Synthesis and structure of dinuclear palladium(II) complexes with bridging hydrido and phosphido ligands

Article abstract of DOI:10.1021/om000350u

The reaction of Pd(dppf)(Ph)(I) (1, dppf = Ph₂PC₅H₄FeC₅H₄PPh₂) with 1.5 equiv of PPh₂H leads to the formation of the Pd(II) dinuclear complex Pd₂I₂(μ-dppf)(

Full text of DOI:10.1021/om000350u

Organometallics 2000, 19, 3447-3454
3447
Syn th esis a n d Str u ctu r e of Din u clea r P a lla d iu m (II)
Com p lexes w ith Br id gin g Hyd r id o a n d P h osp h id o
Liga n d s
Michael A. Zhuravel, J illian R. Moncarz, and David S. Glueck*
Department of Chemistry, 6128 Burke Laboratory, Dartmouth College,
Hanover, New Hampshire 03755
Kin-Chung Lam and Arnold L. Rheingold
Department of Chemistry, University of Delaware, Newark, Delaware 19716
Received April 24, 2000
The reaction of Pd(dppf)(Ph)(I) (1, dppf ) Ph2PC5H4FeC5H4PPh2) with 1.5 equiv of PPh2H
leads to the formation of the Pd(II) dinuclear complex Pd2I2(µ-dppf)(µ-H)(µ-PPh2) (2) and
the phosphines PPh3 and dppf. The reaction of 1 with 1 equiv of PCy2H (Cy ) cyclo-C6H11)
slowly gives Pd2I2(µ-dppf)(µ-H)(µ-PCy2) (3). Complex 2 reacts further with PPh2H to give
the known [Pd(µ-PPh2)(I)(PPh2H)]2 (4). Reaction of Pd(dcpm)(Ph)(I) (dcpm ) Cy2PCH2PCy2)
with PPh2H gives [Pd2(PPh2H)2(µ-dcpm)(µ-PPh2)][I] (5). Treatment of Pd(dmpe)(Me)(Cl)
(dmpe ) Me2PCH2CH2PMe2) with AgOTf and PPh2H gives [Pd(dmpe)(µ-PPh2)]2[OTf]2 (6,
OTf ) OSO2CF3) as well as a small amount of [Pd2(dmpe)2(µ-H)(µ-PPh2)][OTf]2 (7). Slow
decomposition of [Pd(dmpe)(Me)(PCy2H)]+, prepared by the reaction of Pd(dmpe)(Me)(Cl),
AgOTf, and PCy2H, gives [Pd2(dmpe)2(µ-H)(µ-PCy2)][OTf]2 (8), which was also prepared from
Pd(dmpe)Cl2, AgOTf, Pd(dmpe)(dba) (dba ) dibenzylideneacetone), and PCy2H. Complexes
3, 4, 5, and 8 were structurally characterized by X-ray crystallography.
In tr od u ction
FeC5H4PPh2, OTf ) OSO2CF3) by treatment of Pd(dppf)-
(Ph)(I) (1) with AgOTf and PPh2H produces an ill-
defined mixture of products. However, when ca. 1.5
equiv of PPh2H is added to a yellow slurry of 1 in THF/
MeCN, the starting material dissolves instantly, form-
ing a dark orange solution. Addition of petroleum ether
and cooling to -25 °C affords orange crystals in 75%
yield, based on palladium. The reaction also produces
PPh3 and dppf, according to 31P NMR and comparison
with authentic samples.
The 31P{1H} NMR spectrum of the Pd-containing
product (CD2Cl2) shows a doublet at δ 15.0 and a triplet
at δ 266.2 with J PP ) 332 Hz. The large coupling
constant is indicative of trans location of the P nuclei,
while the chemical shift at low field is consistent with
the presence of a phosphido bridge and a metal-metal
bond.2 The 1H NMR spectrum includes three multiplets
at δ 8.06-7.40, two broad singlets at δ 4.50 and 3.98,
and a broad resonance at δ -8.27 consistent with the
presence of 30 phenyl, eight Cp, and one hydride proton.
No Pd-H stretch can be seen in the IR spectrum (KBr),
suggesting that the hydride is bridging. The FAB-MS
spectrum shows a parent ion peak at 1207.8 amu. These
spectroscopic data and the observed phosphine products
suggest the formation of the neutral dinuclear complex
Pd2(I)2(µ-dppf)(µ-H)(µ-PPh2) (2) according to the stoi-
chiometry shown in Scheme 1.
We previously reported that deprotonation of [Pd-
(dppe)(Me)(PH2Mes*)][BF4] (dppe ) Ph2PCH2CH2PPh2,
Mes* ) 2,4,6-(t-Bu)3C6H2) gave Pd(dppe)(Me)(PHMes*),
which underwent reductive elimination to give PH(Me)-
(Mes*) and Pd(0). Since this type of P-C bond-forming
step is important in Pd-catalyzed cross-coupling reac-
tions used for synthesis of tertiary phosphines, we have
investigated its generality and mechanism. Several
complexes [Pd(diphos)(R)(PR′2H)]+ could be prepared by
the reaction of Pd(diphos)(R)(X) (diphos ) dppe or dcpe
(Cy2PCH2CH2PCy2, Cy ) cyclo-C6H11); R ) Me, Ph, Mes
(2,4,6-Me3C6H2); R′ ) Ph, Cy, Mes; X ) Cl, Br, I) with
Ag+ and secondary phosphines.1 However, attempts to
extend these syntheses to complexes with diphosphines
having different bite angles and/or steric bulk did not
give analogous products. We report here that, instead,
dinuclear complexes with bridging phosphido, hydrido,
and diphosphine ligands were formed via some interest-
ing transformations, such as P-C bond formation, P-H
bond activation, and conversion of a chelate diphosphine
to one bridging two metal centers.
Resu lts a n d Discu ssion
Dp p f Com p lexes An attempt to prepare the cationic
complex [Pd(dppf)(Ph)(PPh2H)][OTf] (dppf ) Ph2PC5H4-
Treatment of 1 with 1.5 equiv of PCy2H results in
decomposition, but using 1 equiv of PCy2H gives the
dinuclear complex Pd2(I)2(µ-dppf)(µ-H)(µ-PCy2) (3, eq 1),
* Author for correspondence. E-mail: Glueck@Dartmouth.Edu.
(1) (a) Wicht, D. K.; Kourkine, I. V.; Lew, B. M.; Nthenge, J . M.;
Glueck, D. S. J . Am. Chem. Soc. 1997, 119, 5039-5040. (b) Zhuravel,
M. A.; Grewal, N. S.; Glueck, D. S.; Lam, K.-C.; Rheingold, A. L.
Organometallics, in press. (c) Zhuravel, M. A. Ph.D. Thesis, Dartmouth
College, J une 2000. (d) Zhuravel, M. A.; Wicht, D. K.; Moncarz, J . R.;
Sweeder, R. D.; Glueck, D. S.; Lam, K.-C.; Liable-Sands, L. M.;
Rheingold, A. L. Manuscript in preparation.
