Synthesis and characterization of complexes of PdII and PtII containing the iminophosphorane ligand Ph3P=NC≡N

Article abstract of DOI:10.1039/a805147j

The chemistry of the iminophosphorane Ph₃P=NC≡N towards different palladium(II) and platinum(II) subtrates has been investigated. This ligand shows a high selectivity for co-ordination through the terminal N atom (that of the cyanide group), while the phosphoiminic N atom shows very poor nucleophilic ability. The reaction of [PdCl₂(NCPh)₂] with Ph₃P=NCN (1:2 molar ratio) gives trans-[PdCl₂(NCNPPh₃)₂] 1. The crystal structure of 1 has been determined and shows the iminophosphorane co-ordinated selectively through the nitrilic N atom. The reaction of the cationic derivatives [M(C-P)(NCMe)₂][ClO₄] [M = Pd or Pt; C-P = o-CH₂C₆H₄P(C₆H₄Me-o) ₂] with Ph₃P=NCN (1:2 molar ratio) resulted in the formation of [M(C-P)(NCN=PPh₃)₂][ClO₄] (M = Pd 2 or Pt 3), for which the same terminal N-co-ordination has been observed. The reaction of [Pd(dmba)(NCMe)₂][ClO₄] (dmba = C₆H₄CH₂NMe₂-2) with Ph₃P=NCN (1:1 molar ratio) gave the dinuclear derivative [{Pd(μ-NCN=PPh₃)-(dmba)}₂][ClO₄]₂ 4 in which the iminophosphorane acts as an N,N-bridging ligand, while reaction in 1:2 molar ratio gave [Pd(dmba)(NCN=PPh₃)₂][ClO₄] 5 which possess N-terminal co-ordination. The reaction of this iminophosphorane with monosolvate complexes [Pd(dmba)(PPh₃)(THF)][ClO₄] or [Pt(C-P)(PPh₃)(NCMe)][ClO₄] (1:1 molar ratio) resulted in the formation of [Pd(dmba)(PPh₃)(NCN=PPh₃)][ClO₄] 6 or [Pt(C-P)(PPh₃)-(NCN=PPh₃)][ClO₄] 7, and the reaction with the halide bridging derivatives [{Pd(μ-Cl)(dmba)}₂] or [{Pt(μ-Cl)-(C-P)}₂] (2:1 molar ratio) produced cleavage of the bridging system and formation of [PdCl(dmba)(NCN=PPh₃)] 8 and [PtCl(C-P)(NCN=PPh₃)] 9. The same N-terminal co-ordination mode is observed in complexes 6-9.

Full text of DOI:10.1039/a805147j

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Synthesis and characterization of complexes of PdII and PtII
᎐
containing the iminophosphorane ligand Ph P᎐NC᎐N
᎐
᎐
3
Larry R. Falvello, Susana Fernández, María M. García, Rafael Navarro* and
Esteban P. Urriolabeitia
Departamento de Química Inorgánica, Instituto de Ciencia de Materiales de Aragón,
Universidad de Zaragoza, Consejo Superior de Investigaciones Científicas, 50009 Zaragoza,
Spain. E-mail: rafanava@posta.unizar.es; esteban@posta.unizar.es
Received 3rd July 1998, Accepted 30th September 1998
᎐
The chemistry of the iminophosphorane Ph P᎐NC᎐N towards different palladium() and platinum() subtrates
᎐
᎐
3
has been investigated. This ligand shows a high selectivity for co-ordination through the terminal N atom (that
of the cyanide group), while the phosphoiminic N atom shows very poor nucleophilic ability. The reaction of
[PdCl (NCPh) ] with Ph P᎐NCN (1:2 molar ratio) gives trans-[PdCl (NCNPPh ) ] 1. The crystal structure of 1
᎐
2
2
3
2
3 2
has been determined and shows the iminophosphorane co-ordinated selectively through the nitrilic N atom. The
reaction of the cationic derivatives [M(C–P)(NCMe)2][ClO4] [M = Pd or Pt; C–P = o-CH2C6H4P(C6H4Me-o)2]
with Ph P᎐NCN (1:2 molar ratio) resulted in the formation of [M(C–P)(NCN᎐PPh ) ][ClO ] (M = Pd 2 or Pt 3),
᎐
᎐
3
3
2
4
for which the same terminal N-co-ordination has been observed. The reaction of [Pd(dmba)(NCMe)2][ClO4]
(dmba = C H CH NMe -2) with Ph P᎐NCN (1:1 molar ratio) gave the dinuclear derivative [{Pd(µ-NCN᎐PPh )-
᎐
᎐
6
4
2
2
3
3
(dmba)}2][ClO4]2 4 in which the iminophosphorane acts as an N,N-bridging ligand, while reaction in 1:2 molar
ratio gave [Pd(dmba)(NCN᎐PPh ) ][ClO ] 5 which possess N-terminal co-ordination. The reaction of this imino-
᎐
3
2
4
phosphorane with monosolvate complexes [Pd(dmba)(PPh3)(THF)][ClO4] or [Pt(C–P)(PPh3)(NCMe)][ClO4]
(1:1 molar ratio) resulted in the formation of [Pd(dmba)(PPh )(NCN᎐PPh )][ClO ] 6 or [Pt(C–P)(PPh )-
᎐
3
3
4
3
(NCN᎐PPh )][ClO ] 7, and the reaction with the halide bridging derivatives [{Pd(µ-Cl)(dmba)} ] or [{Pt(µ-Cl)-
᎐
3
4
2
(C–P)} ] (2:1 molar ratio) produced cleavage of the bridging system and formation of [PdCl(dmba)(NCN᎐PPh )]
᎐
2
3
8 and [PtCl(C–P)(NCN᎐PPh )] 9. The same N-terminal co-ordination mode is observed in complexes 6–9.
