New dinuclear diphenylphosphido-bridged palladium(I) derivatives and the X-ray crystal and molecular structures of the mononuclear homoleptic diphenylphosphine complexes Pd(PPh2H)4 and [Pd(PPh2H)4](BF4)2

Article abstract of DOI:10.1016/S0022-328X(99)00276-4

By reacting CpPd(η³-C₃H₅) with PPh₂H we isolated the doubly bridged dinuclear complex [Pd₂(μ-PPh₂)₂(PPh₂H)₃] (1). This reacts with HBF₄ yielding the mono-phosphido-bridged cationic derivative [Pd₂(μ-PPh₂)(PPh₂H)₄]BF₄ (2)BF₄, arising from the protonation of one of the bridging phosphides. Contrary to our previous data on the parent t-butyl systems, a mononuclear homoleptic phosphine complex is not an intermediate in the formation of 1. Pd(PPh₂H)₄ (3), was in fact prepared by an independent route and was shown to decompose thermally to another (uncharacterized) polynuclear derivative; fluoboric acid reacts with 3 yielding its palladium(II) analogue [Pd(PPh₂H)₄](BF₄)₂ (3)(BF₄)₂, with dihydrogen evolution. We also report the crystal and molecular structures of 3 and (3)(BF₄)₂, the first homoleptic transition metal complexes of diphenylphosphine to be structurally characterized.

Full text of DOI:10.1016/S0022-328X(99)00276-4

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 593–594 (2000) 12–18
New dinuclear diphenylphosphido-bridged palladium(I) derivatives
and the X-ray crystal and molecular structures of the mononuclear
homoleptic diphenylphosphine complexes Pd(PPh2H)4 and
[Pd(PPh2H)4](BF4)2
Piero Leoni a,b,*, Fabio Marchetti c, Stefano Papucci a, Marco Pasquali a,1
a Dipartimento di Chimica e Chimica Industriale, Uni6ersita` di Pisa, I-56126 Pisa, Italy
b Scuola Normale Superiore, Piazza dei Ca6alieri, I-56126 Pisa, Italy
c Dipartimento di Ingegneria Chimica dei Materiali, delle Materie Prime e Metallurgia, Uni6ersita` di Roma ‘La Sapienza’,
Via del Castro Laurenziano 7, I-00195 Roma, Italy
Received 2 March 1999; accepted 10 May 1999
Dedicated to Professor Fausto Calderazzo on the occasion of his 70th birthday and in recognition of his fundamental contributions to the
advancement of inorganic and organometallic chemistry.
Abstract
By reacting CpPd(h3-C3H5) with PPh2H we isolated the doubly bridged dinuclear complex [Pd2(m-PPh2)2(PPh2H)3] (1). This
reacts with HBF4 yielding the mono-phosphido-bridged cationic derivative [Pd2(m-PPh2)(PPh2H)4]BF4 (2)BF4, arising from the
protonation of one of the bridging phosphides. Contrary to our previous data on the parent t-butyl systems, a mononuclear
homoleptic phosphine complex is not an intermediate in the formation of 1. Pd(PPh2H)4 (3), was in fact prepared by an
independent route and was shown to decompose thermally to another (uncharacterized) polynuclear derivative; fluoboric acid
reacts with 3 yielding its palladium(II) analogue [Pd(PPh2H)4](BF4)2 (3)(BF4)2, with dihydrogen evolution. We also report the
crystal and molecular structures of 3 and (3)(BF4)2, the first homoleptic transition metal complexes of diphenylphosphine to be
structurally characterized. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Dinuclear; Homoleptic; Palladium; Phosphido-bridged; Secondary phosphine
1. Introduction
Late transition metal complexes [4,5] are by far the
most numerous. With M=Co, Rh, Ir [4], these are
mainly [CpM(m-PR2)]2 and derivatives, studied by
Werner and coworkers [4a–d], and [L2M(m-PR2)]2 (L=
CO, PR3) and derivatives, developed by Jones and
coworkers [4e–h].
Most derivatives [5] of Group 10 metals have the
general formula [LM(m-PR2)]2 (L=mainly phosphines,
[5a–c]) with two M(I) centers, or [(R3P)(X)M(m-
PR2)]n2+ (n=0, X=Cl, Br; n=2, X=PR3, [5d–g])
with two M(II) centers.
