Proton lability in highly hindered dinuclear palladium(I) μ-phosphido-secondary phosphine complexes. Crystal structures of [Pd2 (μ-PBut2)(PCy2H)3(CO)]BF4 and [Pd2(μ-PBut</su

Article abstract of DOI:10.1021/om9509148

The reactions of the dinuclear cationic complexes [Pd₂(μ-PBu^t₂)(PR₃) ₄]⁺ (PR₃ = PCy₂H, PMe₃) with CO or isoprene proceed with substitution of one or two pho

Full text of DOI:10.1021/om9509148

Organometallics 1996, 15, 2047-2052
2047
P r oton La bility in High ly Hin d er ed Din u clea r
P a lla d iu m (I) µ-P h osp h id o-Secon d a r y P h osp h in e
Com p lexes. Cr ysta l Str u ctu r es of
[P d 2(µ-P Bu t )(P Cy2H)3(CO)]BF 4 a n d
2
[P d 2(µ-P Bu t )(P Cy2H)2(µ,η2,η2-isop r en e)]BF 4
2
Piero Leoni,*,†,‡ Marco Pasquali,*,† Milena Sommovigo,† Alberto Albinati,*,§
Paul S. Pregosin,*,| and Heinz Ru¨egger|
Dipartimento di Chimica e Chimica Industriale, Via Risorgimento 35, I-56126 Pisa, Italy,
Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56100 Pisa, Italy, Istituto di Chimica
Farmaceutica, Viale Abruzzi 42, I-20131 Milano, Italy, and Inorganic Chemistry,
ETH Zentrum, CH-8092 Zu¨rich, Switzerland
Received November 27, 1995X
The reactions of the dinuclear cationic complexes [Pd2( -PBut )(PR3)4]+ (PR3 ) PCy2H,
2
PMe3) with CO or isoprene proceed with substitution of one or two phosphine ligands giving
2
the corresponding [Pd2( -PBut )(PR3)3(CO)]+ and [Pd2( -PBut ) ( ,
,
2-isoprene)(PR3)2]+
2
2
cations. [Pd2( -PBut )(PCy2H)3(CO)]+ equilibrates in solution to a mixture of monocarbonyl
2
derivatives arising from bridging phosphido/terminal phosphine interchange. The complexes
were characterized by multinuclear 1-D and 2-D NMR spectroscopy. The crystal and
2
2
molecular structures of [Pd2( -PBut )(PCy2H)3(CO)]BF4 and [Pd2( -PBut )(PCy2H)2( ,
, -
2
2
isoprene)]CF3SO3 were solved by single-crystal X-ray diffraction studies.
In tr od u ction
as PMe3 or PCy2H giving [Pd2( -PBut )(PR3)4]X [(2)+,
2
PR3 ) PMe3; (3)+, PR3 ) PCy2H] (Scheme 1).
Steric crowding around metal centers has proven a
powerful tool in the synthesis of new compounds with
both low coordination number and a high electron
deficiency at the metal.1 In such compounds the metal
center is highly reactive but often inaccessible for
sterically demanding reactive ligands. This promotes
weak interactions, e.g. agostic interactions with bonds
of the ligands,2 provided empty orbitals of suitable
symmetry are available at the metal. Ligand discrimi-
nation and eventually activation based on its dimen-
sions can also be effective.3 This can, in principle, be
exploited in the selective coordination of small molecules
in the presence of larger ones, even if the latter would
be more reactive under normal reaction conditions.
The reactions of the cations (2)+ and (3)+ with CO and
isoprene and a comparison of these results with those
obtained4b,6 in the analogous reactions of (1)+ are now
reported. We also describe the interchange of the
phosphido and secondary phosphine ligands observed
in some of the complexes.
Resu lts a n d Discu ssion
Rea ction s w ith CO. Either (2)CF3SO3 or (3)BF4
react under mild conditions with carbon monoxide
giving the reversible formation of the monocarbonyl
derivatives [Pd2( -PBut )(PMe3)3(CO)]CF3SO3, (4)CF3-
2
SO3, and [Pd2( -PBut )(PCy2H)3(CO)]BF4, (5)BF4 (Scheme
2
We have recently reported the synthesis4 of [Pd2( -
1). The complexes were isolated in good yields as yellow
crystalline solids and represent two relatively rare
examples of Pd(I) complexes with terminal CO ligands.