(2) (a) Carty, A. J.; MacLaughlin, S. A.; Nucciarone, D. In Phosphorus-
31 NMR Spectroscopy in Stereochemical Analysis; Verkade, J . G., Quin,
L. D., Eds.; VCH: Deerfield Beach, FL, 1987; pp 559-619. (b) Carty,
A. J . Adv. Chem. Ser. 1982, 196, 163-193.
10.1021/om000350u CCC: $19.00 © 2000 American Chemical Society
Publication on Web 07/27/2000

3448 Organometallics, Vol. 19, No. 17, 2000
Zhuravel et al.
which was characterized spectroscopically as well as by
elemental analysis and X-ray crystallography. We were
(1)
not able to identify the other products of the reaction.
Unlike 2, 3 does not form instantly on addition of the
phosphine to 1, probably due to the relatively large size
of PCy2H. Spectroscopic data for 3 are similar to that
of 2. The 31P NMR spectrum (CD2Cl2) contains signals
due to dppf (d, δ 14.0) and the bridging phosphido group
F igu r e 1. ORTEP diagram of 3‚THF with thermal ellip-
soids at 30% probability. For clarity the THF molecule and
hydrogen atoms, except the bridging hydrogen, are omitted.
Selected bond lengths (Å) and angles (deg): Pd(1)-H(1)
1.77(12), Pd(2)-H(1) 1.85(11), Pd(1)-Pd(2) 2.8008(14),
Pd(1)-P(1) 2.386(3), Pd(2)-P(2) 2.375(4), Pd(1)-P(3)
2.264(3), Pd(2)-P(3) 2.257(4); Pd(2)-P(3)-Pd(1) 76.55(11),
P(3)-Pd(2)-P(2) 169.64(14), P(3)-Pd(1)-P(1) 168.80(14).
2
(t, δ 349.6) with J PP ) 299 Hz. In the 1H NMR spectrum
(CD2Cl2), the bridging hydride signal appears at δ
-8.84.
An X-ray crystallography study of a THF solvate
confirmed the proposed structure of 3 (Figure 1). Data
collection and structure refinement are summarized in
Table 1, selected bond lengths and angles appear in the
figure caption, and additional details are given in the
Experimental Section and the Supporting Information.
The structure of 3 shows slightly distorted square
planar geometry at each metal center with both dppf P
atoms trans to the bridging phosphido group. The
ferrocene backbone is twisted out of the square plane
of the molecule and, thus, is able to accommodate the
P-P distance of 5.129 Å, which is considerably smaller
than the distance of 6.920 Å found in the free ligand.3
The conformation of the ferrocene is gauche eclipsed4
with the torsion angle 70.42°.5 The ferrocene backbone
is slightly distorted, with the angle between Cp planes
being 2.7(5)°. The 1H NMR spectrum of 3 shows two
signals due to the Cp protons, instead of the eight
expected for the solid-state structure, perhaps due to a
dynamic process in solution.
Sch em e 1
Dppf is known to act as a bridging ligand with a
variety of transition metals.4 Recently, for example, the
Pd(II) cluster [Pd3Cl2(dppf)(µ-dppf)(µ3-S)2] was charac-
terized crystallographically.6 There is also precedent for
complexes like 2 and 3, which contain bridging phos-
phido, hydrido, and diphosphine ligands, such as [Co2-
(CO)4(µ-H)(µ-PPh2)(µ-dppm)],7 [Fe2(Cp)2(µ-H)(µ-PPh2)(µ-
dppm)],8 and [Fe2(CO)4(µ-H)(µ-CO)(µ-PCy2)(µ-dppm)]9
(dppm ) Ph2PCH2PPh2).
The proposed dinuclear structure of 2 suggested two
other syntheses using sources of Pd(0), Pd(II), iodide,
and diphenylphosphine (Scheme 1). When PPh2H and
NaI are added to a mixture of Pd(dba)2 and Pd(dppf)-
Cl2 in THF, 2 forms rapidly in modest yield. Similarly,
the reaction of Pd(dppf)(dba), Pd(dppf)Cl2, PPh2H, and
NaI gives 2 in low yield.
Complex 2 decomposes in the presence of PPh2H. This
reaction was first observed in the original synthesis and
during recrystallization of impure samples of 2; it can
be avoided by using a substoichiometric amount of the
phosphine. Deliberate addition of 3 equiv of PPh2H to
2 gives the known phosphido-bridged dimer [Pd(I)-
(PPh2H)(µ-PPh2)]2 (4) (Scheme 1) over 2 days.10 Direct
reaction of 1 with 3 equiv of PPh2H in THF with heating
at 60 °C for 2 h also gives 4 in good yield; as expected,
PPh3 and dppf are also formed.
(3) Caseallato, U.; Ajo, D.; Valle, G.; Corain, B.; Longato, B.;
Graziani, R. J . Crystallogr. Spectrosc. Res. 1988, 18, 583-590.
(4) (a) Gan, K.-S.; Hor, T. S. A. In Ferrocenes. Homogeneous
Catalysis, Organic Synthesis, Materials Science; Togni A., Hayashi,
T., Eds.; VCH: Weinheim, Germany, 1995; pp 3-104.
(5) The torsion angle is defined as PA-CA-CB-PB where A and B
are the two Cp rings of ferrocene.
(6) Yeo, J . S. L.; Li, G.; Yip, W. H.; Henderson, W.; Mak, T. C. W.;
Hor, T. S. A. J . Chem. Soc., Dalton Trans. 1999, 435-442.
(7) Hanson, B. E.; Fanwick, P. E.; Mancini, J . S. Inorg. Chem. 1982,
21, 3811-3815.
(8) Raubenheimer, H. G.; Scott, F.; Cronje, S.; van Rooyen, P. H. J .
Chem. Soc., Dalton Trans. 1992, 1859-1863.
(9) Hogarth, G.; Lavender, M. H.; Shukri, K. Organometallics 1995,
14, 2325-2341.
(10) Hayter, R. G. J . Am. Chem. Soc. 1962, 84, 3046-3053.