Doubly bridged hetero- [1] and homobimetallic [2]
phosphides [LnM(m-PR2)2M%L% ] of several transition
m
metals have been described. Restricting the field to
homonuclear systems, the relatively few examples con-
taining early transition metals are mainly bis- [2a,c] or
monocyclopentadienyls [2d] of Group 4, but niobium
[2e], vanadium [2f] or lanthanide (Sm [2g]) derivatives
are also known. Moving toward the central triads
(Groups 6–8), molybdenum [3a,c] and iron [3d,h] com-
plexes have been more extensively investigated, but
others containing Cr [3i], W [3a], Mn [3i–n], Ru [3o–q]
and Os [3r] have been reported.
The structural features of these systems have been
thoroughly investigated, and the M2(m-P)2 core has
shown a remarkable flexibility. The MꢀPmꢀM and
PmꢀMꢀPm bond angles vary through a wide range (60–
125°), thus allowing variable MꢀM bond distances
* Corresponding author. Tel.: +39-050-918111; fax: +39-050-
918260.
1 Also corresponding author.
(2.375–4.3 A) and orders (0–3) [2–5]. The central core
,
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00276-4

P. Leoni et al. / Journal of Organometallic Chemistry 593–594 (2000) 12–18
13
was most frequently found to be planar or nearly
planar, with rare exceptions of folded structures with
dihedral (flap) angles in the range 105–135°; this fold-
ing is often due to the presence of a third bridging (or
semi-bridging) ligand [1c,2c,g,3b,h,4d].
Our group is involved in the search for synthetic
methods for new doubly bridged phosphido derivatives
of palladium [6] and platinum [7] and in the study of
their reactivity. This report deals with the synthesis of
[Pd2(m-PPh2)2(PPh2H)3] (1), which has been protonated
to give the mono-phosphido bridged cationic derivative
[Pd2(m-PPh2)(PPh2H)4]BF4 (2)BF4. Attempting to clar-
ify the mechanism of formation of 1 we prepared and
characterized the mononuclear binary Pd(0) and Pd(II)
derivatives, Pd(PPh2H)4 (3) and [Pd(PPh2H)4](BF4)2
(3)(BF4)2, whose crystal and molecular structures are
also reported.
The 31P{1H}-NMR spectrum of a sample of the
solution shows the complete disappearance of 1 and the
formation of a new complex with minor amounts of
another two. The main component was isolated in 60%
yield and identified as [Pd2(m-PPh2)(PPh2H)4]BF4
(2)BF4, which can be presumed to form by protonation
of one of the bridging phosphides (Eq. 2).
(2)
The 31P{1H}-NMR spectrum of (2)BF4 (CD2Cl2, 293
K) exhibits a low field (222.4 ppm) and two high field
(−2.07 and −12.3 ppm) resonances, respectively as-
signed to the bridging phosphide (X), and to the mag-
netically non-equivalent couples of phosphines
pseudo-cis (AA%) and pseudo-trans (MM%) to the first
nucleus (spin system AA%MM%X). The spectrum was
satisfactorily simulated by the following set of parame-
ters: lX=222.38 lAA%= −2.08 lMM%= −12.3 ppm;
2. Results and discussion
2
3
2
3
2JMX=270, JAX=6, JMM%=18, JAM=46, JAM%=2,
By adding at −45°C an acetone solution of
CpPd(h3-C3H5) to a 10-fold molar excess of PPh2H
dissolved in the same solvent, a red powder precipitated
out in a few minutes. After work-up the solid was
collected and characterized by IR, showing two wPH
absorptions at 2342 and 2368 cm−1 due to non-equiva-
lent PPh2H molecules, and NMR spectroscopies. The
31P{1H}-NMR spectrum (CDCl3, 293 K) exhibits only
two broad singlets at 164 and −8.2 ppm, the latter
splitting into two broad singlets (−5.8 and −9.9 ppm)
at 233 K. Although the lack of information due to
rapid exchange, also in the low temperature spectra,
precludes an unequivocal assignment, we tentatively
assigned the structure [Pd2(m-PPh2)2(PPh2H)3] (1), to
the new complex, assuming its rapid equilibration with
[Pd2(m-PPh2)2(PPh2H)2], by loss of a PPh2H molecule
(Eq. 1).