Both complexes were characterized by spectroscopic
means, and the crystal structure of (5)BF4 was solved
by diffraction methods (see below). The complexes
exhibit a single CO stretching absorbtion in the IR
spectrum [ CO at 2015, (4)+, and 2017 cm-1, (5)+]; these
frequencies are unusually low7 for terminal Pd-CO
ligands, suggesting significant -back-bonding, despite
the cationic nature of the derivatives. Complex (5)BF4
equilibrates in solution to a mixture of isomers, and
their NMR characterization will be described in the next
section. The 31P{1H} NMR spectrum (CD2Cl2, 273 K)
PBut )( -PBut H)(PBut H)2]X [(1)X, X ) BF4, CF3SO3]
2
2
2
which are stable in the presence of an excess of PBut H
2
but react easily5 with less encumbered phosphines such
† Dipartimento di Chimica e Chimica Industriale.
‡ Scuola Normale Superiore.
§ Istituto di Chimica Farmaceutica.
| ETH Zentrum.
X Abstract published in Advance ACS Abstracts, March 15, 1996.
(1) (a) Covert, K. J .; Neithamer, D. R.; Zonnevylle, M. C.; La Pointe,
R. E.; Schaller, C. P.; Wolczanski, P. T. Inorg. Chem. 1991, 30, 2494.
(b) Chen, H.; Bartlett, R. A.; Dias, H. V. R.; Olmstead, M. M.; Power,
P. P. Inorg. Chem. 1991, 30, 2487. (c) Arduengo, A. J ., III; Gamper, S.
F.; Calabrese, J . C.; Davidson, F. J . Am. Chem. Soc. 1994, 116, 4391.
(d) Wolf, J . R.; Bazan, G. C.; Schrock, R. R. Inorg. Chem. 1993, 32,
4155. (e) Hermes, A. R.; Girolami, G. S. Inorg. Chem. 1988, 27, 1775.
(2) (a) Wasserman, H. J .; Kubas, G. J .; Ryan, R. R. J . Am. Chem.
Soc. 1986, 108, 2294. (b) Gonzales, A. A.; Zhang, K.; Hoff, C. D. Inorg.
Chem. 1989, 28, 4285. (c) Matsumoto, M.; Yoshioka, H.; Nakatsu, K.;
Yoshida, T.; Otsuka, S. J . Am. Chem. Soc. 1974, 96, 3322.
(3) Campion, B. K.; Heyn, R. H.; Tilley, T. D. J . Chem. Soc., Chem.
Commun. 1992, 1201.
(5) Leoni, P.; Pasquali, M.; Sommovigo, M.; Laschi, F.; Zanello, P.;
Albinati, A.; Lianza, F.; Pregosin, P. S.; Ru¨egger, H. Organometallics
1994, 13, 4017.
(6) Leoni, P.; Pasquali, M.; Sommovigo, M.; Laschi, F.; Zanello, P.;
Albinati, A.; Lianza, F.; Pregosin, P. S.; Ru¨egger, H. Organometallics
1993, 12, 4503.
(4) (a) Albinati, A.; Lianza, F.; Pasquali, M.; Sommovigo, M.; Leoni,
P.; Pregosin, P. S.; Ru¨egger, H. Inorg. Chem. 1991, 30, 4690. (b) Leoni,
P.; Pasquali, M.; Sommovigo, M.; Laschi, F.; Zanello, P.; Albinati, A.;
Lianza, F.; Pregosin, P. S.; Ru¨egger, H. Organometallics 1993, 12, 1702.
(7) Wang, C.; Willner, H.; Bodenbinder, M.; Batchelor, R. J .;
Einstein, F. W. B.; Aubke, F. Inorg. Chem. 1994, 33, 3521.
0276-7333/96/2315-2047$12.00/0 © 1996 American Chemical Society

2048 Organometallics, Vol. 15, No. 8, 1996
Leoni et al.