Dinuclear Palladium(II) Complexes
Organometallics, Vol. 19, No. 17, 2000 3449
Ta ble 1. Cr ysta llogr a p h ic Da ta for P d 2I2(µ-d p p f)(µ-H)(µ-P Cy2) (3)‚THF , [P d (P P h 2H)(µ-P P h 2)I]2 (4),
[P d 2(µ-d cp m )(µ-P P h 2)(P HP h 2)2][I] (5), a n d [P d 2(d m p e)2(µ-H)(µ-P Cy2)][OTf]2 (8)‚THF
(3)‚THF
(4)
(5)
(8)‚THF
formula
fw
space group
a, Å
b, Å
c, Å
C
50H59FeI2OP3Pd2
C48H42I2P4Pd2
1209.30
C61H78IP5Pd2
1305.78
C30H63F6O7P5Pd2S2
1081.57
1291.33
P1h
P21/n
I2
P21/n
10.9984(4)
12.2340(4)
20.2598(6)
97.8289(8)
99.4108(9)
111.0779(8)
2452.5(2)
2
10.4481(2)
9.3127(2)
23.2617(3)
21.9383(1)
25.3614(3)
23.0561(1)
15.5310(2)
17.6718(2)
16.6645(2)
R, deg
â, deg
90.3660(5)
90.130(1)
92.1200(2)
γ, deg
V, Å3
2263.32(5)
2
12828.06(17)
8
4570.64(7)
4
Z
cryst color, habit
D(calc), g/cm3
µ(Mo KR), cm-1
temp, K
diffractometer
radiation
R(F), %a
R(wF2), %a
orange plate
1.749
orange block
1.774
orange block
1.352
colorless block
1.572
24.09
23.33
12.0
11.16
233(2)
173(2)
173(2)
173(2)
Siemens P4/CCD
Mo KR (λ ) 0.71073 Å)
5.31
18.93
2.20
9.09
10.58
26.43
2.83
10.92
Quantity minimized ) R(wF2) ) ∑[w(Fo - Fc2)2]/∑[(wFo2)2]1/2; R ) ∑∆/∑(Fo), ∆ ) |(Fo - Fc)|, w ) 1/[σ2(Fo2) + (aP)2 + bP], P ) [2Fc
a
2
2
+ max(Fo,0)]/3.
Ch a r t 1. Atom La belin g a n d Cou p lin g Con sta n ts
2
2
(in Hz) for Com p lex 4: J 13 ) 423.7, J 14 ) 23.5,
2J 34 ) -263a ,b
a
The results are in good agreement with the coupling
2
constants (in Hz) reported for [Pd(Cl)(PPh2H)(µ-PPh2)]2: J 13
) 423.1, 2J 14 ) 20.9, 2J 34 ) -261.1. See: Brandon, J . B.; Dixon,
K. R. Can. J . Chem. 1981, 59, 1188-1200. bThe sign of J 34
2
was preserved in agreement with the previously reported data,
but it did not affect the results of the simulation.
complex occurs with the small bite angle ligand dcpm
(Cy2PCH2PCy2), but with some important differences.
Treatment of Pd(dcpm)(Ph)(I) with 1.5 equiv of PPh2H
gives a mixture of products. The 31P{1H} NMR spectrum
of the major product (CD3CN) shows three peaks: a
triplet of triplets at δ 222.5 (2J PP ) 192, 26 Hz), a
doublet of multiplets at δ 9.5 (2J PP ) 192 Hz), and a
multiplet at δ -14.5. No hydride resonance is visible in
F igu r e 2. ORTEP diagram of 4 with thermal ellipsoids
at 30% probability. All hydrogen atoms, except those of the
phosphine ligand, are omitted for clarity. Selected bond
lengths (Å) and angles (deg): Pd(1)-Pd(1A) 3.6400(7),
Pd(1)-P(2) 2.2901(7), Pd(1)-P(1) 2.3289(7), Pd(1)-P(2A)
2.3311(7), Pd(1)-I(1) 2.6630(3); P(2)-Pd(1)-P(2A)
76.08(3), Pd(1)-P(2)-Pd(1A) 103.92(3).
1
Complex 4 was also prepared independently from the
corresponding chloride dimer [Pd(Cl)(PPh2H)(µ-PPh2)]2
by a modification of the original synthesis of Hayter and
was characterized spectroscopically as well as by X-ray
crystallography (Table 1). The 31P{1H} NMR spectrum
of 4 (CD2Cl2) shows two multiplets at δ 2.8 and -152.1,
consistent with the AA′BB′ spin system (Chart 1). The
X-ray crystal structure of 4 (Figure 2) is very similar to
that of the chloride complex [Pd(Cl)(PPh2H)(µ-PPh2)]2.11
The Pd-I bond (2.6630(3) Å) is longer than the Pd-Cl
one (2.369(1) and 2.382(3) Å), and the Pd-P bond length
for the phosphorus trans to halide is only slightly larger
for 4 (2.2901(7) Å) than in the chloride complex, in which
these Pd-P bond lengths are 2.266(1) and 2.275(3) Å.
Otherwise, there is no significant difference between the
two structures.
the H NMR spectrum. These observations are consis-
tent with the formation of the Pd(I) complex [Pd2(µ-
dcpm)(µ-PPh2)(PPh2H)2] [I] (5) (eq 2). This structural
(2)
formulation was confirmed by X-ray crystallography
(Figure 3 and Table 1), which, due to the high R-factor,
was used only to establish the connectivity and will not
be discussed in detail. Unfortunately, cation 5 is formed
along with Pd(dcpm)I2 (identified by independent syn-
thesis) and other unidentified products, from which it
is difficult to separate, so it could not be obtained in
pure form for elemental analysis. However, the presence
of PH groups was confirmed by both the IR spectrum
Dcp m Com p lexes Similar chemistry leading to the
formation of a dinuclear µ-diphosphine µ-phosphido
1
(KBr, 2292 cm-1) and the H NMR spectrum (CD2Cl2,
(11) Gebauer, T.; Frenzen, G.; Dehnicke, K. Z. Naturforsch. B 1992,
1505-1512.
m, δ 6.46).

3450 Organometallics, Vol. 19, No. 17, 2000
Zhuravel et al.
F igu r e 4. ORTEP diagram of 8‚THF with thermal el-
lipsoids at 30% probability. The triflate counterion, THF
solvent molecule, and all hydrogen atoms, except the
bridging hydrogen atom, are omitted for clarity. Selected
bond lengths (Å) and angles (deg): Pd(1)-H(1) 1.80(3),
Pd(2)-H(1) 1.72(3), Pd(1)-P(1) 2.3216(8), Pd(1)-P(2)
2.2778(7), Pd(1)-P(5) 2.3023(7), Pd(1)-Pd(2) 2.8041(3),
Pd(2)-P(3) 2.3311(7), Pd(2)-P(4) 2.2879(7), Pd(2)-P(5)
2.3153(6); P(2)-Pd(1)-P(1) 86.44(3), P(4)-Pd(2)-P(3)
85.86(2), Pd(1)-P(5)-Pd(2) 74.78(2), P(5)-Pd(1)-P(1)
168.71(3), P(5)-Pd(2)-P(3) 167.45(2).