3JAA%=53 Hz (see Fig. 1).
2.1. Preparation of Pd(PPh2H)4 (3)
As shown in our preceding reports, CpPd(h3-C3H5)
reacts with either PtBu2H [9] or PCy2H [10] yielding the
corresponding dinuclear derivative [Pd(m-PR2)(PR2H)]2.
It was also established that the mechanism of these
transformations is strongly dependent upon the sec-
ondary phosphine. With suitable modifications of the
reaction procedures the different key intermediates, i.e.
the mononuclear Pd(0) homoleptic Pd(PtBu2H)3 in the
first case [9b], or the dinuclear Pd2(m-PCy2)(m,h3-
C3H5)(PCy2H)2 in the latter [10], were isolated and
characterized (Scheme 1).
(1)
Elemental analyses confirm structure 1, which has
been observed in Ni(I) [5a,8] derivatives (Chart A), but
is unprecedented for palladium(I).
(Chart A)
A further support to structure 1 comes from the
result of its reaction with acids. In fact, a red chloro-
form solution of complex 1 reacts with an excess of
HBF.4Et2O; the solution turns immediately deep violet,
then slowly red, orange and, finally, yellow.
Fig. 1. High field region of the 31P{1H}-NMR spectrum (CD2Cl2, 293
K) of (2)BF4: (a) experimental; (b) calculated.

14
P. Leoni et al. / Journal of Organometallic Chemistry 593–594 (2000) 12–18
Scheme 1.
tions at 2365 and 1030 cm−1, respectively. The
The different type of mechanism can be attributed to
31P{1H}-NMR spectrum exhibits a singlet at 3.5 ppm
which splits, in the corresponding proton coupled spec-
trum, into a six-line signal typically found in derivatives
containing the trans-(PR2H)2M subunit [9b,12].
differences in the reactivity of the Pd(PR2H)n homolep-
tic derivative which, when R=Cy, should react with
CpPd(h3-C3H5) as soon as it is formed, yielding the
allyl-bridged intermediate shown in Scheme 1.
We could not isolate or even observe any intermedi-
ate preceding the formation of 1 from CpPd(h3-C3H5)
and PPh2H, and decided to attempt an alternative route
to a potential candidate, i.e. a mononuclear Pd(0)
derivative Pd(PPh2H)n. A successful synthetic proce-
dure was found by reacting the known [9b]
Pd(PtBu2H)3 with a 10-fold excess of PPh2H in toluene
at −20°C. After work-up the tetrakis-substituted
Pd(PPh2H)4 (3), was isolated in 86% yield [11]. Com-
plex 3 was isolated as a yellow crystalline solid which
shows a single wPH absorption at 2268 cm−1 in the IR
spectrum and a singlet at −9.8 ppm in the 31P{1H}-
NMR spectrum (−80°C). It is thermally stable as a
solid and can be stored at room temperature for weeks
without decomposition, but its solutions are stable only
in the presence of an excess of the phosphine. Crystals
suitable for the diffractometric determination (see Sec-
tion 2.2) could be obtained only by recrystallization
from toluene/Et2O mixtures in the presence of a 10-fold
excess of PPh2H. In the absence of added phosphine the
yellow solutions of 3 become rapidly red at room
temperature while new 31P{1H}-NMR resonances grow
at 227 and 237 ppm. These can be assigned to bridging
phosphides of di- or polynuclear systems different from
2.2. Crystal structures
Although the chemistry of palladium phosphine com-
plexes has been extensively investigated, the number of
crystallographic studies concerning homoleptic deriva-
tives is rather limited. In the case of palladium(0)
tetrasubstituted derivatives of monodentate tertiary
phosphines, up to now only Pd(PPh3)4 [13],
Pd[P(CꢁCꢀPh)3]4 [14], Pd[P(CH2OH)3]4 [15] and
[Pd(P)4](Cl)4 [16] have been described.