᎐
3
(M = Pd or Pt),12 [M(C–P)(NCMe)2][ClO4] (M = Pd† or Pt13)
and [Pd(dmba)(NCMe)2][ClO4]16 [C–P = o-CH2C6H4P(C6H4-
Me-o)2; dmba = C6H4CH2NMe2-2], complexes with one labile
ligand such as [Pt(C–P)(PPh3)(NCMe)][ClO4]5 and [Pd(dmba)-
(PPh3)(THF)][ClO4]17 and dinuclear complexes such as [{M(µ-
Cl)(C–P)}2] (M = Pd14 or Pt13) and [{Pd(µ-Cl)(dmba)}2]18 in
order to explore the co-ordination properties (nucleophilic
ability of the iminic N atom and steric requirements) of this
ligand in different environments. In this paper we report the
results obtained from this chemistry.
Introduction
We have been studying the co-ordination chemistry of α-
stabilized phosphorus ylides Ph P᎐C(H)R (R = COMe, COPh,
᎐
3
COOMe, CONMe2 or CN) and their behaviour as ambidentate
ligands.1–6 The reactivity of these ylides towards several ortho-
metallated complexes of PdII and PtII has been examined and
their ambidentate character observed. Furthermore, we have
found that, in many cases, it is possible to predict both the co-
ordination site of the ylide and the donor atom linked to the
metal (O- versus C-bonding, N- versus C-bonding) using as
simple a concept as the antisymbiotic effect.7,8
Results and discussion
The iminophosphoranes, compounds of general structure
R P᎐NRЈ, are an interesting class of compounds closely related
᎐
3
The reaction of [PdCl (NCPh) ] with Ph P᎐NCN (1:2 molar
᎐
3
2
2
to the phosphorus ylides and showing numerous applications to
organic synthesis (for instance, the formation of C᎐N bonds
ratio) in acetone at room temperature results in the precipita-
tion of an orange solid of stoichiometry [PdCl2(NCNPPh3)2]
1 as deduced from its elemental analysis. The reaction of
᎐
through the Aza–Wittig reaction).9a Moreover, they can behave
as ligands towards transition metals through, at least, the lone
pair on the N atom. In spite of the similarities, their use as
ligands is less developed than that of the ylides,9 although
in recent years several groups have focused their interest on
the co-ordinative properties and reactivity of iminophos-
phoranes.9,10
[PtCl (NCPh) ] with Ph P᎐NCN (1:2 molar ratio) performed
᎐
3
2
2
under the same conditions (acetone; room temperature, r.t.)
gives a mixture of the starting products. If the reaction is
performed in refluxing toluene the spectroscopic data of the
resulting solid show the presence of both starting materials
together with at least three products which appear to contain
co-ordinated iminophosphorane. However, the recrystallization
of this mixture failed in all attempted cases and we were not
Prompted by the results obtained with the α-stabilized ylides,
we have decided to explore the co-ordination chemistry of
the α-stabilized iminophosphorane Ph P᎐NC᎐N,11 a compound
᎐
᎐
᎐
3
able to isolate a Pt–NCN᎐PPh derivative free of the starting
᎐
3
for which there is no precedent in co-ordination chemistry.