F igu r e 3. ORTEP diagram of 5 with thermal ellipsoids
at 30% probability. The iodide counterion and all hydrogen
atoms, except those of the phosphine ligand, are omitted
for clarity.
Ch a r t 2. Atom La belin g a n d Cou p lin g Con sta n ts
2
2
(in Hz) for Com p lex 6: J 16 ) 312.5, J 15 ) 8.3,
2J 12 ) -3.2, J 14 ) -12.1, J 13 ) -3.4, J 56 ) -234.4a
4
4
2
constants for this AA′A′′A′′′XX′ spin system, found by
spectral simulation, agree reasonably well with the
results for the known [Pd(dppe)(µ-PPh2)]22+ (Chart 2).16
Although hydride 7 could not be separated from 6, it
was identified by NMR in comparison to the analogous
µ-PCy2 complex 8 (see below). The 31P NMR spectrum
of 7 (acetone-d6) contains an apparent triplet at δ 168.3
(2J PP ) 285 Hz, PCy2) and a set of multiplets at δ 43.3-
40.7 (dmpe). The bridging hydride signal appears in the
1H NMR spectrum (acetone-d6) at δ -6.04 (t (2J PH ) 80
Hz) of d (2J PH ) 17 Hz)).
Analogous chemistry with PCy2H (Scheme 2) is not
so clean. Reaction of Pd(dmpe)(Me)(Cl) with AgOTf and
PCy2H gives a clear solution containing mostly the
expected cationic complex [Pd(dmpe)(Me)(PCy2H)]+ (iden-
tified by 31P{1H} NMR) and a small amount of unidenti-
fied impurities. Attempted workup led to substantial
decomposition. A single crystal was isolated from such
a mixture and shown to be [Pd2(dmpe)2(µ-H)(µ-PCy2)]-
[OTf]2 (8) by X-ray crystallography (Table 1). The crystal
structure of 8‚THF (Figure 4) exhibits slightly distorted
square planar geometry, with a Pd-Pd distance of
2.8041(3) Å.
As with dppf complex 2, complex 8 could also be
produced from (dmpe)Pd(II) and (dmpe)Pd(0) fragments
and PCy2H. Thus, the reaction of in situ prepared Pd-
(dmpe)(dba) and Pd(dmpe)I2 with PCy2H and 2 equiv
of AgOTf gives 8 in low yields. Unfortunately this
reaction was irreproducible, so amounts of pure 8
sufficient for elemental analysis could not be obtained,
and it was characterized spectroscopically. In the 31P
NMR (CD2Cl2) spectrum, the bridging phosphido group
gives rise to an apparent triplet at δ 244.2 (2J PP ) 266
Hz); no coupling to the cis dmpe P nuclei was observed.
The dmpe signals appear as multiplets at δ 38.3 and
a
The results are similar to those reported for [Pd(dppe)(µ-
:
2J 16 ) 311.0, J 15 ) 28.2, J 12 ) -17.5, J 14 ) 0,
2+
2
2
4
PPh2)]2
4J 14 ) 0, 4J 56 ) -349.4. See: Brandon, J . B.; Dixon, K. R. Can.
J . Chem. 1981, 59, 1188-1200.
Complex 5 is structurally similar to several related
Pd(I) complexes with µ-dppm ligands, such as [M2(µ-
PPh2)(µ-dppm)(PPh3)2]+ (M ) Pd, Pt)12 and [Pd(µ-
dppm)(µ-P(t-Bu)2)(PR3)2]+ (R ) Me, Et), reported re-
cently by Leoni.13 However, as far as we know, the only
other Pd(I) compound featuring a bridging dcpm ligand
is [PdCl(µ-dcpm)]2.14
Dm p e Com p lexes The syntheses of the dinuclear
dppf and dcpm complexes described above show that
changes in bite angle significantly affect the observed
chemistry. Similarly, using the smaller dmpe (Me2PCH2-
CH2PMe2) instead of dppe or dcpe gives dinuclear
complexes instead of the expected mononuclear cations.
Treatment of Pd(dmpe)(Me)(Cl)15 with AgOTf and
PPh2H gives a mixture of the phosphido-bridged dimer
[Pd(dmpe)(µ-PPh2)]2[OTf]2 (6) and a trace of [Pd2(dmpe)2-
(µ-H)(µ-PPh2)][OTf]2 (7) (Scheme 2). Alternatively, 6 can
be prepared by reaction of 4 or the analogous chloride
complex [Pd(Cl)(PPh2H)(µ-PPh2)]2 with 2 equiv of dmpe
and AgOTf in THF. Dimer 6 was characterized spec-
troscopically. The 31P NMR (CD2Cl2) spectrum shows
two multiplets at δ 36.2 and -113.3. The coupling
(12) Browning, J .; Dehghan, K.; Dixon, K. R.; Hadj-Bagheri, N.;
Meanwell, N. J .; Vefghi, R. J . Organomet. Chem. 1990, 396, C47-C52.
(13) Leoni, P.; Pasquali, M.; Pieri, G.; Englert, U. J . Organomet.
Chem. 1996, 514, 243-255.
(14) Hashioka, M.; Sakai, K.; Tsubomura, T. Acta Crystallogr. 1998,
C54, 1244-1247.
(15) Kayaki, Y.; Shimizu, I.; Yamamoto, A. Bull. Chem. Soc. J pn.
1997, 70, 917-927.
(16) Brandon, J . B.; Dixon, K. R. Can. J . Chem. 1981, 59, 1188-
1200.

Dinuclear Palladium(II) Complexes
Organometallics, Vol. 19, No. 17, 2000 3451
Sch em e 2
1
38.1. In the H NMR spectrum (CD2Cl2), the bridging
a halide-abstracting agent. The ligands dppf and dcpm,
which have large and small bite angles, respectively,
give dinuclear complexes that both have bridging diphos-
phine and phosphido ligands, but dppf-containing 2 and
3 are Pd(II) complexes with a bridging hydride, and
dcpm complex 5 is a Pd(I) cation with no hydride. The
dmpe ligand was not observed to bridge, but it gave
dinuclear complexes 6-8 with bridging phosphido and/
or hydrido ligands. Presumably, these results are a
consequence of several factors, including the lability of
the diphosphine and halide ligands, the acidity of
coordinated secondary phosphines, and steric effects at
the metal center.