Sch em e 1
Ta ble 1. 31P NMR P a r a m eter s of Ca r bon yl
Com p lexesa
Ch a r t 1
2
2
2
2
3
3
(P1) (P2) (P3)
(P4) J 12 J 13 J 14 J 23 J 24 J 34
(4)+ b 339.5 21.1 -26.2 -32.6 43 227 12 51 187 16
(5)+ c 347.1 -2.3
(6)+ c 341.8 -3
(7)+ c 299.3 10.0
17.8 -3.9 32 201
16.5 35.0 34 200
20.8 -3.9 35 205
19.5 35.8 39 200
9
8
41 159
40 151
166
(8)+ c 295.5
7.7
39 158
a
Chemical shifts are relative to H3PO4, and coupling constants
are in Hz. CD2Cl2 solution at 81 MHz and 273 K. c Recorded in
b
acetone-d6 solution at 202 MHz and room temperature.
of (4)CF3SO3 is consistent with the structure drawn in
Scheme 1. The spectrum exhibits a slightly broadened
doublet of doublets at 340 ppm (J PP ) 227 and ca. 40
Hz) for the bridging phosphido ligand. The larger
coupling confirms the presence of one coordinated PMe3
molecule pseudo-trans to the phosphido ligand. The
solid samples of (5)+ contain a single isomer. However,
the solution chemistry of (5)+ proved unexpectedly
complicated. The 31P{1H} NMR spectrum in acetone-
d6 showed at least six absorptions in the bridging
phosphide region between ca. 180 and 460 ppm. The
relative intensities of these signals changed over a
period of hours and eventually reached an equilibrium
in which two main components remained. Of the six
original high-frequency resonances, four were eventu-
ally assigned to the complexes (5)+-(8)+, with (5)+ the
most prominent immediately after solution (Chart 1).
We believe that the two unassigned, rather weak,
high-frequency signals arise from a complex with a
bridging secondary PHR2 ligand, structurally analogous
to the previously described cation (1)+.4,5 The low-
frequency 31P region (between ca. ) -4 and +40) was
complicated due to the fact that each complex gives
three nonequivalent 31P signals for the terminal phos-
phines. We give a summary of the various 31P param-
eters in Table 1. The assignments were based on
empiricisms derived from our previous studies together
with 2-D exchange spectroscopy. Note that the bridging
2
presence of two smaller unresolved cis J PP couplings
can be determined from the sharper PMe3 absorptions.
These consist of three well-resolved eight-line multiplets
at -21.1, -26.2, and -32.6 ppm, which were assigned,
respectively, to P(2), P(3), and P(4) (see Table 1).
The different behavior of the cation (1)+, with respect
to (2)+ and (3)+, in the reaction with CO should be
emphasized. Under identical experimental conditions
the former gives4b a mixture of two isomeric dicarbonyls
of formula [Pd2( -PBut )(PBut H)2(CO)2]+ while (2)+ and
2
2
(3)+ give only the corresponding monocarbonyl deriva-
tives (4)+ and (5)+, respectively, with no tendency to
further carbonylation (Scheme 1). This observation,
together with the unsuccessful attempt to form5 the
PBut H analogue of the cations (2)+ and (3)+ by reacting
2
(1)+ with a large excess of PBut H (Scheme 1), confirms
2
that two molecules of PBut H are too large to be
2
PBut ligands appear at much higher frequencies than
coordinated terminally to the same metal center of the
2
Pd2( -PBut ) core.
2
the bridging PCy2 ligands; this empirical observation
is also valid in the low-frequency region (see Table 1).
Moreover, the various nJ (P,P) were important in the
assignments, since the pseudo-trans spin-spin cou-
Isom er iza tion of th e Ca tion (5)+. Consistent with
the single carbonyl absorption at 2017 cm-1, and
confirmed by the crystal structure determination, the

Pd(I) Phosphido-Phosphine Complexes
Organometallics, Vol. 15, No. 8, 1996 2049
2
3
plings J (P1,P3) (ca. 200 Hz) and J (P2,P4) (ca. 160 Hz)
are both much larger than the other couplings.
After 24 h the solution contains mostly (8)+; i.e.
complex (5)+ has isomerized to its thermodynamically
more stable isomer with a 2-PCy2 group and a terminal
PHBut ligand. This type of exchange is not totally
2
unprecedented5 and could arise in our complexes via
initial loss of the CO ligand, followed by formation of
the intermediate (A) with a bridging secondary phos-
phine (eq 1, L ) CO); as described previously.5 Complex
(3)+ behaves similarly (eq 1, L ) PCy2H).
