf, P. H.; Taylor, N. J .; Carty, A. J .
Organometallics 1986, 5, 1.
(28) Pregosin, P. S.; Kunz, R. W. In Phosphorus-31 and Carbon-13
Nuclear Magnetic Resonance of Transition Metal Phosphine Complexes;
Diel, D., Fluck, E., Kosfield, R., Eds.; Springer-Verlag: Berlin, 1979.
(29) Storhoff, B. N.; Lewis, H. C. J . Coord. Chem. Rev. 1977, 23,
1-29.
2
and P(c) (2J P(x)P(c) ) 32.5 Hz); the larger value for J P(x)P(c)
is consistent with PPh3 being situated trans to P(x).27,28
(30) Nguyen, M. T.; McGinn, M. A.; Hegarty, A. F. J . Am. Chem.
Soc. 1985, 107, 8029.
1
The MeCN ligand in V exhibits a signal in the H NMR

5282 Organometallics, Vol. 17, No. 24, 1998
Konze et al.
phosphoranes (RNdP(R)dCR2),31 and the chemical shift
difference in P(x) between VIIa (δ 194.9) and VIIb (δ
182.2) is similar to the difference found in the E/Z
isomers around the PdN double bond in Me3SiNd
P[N(SiMe3)2]dC(H)Me (δ 105.5, 98.1).32 However, be-
cause of the complexity of the molecule, this assignment
of the isomers must be regarded as tentative. The
chemical shifts of P(x) in VIIa and VIIb may be
compared with that in the uncoordinated imino(phos-
phoranylidenemethyl)phosphane compound [(Me2N)3P]-
(Me3Si)CdPdN(SiMe3) (δ 407.5 (CdPdN)),33 which
differs from the ligand in VIIa -b only by the P(Me2N)3
group on carbon instead of a PPh3 group; the upfield
shifts of P(x) in VIIa -b are indicative of η2-coordination
of the CdP double bond; such shifts are also known to
occur upon η2-coordination of phosphaalkenes.1-4
Reaction s of P d(P Et3)(Cl)[µ-η1:η2-C(SiMe3)(P Et3)d
P dN(SiMe3)]P d (P Et3)Cl (VIIa -b). When the isomeric
mixture of VIIa -b is reacted (Scheme 4) with 3 equiv of
MeI in THF at room temperature for 24 h under
anhydrous conditions, the color of the solution turns
dark red and the only products are the iodide-substi-
tuted analogues (both isomers) of VIIa -b, Pd(PEt3)(I)-
[µ-η1:η2-C(SiMe3)(PEt3)dPdN(SiMe3)]Pd(PEt3)I (VIIIa -
b). Presumably, MeCl gas is liberated during this
halide exchange reaction. A similar reaction using 3
equiv of NaI resulted in the formation of VIIIa -b in only
5 min, but the product was contaminated with Cl(Et3P)-
Pd[η2-C(SiMe3)(PEt3)dP(dO)NH(SiMe3)] (IX), which
forms when VIIa -b is exposed to traces of water, even
though the NaI was heated under vacuum for several
hours to remove water. When the isomeric mixture of
VIIIa -b is crystallized from Et2O, isomer VIIIb crystal-
lizes preferentially, although some of VIIIa is also
present in the crystals. Compounds VIIIa -b were
characterized by 31P NMR spectroscopy, and the struc-
ture of compound VIIIb was partially determined by
X-ray diffraction studies. Although the refinement of
the structure of VIIIb is not suitable for publication
(final R factor 9%), the connectivity of the molecule was
unambiguously determined. The 31P NMR spectrum of
VIIIa -b is consistent with the structure obtained for
VIIIb, and assignments were made as in the very
similar compounds VIIa -b (see results of VIIa -b).
When a pure sample of VIIa -b is reacted (Scheme 4)
with 2 equiv of degassed, deionized H2O in THF at room
Sch em e 5
two known methylene(oxo)phosphoranes, Mes*P(dO)d
CR(SiMe3) (R ) Ph, δ 153.7; R ) SiMe3, δ 161.1),34
which are somewhat related to the ligand in IX, but
without a phosphonio substituent on the CdP carbon.