The number is somewhat increased by including
some derivatives of chelating diphosphines: Pd(dippe)2
[17], Pd(dppp)2 [18], Pd(dcpe)(dppe) [19], Pd(PP)2 [20].
Structures of palladium(II) PdL4 complexes are limited
to those with polydentate or macrocyclic phosphines:
[Pd(PP)2]2+ [21–24] and [Pd(P4)]2+ [25–27].
Therefore complexes 3 and 32+ constitute the first
structurally characterized homologue pair of Pd(0) and
Pd(II)ML4 derivatives. The unit cell of 3 contains four
(
molecules, each with a metal placed on the 4 axis. The
(
operation 4 on the asymmetric unit [Pd(PPh2H)] makes
the coordination around the metal almost ideally tetra-
hedral (PꢀPdꢀP=108.705(15) and 111.02(3)°).
1 (lP =164 ppm), which were not further character-
The whole molecule may be inscribed in a cube of
m
ized, thus ruling out the intermediacy of a binary
PPh2H complex of Pd(0) from the possible mechanisms
of formation of 1 from CpPd(h3-C3H5).
,
approximately 9 A edge length, with the PꢀH bonds
pointing alternatively in opposite directions, as imposed
by the site symmetry. The structures of 3 and of cation
32+ are shown, respectively in Figs. 2 and 3, and
significant bond distances and angles are given in the
captions. The square coordination (PꢀPdꢀP=
89.912(7)°) around palladium in 32+ is not strictly
planar, since the metal is slightly out of the phosphorus
Complex 3 reacts with HBF.4Et2O with dihydrogen
evolution yielding, as the main product, the corre-
sponding palladium(II) derivative [Pd(PPh2H)4](BF4)2
(3)(BF4)2, which was isolated in 55% yield. Single crys-
tals of this complex were obtained by recrystallization
from CH2Cl2/Et2O mixtures and were analyzed by X-
ray diffractometry (see Section 2.2). The IR spectrum
(Nujol, KBr) of (3)(BF4)2 shows wPH and wBF absorp-
,
atoms plane (0.092 A). The 4-fold axis constrains all the
PꢀH hydrogens to point towards the same direction.
The less disordered anion is placed just on this side, 3.7

P. Leoni et al. / Journal of Organometallic Chemistry 593–594 (2000) 12–18
15
are inconsistent with the point symmetry of the small
tetrafluoroborate anion.
Bond distances and angles of both structures com-
pare well with the corresponding ones for the structures
cited above. As far as we know only two structures of
complexes containing
PPh2)Cl(PPh2H)]2, and PdCl(PPh2H){[PPh2(O)]2H} [28]
have been reported.
a
PdꢀPPh2H bond [Pd(m-
3. Conclusions
This paper reports the preparation of a new palla-
dium derivative which was suggested to be the doubly
bridged phosphide [Pd2(m-PPh2)2(PPh2H)3] (1). As
shown in our previous works [29], the presence of two
phosphido ligands, although reinforcing the dinuclear
structure in Group 10 metal complexes, have some
drawbacks if one is interested in the reactivity of the
system. Particularly if one searches for the cooperation
of the two metals in binding and activation, which can
be precluded by steric crowding and/or metal orbital
occupancy due to the presence of the bridging phos-
phides. We have also shown that protonation, either if
it goes at phosphorus [6] or at one of the metals [29b],
eventually removes one of the bridging ligands and
affords mono-phosphido-bridged cationic derivatives
which can exhibit metal cooperation in ligand bonding.
Since the previous synthetic procedures yielded
derivatives with the central [M2(m-PR2)]+ core (M=Pd,
Pt) with t-butyl or cyclohexyl substituents at phospho-
rus, the protonation of 1, shown here to produce
[Pd2(m-PPh2)(PPh2H)4]BF4 (2)BF4, will offer the possi-
bility to investigate about steric and electronic effects
on the bonding capabilities of the Pd2 core. Finally, the
Fig. 2. ORTEP view of complex 3 (thermal ellipsoids are at 50%
probability, hydrogens are omitted for clarity). PdꢀP 2.3213(6), PꢀC
1.833(2) A; PꢀPdꢀP% 111.02(3), PꢀPdꢀP%% 108.705(15)°. Symmetry
transformations used to generate equivalent atoms: %= −x=1, −
y+3/2, z; %%=y−1/4, −x+5/4, −z+1/4; %%%= −y+5/4, x+1/4,
−z+1/4.