(1)
Either intra- or intermolecular H migration in A from
the bridging PCy2H molecule to the -PBut ligand,
2
followed by recoordination of CO, would provide the
F igu r e 1. Section of the two-dimensional 31P exchange
isomerization of (5)+ to (8)+.
It is obvious from structures (5)+-(8)+ that these
complexes can dissociate one or more of the terminal
phosphines. This is clearly indicated by the presence
of the redistribution products (6)+ and (7)+, which reveal
two But- and four Cy-containing phosphorus ligands,
respectively. Moreover, there is, at least, another
dynamic process which selectively exchanges the pseudo-
trans terminal secondary phosphine ligands (indicated
as spins P2 and P4 in Table 1) in (5)+ and (7)+, as shown
via 2-D 31P exchange NMR (see Figure 1).
spectrum (202 MHz, acetone-d6, room temperature, tmix
)
400 ms) showing exchange between the P4 and P2 (a) and
P4 and P3 (b) sites in (5)+ and positions P4 and P2 (c) in
(7)+, respectively. Note that the cross-peaks for the ex-
change of P4 and P2 lie very close to the diagonal.
[(9)CF3SO3, PR3 ) PMe3; (10)CF3SO3, PR3 ) PCy2H; eq
2], in strict analogy to the reaction of (1)+ with isoprene.6
The latter process could arise via the same intermedi-
ate A discussed above. Re-formation of a coordinated
terminal secondary phosphine, this time at the Pd atom
which previously held the CO, and renewed CO com-
plexation rationalizes the selective P2,P4 exchange
(Scheme 2). However this could be accomplished also
by other routes, i.e. (a) direct 1,2-PCy2H shift from X to
X′, (b) intermediate intramolecular H migration from
A to A′, (c) intermolecular H+ exchange, and (d) dis-
sociation and recoordination of PCy2H molecules 2
and 4.
(2)
What is obvious from the whole of our results is that
several ligands can dissociate and the PH hydrogen
atom of at least one secondary phosphine can easily
migrate, thus explaining the observation of a relatively
large number of compounds in solution. In this par-
ticular case, it was advantageous to have P-donors with
different substitutents in (5)+, as it, unexpectedly,
provided insight into the solution dynamics of our
materials.
The main features of the NMR spectra of the iso-
prene complexes (see Experimental Section) are analo-
2
gous to those of [Pd2( -PBut )(PBut H)2( ,
,
2-trans-
2
2
CH2dC(Me)CHdCH2)]CF3SO3,6 (11)CF3SO3, and will
not be discussed further.
R ea ct ion s w it h Isop r en e. Complexes (2)CF3SO3
and (3)CF3SO3 react with isoprene giving high yields
The reactions of the cations (1)+, (2)+, and (3)+ with
isoprene provide the same type of product, with no
observed effect of the bulkiness of the phosphine. This
may be due to the features of the diene, which favor
of the yellow crystalline derivatives [Pd2( -PBut )-
2
2
(P R3)2( ,
,
2-tr a n s-CH 2dC(Me)CH dCH 2)]CF 3SO3

2050 Organometallics, Vol. 15, No. 8, 1996
Leoni et al.
Sch em e 2
F igu r e 3. ORTEP plot of the cation (10)+, with the atom-
numbering scheme.
PR′2H exchange described above for (5)+. This stability
suggests that a coordinated secondary phosphine does
not readily transfer the P-H hydrogen to the pseudo-
cis bridging phosphide.
F igu r e 2. ORTEP plot of the cation (5)+, with the atom-
numbering scheme.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for (5)BF 4 a n d (10)CF 3SO3 (Esd ’s in
P a r en th eses)
Molecu la r Str u ctu r es of Com p lexes (5)BF 4 a n d
(10)CF 3SO3. The structure of (5)BF4 was determined
by X-ray diffraction, and an ORTEP plot of the molecule
is shown in Figure 2; selected bond distances and angles
are shown in Table 2. The four phosphorus atoms, the
carbonyl carbon, and the two palladium atoms are not
coplanar. The distortions are such that the pseudo-
trans PHCy2 ligands, P(2) and P(3), are on opposite sides
of the least-squares plane defined by Pd(1), Pd(2), P(1),
and P(4) by ca. -0.49 and +0.25 Å, respectively. The
ligand atom P(4) is on the same side of this plane as
P(2), i.e. away from P(3) by 0.07 Å. This type of
distortion is not uncommon.