This upfield shift is consistent with the upfield shifts
found in η2-coordinated phosphaalkene compounds.1-4
As in compounds VIIa -b and VIIIa -b, the coupling
constants between the PEt3 groups and the P(x) atom
in IX are quite small (2J P(x)P(b) ) 11.0 Hz, J P(x)P(a) ) 0
2
Hz), much smaller than the large coupling constant
found in IIIa (2J P(x)P(a) ) 91.4 Hz). This is most likely
due to the pentavalent nature of the P(x) atom in VIIa -
b, VIIIa -b, and IX, which allows for less phosphorus
s-character in the bonding and results in smaller
coupling constants.
Discu ssion
Cl(P h 3P )P d [η2-C(Cl)(P P h 3)dP N(SiMe3)2] (IIIa ),
[(P h 3P )2P d (η2-C(Cl)(P P h 3)dP N(SiMe3)2)](P F 6) (IV),
an d [(P h 3P )(MeCN)P d(η2-C(Cl)(P P h 3)dP N(SiMe3)2)]-
(P F 6) (V). In contrast to the reaction (eq 2) of Pd(PPh3)4
with Cl2CdPMes* (Mes* ) 2,4,6-tri-tert-butylphenyl)16
which results in the migration of the Mes* group to
carbon to form Mes*-CtP and Pd(PPh3)2Cl2 with no
observed intermediates, the reaction of Pd(PPh3)4 with
Cl2CdPN(SiMe3)2 results in the formation of the η2-
coordinated phosphavinyl phosphonium compound Cl-
(Ph3P)Pd[η2-C(Cl)(PPh3)dPN(SiMe3)2] (IIIa ) via inter-
mediates (Ph3P)2Pd[η2-C(Cl)2dPN(SiMe3)2] (Ia ) and
trans-Cl(Ph3P)2Pd[C(Cl)dPN(SiMe3)2] (IIa ). This rear-
rangement is analogous to the reported reaction of an
η1-vinyl complex of palladium which rearranged upon
heating to an η2-vinyl phosphonium complex.35 We
previously obtained a nickel analogue (3) of IIIa in a
reaction (eq 3) of Ni(PPh3)4 with Cl2CdPN(SiMe3)2, but
in that case the product was unstable and reacted
further with another equivalent of Ni(PPh3)4 to generate
the dinuclear phosphavinylidene phosphorane complex
(4).17 However, compound IIIa is air stable and does
not react with Pd(PPh3)4. The isomerization reaction
of IIa to IIIa can be rationalized by proposing (Scheme
5) the rearrangement of the η1-phosphavinyl (IIa ) to an
η2-phosphavinyl (IIa ′ and IIa ′′) intermediate, which is
attacked by PPh3 to form the phosphavinyl phospho-
nium complex IIIa . The carbene-phosphido resonance
structure (IIa ′′) is probably more favored than the
alkyl-phosphine resonance form (IIa ′) because the
high-energy CdP double bond36 is avoided; the electro-
philic nature of the carbene-like carbon atom provides
the driving force for nucleophilic attack by the PPh3
group to form IIIa . This carbene-like resonance struc-
ture in the η2-phosphavinyl ligand (IIa ′′) is precedented
temperature, the color darkens immediately and the 31
P
NMR spectrum shows the formation of the phosphonio-
methylene(oxo)phosphorane compound IX along with
two singlets that are most likely due to palladium
phosphine complexes. Although these byproducts were
not identified, they were easily separated from IX.
Compound IX was characterized by 31P NMR spectros-
copy, and FAB mass spectrometry, and the structure
was determined by X-ray diffraction. The peak corre-
sponding to P(x) at δ 80.0 in the 31P NMR spectrum of
IX is readily assigned by the proton-coupled 31P NMR
spectrum, in which the P(x) signal remains sharp, while
the PEt3 signals at δ 37.1 and 24.2 are broadened
dramatically by coupling to the ethyl protons. In IX,
the chemical shift of P(x) at δ 80.0 is upfield from the
(34) Appel, R.; Casser, C. Tetrahedron Lett. 1984, 25, 4109.
(35) Rybin, L. V.; Petrovskaya, E. A.; Rubinskaya, M. I.; Kuz’mina,
L. G.; Struchkov, Y. T.; Kaverin, V. V.; Koneva, N. Y. J . Organomet.
Chem. 1985, 288, 119-129.