Its reactivity has been explored towards several palladium()
and platinum() substrates (see Scheme 1). We have chosen
complexes with two labile ligands in different arrange-
ments and with different trans atoms, such as [MCl2(NCPh)2]
† The complex [Pd(C–P)(NCMe)2][ClO4] was prepared in a way similar
to that described in ref. 13 for [Pt(C–P)(NCMe)2][ClO4], with the excep-
tion that the reaction was performed starting from [{Pd(µ-Cl)(C–P)}2]
(see ref. 14) under a nitrogen atmosphere in dry NCMe (ref. 15).
J. Chem. Soc., Dalton Trans., 1998, 3745–3750
3745

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Cl
C
X
NCN=PPh3
Cl
C
P
NCN=PPh3
NCN=PPh3
Ph3P=NCN Pd NCN=PPh3
M
M
Cl
1
M = Pd, X = NMe2 8
M = Pt, X = P(C6H4Me-o)2
M = Pd 2, Pt 3
9
(A)
(F), (G)
(E)
(B)
C
N
NCN=PPh3
C
P
PPh3
N
Pd
5
Pt
(C)
C
NCN=PPh3
NCN=PPh3
Ph3P
N
7
(C)
Ph3P=NCN
(C)
(D)
2
PPh3
N
Pd
N
N
C
C
C
PPh3
C
N
N
4
Pd
Pd
C
NCN=PPh3
N
N
PPh3
6
Cl
NCPh
PhCN
Cl
M
(A); M = Pd, Pt
Cl
2
PPh3
THF
NCMe
Pd
Pd
Pd
N
N
NCMe
N
Me2
Me2
Me2
(F)
(D)
(C)
H2
C
H2
C
H2
C
Cl
PPh3
NCMe
M
Pt
M
NCMe
2
P
NCMe
P
P
(C6H4Me-o)2
(C6H4Me-o)2
(C6H4Me-o)2
(B); M = Pd, Pt
(E)
(G); M = Pd, Pt
Scheme 1
Table 1 Selected bond lengths (Å) and angles (Њ) for complex 1
Pd(1)–N(1)
Pd(1)–Cl(1)
P(1)–N(2)
P(1)–C(8)
1.971(3)
2.2969(9)
1.609(3)
1.789(3)
P(1)–C(2)
P(1)–C(14)
N(1)–C(1)
C(1)–N(2)
1.791(3)
1.796(3)
1.151(4)
1.292(4)
N(1A)–Pd(1)–N(1)
N(1)–Pd(1)–Cl(1)
N(2)–P(1)–C(2)
N(2)–P(1)–C(14)
C(2)–P(1)–C(14)
N(1)–C(1)–N(2)
180.0
N(1A)–Pd(1)–Cl(1)
N(2)–P(1)–C(8)
C(8)–P(1)–C(2)
C(8)–P(1)–C(14)
C(1)–N(1)–Pd(1)
C(1)–N(2)–P(1)
88.84(9)
105.74(14)
107.65(14)
108.84(14)
161.9(3)
91.16(9)
111.91(14)
112.23(14)
110.22(14)
175.2(3)
122.3(2)
Fig. 1 Thermal ellipsoid plot of trans-[PdCl2(NCN᎐PPh3)2] 1. Hydro-
gen atoms have been omitted for clarity. Atoms are drawn at the 50%
probability level; Pd(1) lies on a crystallographic inversion center.
᎐
Symmetry transformation used to generate equivalent atoms: A Ϫx,
Ϫy, Ϫz.
materials, probably due to the similar solubility of the species
involved.
distance [1.292(4) Å] is shorter than other distances reported
for this kind of bond in iminophosphoranes [ranging from
1.351(6) to 1.461(6) Å],9,10,21,22 regardless of whether the ligand
is co-ordinated or not, and is similar within experimental error
The molecular structure of complex 1 has been determined
by X-ray diffraction methods. A drawing of the molecule is
shown in Fig. 1 and selected bond distances and angles are
presented in Table 1. The palladium atom lies on a crystallo-
graphic inversion center and has a very slightly distorted
square-planar environment. The Pd–Cl bond distance
[2.2969(9) Å] falls within the usual range of distances found for
this kind of bond,19 while the Pd–N(1) bond distance [1.971(3)
Å] is shorter than other Pd–N (nitrile) bond lengths found
in the literature (2.065(14) Å for [(MeNC)PdCl2(µ-dpmp)-
PdCl2]ؒNCMe20 and 2.076(3) Å for [Pd(dmba){P(OMe)3}-
to that reported for [Ph P᎐NC᎐NC H -1][SbCl ]23 [1.25(2) Å]
᎐
᎐
᎐
3
10 15
6
(C10H15 = adamantyl). The N(2)–P(1) bond [1.609(3) Å] is
shorter than that reported for the latter salt [1.64(1) Å], is simi-
lar to (within experimental error) or shorter than those found in
N-co-ordinated iminophosphoranes [range 1.604(7)–1.627(4)
Å], but is longer than those found in free iminophosphoranes
[range 1.569(4)–1.585(4) Å].10 This phosphorus–nitrogen bond is
seen to have considerable single bond character if compared to
the “true” P᎐N double bond in [Ph P᎐N᎐PPh ]ϩ [1.547(2) Å].24
᎐
᎐ ᎐
3
3
{NCC(H)᎐PPh }][ClO ]2).