hydride signal appears at δ -6.38 as a triplet (2J PH
)
77 Hz) of doublets (2J PH ) 14 Hz).
P d -P d Bon d in g in Din u clea r Com p lexes. Pd-
Pd bonding in dinuclear phosphido-bridged Pd(I) com-
plexes such as 5 has been characterized structurally and
by computational studies, as discussed recently by
Mealli and co-workers.17 However, the presence of Pd-
Pd bonding in dinuclear Pd(II) complexes has been more
controversial. As discussed by Clegg, short Pd-Pd
distances observed in X-ray crystal structures of Pd(II)
complexes do not require the presence of Pd-Pd inter-
actions.18 The very long Pd-Pd distance in 4 (3.6400-
(7) Å) and the upfield 31P NMR chemical shift for the
µ-PPh2 groups (δ -152.1) suggest, as expected for
square planar Pd(II), that there is no Pd-Pd bonding
in this complex. In contrast, the downfield 31P NMR
chemical shifts for the µ-phosphido ligands in 2, 3, 7,
and 8 (δ 266.2, 349.6, 168.3, and 244.2, respectively) are
usually considered to indicate the presence of a metal-
metal bond. The Pd-Pd distances in 3 (2.8008(14) Å)
and 8 (2.8041(3) Å) are much shorter than in 4,
consistent with the NMR data. As noted by van Leeu-
wen et al., however, such low-field 31P NMR chemical
shifts are routinely observed in dinuclear complexes
containing both µ-phosphido and µ-hydrido ligands. The
three-center, two-electron interaction in the MHM unit
may also be described as a protonated metal-metal
bond.19
Exp er im en ta l Section
Gen er a l Exp er im en ta l Deta ils. Unless otherwise noted,
all reactions and manipulations were performed in dry glass-
ware under a nitrogen atmosphere at 20 °C in a drybox or
using standard Schlenk techniques. Petroleum ether (bp 38-
53 °C), ether, THF, and toluene were dried and distilled before
use by employing Na/benzophenone. CH2Cl2 was distilled from
CaH2. Acetone and acetonitrile were degassed by purging with
N2 and stored over molecular sieves.
Unless otherwise noted, all NMR spectra were recorded by
using a Varian 300 MHz spectrometer. 1H or 13C NMR
chemical shifts are reported vs Me4Si and were determined
1
by reference to the residual H or 13C solvent peaks. 31P NMR
chemical shifts are reported vs H3PO4 (85%) used as an
external reference. Coupling constants are reported in hertz
as absolute values unless noted otherwise. Unless indicated,
peaks in NMR spectra are singlets. Infrared spectra were
recorded on a Perkin-Elmer 1600 series FTIR machine and
are reported in cm-1. Elemental analyses were provided by
Schwarzkopf Microanalytical Laboratory. Low-resolution FAB
mass spectroscopy was performed on a VG ZAB-SE instrument
at the University of Illinois.
Unless otherwise noted, reagents were from commercial
suppliers. The following compounds were made by the litera-
ture methods: [Pd(µ-PPh2)(Cl)(PPh2H)]2,10 Pd(dppf)(Ph)(I),20
Pd(cod)(Me)(Cl),21 Pd(dppf)Cl2,22 Pd(dba)2,23 Pd(dppf)(dba),24
trans-Pd(PPh3)2(Ph)(I),25 and Pd(cod)Cl2.26
Con clu sion . Small changes in the diphosphine ligand
lead to big differences in the reaction of complexes Pd-
(diphosphine)(R)(X) (R ) Ph or Me, X ) halide) with
secondary phosphines with or without added AgOTf as
(17) Mealli, C.; Ienco, A.; Galindo, A.; Carreno, E. P. Inorg. Chem.
1999, 38, 4620-4625.
(18) (a) Clegg, W.; Garner, C. D.; Al-Samman, M. H. Inorg. Chem.
1982, 21, 1897-1901. (b) For a similar, recent report of a Pd(II)
dinuclear complex with a short Pd-Pd distance but no formal metal-
metal bond, see: Cotton, F. A.; Gu, J .; Murillo, C. A.; Timmons, D. J .
J . Am. Chem. Soc. 1998, 120, 13280-13281.
P d 2(I)2(µ-H)(µ-P P h 2)(µ-d p p f) (2). 1. To a yellow slurry of
Pd(dppf)(Ph)(I) (117 mg, 0.14 mmol) in THF/MeCN (2 mL, 5:1
(19) van Leeuwen, P. W. N. M.; Roobeek, C. F.; Frijns, J . H. G.;
Orpen, A. G. Organometallics 1990, 9, 1211-1222.

3452 Organometallics, Vol. 19, No. 17, 2000
Zhuravel et al.
mixture) was added PPh2H (38 mg, 0.20 mmol). The remaining
solid rapidly dissolved, forming an orange solution. After 15
min of stirring the solution acquired a dark orange/purple
color. Petroleum ether was added, and cooling to -25 °C gave
the product as 61 mg (75% yield) of orange solid. The other
products were isolated together from the mother liquor and
identified as PPh3 and dppf by spiking (31P{1H} NMR). Anal.
was filtered twice, and the solid residue was dried in a vacuum
to give 248 mg (82% yield) of orange solid product. Anal. Calcd
for C48H42P4I2Pd2: C, 47.67; H, 3.50. Found: C, 47.73; H, 3.37.
2. Pd(dppf)(Ph)(I) (66 mg, 0.08 mmol) was suspended in 1
mL of THF. Upon addition of PPh2H (43 mg, 0.24 mmol) to
the slurry the remaining solid dissolved and the solution
acquired a dark orange color. The solution was heated at 60
°C for 2 h, causing a color change to light orange. Addition of
petroleum ether and cooling to -25 °C afforded the product
as 35 mg of orange crystals (76% yield). Additional recrystal-
lization from CH2Cl2 gave crystals of X-ray quality.
Calcd for
C46H39P3I2FePd2‚1.25THF: C, 47.22; H, 3.81.
Found: C, 47.11; H, 3.54. The presence of THF was confirmed
quantitatively by H NMR.
1
2. To a slurry of Pd(dppf)Cl2 (69 mg, 0.09 mmol) and Pd-
(dba)2 (54 mg, 0.09 mmol) in 3 mL of THF were added PPh2H
(17 mg, 0.09 mmol, via microliter syringe) and NaI (30 mg,
0.20 mmol), and the resulting black slurry was allowed to
stand for 5 days. The slurry was filtered, and 11 mg of red
crystals was separated. The solid residue was redissolved in
CH2Cl2 and filtered. Ether was added, and cooling to -30 °C
gave an additional 10 mg of the product (21 mg, 19% total
yield) as red crystals.
3. To a stirred slurry of Pd(dppf)(dba) (30 mg, 0.03 mmol)
and Pd(dppf)Cl2 (25 mg, 0.03 mmol) in 3 mL of THF were
added PPh2H (6 mg, 0.03 mmol) and NaI (10 mg, 0.07 mmol).
The initially orange slurry darkened and then slowly turned
purple. The mixture was filtered; the 31P NMR spectrum of
the filtrate showed that complexes 2 and 4 were formed.