(31) Germa, H.; Navech, J . Phosphorus Sulfur 1986, 26, 327.
(32) Niecke, E.; Wildbredt, D.-A. Chem. Ber. 1980, 113, 1549.
(33) Kru¨ger, U.; Pritzkow, H.; Gru¨tzmacher, H. Chem. Ber. 1991,
124, 329-331.
(36) Schleyer, P. v. R.; Kost, D. J . Am. Chem. Soc. 1988, 110, 2105.

Pd Coordination Compounds of σ3λ5-Phosphoranes
Organometallics, Vol. 17, No. 24, 1998 5283
by the X-ray structure of a similar η2-phosphavinyl
complex of tungsten Cp(CO)2W[η2-C(Ph)dPPh{W(CO)5}]
which exhibited a W-C bond length (1.954(8) Å) that
is typical of a WdC double bond.37 A similar mecha-
nism for this phosphine migration was proposed previ-
ously for the formation of the nickel analogue (3, eq 3)
of IIIa .17
When Cl2CdPN(SiMe3)2 is reacted with Pd(dba)-
(PPh3)2, the formation of IIIa occurs quantitatively
under the same conditions in the same amount of time.
In this case there is no excess PPh3 present in the
reaction, which suggests that the PPh3 that attacks the
CdP carbon atom in IIa ′′ must have dissociated from
palladium. Since dissociative mechanisms in square
planar group 10 complexes are very rare, the most likely
mechanism is an associative mechanism where the Cd
P phosphorus lone pair attacks above the square plane
in IIa with loss of a PPh3 ligand to generate IIa ′ and
IIa ′′. When Pd(dba)(dppe) is used as the Pd(0) reagent,
the reaction (eq 5) stops at the phosphavinyl compound
cis-Cl(dppe)Pd[C(Cl)dPN(SiMe3)2] (VI). Here, dissocia-
tion of one P-donor of the chelating phosphine ligand is
more difficult, and an analogue of IIIa does not form.
Compound VI does not react with PPh3 and KPF6 to
generate an analogue of IV containing a dppe ligand in
place of the two PPh3 ligands on palladium, presumably
because the chelating phosphine and chloride ligands
in VI are not displaced easily enough to form an η2-
phosphavinyl intermediate.
The chloride ligand in compound IIIa is easily sub-
stituted (Scheme 2) by neutral ligands upon addition
of KPF6; stirring in MeCN results in formation of the
cationic phosphavinyl phosphonium complex [(Ph3P)-
(MeCN)Pd(η2-C(Cl)(PPh3)dPN(SiMe3)2)](PF6) (V), while
addition of PPh3 leads to [(Ph3P)2Pd(η2-C(Cl)(PPh3)d
PN(SiMe3)2)](PF6) (IV). One of the palladium-coordi-
nated PPh3 ligands in IV is replaced by stirring in
MeCN to generate V; the MeCN ligand in V is displaced
by CD3CN by stirring in CD3CN, or by PPh3 to generate
IV, or by Cl- to generate IIIa . Thus, each of the
compounds IIIa , IV, and V contains a labile ligand on
palladium, which is evident in the electrospray mass
spectra, which show the same highest molecular ion
peak at m/e 870, corresponding to the fragment (Ph3P)-
Pd(η2-C(Cl)(PPh3)dPN(SiMe3)2)]+, generated by the loss
of Cl-, PPh3, and MeCN from IIIa , IV, and V, respec-
tively.
F igu r e 1. Thermal ellipsoid drawing of [(Ph3P)(MeCN)-
Pd(η2-C(Cl)(PPh3)dPN(SiMe3)2)](PF6) (V).