Another interesting feature of the structure is the bond angle
Pd(1)–N(1)–C(1) [161.9(3)Њ], the value of which is less than the
180Њ expected for sp hybridization of the nitrogen atom. The
bond angle N(1)–C(1)–N(2) is 175.2(3)Њ and indicates an almost
᎐
3
4
With respect to the internal bond distances and angles of
the iminophosphorane ligand, the N(1)–C(1) bond distance
[1.151(4) Å] is fairly typical for nitriles.2,21 The C(1)–N(2) bond
3746
J. Chem. Soc., Dalton Trans., 1998, 3745–3750

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linear disposition of these bonds, in accord with the presence
of a cyanide unit. The environment around the N(2) atom is
trigonal planar [C(1)–N(2)–P(1) 122.3(2)Њ] and that around the
phosphorus atom P(1) is tetrahedral.
δ 27.76 and 29.18 for 2 and at 28.06 and 29.52 for 3. The close
similarity of these resonances to each other and to that of
free Ph P᎐NCN clearly suggests an N-terminal (nitrile)
᎐
3
co-ordination of the ligand, as also deduced for complex 1.
All of these facts imply that there is an extensive delocaliza-
tion of the charge density in the P(1)–N(2)–C(1)–N(1) system.
The distances and angles taken together suggest participation
of the resonance forms B and D in the bonding description with
only small contributions of A and C. However, the question of
why the iminophosphorane co-ordinates selectively through the
nitrilic N atom instead of through the iminic N atom remains
unanswered. In our experience, the co-ordinative ability of
the iminic N atom is worse than those of other donor atoms
Additional evidence is the absence of coupling between the P
atom of the C–P ligand and the P atom of the trans Ph P᎐NCN
᎐
3
ligand. Such coupling is observable when a C-coordinated ylide
is trans to the P atom of the C–P group5 and also when an
iminophosphorane is co-ordinated through the iminic N
atom22 trans to the P atom of the C–P ligand. The structure
represented in Scheme 1 accounts for all of these facts.
The observed reactivity contrasts with that reported for
the phosphoylide Ph P᎐C(H)CN5 and C–P complexes. There,
᎐
3
present in the ligand. For instance, in Ph P᎐NCOC H N-2
[Pt(C–P)(NCMe)2][ClO4] reacts with 1 equivalent of Ph3-
᎐
3
6
4
both the carbonylic oxygen atom and the pyridinic N atom have
the same or even a better co-ordination ability than the iminic
N atom.22 This fact would probably be due to the delocalization
of the electronic density, which results in a lower charge density
at the iminic N atom. It is also worth noting the different
P᎐C(H)CN to give [Pt(C–P){C(H)(CN)PPh }(NCMe)][ClO ]
᎐
3 4
which reacts with a second equivalent of the ylide to give [Pt-
(C–P){C(H)(CN)PPh }{NCC(H)᎐PPh }][ClO ]. It is clear that
᎐
3
3
4
for the phosphoylide there is a high tendency to co-ordinate
through the ylidic carbon atom and that the N-co-ordination of
the second ylide is driven by the electronic and steric require-
ments of the first C-co-ordinated ylide. This tendency does not
carry over to the iminic N atom of the iminophosphorane and,
hence, selective N(nitrile) co-ordination is observed.
The reactivity of the iminophosphorane towards
[Pd(dmba)(NCMe)2][ClO4] more nearly resembles that reported
for the analogous phosphoylide. Thus, [Pd(dmba)-
behaviour of the phosphoylide Ph P᎐C(H)CN and the imino-
᎐
3
phosphorane Ph P᎐NCN towards the same precursor, in this
᎐
3
case [PdCl2(NCPh)2]. While the former ligand co-ordinates
selectively through the ylidic carbon atom, giving a mixture
of diastereoisomers (RR/SS and RS/SR) trans-[PdCl2{C(H)-
(CN)PPh3}2], the latter gives 1 which shows selective “end-on”
N(nitrile) co-ordination.