,
,
A above. The second one is placed on the other side,
,
5.7 A below. Ligand crowding in the square plane
,
makes the PdꢀP bonds slightly longer (0.02 A) than in
3, in spite of the metal radius reduction due to oxida-
tion. The bulkiness of the cation and its 4-fold symme-
try constrains the crystal packing and produces a
tetragonal structure although its symmetry operators
achievement
of
Pd(PPh2H)4
(3),
and
[Pd(PPh2H)4](BF4)2 (3)(BF4)2, the first structurally char-
acterized homologue pair of Pd(0) and Pd(II) binary
phosphine complexes, allowed us to compare their solid
state features. As reported above, the crystallographic
study has shown that ligand crowding in the cation 32+
makes the PdꢀP bonds longer than in 3, in spite of the
metal radius reduction due to oxidation.
4. Experimental
All manipulations were performed under an atmo-
sphere of purified nitrogen or carbon monoxide by
using standard Schlenck techniques. Solvents were
dried by standard procedures and freshly distilled under
nitrogen. Deuterated solvents were used as purchased
and stored on molecular sieves under an inert atmo-
sphere. CpPd(h3-C3H5) [30], PPh2H [31] and
Pd(PtBu2H)3 [9b] were prepared as previously de-
scribed. IR spectra were registered with a Perkin–
Fig. 3. ORTEP view of cation 32+ (thermal ellipsoids are at 30%
probability, hydrogens are omitted for clarity). PdꢀP 2.340(3), PꢀC
1.813(12) A; PꢀPdꢀP% 175.5(2), PꢀPdꢀP%% 89.91(1)°. Symmetry trans-
formations used to generate equivalent atoms: %= −x+1/2, −y+
1/2, z; %%= −y+1/2, x, z; %%%=y, −x+1/2, z.
,

16
P. Leoni et al. / Journal of Organometallic Chemistry 593–594 (2000) 12–18
Elmer FT-IR 1725X spectrophotometer and NMR
spectra with a Varian Gemini 200BB spectrometer.
4.33. IR (Nujol, KBr) 2365 w (wPH) and 1030 vs (wBF
)
cm−1
.
4.5. Preparation of [Pd(PPh2H)4](CF3SO3)2
(3)(CF3SO3)2
4.1. Preparation of [Pd2(v-PPh2)2(PPh2H)3] (1)
A red acetone (10 ml) solution of CpPd(h3-C3H5)
(300 mg, 1.4 mmol) was slowly dropped at −45°C into
an acetone (10 ml) solution of PPh2H (2.5 ml, 14.1
mmol). A red solid precipitated out in a few minutes;
the suspension was stirred for 30 min while the flask
was warmed at room temperature. The solid 1 was
filtered, washed with acetone, and vacuum dried (567
mg, 70% yield). Anal. Found: C, 64.0, H, 4.73.
C60H53P5Pd2 requires: C, 63.1, H, 4.68. IR (Nujol,
A 10-fold excess of CF3SO3H was added at −70°C
to a yellow DME (20 ml) solution of complex 3 (160
mg, 0.188 mmol). The solution was slowly allowed to
reach room temperature and stirred until the evolution
of dihydrogen (GC analysis) was complete (5 h). Most
of the solvent was evaporated and Et2O (15 ml) was
added. A colorless solid precipitated out and was
filtered and vacuum dried (155 mg, 72% yield). Anal.
Found: C, 52.0; H, 3.82. C50H44F6O6P4PdS2 requires:
C, 52.2; H, 3.86. IR (Nujol, KBr) 2362 w (wPH) and
1270 vs, 1144 s, 1030 s and 639 s cm−1 vs (uncoordi-
KBr): 2342, 2268 (wPH) cm−1
.
4.2. Preparation of [Pd2(v-PPh2)(PPh2H)4]BF4 (2)BF4
nated triflate) [32] cm−1
.