Sch em e 6
(for example, in Ni(PMe3)2[η2-(Me3Si)2CHPdC(SiMe3)2],
the sum of angles around the CdP carbon is 343.5°).4
The structure of V is similar to that of the nickel η2-
phosphavinyl phosphonium complex Cl(Ph3P)Ni[η2-
C(H)(PPh3)dPMes*] (5, eq 4).17 The C(1)-P(1) distance
in V (1.803(4) Å) is the same within error as that in the
nickel complex Cl(Ph3P)Ni[η2-C(H)(PPh3)dPMes*] (5)
(1.796(5) Å);17 both of these distances are much longer
than the corresponding CdP distance in the free phos-
phavinyl phosphonium salt [(PPh3)(H)CdPN(i-Pr)2)]-
(BF4) (1.684(14) Å),26 which is consistent with η2-
coordination of the phosphavinyl phosphonium ligand
and is similar to the lengthening of CdP bonds that
occurs upon η2-coordination of phosphaalkenes.1-4 The
C(1)-P(2) distance in V (1.771(4) Å) is slightly longer
than the C-PPh3 distance in Cl(PPh3)Ni[η2-C(H)(PPh3)d
PMes*] (5) (1.742(5) Å); both of these distances are
much longer than typical ylide C-P bond lengths, e.g.,
1.661(8) Å in Ph3PdCH2,38 but are shorter than the
phosphonium-type C-PPh3 distance in [(PPh3)(H)Cd
PN(i-Pr)2)](BF4) (1.798(14) Å), indicating that there is
more phosphonium (C-P+) than ylidic (C--P+) char-
acter in the C-PPh3 bond in V. The Pd-P(1) distance
in V (2.2688(11) Å) is significantly shorter than the Pd-
P(3) distance (2.3451(11)). The bonding in V may be
described as a mixture of two resonance structures
(Scheme 6), analogous to those proposed for the bonding
in Cl(Ph3P)Ni[η2-C(H)(PPh3)dPMes*] (5).17 Resonance
form a is an ylide-phosphido structure with a dative
two-electron donation from C(1) and a phosphido-type
covalent bond between P(1) and palladium, where the
[C(Cl)(PPh3)dPN(SiMe3)2] group donates three electrons
to the 13-electron cationic metal fragment (Ph3P)-
(MeCN)Pd+. Resonance form b is an η2-phosphavinyl
phosphonium cation (1+) which donates two electrons
X-r a y Cr ysta l Str u ctu r e of [(P h 3P )(MeCN)P d (η2-
C(Cl)(P P h 3)dP N(SiMe3)2)](P F 6) (V). A thermal el-
lipsoid drawing of V (Figure 1) shows that the palladium
atom is in a planar environment as defined by the
coordinating atoms of the PPh3, MeCN, and [C(Cl)-
(PPh3)dPR] ligands; the sum of angles around the
palladium atom is 359.9°. The [C(Cl)(PPh3)dPN-
(SiMe3)2] ligand is coordinated η2 to palladium through
the C(1) and P(1) atoms, with the Cl, PPh3, and
N(SiMe3) groups bent back from planarity in the [C(Cl)-
(PPh3)dPN(SiMe3)2] ligand; the sum of angles around
C(1) involving P(1), P(3), and Cl(1) of 347.4° indicates
that C(1) is roughly intermediate between sp2 (360°) and
sp3 (328.5°) hybridization, which is similar to structural
features of η2-coordinated olefins and phosphaalkenes
(37) Huy, N. H. T.; Fischer, J .; Mathey, F. Organometallics 1988,
7, 240.
(38) Bart, J . C. J . Angew. Chem., Int. Ed. Engl. 1968, 7, 730.

5284 Organometallics, Vol. 17, No. 24, 1998
Konze et al.
in the chemistry of phosphaalkenes39 and amino meth-
ylene phosphoranes40 and has also been proposed to
occur (eq 6) in the formation of an imino(phosphor-
Sch em e 7
to a formally Pd(0) metal fragment. The somewhat long
C(1)-P(2) distance argues for a contribution from form
b, where the PPh3 group on carbon has more phospho-
nium than ylide character.
anylidenemethylene)phosphine (7) from a phosphavin-
ylidene phosphorane intermediate (6).33 The proposed
intermediate (6) is the same as the ligand in VII, but
with a P(Me2N)3 group on carbon instead of PPh3, while
compound 7, which was characterized by an X-ray
diffraction study, is analogous to the ligand in VIIa -b,
thus supporting VII as a reasonable intermediate that
undergoes 1,3 SiMe3 migration to form VIIa -b.