(NCMe) ][ClO ] reacts with Ph P᎐NCN (1:1 molar ratio)
᎐
3
2
4
giving a pale yellow solid of stoichiometry [Pd(dmba)-
(NCNPPh3)][ClO4], as deduced from its elemental analysis.
The mass spectrum (positive ion FAB) of this solid shows a
peak at m/z 542 which corresponds to the cationic fragment
[Pd(dmba)(NCNPPh3)]ϩ. The IR spectrum shows a sharp
absorption at 2249 cmϪ1, attributed to the cyano group of the
iminophosphorane ligand, and does not show the presence
of co-ordinated NCMe which usually appears at higher
frequencies. The 1H NMR spectrum shows the presence of the
expected resonances for the Ph, C6H4, CH2N and NMe2 groups,
which integrated as 15:4:2:6, thus confirming the presence
of only one iminophosphorane group per dmba ligand. The
observation of only one set of signals indicates the presence
of only one isomer. Similarly, the 31P-{1H} NMR spectrum
shows a singlet resonance at δ 29.16. Excluding the possibility
of chelation of the ligand because of the constraint imposed
by the nitrile group, we can propose two possible structures for
this complex. One is mononuclear with a covalent perchlorate
group. This proposition is immediately discarded because
PPh3
Pd
Pd
N
C N
N
C N PPh3
A
B
Pd
Pd
N
C N
N
C
N
PPh3
PPh3
C
D
Complex 1 was also characterized by spectroscopic methods.
The IR spectrum shows a trans arrangement of the chloride
ligands, and hence of the iminophosphorane ligands, as
deduced from the observation of a sharp absorption at 348
cmϪ1. Moreover, the IR spectrum shows a strong band at
2256 cmϪ1 attributed to the C᎐N stretch. This absorption is
᎐
᎐
shifted to higher energy with respect to that of free Ph P᎐NCN
᎐
3
(2176 cmϪ1); this shift can be interpreted as a consequence
of co-ordination of the iminophosphorane through the iminic
N atom, by analogy with the results obtained with the C-co-
ordinated phosphoylide Ph P᎐C(H)CN2 and N(imine)-bonded
Ϫ
the absorptions corresponding to the ClO4 group are not
split.2 The other possibility is a dinuclear structure with the
iminophosphorane acting as a bridging ligand. This second
proposition is supported by two facts: the position of the ν(CN)
absorption at 2249 cmϪ1 shifted to high wavenumber with
᎐
3
keto-stabilized iminophosphoranes Ph P᎐NC(O)R.22 The 31P-
᎐
3
{1H} NMR spectrum of 1 shows a singlet resonance at δ 27.44
which is shifted to low field by only about 2 ppm with respect to
free Ph P᎐NCN (δ 25.25). The deshielding of the phosphorus
respect to that of [Pd(dmba)(NCNPPh3)2][ClO4] 5 (2211 cmϪ1
,
᎐
3
nucleus that would be expected to result from iminic N-bonding
is not observed22 thus suggesting that an “end-on” nitrile co-
ordination has taken place, as is depicted in Scheme 1.
Further study of the reactivity of this iminophosphorane
ligand gives additional evidence of the poor co-ordinating ability
of the iminic N atom. The reaction of [M(C–P)(NCMe)2][ClO4]
see below) in which both iminophosphorane ligands are
N(nitrile)-co-ordinated, and the position of the phosphorus
resonance at δ 29.16, shifted downfield with respect to those of
5 (δ 26.60 and 26.41, see below). Both the increase in the ν(CN)
wavenumber and the deshielding of the phosphorus resonance
strongly suggest that both N atoms of Ph P᎐NCN are bonded
᎐
3
(M = Pd or Pt) with 2 equivalents of Ph P᎐NCN results in
the formation of white solids of stoichiometry [M(C–P)-
to the palladium center. A more accurate definition of the
nature of the product is given by the measurement of the molar
conductance in acetone solution (c = 5 × 10Ϫ4 M), which is
ΛM = 268 ΩϪ1 cm2 molϪ1 corresponding to a 2:1 electrolyte.25
Thus, the product can be formulated as the dinuclear complex
᎐
3
(NCN᎐PPh ) ][ClO ] (M = Pd 2 or Pt 3) as indicated by their
᎐
3
2
4
elemental analyses and mass spectra (see Experimental section).