(5)BF4
(10)CF3SO3
Pd(1)-Pd(2)
Pd(1)-P(1)
Pd(1)-P(2)
Pd(2)-P(1)
Pd(2)-P(3)
Pd(2)-P(4)
Pd(1)-C(1)
2.7436(5)
2.272(2)
2.341(1)
2.260(2)
2.361(2)
2.316(1)
1.940(8)
2.713(2)
2.260(6)
2.280(5)
2.253(6)
2.280(5)
2.24(2)
Pd(1)-P(1)-Pd(2)
P(1)-Pd(1)-Pd(2)
P(1)-Pd(2)-Pd(1)
P(1)-Pd(1)-P(2)
P(2)-Pd(1)-C(1)
P(3)-Pd(2)-C(4)
P(1)-Pd(2)-P(4)
P(3)-Pd(2)-P(4)
74.50(5)
52.55(4)
52.95(4)
106.75(6)
99.7(2)
73.9(2)
52.9(1)
53.2(1)
110.8(2)
90.5(5)
94.5(5)
The bond lengths within the immediate coordination
spheres of the two Pd atoms are comparable to those
t
found in [Pd2( -PBu2 )(PHCy2)4]+, (3)+, although the
106.70(6)
99.69(5)
Pd-Pd separation in (5)+, 2.7436(5) Å, is significantly
shorter than that found in (3)+, 2.834(4) Å. The P(3)-
Pd(2)-P(4) angle, 99.65(5)°, presumably arises as a
consequence of interligand steric interactions. This
angle, and the somewhat longish Pd(2)-P(4) bond
distance of 2.316(1) Å, are suggestive of where this
cation might develop dynamic character.
the formation of chelate rather than monoolefin-bonded
derivatives. Differences were observed in the reactivity
of the isoprene complexes; in fact while CO reacts
promptly and reversibly with the tert-butyl derivative
(11)+ to give [Pd2( -PBut )(PBut H)2(CO)2]+, the analo-
2
2
gous reactions with (9)+ or (10)+ are much slower. This
We also managed to obtain suitable crystals of (10)-
CF3SO3, the PHCy2 dinuclear analog of our previously
can be reasonably attributed to the greater bulkiness
of the PBut H ligands.
t
t
reported [Pd2( -PBu2 )(PHBu2 )2(isoprene)]+ cation, (11)+.
An ORTEP view of the cation (10)+ is shown in Figure
3, and selected bond distances and angles are shown in
2
It should also be pointed out that solutions of complex
(10)CF3SO3 are stable, giving no evidence of the -PR2/

Pd(I) Phosphido-Phosphine Complexes
Organometallics, Vol. 15, No. 8, 1996 2051
Table 2. A comparison of the bond lengths in (11)+ with
those of (10)+ reveals that (10)+ is slightly compressed;
e.g. the Pd-Pd separation in (10)+ is 2.713(2) Å, and
that for (11)+, 2.751(2) Å. There are, however, no major
structural differences between the two cations. If one
defines a plane using P(1), P(2), Pd(1), and Pd(2), then
one finds that these four atoms are almost co-planar,
in contrast to our observations for (5)+.
Ta ble 3. Exp er im en ta l Da ta for th e X-r a y
Diffr a ction Stu d y of (5)BF 4 a n d (10)CF 3 SO3
compound
(5)BF4
(10)CF3SO3
formula
mol wt
C49H84BF4P4Pd2
1112.72
C38H70F3O3P3Pd2S
969.76
crystal dimens, 0.40 × 0.35 × 0.25
0.20 × 0.10 × 0.09
mm
data collcn
T, °C
23
23
Exp er im en ta l Section
cryst syst
space group
a, Å
triclinic
Ph1
monoclinic
P21/n
12.006(1)
22.991(5)
17.327(3)
90
1044.45(2)
90
4631.5(9)
4
Gen er a l Da ta . All manipulations were carried out under
a nitrogen atmosphere using standard Schlenk techniques.