The isomeric mixture VIIa -b reacts (Scheme 4) with
MeI or NaI to form the iodide-substituted isomeric
mixture VIIIa -b. The structure of VIIIb was deter-
mined by X-ray diffraction studies, but the final refine-
ment was unacceptable for publication. However, the
connectivity was unambiguously determined and the
bond lengths and angles were reasonable with respect
to related structures. Because of the similarity of their
31P NMR spectra, compounds VIIa -b and VIIIa -b are
very likely isostructural. The (Et3P)(Me3Si)CdPd
NSiMe3 ligand in VIIa -b and VIIIa -b is best described
as an η2-coordinated phosphonio-methylene(imino)-
metallophosphorane ligand (c), which is a zwitterionic
P d(P Et3)(Cl)[µ-η1:η2-C(SiMe3)(P Et3)dP dN(SiMe3)]-
P d(P Et3)Cl (VIIa-b)an d P d(P Et3)(I)[µ-η1:η2-C(SiMe3)-
(P Et3)dP dN(SiMe3)]P d (P Et3)I (VIIIa -b). The reac-
tion of Pd(PEt3)3 with 1 equiv of Cl2CdPN(SiMe3)2
(Scheme 3) in hexanes or CH2Cl2 resulted in the
formation of trans-Cl(Et3P)2Pd[C(Cl)dPN(SiMe3)2] (IIb)
through the intermediate (Et3P)2Pd[η2-C(Cl)2dPN-
(SiMe3)2] (Ib), as occurred in the reaction (Scheme 1)
involving Pd(PPh3)4. However, IIb did not undergo
PEt3 migration from Pd to the CdP carbon, as in the
PPh3 case, to form a PEt3 analogue of IIIa , even after
stirring overnight followed by refluxing in hexanes for
4 h. A possible explanation is that the weaker coordi-
nating ability of PPh3 as compared with PEt3 allows the
dissociation of PPh3, which results in the formation of
IIIa ; on the other hand, the PEt3 ligands in IIb are so
strongly bound that formation of the η2-phosphavinyl
intermediate analogous to IIa ′, IIa ′′ (Scheme 5) is
unfavorable.
When the reaction of Pd(PEt3)3 is carried out with
only 0.5 equiv of Cl2CdPN(SiMe3)2 (Scheme 3) and
warmed to room temperature, the reaction takes a
different route, forming the dimeric complex Pd(PEt3)-
(Cl)[µ-η1:η2-C(SiMe3)(PEt3)dPdN(SiMe3)]Pd(PEt3)Cl (VI-
Ia -b), in which a PEt3 group and an SiMe3 group have
migrated to the CdP carbon atom. This reaction again
goes through intermediate Ib, and a small amount of
IIb forms as a byproduct. As mentioned in the Results,
compound IIb is apparently not an intermediate in the
formation of VIIa -b. Evidently, when 2 equiv of Pd-
(PEt3)3 are used in this reaction, Ib reacts with Pd-
(PEt3)3 to form VIIa -b before undergoing oxidative
addition to form IIb. When the reaction of Pd(PEt3)3
with 0.5 equiv of Cl2CdPN(SiMe3)2 is carried out and
kept at -30 °C for one week as opposed to warming to
room temperature above, the oxidative addition reaction
prevails and compound IIb forms along with unreacted
Pd(PEt3)3, with no formation of VIIa -b. Although Ib
was the only observable intermediate in 31P NMR
spectra recorded during the formation of VIIa -b, a
plausible intermediate to explain its formation (Scheme
7) is the dinuclear phosphavinylidene phosphorane
complex Pd2Cl2(PEt3)2[µ2-η2:η2-C(PEt3)dPN(SiMe3)2]
(VII).