Two equivalents of HBF.4Et2O were added to a red
THF (10 ml) solution of 1 (180 mg, 0.158 mmol). The
color of the solution turned immediately violet and then
slowly (12 h) orange, and by addition of Et2O (2)BF4
precipitated out as a yellow powder which was filtered,
washed with Et2O, and vacuum dried (116 mg, 60%).
Anal. Found: C, 58.2, H, 4.50. C60H54BF4P5Pd2 re-
quires: C, 58.6, H, 4.43. IR (Nujol, KBr) 2360 w br
4.6. X-ray diffraction study
Some single crystals of 3 and 3(BF4)2 · C6D6, ob-
tained as described in the paragraph before, were se-
lected in air and glued at the end of glass fibers. All the
X-ray diffraction measurements were done on
Siemens P4 four-circle diffractometer, equipped with
a
graphite monochromatized MoꢀKa radiation (u=
(wPH), 1030 s br (wBF), cm−1
.
,
0.71073 A). All data collections were made in ꢀ/2q
scan mode. Three standard reflections were measured
every 97 measurements, to control the absence of decay
and equipment stability. Data reductions were made by
means of the XSCANS [33] program.
4.3. Preparation of Pd(PPh2H)4 (3)
A toluene (15 ml) solution of Pd(PtBu2H)3 (1.29 g,
2.36 mmol) was dropped at −20°C into a toluene
(25 ml) solution of PPh2H (5 ml, 28.7 mmol). The
solution was stirred 30 min while the flask was heated
to room temperature. Most of the solvent was evapo-
rated and a pale yellow solid was precipitated by addi-
tion of Et2O (20 ml). The solid was filtered, washed
with Et2O, vacuum dried and stored in the dark (1.735
g, 86%). Anal. Found: C, 66.9, H, 5.26. C48H44P4Pd
4.7. Crystal structure determination of 3
Crystals of 3 are light yellow tetragonal prisms. One
of them was mounted on the diffractometer at room
temperature and the cell parameters listed in the second
column of Table 1 were obtained. The diffraction sym-
metry and systematic absences indicated the tetragonal
I41/a space group. A redundant set of data was mea-
sured collecting a total of 2484 reflections. They were
corrected for Lorentz and polarization effects and for
absorption by using the „-scan method and obtaining
0.444 and 0.513 as the minimum and the maximum
transmission factors. After merging the equivalents
requires: C, 67.7, H, 5.21. IR (Nujol, KBr) 2268 (wPH
)
cm−1
.
4.4. Preparation of [Pd(PPh2H)4](BF4)2 (3)(BF4)2
A 10-fold excess of HBF.4Et2O was added at −70°C
to a yellow CH2Cl2 (15 ml) solution of complex 3
(145 mg, 0.170 mmol). The solution was slowly
allowed to reach room temperature and stirred until
the evolution of dihydrogen (GC analysis) was com-
plete (5 h). Most of the solvent was evaporated and
n-hexane (10 ml) was added. The pale yellow oil that
precipitated out was recrystallized from a CH3CN/
Et2O. The pale yellow solid obtained was filtered and
vacuum dried (95 mg, 54.6% yield). Anal. Found: C,
56.7; H, 4.35. C48H44B2F8P4Pd requires: C, 56.3; H,
(Rint=[S ꢀF2o−Fo2(mean)ꢀ/S (Fo2)]=0.0276),
a set 1874
unique reflections was obtained. The structure was
solved by the automatic statistical procedure contained
in the SHELXTL [34] program and was refined by the
least-squares method contained in the same program.
The hydrogen atoms were introduced in calculated
positions and during the refinement were let ride on the
connected carbon atoms. The final refinement cycle
with anisotropic thermal factors for all the non-hydro-
gen atoms gave the reliability factors listed in Table 1.

P. Leoni et al. / Journal of Organometallic Chemistry 593–594 (2000) 12–18
17
Table 1
two groups of maxima on both sides of the cation at
Crystal data and structure refinement
z=0.74 and z=0.46. They were interpreted as being
−
due to the disorderly distribution of BF4 groups
Compound
3
3(BF4)2·C6D6
C54H50B2F8P4Pd
1102.84
293(2)
Tetragonal
P4/ncc (n.130)
among several possible positions. We therefore placed
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
C48H44P4Pd
851.11
293(2)
Tetragonal
I41/a (n.88)
−
an ‘ideal’ BF4 group with the central atom at 0.25,
0.25, 0.742 and occupancy of 0.25. To account for the
larger disorder of the anion on the other side, two
−
further ‘ideal’ BF4 groups were introduced with he
Unit cell dimensions
central atoms at 0.25, 0.25, 0.455 and 0.25, 0.25, 0.460
with occupancy 0.125+h and 0.125−h, respectively.