If the reaction is carried out in 1:1 molar ratio complex
mixtures of 2 or 3 and other unidentified products are obtained.
The IR spectra of 2 and 3 show absorptions corresponding
[{Pd(µ-NCN᎐PPh )(dmba)} ][ClO ] 4. The observation of
᎐
3
2
4 2
only one set of resonances in the NMR spectra shows that
4 must be a product of high symmetry and that of the two
highest symmetry isomers only one is present. The 1H–1H
NOESY spectrum of complex 4 shows a strong NOE inter-
action between the ortho protons of phenyl groups and the
methyl protons of the NMe2 group, showing their mutually cis
to the C᎐N group at 2215 and 2228 cmϪ1, respectively, and the
᎐
᎐
31P-{1H} NMR spectra show resonances attributed to the
phosphorus atom of the C–P ligands [δ 37.54 for 2 and 16.10
for 3 (1JPtP = 4551 Hz)] together with resonances attributed to
the iminophosphorane which appear as two close singlets at
J. Chem. Soc., Dalton Trans., 1998, 3745–3750
3747

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disposition. The dimeric structure depicted in Scheme 1
accounts for these observations.
data and by analogy to the splitting of the M(µ-Cl)2M (M = Pd
or Pt) system by N-donor ligands.5,17
When the reaction between [Pd(dmba)(NCMe)2][ClO4]
and Ph P᎐NCN is performed in 1:2 molar ratio a solid of
᎐
3
Conclusion
stoichiometry [Pd(dmba)(NCNPPh3)2][ClO4] 5 is obtained as
deduced from its elemental analysis and mass spectrum. The
characterization of complex 5 follows the same key features as
The iminophosphorane Ph P᎐NCN behaves as an N(nitrile)-
᎐
3
donor ligand towards complexes of PdII and PtII, regardless of
the electronic and steric requirements of the other ligands
around the metal centre. Only in one case we have been able to
co-ordinate this ligand through both the iminic N atom and the
nitrilic N atom, in a bridging mode. No examples have been
found with selective iminic N-co-ordination. This behaviour
could be due to an extensive delocalization of the electron
density along the P–NC–N system, which reduces the charge
density, and thus the coordinating ability, of the iminic N
atom.
those reported for 1–4. The ν(CN) of 5 appears at 2211 cmϪ1
,
shifted to high frequencies with respect to free Ph P᎐NCN,
᎐
3
and the 31P-{1H} NMR spectrum shows two close singlet
resonances (δ 26.60 and 26.41), very similar to the resonance
of free Ph P᎐NCN. All of these facts mean that both imino-
᎐
3
phosphorane ligands are N(nitrile)-co-ordinated, as depicted
in Scheme 1.
Complexes 4 and 5 can also be obtained by mutual inter-
conversion (see Scheme 1). Thus, 4 reacts with an additional
equivalent of Ph P᎐NCN to give 5 while 5 reacts with 1 equiva-
᎐
3
lent of the solvate [Pd(dmba)(NCMe)2][ClO4] to give 4.
Experimental
The reactivity observed for the iminophosphorane is in this
case somewhat similar to that reported for the phosphoylide
towards C,N-orthometallated derivatives of PdII.2 Thus, Ph3-
CAUTION: perchlorate salts of metal complexes with organic
ligands are potentially explosive. Only small amounts of these
materials should be prepared and handled with great caution.
See ref. 26.
P᎐C(H)CN reacted with [Pd(dmba)(NCMe) ][ClO ] (1:1 molar
᎐
2
4
ratio) to give the dimer [{Pd[µ-NCC(H)PPh3](dmba)}2][ClO4]2.
To this point the behaviour of the two ligands is analogous.
However, the dinuclear complex further reacts with the ylide
General procedures
giving [Pd(dmba){C(H)(CN)PPh }{NCC(H)᎐PPh }][ClO ] in
᎐
3
3
4
Solvents were dried and distilled by standard methods prior to
use. Elemental analyses of C, H, N were carried out on a
Perkin-Elmer 2400 microanalyser. Infrared spectra (4000–200
cmϪ1) were recorded on a Perkin-Elmer 883 spectrophotometer
which the two ylides are co-ordinated in different ways, one
through the C atom and the other through the N atom. Its
analogous derivative 5 possess the two iminophosphorane
ligands co-ordinated in the same way as a result, once again, of
the poor nucleophilicity of the iminic N atom.