structure with the positive charge on the phosphonium
PEt3 group and the minus charge on Pd(2). Both
palladium atoms are then formally +1 with Pd(2)
bonded covalently to the CdP phosphorus and Pd(1)
bonded η2 to the CdP double bond. If the phosphonium
(PEt3)+ and [(X)(PEt3)Pd(2)]- groups are mentally re-
placed with R-groups, this complex is then analogous
to an η2-coordinated methylene(imino)phosphorane. Com-
pounds VIIa -b and VIIIa -b are the first to contain a
phosphonio-methylene(imino)meta llophosphora ne
ligand; they are also the first examples of complexes
with an η2-methylene(imino)phosphorane ligand, in
general. An analogue, [(Me2N)3P](Me3Si)CdPdN(SiMe3)
(7, eq 6), of the free ligand (Ph3P)(Me3Si)CdPdN(SiMe3)
in VIIa -b and VIIIa -b, except possessing a P(NMe2)3
group on the CdP carbon instead of PPh3, is known,33
but no attempts to coordinate it to a transition metal
Intermediate VII is analogous to the nickel complex
Ni2Cl2(PPh3)2[µ2-η2:η2-C(PPh3)dPN(SiMe3)2] (4, eq 3)
that was previously characterized by X-ray diffraction
studies.17 This intermediate must isomerize quickly to
VIIa -b by undergoing a 1,3 SiMe3 migration from
nitrogen to carbon, a process that is well documented
(39) Appel, R. In Multiple Bonds and Low Coordination in Phos-
phorus Chemistry; Regitz, M., Scherer, O. J ., Eds.; Thieme: Stuttgart,
1990; pp 157-219.
(40) Boske, J .; Niecke, E.; Nieger, M.; Ocando, E.; Majoral, J . P.;
Bertrand, G. Inorg. Chem. 1989, 28, 499.

Pd Coordination Compounds of σ3λ5-Phosphoranes
Organometallics, Vol. 17, No. 24, 1998 5285
Sch em e 8
sum of angles around C(1) involving P(1), P(2), and Si-
(2) is 357.3°, which suggests that C(1) is close to sp2
hybridization. This contrasts with η2-phosphaalkenes
in which both the carbon and phosphorus are generally
pyramidalized between sp2 and sp3 hybridization. The
C(1)-P(1) distance in IX (1.787(6) Å) is much longer
than the CdP distance in [(Me3Si)(Ph)CdP(dO)Mes*]
(1.657(4) Å), which is indicative of η2-coordination of the
phosphonio-methylene(oxo)phosphorane ligand and is
consistent with the lengthening of CdP bonds which
occurs upon η2-coordination of phosphaalkenes.1-4 The
PdO distance in IX (1.489(4) Å) is similar to that in
[(Me3Si)(Ph)CdP(dO)Mes*] (1.458(3) Å). The C(1)-P(2)
distance in IX (1.744(5) Å) is similar to the C-PPh3
F igu r e 2. Thermal ellipsoid drawing of Cl(Et3P)Pd[η2-
C(SiMe3)(PEt3)dP(dO)NH(SiMe3)] (IX).
complex were reported. In light of the fact that the
(Ph3P)(Me3Si)CdPdN(SiMe3) group has been coordi-
nated for the first time in VIIa -b and VIIIa -b, it seems
reasonable that the coordination chemistry of these
types of ligands could be explored further, as the PdN
bond and the lone pair electrons on nitrogen are also
available for bonding. It is also reasonable to assume
that the well-known class of methylene(imino)phospho-
ranes (R2CdP(dNR)R)13 should show interesting coor-
dination properties, especially with respect to coordi-
nation of the CdP double bond as in VIIa -b and VIIIa -
b.
distance
in
Cl(PPh3)Ni[η2-C(H)(PPh3)dPMes*]
(1.742(5) Å);17 both of these distances are much longer
than typical ylide C-P bond lengths, e.g., 1.661(8) Å in
Ph3PdCH2,38 but are shorter than the phosphonium
C-PPh3 distance in [(PPh3)(H)CdPN(i-Pr)2)](BF4)
(1.798(14) Å),26 suggesting that the C(1)-P(2) bond in
IX has more phosphonium (C-P+) than ylidic (C--P+)
character. The Pd-P(1) distance in IX (2.1696(13) Å)
is significantly shorter than the Pd-P(3) distance
(2.270(2) Å).