Complexes [Pd2( -PBut )(PCy2H)4]X and [Pd2( -PBut )(PMe3)4]X
14.412(5)
14.416(3)
15.193(3)
66.89(2)
72.19(2)
77.82 (2)
2749.2(7)
2
b, Å
c, Å
2
2
were prepared as previously described.5 PCy2H was purchased
from Argus Chemicals and used as received. Solvents were
dried by conventional procedures and distilled prior to use.
IR spectra (Nujol mull, KBr plates) were recorded on a Perkin-
Elmer FT-IR 1725X spectometer. NMR spectra were mea-
sured on an AMX500 as described previously.4-6 Elemental
analyses are from the Microanalyses Laboratory of the Faculty
of Pharmacy, Pisa, Italy.
R, deg
, deg
, deg
V, Å3
Z
F(calcd),
g cm-3
, cm-1
1.344
1.391
8.045
9.539
radiation
( , Å)
Mo KR graphite monochromated (0.710 69)
P r ep a r a tion of [P d 2(µ-P Bu t2)(P Me3)3(CO)]CF 3SO3, (4)-
range, deg
scan type
no. indep
data collcd
no. obs
refcns (no)
Ra
2.5 e e 23.0
/2
7923
2.5 e e 25.0
/2
6980
CF 3SO3. A red solution of [Pd2( -PBut )(PMe3)4]CF3SO3 (129
2
mg, 0.159 mmol) in DME (10 mL) was saturated with CO. The
solution was left overnight at room temperature and became
orange-yellow. An orange solid precipitated after addition of
Et2O (20 mL). The suspension was cooled 3 h at -30 °C, and
the precipitate was isolated by filtration and vacuum dried
yielding 66 mg (0.086 mmol, 54%) of (5)CF3SO3. Anal. Calcd
for C19H45F3O4P4Pd2S: C, 29.8; H, 5.94. Found: C, 30.1; H,
6.01. IR (Nujol, KBr): 2014 vs ( CO), 1271 vs, 1150 vs, 1031
2
2
2
2
5667 (|Fo| >5.0 (|F| )) 2202 (|Fo| > 3.0 (|F| ))
0.043
0.058
0.053
0.066
a
Rw
R ) ∑(|Fo - (1/k)Fc|)/∑|Fo|. Rw ) [∑w(Fo - (1/k)Fc)2/∑w|Fo| ]1/2
,
a
2
where w ) [ 2(Fo)]-1
;
(Fo) ) [ 2(Fo2) +f 4 (Fo2)]1/2/2Fo.
s, 638 m (uncoordinated triflate) cm-1
. NMR (CD2Cl2, 273
K): 31P{1H}, 340 (br dd, 2J PP ) 227, 2J PP ) 43 Hz), -21.1 (ddd,
cristals were isolated by filtration and vacuum dried (yield 57
mg, 0.059 mmol, 68%) Anal. Calcd for C38H72F3O3P3Pd2S: C,
47.0; H, 7.47. Found: C, 47.1; H, 7.72. IR (Nujol, cm-1): 1279
(vs), 1145 (vs), 1032 (vs), 636 (s) (uncoordinated triflate). NMR
(CD2Cl2, 293 K): 31P{1H}, 377.6 (dd, 2J PP ) 27.7, 2J PP ) 25.1
Hz, -P), 7.5 (dd, 2J PP ) 25.1, 3J PP ) 55.3 Hz, PCy2H), 6.0 ppm
2
3
2
2J PP ) 51, J PP ) 43, J PP ) 187 Hz), -26.2 (ddd, J PP ) 51,
2J PP ) 227, 3J PP ) 11.5 Hz), -32.6 ppm (ddd, 2J PP ) 11.5, 3J PP
3
) 11.5, J PP ) 187 Hz).
P r ep a r a tion of [P d 2(µ-P Bu t2)(P Cy2H)3(CO)]BF 4, (5)BF 4.