1
in Nujol mulls between polyethylene sheets, H (300.13 MHz)
and 31P-{1H} (121.49 MHz) NMR spectra from CDCl3 or
CD2Cl2 solutions at room temperature (unless otherwise stated)
on a Bruker ARX-300 spectrometer; 1H spectra were referenced
using the solvent signal as an internal standard and 31P-{1H}
spectra were externally referenced to H3PO4 (85%). The two
dimensional 1H–1H NOESY experiment for complex 4 was
performed at a measuring frequency of 300.13 MHz. The data
were acquired into a 512 × 1024 matrix, and then transformed
into 1024 × 1024 points using a sine window in each dimension.
The mixing time was 400 ms. Mass spectra (positive ion FAB)
were recorded on a V.G. Autospec. spectrometer from CH2Cl2
solutions. Electrical conductivity measurements were per-
formed in acetone solutions with concentrations of about
5 × 10Ϫ4 M using a Philips PW 9509 conductivity cell. The
The reaction of the monosolvate complexes [Pd(dmba)-
(PPh3)(THF)][ClO4] or [Pt(C–P)(PPh3)(NCMe)][ClO4] with
Ph P᎐NCN (1:1 molar ratio) gives the corresponding cationic
᎐
3
derivatives [Pd(dmba)(PPh )(NCN᎐PPh )][ClO ] 6 and [Pt-
᎐
3
3
4
(C–P)(PPh )(NCN᎐PPh )][ClO ] 7, as deduced from their
᎐
3
3
4
elemental analyses and mass spectra. The IR spectra of 6 and 7
show a strong absorption at 2239 cmϪ1 in both cases, and their
31P-{1H} NMR spectra show the expected resonances for the
presence of the PPh3 (6) and C–P and PPh3 in trans positions
(7) together with the signals attributed to the iminophos-
phorane (δ 27.69 for 6 and 27.27 for 7). As discussed in the
preceding paragraphs, these data imply an N(nitrile) co-
ordination of the Ph P᎐NCN ligand. Similar results (N-co-
᎐
3
ordination) have been obtained with the ylide Ph P᎐C(H)CN
11
᎐
3
᎐
ligand Ph P᎐NC᎐N
and the complexes [MCl2(NCPh)2]
᎐
᎐
3
and the same precursors.2,5
(M = Pd or Pt),12 [M(C–P)(NCMe)2][A] (M = Pd15 or Pt13),
Finally, the iminophosphorane Ph P᎐NCN is able to pro-
[Pd(dmba)(NCMe)2][A],16
[Pd(dmba)(PPh3)(THF)][A],17
᎐
3
mote the cleavage of the halide bridging systems in the dinu-
clear complexes [{Pd(µ-Cl)(dmba)}2] and [{Pt(µ-Cl)(C–P)}2].
[Pt(C–P)(PPh3)(NCMe)][A]5 (A = ClO4Ϫ), [{M(µ-Cl)(C–P)}2]
(M = Pd,14 or Pt13) and [{Pd(µ-Cl)(dmba)}2]18 were prepared
according to published methods.
Thus, the reaction of these compounds with Ph P᎐NCN (1:2
᎐
3
molar ratio) results in the formation of solids of stoichiometry
[PdCl(dmba)(NCN᎐PPh )] 8 and [PtCl(C–P)(NCN᎐PPh )] 9
in accord with their elemental analyses. However, the reaction
᎐
᎐
3
3
Preparations
᎐
trans-[PdCl (N᎐CN᎐PPh ) ] 1. To a solution of [PdCl -
of [{Pd(µ-Cl)(C–P)} ] with Ph P᎐NCN (1:2 molar ratio) under
᎐
᎐
᎐
2
3
2
2
2
3
(NCPh)2] (0.100 g, 0.260 mmol) in 20 cm3 of acetone the
the same conditions does not promote cleavage and the starting
᎐
᎐
iminophosphorane Ph P᎐NC᎐N (0.157 g, 0.521 mmol) was
products are recovered. The IR spectrum of 8 shows the ν(C᎐N)
᎐
3
᎐
᎐
absorption at 2243 cmϪ1 and the Pd–Cl stretch at 305 cmϪ1
,
added. After a few minutes an orange solid precipitated which
while that of 9 shows the ν(C᎐N) absorption at 2233 cmϪ1 and
was collected, washed with additional acetone (10 cm
3), Et O
᎐
᎐
2
(25 cm3), air-dried and identified as complex 1, 0.117 g
(58% yield). The acetone solution was evaporated to dryness
and the residue treated with Et2O (25 cm3), giving a second
fraction of 1, 0.035 g (17% yield, net yield 75%) (Found: C,
57.98; H, 3.86; N, 7.13. Calc. for C38H30Cl2N4P2Pd: C, 58.37;
the Pt–Cl stretch at 292 cmϪ1. Both facts, the increase in
᎐
energies of the ν(C᎐N) absorption and the shift to higher fre-
᎐
quency of the M᎐Cl stretch, point to the presence of a terminal
chloride ligand and an N-bonded iminophosphorane ligand as
a result of the cleavage of the halide bridging system. That is,
these products are not simply mixtures of the starting materials.