1H NMR (CD2Cl2): δ 8.06-8.00 (m, 4H, Ph), 7.70-7.55 (m,
8H, Ph), 7.55-7.35 (m, 18H, Ph), 4.50 (br, 4H, Cp), 3.98 (broad,
4H, Cp), -8.27 (br, 1H, Pd-H-Pd). 31P{1H} NMR (CD2Cl2):
δ 266.2 (t, 2J PP ) 332), 15.0 (d, 2J PP ) 332). 13C{1H} NMR (CD2-
Cl2): δ 136.3 (m), 136.1-135.8 (m), 131.4 (m), 130.1, 128.2-
127.9 (m), 77.0-76.3 (m), 72.9 (broad), 68.0. IR: 3049, 2974,
2858, 1959, 1584, 1479, 1433, 1385, 1307, 1168, 1096, 1066,
1027, 998, 898, 838, 742, 693. Low-resolution FAB-MS (3-
NBA): 1207.8 (parent ion), 1078.9 (Pd2(dppf)(PPh2)(I)), 951.0,
894.8 (Pd2(dppf)(I)), 685.9, 660, 583.0, 500.8, 460.1.
P d 2(I)2(µ-H)(µ-P Cy2)(µ-d p p f) (3). To a yellow slurry of Pd-
(dppf)(Ph)(I) (197 mg, 0.23 mmol) in THF/MeCN (2 mL, 5:1
mixture) was added PCy2H (45 mg, 0.23 mmol). The remaining
solid dissolved, forming a yellow solution. The solution was
allowed to stand for 3 days; then petroleum ether was added,
and cooling to -25 °C gave the product as 81 mg (58% yield)
of olive-green solid. Prolonged standing of the original reaction
mixture gave crystals of a THF solvate, as shown by X-ray
crystallography and elemental analysis. Anal. Calcd for
C46H51P3I2FePd2‚THF: C, 46.50; H, 4.61. Found: C, 46.58; H,
4.53.
1H NMR (CD2Cl2): δ 7.60-7.36 (m, 20H, Ph), 4.38 (4H, Cp),
3.92 (4H, Cp), 3.30-3.07 (m, 2H, Cy), 2.20-2.05 (m, 3H, Cy),
1.96-1.61 (m, 9H, Cy), 1.45-1.16 (m, 6H, Cy), 0.90-0.83 (m,
2H, Cy), -8.84 (1H, Pd-H-Pd). 31P{1H} NMR (CD2Cl2): δ
349.6 (t, 2J PP ) 299), 14.0 (d, 2J PP ) 299). IR: 3052, 2925, 2849,
1628, 1481, 1434, 1385, 1169, 1099, 1028, 999, 846, 818, 742.
[P d (P P h 2H)(I)(µ-P P h 2)]2 (4). 1. This is a minor modifica-
tion of Hayter’s synthesis.10 [Pd(PPh2H)(Cl)(µ-PPh2)]2 (257 mg,
0.25 mmol) was dissolved in 10 mL of CH2Cl2. NaI (80 mg,
0.54 mmol) was added as a solid, and the yellow slurry was
stirred for 16 h. Over the course of the reaction the color of
the slurry changed from yellow to bright orange. The solution
1
1H NMR (CDCl3): δ 8.00-7.00 (m, 40H, Ar), 5.08 (m, J PH
) 358, 2H, P-H). 31P{1H} NMR (CDCl3): δ 2.8 (m), -152.1
(m). IR: 3049, 2923, 2850, 2321 (PH), 1962, 1887, 1811, 1662,
1581, 1476, 1433, 1304, 1261, 1181, 1157, 1093, 1025, 854, 737,
690.
P d (d cp m )(P h )(I). To a solution of trans-Pd(PPh3)2(Ph)(I)
(1.20 g, 1.44 mmol) in toluene (6 mL) was transferred a
solution of dcpm (589 mg, 1.44 mmol) in toluene (6 mL). The
pale yellow suspension was stirred at room temperature for
12 h. The solid was collected on a fine frit and washed with
petroleum ether (20 mL) to give 994 mg (96%) of crude product.
A sample recrystallized from CH2Cl2/ether at -25 °C was
found to be a CH2Cl2 solvate by elemental analysis. Anal. Calcd
for C31H51P2IPd‚CH2Cl2: C, 47.81; H, 6.65. Found: C, 47.74;
H, 6.80.
1H NMR (CDCl3): δ 7.55-7.33 (m, 2H, Ar), 6.96 (br, 2H,
Ar), 6.79-6.75 (m, 1H, Ar), 2.85-2.79 (m, 2H, CH2), 2.15-
1.21 (m, 42H, Cy), 0.98 (br, 2H, Cy).31P{1H} NMR (CDCl3): δ
2
2
-15.6 (d, J PP ) 69), -38.8 (d, J PP ) 69). 13C{1H} NMR
(CDCl3): δ 154.1 (dd, 2J PC ) 13, 147, Ar), 137.7 (Ar, CH), 126.8
(d, J PC ) 9, Ar, CH), 122.6 (Ar, CH), 34.8-34.7 (m, Cy, CH),
3
33.5 (dd, J PC ) 3, 20, Cy, CH), 29.3 (Cy, CH2), 29.1 (Cy, CH2),
27.9 (Cy, CH2), 27.4 (Cy, CH2), 27.2 (Cy, CH2), 27.1 (Cy, CH2),
27.0 (Cy, CH2), 26.8 (Cy, CH2), 26.6 (Cy, CH2), 26.4 (Cy, CH2),
26.0 (Cy, CH2), 25.8 (Cy, CH2), 23.9-22.8 (CH2). IR: 2919,
2837, 1560, 1443, 720, 691.
[P d 2(µ-P P h 2)(µ-d cp m )(P P h 2H )2][I] (5). To a slurry of
Pd(dcpm)(Ph)(I) (148 mg, 0.21 mmol) in 2 mL of THF was
added PPh2H (57 mg, 0.31 mmol). The remaining solid
dissolved, forming a yellow solution. After 12 h the solution,
now dark orange, was filtered. The solvent was removed under
vacuum, and the residue was redissolved in toluene (5 mL).
The dark orange solution was filtered and allowed to stand at
room temperature. After 2 days the crude product precipitated
as 85 mg of orange solid, which was a mixture of 5 (major)
and Pd(dcpm)I2 (minor, identified by the independent synthe-
sis below). Orange crystals of 5 separated manually from this
material were used for X-ray crystallography, but the bulk
material could not be obtained analytically pure and free of
Pd(dcpm)I2.
31P{1H} NMR (CD3CN): δ 222.5 (tt, 2J PP ) 192, 26), 9.5 (dm,
2J PP ) 192), -14.5 (m). 1H NMR (CD2Cl2): δ 7.40-7.17 (m,
30H, Ph), 6.46 (m, 2H, PH), 3.23 (m, 2H, CH2), 2.40-1.01 (m,
44H, Cy). IR: 3048, 2924, 2849, 2292, 1479, 1435, 1179, 1094,
850, 735.