[Pd2( -PBut )(PCy2H)4]BF4 (191 mg, 0.154 mmol) was sus-
2
2
3
1
(dd, J PP ) 27.7, J PP ) 55.3 Hz, PCy2H); 1H, 5.33 (dm, J PH
pended in DME (15 mL). The reaction flask was evacuated
and filled with CO. The orange suspension turned im-
mediately to yellow, and the solid dissolved after stirring 5
min. The solution was concentrated to ca. 5 mL, and Et2O
(10 mL) was added. After being cooled at -30 °C overnight,
the suspension was filtered and the solid product vacuum
dried (yield: 125 mg, 0.117 mmol, 76%). Anal. Calcd for
1
) 330.0 Hz, 1H, P-H), 5.30 (dm, J PH ) 327.0 Hz, 1H, P-H),
4.78 (dd, J PH ) 2.7, 2.8 Hz, 1H), 4.03 (ddd, J PH ) 3.1, 3.4, J HH
) 8.8 Hz, 1H), 3.30 (ddt, J PH ) 2.1, 2.1, J HH ) 14.6, 8.8 Hz,
1H), 3.04 (d, J PH ) 4.5 Hz, 1H), 2.94 (dd, J PH ) 5.2, J HH
)
3
3
14.6 Hz, 1H), 1.34 (d, J PH ) 14.0 Hz, 9H, C4H9), 1.33 (d, J PH
) 14.0 Hz, 9H, C4H9), 2.6, 2.2, 1.9-1.2 (broad signals, 44 H,
C6H11), 0.78 (d, J PH ) 1.3 Hz, 3H, dCCH3).
C
45H87BF4OP4Pd2: C, 50.6; H, 8.21. Found: C, 50.2; H, 8.03.
IR (Nujol, cm-1): 2312 (w), (PH); 2017 (vs), (CO); 1056 (vs),
(BF). See text for NMR spectral data.
Cr ysta llogr a p h y. Crystals suitable for X-ray diffraction
of (5)BF4 and (10)CF3SO3 were obtained by crystallization from
DME/ether. Crystals of both compounds were mounted on
glass fibers (covered for protection with acrylic resin) at a
random orientation on an Enraf-Nonius CAD4 diffractometer
for the unit cell and space group determinations and for the
data collection. Unit cell dimensions were obtained by least-
squares fit of the 2 values of 25 high-order reflections using
the CAD4 centering routines. Selected crystallographic and
other relevant data are listed in Table 3. For compound
(5)BF4 the possibility of a higher cell symmetry, given the
equal values of two axes, was also tested; no higher symmetry
was found in the diffraction pattern.
Data were measured with variable scan speed to ensure
constant statistical precision on the collected intensities.
Three standard reflections were used to check the stability of
the crystal and of the experimental conditions and measured
every 1 h. The orientation of the crystal was checked by
measuring three reflections every 300 measurements. Data
have been corrected for Lorentz and polarization factors and
for decay [compound (10)CF3SO3] using the data reduction
programs of the MOLEN package.8 Empirical adsorption
corrections were applied by using azimuthal (Ψ) scans of three
“high- ” angle reflections for both sets of data. The standard
P r ep a r a t ion of [P d 2(µ-P Bu t 2)(µ,η2,η2-CH 2dC(CH 3)-
CHdCH2)(P Me3)2]CF 3SO3, (9)CF 3SO3. Isoprene (3 mL) was
added to a solution of [Pd2( -PBut )(PMe3)4]CF3SO3 (100 mg,
2
0.123 mmol) in DME (10 mL). After 5 d at room temperature
Et2O (25 mL) was added to the orange solution. The yel-
low solid which precipitated was isolated by filtration and
vacuum dried (49 mg, 0.067 mmol, 54%). Anal. Calcd for
C
20H44F3O3P3Pd2S: C, 33.0; H, 6.10. Found: C, 33.0; H, 6.45.
2
2
NMR (CD2Cl2), 293 K): 31P{1H}, 358.6 (dd, J PP ) 32.8, J PP
) 32.8 Hz, -P), -21.7 (dd, 2J PP ) 32.8, 3J PP ) 61.6 Hz, PMe3),
-23.1 ppm (dd, J PP ) 32.8, J PP ) 61.6 Hz, PMe3); 1H, 4.20
2
3
(t, 1H) 3.60 (m, 1H) 3.06 (ddt, 1H) 2.99 (d, 1H) 2.81 (dd, 1H)
2
2
(dCH), 1.83 (d, J PH ) 8.5 Hz, PMe3), 1.81 (d, J PH ) 8.3 Hz,
PMe3), 1.20 (d, 3J PH ) 14.3 Hz, 9H, C4H9), 1.18 (d, 3J PH ) 14.0
Hz, 9H, C4H9), 0.64 (s, 3H, dCCH3).