The bonding in IX may be described as a mixture of
two resonance structures as shown in Scheme 8. Reso-
nance form d is an ylide-phosphido structure with a
dative two-electron donation from C(1) and a phosphido-
type covalent bond between P(1) and palladium, where
the (Et3P)(Me3Si)CdP(dO)NH(SiMe3) group acts as a
three-electron donor to the 13-electron Pd(PEt3)Cl frag-
ment. Resonance form e is a zwitterionic structure,
where the minus charge is located on palladium, with
the η2-phosphonio-methylene(oxo)phosphorane cation
(1+) donating two electrons to a formally Pd(0) metal
fragment. The somewhat long C(1)-P(2) distance ar-
gues for a contribution from form e, where the PPh3
group on carbon has more phosphonium than ylide
character. Although only two stable methylene(oxo)-
phosphoranes are known,34,41 quite a few have been
postulated as intermediates and characterized by trap-
ping experiments.13 Coordination of the phosphonio-
methylene(oxo)phosphorane ligand in IX suggests that
these compounds should have the ability to coordinate
through the CdP bond in other transition metal com-
plexes and may be a way of stabilizing these reactive
compounds for further study.
C l(E t 3P )P d [η2-C (S iMe 3)(P E t 3)dP (dO )N H (S i-
Me3)] (IX). The isomeric mixture of dimeric VIIa -b
undergoes hydrolysis with even traces of water (Scheme
4) to form one isomer of the mononuclear compound Cl-
(Et3P)Pd[η2-C(SiMe3)(PEt3)dP(dO)NH(SiMe3)] (IX). This
is analogous to the known hydrolysis reaction (eq 7) of
methylene(imino)phosphoranes (R2CdP(dNR)R).13 In
the formation of IX, the oxygen from the water adds to
the phosphorus and a hydrogen adds to the nitrogen.
The second hydrogen from the water presumably leaves
with the Pd(PEt3)Cl fragment, but the complex that
forms was not isolated.
X-r a y Cr ysta l Str u ctu r e of Cl(Et 3P )P d [η2-C(Si-
Me3)(P Et3)dP (dO)NH(SiMe3)] (IX). The structure of
IX exhibits an η2-coordinated phosphonio-methyle-
ne(oxo)phosphorane (Et3P)(Me3Si)CdP(dO)NH(SiMe3)
ligand. The thermal ellipsoid drawing of IX (Figure 2)
shows that the palladium atom is in a planar environ-
ment defined by the donor atoms of the PEt3, Cl, and
(Et3P)(Me3Si)CdP(dO)NH(SiMe3) ligands; the sum of
angles around the palladium atom is 360.2°. In contrast
to the one structurally characterized methylene(oxo)-
phosphorane compound [(SiMe3)(Ph)CdP(dO)Mes*],41
which has a trigonal planar geometry at phosphorus,
the η2-coordinated ligand in IX contains a pyramidalized
CdP phosphorus atom (sum of angles around P(1)
involving O(1), C(1), and N(1) is 342.3°). However, the
Con clu sion
In contrast to the reactions of Pt(PR3)4 or Pd(PR3)4
with Cl2CdPMes* which result in the rearrangement
of the aromatic Mes* group from phosphorus to carbon
to generate Mes*-CtP via phosphavinyl intermedi-
(41) Appel, R.; Knoch, F.; Kunze, H. Angew. Chem., Int. Ed. Engl.
1984, 23, 157.

5286 Organometallics, Vol. 17, No. 24, 1998
Konze et al.
ates,15,16 the reactions of Pd(0) reagents with Cl2CdPN-
(SiMe3)2 resulted in the formation of complexes con-
taining new carbon-phosphorus multiply bonded ligands.