The successive least-squares refinement cycles gave a
distribution of the BF4 anions better fitting experi-
mental data, within the constraints of tetrahedral geo-
metric ideality. Other diffused maxima, placed around
,
a (A)
19.061(1)
19.061(1)
11.631(1)
4225.8(5)
4
12.530(2)
12.530(2)
33.122(7)
5200.2(15)
4
,
b (A)
,
c (A)
V (A )
3
,
−
Z
Dcalc (Mg m−3
)
1.338
1.409
0.544
Absorption coefficient 0.623
(mm−1
F(000)
(
)
the 4 axis at 0.75, 0.25, z, then became present in the
1752
0.62×0.48×0.25
2.05–24.97°
2248
0.44×0.36×0.20
2.04–22.49°
difference Fourier map. They were attributed to a
disordered molecule of C6D6 (crystals were grown in a
solution previously used in NMR spectra, where a few
drops of C6D6 had been added for the lock signal
capture and the field homogeneity optimization opera-
tions). The refinement of this last model gave the
reliability factors listed in the last column of Table 1.
Crystal size (mm3)
q range for data
collection
Index ranges
−15h522 (15
k522 (15l513
2484
−15h513 (15
k513 (15l535
4173
Reflections collected
Independent reflections 1874 [Rint=0.0276] 1718 [Rint=0.0522]
Refinement method
Full-matrix least-
squares on F2
1874/0/140
Full-matrix least-
squares on F2
1718/0/158
Data/restraints/
parameters
5. Supplementary material
Goodness-of-fit a on
F2
1.034
1.259
Final R indices a
[I\2| (I)]
R1=0.0263,
wR2=0.0607
R1=0.0365,
wR2=0.0654
0.0307; 2.51
R1=0.0748,
wR2=0.2229
R1=0.1261,
wR2=0.2507
0.1126; 9.87
1.029 and −0.616
Crystallographic data for the structural analyses has
been deposited with the Cambridge Crystallographic
Data Centre, CCDC No. 115355 for complex 3 and
No. 115356 for (3)(BF4).2C6D6. Copies of this informa-
tion may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK
(Fax: +44-1223-336033; email: deposit@ccdc.cam.ac.
uk or www: http://www.ccdc.cam.ac.uk.
R indices a (all data)
A; B (w) a
Largest diff. peak and 0.242 and −0.262
hole (e A
−3
,
)
a Goodness-of-fit=[S [w(Fo2−Fc2)2]/(N−P)]1/2, where N, P are the
numbers of observations and parameters, respectively, R1=S ꢀꢀFoꢀ−
ꢀFcꢀꢀ/S ꢀFoꢀ; wR2=[S [w(F2o−Fc2)2]=S[w(Fo2)2]]1/2
;
w=1/[| 2(F2o)+
(AQ)2+BQ] where Q=[MAX(Fo2, 0)+2Fc2]/3.
Acknowledgements
4.8. Crystal structure determination of 3(BF4)2 · C6D6
Financial support from the ‘Ministero della Ricerca
Scientifica e Tecnologica’ (MURST) and the Consiglio
Nazionale delle Ricerche (CNR, Rome) is gratefully
acknowledged.
A yellow prism with square section of 3(BF4)2 · C6D6
was selected for the diffractometric study and the lattice
parameters listed in Table 1 were observed. The diffrac-
tion symmetry and systematic absences suggested the
tetragonal P4/ncc space group. The intensity of 2484
reflections having q between 3.22 and 25.0° were col-
lected and were corrected for Lorentz and polarization
effects and for absorption by using the „-scan method
yielding 0.232 and 0.273 as the minimum and the
maximum transmission factors. After merging the
equivalents (Rint=0.0522), a set of 1718 unique reflec-
tions was obtained.
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