P r ep a r a t ion of [P d 2(µ-P Bu t 2)(µ,η2,η2-CH 2dC(CH 3)-
CHdCH2)(P Cy2H )2]CF 3SO3, (10)CF 3SO3. [Pd2( -PBut )-
2
(PCy2H)4]CF3SO3 (113 mg, 0.087 mmol) was suspended in
DME (10 mL), and isoprene (2 mL) was added under stirring.
The suspension turned immediately from orange to bright
yellow, and the solid dissolved in 10 min. Et2O (25 mL) was
added and the solution cooled at -30 °C overnight. The yellow

2052 Organometallics, Vol. 15, No. 8, 1996
Leoni et al.
deviations on intensities were calculated in terms of statistics
alone, while those on Fo were calculated as shown in Table 3.
The structures were solved by a combination of Patterson
and Fourier methods and refined by full-matrix least squares9
(the function minimized being ∑[w(Fo - 1/kFc)2]). No extinc-
tion correction was found to be necessary. The scattering
factors used, corrected for the real and imaginary parts of the
anomalous dispersion,9 were taken from ref 9.
All calculations were carried out using the Enraf-Nonius
MOLEN package.8
Str u ctu r a l Stu d y of (5)BF 4. A total of 7923 independent
data were collected of which 5667 were considered as observed
(cf. Table 3) and used for the refinement.
As always in this class of compounds, some of the carbon
atoms of the phosphines are found to be disordered (as can be
judged by the values of the displacement parameters) resulting
in a somewhat large spread of the C-C bond distances.
Moreover the BF4 - counterion was also found to de disordered;
therefore an idealized model, based on the strongest peaks in
the Fourier difference maps, was constructed and the geometry
was kept fixed during the last cycles of refinement.
The refinement was carried out using anisotropic displace-
ment parameters for the atoms of the cation while the B and
F atoms were treated isotropically. Upon convergence the final
Fourier difference map showed no significant feature.
The contribution of the hydrogen atoms in calculated
positions (C-H ) 0.95 Å, B(H) ) 1.3B(Cbonded) Å2) was taken
into account but not refined.
Str u ctu r a l Stu d y of (10)CF 3SO3. It proved impossible to
find good quality crystals of this compound: only a fairly small,
weakly diffracting crystal proved to be suitable for the data
collection. As a result, only a very limited number of reflec-
tions are observed at the 3 level.
An idealized model for the disordered triflate molecule was
constructed, on the basis of the strongest peaks of the
difference Fourier map; only the isotropic displacement pa-
rameters were refined.
The refinement was carried out, as described above, using
anisotropic parameters for the palladium and phosphorus
atoms and for the carbons of the isoprene moiety; all other
atoms were refined using isotropic displacement parameters.
The contribution of the hydrogen atoms in idealized posi-
tions, using the values given previously, was taken into
account but not refined. Upon convergence the final Fourier
difference map showed no significant feature.
Ack n ow led gm en t. Financial support from the Min-
istero dell’Universita` e della Ricerca Scientifica e Tec-
nologica (MURST) and from the CNR (Rome) is grate-
fully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: Tables of complete
crystallographic and other relevant data, final atomic and
equivalent isotropic displacement parameters, calculated po-
sitional and thermal parameters for the hydrogen atoms,
anisotropic displacement parameters, and extended bond
distances, bond angles, and torsion angles and ORTEP views
of the cations (5)+ and (10)+, showing the complete numbering
scheme (35 pages). Ordering information is given on any
current masthead page.
(8) MolEN: Molecular Structure Solution Procedure; Enraf-Non-
ius: Delft, The Netherlands, 1990.
(9) International Tables for X-ray Crystallography; Kynoch: Bir-
mingham, England, 1974; Vol. IV.
OM9509148