The reaction (Scheme 1) of Pd(PPh3)4 with Cl2CdPN-
(SiMe3)2 formed the phosphavinyl phosphonium complex
Cl(Ph3P)Pd[η2-C(Cl)(PPh3)dPN(SiMe3)2] (IIIa ) via the
η2-phosphaalkene (Ph3P)2Pd[η2-C(Cl)2dPN(SiMe3)2] (Ia )
and the η1-phosphavinyl trans-Cl(Ph3P)2Pd[C(Cl)dPN-
(SiMe3)2] (IIa ). The labile chloride ligand on palladium
in IIIa was substituted (Scheme 2) by PPh3 or MeCN
in the presence of KPF6 to generate [(Ph3P)2Pd(η2-C(Cl)-
(PPh3)dPN(SiMe3)2)](PF6) (IV) or [(Ph3P)(MeCN)Pd(η2-
C(Cl)(PPh3)dPN(SiMe3)2)](PF6) (V), respectively. The
structure of V was determined by X-ray diffraction
studies, which confirmed the η2-coordination of the
C(Cl)(PPh3)dPN(SiMe3)2 ligand. When Pd(PEt3)3, in-
stead of Pd(PPh3)4, was reacted (Scheme 3) with Cl2Cd
PN(SiMe3)2, the phosphavinyl complex trans-Cl(Et3P)2-
Pd[C(Cl)dPN(SiMe3)2] (IIb) formed but did not rearrange
to form a phosphavinyl phosphonium complex analogous
to IIIa . However, when 2 equiv of Pd(PEt3)3 were
reacted (Scheme 3) with Cl2CdPN(SiMe3)2, the novel,
dimeric phosphonio-methylene(imino)metallophospho-
rane complex Pd(PEt3)(Cl)[µ-η1:η2-C(SiMe3)(PEt3)dPd
N(SiMe3)]Pd(PEt3)Cl (VIIa -b) formed as a mixture of
two isomers; its formation involved migration of a SiMe3
group from nitrogen to carbon and a PEt3 group from
palladium to the CdP carbon. The chloride ligands in
VIIa -b were substituted by iodide using MeI or NaI to
generatePd(PEt3)(I)[µ-η1:η2-C(SiMe3)(PEt3)dPdN(SiMe3)]-
Pd(PEt3)I (VIIIa -b); the structure of VIIIb was par-
tially determined by X-ray diffraction studies. Com-
pound VIIa -b also undergoes hydrolysis with traces of
water to form the phosphonio-methylene(oxo)phospho-
rane complex Cl(Et3P)Pd[η2-C(SiMe3)(PEt3)dP(dO)NH-
(SiMe3)] (IX), the structure of which was determined
by X-ray diffraction studies. The ligands in VIIa -b,
VIIIa -b, and IX represent the first examples of coordi-
nated methylene(imino, oxo)phosphorane ligands.
The results for Pd(0) obtained herein may be com-
pared with those from reactions of Ni(0) and Pt(0)
reagents with Cl2CdPN(SiMe3)2, which in some cases
gave much different results (Scheme 9).17 When
M(PEt3)4 was reacted with Cl2CdPN(SiMe3)2, phos-
phavinyl complexes were observed with M ) Pd, Pt, and
Ni, and there was no evidence for PEt3 migration to
carbon. However, when M(PPh3)4 was reacted with
Cl2CdPN(SiMe3)2, only in the case of M ) Pd was a
phosphavinyl complex observed (Scheme 1), which
Sch em e 9
underwent PPh3 rearrangement upon warming to form
a phosphavinyl phosphonium complex. In the case of
M ) Ni, a phosphavinyl intermediate was postulated,
but only the phosphavinyl phosphonium complex (3, eq
3) was observed. Compound 3 was not isolated, but
reacted with another equivalent of Ni(PPh3)4 to generate
the novel dinuclear phosphavinylidene phosphorane
complex (4, eq 3). In all of the reactions with Cl2-
CdPN(SiMe3)2, there is no R-group rearrangement from
phosphorus to carbon as in the reactions with Cl2-
CdPMes*.15,16 Evidently, the presence of PPh3 ligands
favors the formation of the phosphavinyl phosphonium
complexes, while PEt3 tends to stabilize the phospha-
vinyl complexes.
Ack n ow led gm en t. We thank the donors of the
Petroleum Research Fund, administered by the Ameri-
can Chemical Society, for the support of this research
through Grant 27360-AC3.
Su p p or tin g In for m a tion Ava ila ble: A fully labeled
structural drawing of V, tables of non-hydrogen atomic coor-
dinates and equivalent isotropic parameters, anisotropic dis-
placement parameters, complete bond distances and angles,
hydrogen coordinates and isotropic diplacement parameters,
torsion angles, and unit cell and packing diagrams for V and
IX (20 pages). This material is contained in many libraries
on microfiche, immediately follows this article in the microfilm
version of the journal, can be ordered from the ACS, and can
be downloaded from the Internet; see any current masthead
page for ordering information and Internet access instructions.
OM9801913