P d (d cp m )I2. To Pd(cod)Cl2 (73 mg, 0.26 mmol) in 2 mL of
toluene was added dcpm (105 mg, 0.26 mmol), and the
resulting slurry was stirred for 5 min. The solution was
decanted and the solid was washed with 3 × 10 mL of
petroleum ether and dried under vacuum to give Pd(dcpm)-
Cl2 as 147 mg (98% yield) of off-white solid, which was used
without additional purification. To a white slurry of Pd(dcpm)-
(Cl)2 (53 mg, 0.09 mmol) in 3 mL of toluene was added NaI
(at least a 2-fold excess). After 30 min of stirring, the yellow
solution was decanted and the solid residue was washed with
ether and dried under vacuum. The yellow solid was recrystal-
lized from CH2Cl2/ether at -25 °C to give 59 mg (85% yield)
of yellow crystalline solid. Anal. Calcd for C25H46P2I2Pd: C,
39.06; H, 6.03. Found: C, 39.49; H, 6.14.
(20) (a) Driver, M. S.; Hartwig, J . F. J . Am. Chem. Soc. 1997, 119,
8232-8245. (b) Brown, J . M.; Guiry, P. J . Inorg. Chim. Acta 1994, 220,
249-258.
(21) Ladipo, F. T.; Anderson, G. K. Organometallics 1994, 13, 303-
306.
(22) Hayashi, T.; Konishi, M.; Kobori, Y.; Kumada, M.; Higuchi, T.;
Hirotsu, K. J . Am. Chem. Soc. 1984, 106, 158-163.
(23) Maitlis, P. M.; Rettig, M. F. Inorg. Synth. 1990, 28, 110-113.
(24) Pd(dppf)(dba) was prepared by the general procedure described
in: Herrmann, W. A.; Thiel, W. R.; Brossner, C.; Ofele, K.; Priermeier,
T.; Scherer, W. J . Organomet. Chem. 1993, 461, 51-60.
(25) Fitton, P.; J ohnson, M. P.; McKeon, J . E. J . Chem. Soc., Chem.
Commun. 1968, 6-7.
(26) Drew, D.; Doyle, J . R. Inorg. Synth. 1990, 28, 346-349.

Dinuclear Palladium(II) Complexes
Organometallics, Vol. 19, No. 17, 2000 3453
2
1H NMR (CD2Cl2): δ 3.14 (t, 2H, J PH ) 10, CH2), 2.44-
2.28 (m, 8H, Cy), 2.23-2.11 (m, 4H, Cy), 2.04-1.90 (m, 8H,
Cy), 1.84-1.75 (m, 4H, Cy), 1.67-1.24 (m, 20H, Cy). 31P{1H}
NMR (CD2Cl2): δ -42.1. 13C{1H} NMR (CD2Cl2): δ 36.9 (m,
added, and the solution was stored at -25 °C for 3 weeks to
give a single clear crystal used for the crystal structure
determination.
2. To a slurry of Pd(dba)2 (89 mg, 0.15 mmol) in 3 mL of
THF was added dmpe (25 µL, 0.15 mmol) via microliter
syringe. After 20 min of stirring the dark solution was filtered
and PCy2H (31 mg, 0.15 mmol) was added via microliter
syringe. In a separate flask, to a slurry of Pd(cod)Cl2 (44 mg,
0.15 mmol) in 3 mL of THF was added dmpe (25 µL, 0.15
mmol), and the slurry was stirred for 30 min. AgOTf (80 mg,
0.31 mmol) was added to the slurry in 1 mL of THF. A gray
precipitate formed, and the yellow solution was filtered and
added to the Pd(dba)2/dmpe/PCy2H solution immediately after
the addition of PCy2H. No visible reaction occurred. The dark
orange solution was allowed to stand at room temperature for
5 days, during which time black solid precipitated. The solution
was decanted, and the solid residue was washed with 3 × 5
mL of ether and dried under vacuum. The solid was suspended
in 5 mL of CH2Cl2 and stirred for 1 h, then filtered. Ether was
added to the clear solution, and cooling to -25 °C gave the
product as 7 mg (9% yield) of beige solid, which still contained
impurities.
1
CH), 29.4, 28.4, 27.2 (m), 26.8 (m), 26.0, 21.5 (t, J PC ) 20,
CH2). IR: 2928, 2850, 2666, 1623, 1445, 1346, 1326, 1293,
1268, 1199, 1179, 1114, 1001, 916, 888, 851, 821, 770.
P d (d m p e)(Me)(Cl). This complex was reported previously
by Yamamoto and co-workers.15 We describe an alternative
synthesis and additional (31P and 13C NMR) spectroscopic
characterization. To a white slurry of Pd(cod)(Me)(Cl) (525 mg,
1.98 mmol) in 5 mL of toluene was added dmpe (330 µL,
1.98 mmol) via microliter syringe. The color of the slurry
immediately changed to beige. After 1 h of stirring the slurry
was filtered on a frit. The solid residue was washed with 4 ×
5 mL of petroleum ether and dried in vacuo to give the product
as 403 mg (1.31 mmol, 66% yield) of gray solid. Anal. Calcd
for C7H19ClP2Pd: C, 27.38; H, 6.24. Found: C, 27.32; H, 6.27.
1H NMR (CD2Cl2): δ 2.00-1.55 (m, 4H, CH2), 1.53 (d, J PH
2
2
3
) 11, 6H, Me), 1.43 (d, J PH ) 9, 6H, Me), 0.30 (dd, J PH ) 4,
8, 3H, Me). 31P{1H} NMR (CD2Cl2): δ 39.8 (d, 2J PP ) 23), 26.8
(d, J PP ) 23). 13C{1H} NMR (CD2Cl2): δ 31.2 (dd, J PC ) 21,
2
1
15, CH2), 25.4 (dd, J PC ) 16, 6, CH2), 13.7 (d, J PC ) 20, Me),
12.0 (d, J PC ) 11, Me), 3.4 (dd, J PC ) 69, 3, Me).
1H NMR (CD2Cl2): δ 2.48-2.10 (m, 8H, CH2), 1.96-1.66 (m),
1
2
2
1.40-1.22 (m), 1.10-0.96 (m), -6.39 (td, J PH ) 17, 77, 1H,
[P d (µ-P P h 2)(d m p e)]2[OTf]2 (6). 1. Pd(dmpe)(Me)(Cl) (43
mg, 0.14 mmol) was suspended in 2 mL of 1:1 THF/MeCN.
AgOTf (36 mg, 0.14 mmol) and PPh2H (26 mg, 0.14 mmol) were
added. The solution was stirred for 5 min and filtered. The
resulting yellow solution was kept at room temperature for 1
day, petroleum ether was added, and cooling to -30 °C gave
the crude product as 48 mg (93% yield) of orange solid
contaminated with a small amount of [Pd2(dmpe)2(µ-H)(µ-
2
PH). 31P{1H} NMR (CD2Cl2): δ 244.2 (t, J PP ) 266, PCy2),
38.3 (m, trans-dmpe), 38.1 (m, cis-dmpe).
Cr ysta llogr a p h ic Str u ctu r a l Deter m in a tion . Crystal,
data collection, and refinement parameters are given in Table
1. The systematic absences in the diffraction data for 8 and 4
are uniquely consistent for the reported space group. No
evidence of symmetry higher than triclinic was observed in
the diffraction data for 3. The centrosymmetric space group
P1h was chosen for 3, which yielded chemically reasonable and
computationally stable results of refinement. The structures
were solved using direct methods, completed by subsequent
difference Fourier syntheses, and refined by full-matrix least-
squares procedures. SADABS empirical absorption corrections
were applied to all four structures.
PPh2)][OTf]2 (7). 31P{1H} NMR (acetone-d6): δ 168.3 (t, J PP
) 285), 43.3-40.7 (m). Selected H NMR (acetone-d6): δ -6.04
2
1
2
(dt, J PH ) 80, 17).
2. To a slurry of [Pd(Cl)(µ-PPh2)(PPh2H)]2 (74 mg, 0.07
mmol) in 2 mL of THF were added AgOTf (37 mg, 0.14 mmol)
and dmpe (22 mg, 0.14 mmol). The resulting yellow solution
was allowed to stand for 12 h and then filtered. Petroleum
ether was added, and cooling to -30 °C gave the product as
65 mg (76% yield) of orange solid. Anal. Calcd for C38H52P6F6-
S2O6Pd2: C, 38.63; H, 4.44. Found: C, 38.39; H, 4.37.
1H NMR (CD2Cl2): δ 7.60-7.51 (m, 8H, Ph), 7.32-7.21 (m,
12H, Ph), 2.04-1.81 (m, 8H, CH2), 1.16-1.13 (m, 24H, Me).
31P{1H} NMR (CD2Cl2): δ 38.8-33.6 (m), -109.4 to -117.2
(m). 13C{1H} NMR (CD2Cl2): δ 135.8 (m), 133.4-133.1 (m),
130.4, 129.2 (m), 28.5-27.9 (m), 13.0-12.6 (m). IR: 3052, 2987,
2908, 1631, 1582, 1475, 1435, 1260, 1223, 1153, 1094, 1030,
941, 901, 844, 798, 747.
The asymmetric unit of 3 contains a palladium dimer
complex and a THF molecule. All non-hydrogen atoms of 3,
except C(9), C(35), C(36), C(44), and C(45), which persistently
remained nonpositive definite, and the non-hydrogen atoms
of the THF molecule were refined with anisotropic displace-
ment parameters. All phenyl rings of 3 were fixed as rigid
planar groups. The bridging hydrogen atom was located from
a difference map in which the coordinate was free to refine
and the thermal parameter was set as an idealized contribu-
tion. All other hydrogen atoms of 3 were treated as idealized
contributions. The asymmetric unit of 4 contains half of a
palladium dimer, which lies on an inversion center. All non-
hydrogen atoms of 8 and 4 were refined with anisotropic
displacement coefficients. The bridging hydrogen atom of 8 and
the phosphine hydrogen atom of 4 were located from the
difference map.
Syn t h esis a n d Decom p osit ion of [P d (d m p e)(Me)-
(P Cy2H)][OTf]. To a white slurry of Pd(dmpe)(Me)(Cl) (60 mg,
0.20 mmol) in 5:1 THF/MeCN was added AgOTf (50 mg, 0.20
mmol) in 1 mL of THF, then PCy2H (39 mg, 0.20 mmol) via
microliter syringe. The resulting gray slurry was stirred for 5
min and filtered to give a yellow solution, containing [Pd-
(dmpe)(Me)(PCy2H)][OTf]. 31P{1H} NMR (THF): δ 31.8 (dd,
For 5, diffraction symmetry was restricted to the monoclinic
crystal system, and systematic absences in the data indicated
the space groups I2, Im, or I2/m. E-statistics strongly sug-
gested a noncentrosymmetric setting; I2 was initially chosen
based on its higher frequency of occurrence and later confirmed
by the results of the refinement process. The structure was
solved by direct methods. The asymmetric unit consists of two
independent cations and two iodide counterions, one located
in a general position and the other divided between two 2-fold
sites. The hand reported was confirmed by refinement of the
Flack parameter, 0.10(5). All phenyl rings were treated as
rigid, planar hexagons. The low quality of the data due to a
very high mosaic spread in all specimens examined allowed
anisotropic refinement of only the Pd and P atoms. All H atoms
were treated as idealized contributions (d(CH) ) 0.95, d(P-
2J PP ) 374, 25), 20.0 (dd, J PP ) 36, 25), 8.5 (dd, J PP ) 374,
2
2
36).
The solvent was removed under vacuum, and the resulting
oily residue was washed with petroleum ether, dried, and
dissolved in 2 mL of THF, then filtered to give a tan solution.
No visible change in the solution occurred after 1 day of
standing, but the 31P{1H} NMR spectrum showed decomposi-
tion of [Pd(dmpe)(Me)(PCy2H)][OTf] and formation of at least
three new products.
[P d 2(d m p e)2(µ-H)(µ-P Cy2)][OTf] 2 (8). 1. To a slurry of Pd-
(dmpe)(Me)(Cl) (75 mg, 0.24 mmol) in 2 mL of 5:1 THF/MeCN
were added AgOTf (63 mg, 0.24 mmol) and PCy2H (49 mg, 0.24
mmol). The solvent was removed under vacuum, the solid
residue was dissolved in THF (2 mL), petroleum ether was

3454 Organometallics, Vol. 19, No. 17, 2000
Zhuravel et al.
H) ) 1.40 Å). All software and sources of the scattering factors
sity of Delaware acknowledges the NSF (Grant CHE-
9628768) for their support of the purchase of the CCD-
based diffractometer.
are contained in the SHELXTL (5.10) program library.27
Ack n ow led gm en t. We thank the NSF Career Pro-
gram, DuPont, and Union Carbide (Innovation Recogni-
tion Award) for support, the Department of Education
for a GAANN fellowship for M.A.Z, and J eff Nagle
(Bowdoin College) for a helpful discussion. The Univer-
Su p p or tin g In for m a tion Ava ila ble: Details of the crys-
tal structure determinations. This material is available free
of charge via the Internet at http://pubs.acs.org.
(27) Sheldrick, G. SHELXTL; Siemens XRD: Madison, WI.
OM000350U