The NMR spectra of 8 and 9 (see Experimental section)
show the expected resonances for all groups present in these
molecules and also show only one set of resonances; that is,
only one isomer (of the two possible) is present in solution. The
sterochemistry of this isomer has been assigned as Cl-trans-to-
C, as depicted in Scheme 1, on the basis of the spectroscopic
H, 3.87; N, 7.16%). IR (ν/cmϪ1): 2256 (νNC), 348 (νPd–Cl). H
1
NMR (CDCl3): δ 7.63–7.48 (m, Ph). 31P-{1H} NMR (CDCl3):
δ 27.44 (s, NPPh3).
᎐
[Pd(C–P)(N᎐CN᎐PPh ) ][ClO ] 2. To a solution of [Pd(C–P)-
᎐
᎐
3
2
4
(NCMe)2][ClO4] (0.100 g, 0.169 mmol) in 20 cm3 of CH2Cl2 the
᎐
iminophosphorane Ph P᎐NC᎐N (0.102 g, 0.338 mmol) was
᎐
᎐
3
3748
J. Chem. Soc., Dalton Trans., 1998, 3745–3750

View Article Online
᎐
added, and the resulting solution stirred at room temperature
for 30 min. The solvent was then evaporated to dryness and the
residue washed with Et2O (25 cm3), giving complex 2 as a white
solid which was collected and air-dried, 0.104 g (55% yield)
(Found: C, 63.79; H, 4.18; N, 5.00. Calc. for C59H50-
ClN4O4P3Pd: C, 63.62; H, 4.52; N, 5.03%). IR (ν/cmϪ1): 2215
(νNC). Mass spectrum (FABϩ) [m/z, (%)]: 1013 (15, Mϩ) and
711 (55% [M Ϫ NCNPPh3]ϩ). 1H NMR (CDCl3, 213 K):
δ 7.69–6.64 (m, 42H, Ph ϩ o-MeC6H4), 2.95 (s, broad, 2H,
CH2Pd), 2.44 and 2.16 (2s, 6H, 2o-MeC6H4). 31P-{1H} NMR
(CDCl3, 213 K): δ 37.54 (s, C–P), 29.18 (s, NPPh3) and 27.76
(s, NPPh3).
[Pt(C–P)(PPh )(N᎐CN᎐PPh )][ClO ] 7. Complex 7 was syn-
᎐ ᎐
3 3 4
thesized in the same way as 2: [Pt(C–P)(PPh3)(NCMe)][ClO4]
(0.100 g, 0.111 mmol) was treated with Ph P᎐NC᎐N (0.034 g,
᎐
᎐
᎐
3
0.11 mmol) in CH2Cl2 to give 7 as a white solid, 0.089 g
(69% yield) (Found: C, 59.56; H, 4.23; N, 2.34. Calc. for
C58H50ClN2O4P3Pt: C, 59.92; H, 4.33; N, 2.41%). IR (ν/cmϪ1):
2353, 2340 (νNCMe), 2239 (νNC). Mass spectrum (FABϩ) [m/z
(%)]: 1062 (100, Mϩ), 800 (25, [M Ϫ PPh3]ϩ), 760 (65, [M Ϫ NC-
NPPh3]ϩ). H NMR (CDCl3, 213 K): δ 7.71–6.76 (m, 42 H,
1
Ph ϩ o-MeC6H4), 3.14, 2.21 (AX spin system, 2H, CH2Pt,
2JHH = 15.9 Hz), 2.38, 2.26 (2s, 6H, 2o-MeC6H4). 31P-{1H}
NMR (CDCl3, 213 K): δ 31.55, 27.22 (AB spin system, C–
1
1
2
P ϩ PPh3, JPtP = 3005, JPtPЈ = 2968, JPPЈ = 408 Hz) and 27.27
᎐
[Pt(C–P)(N᎐CN᎐PPh ) ][ClO ] 3. Complex 3 was syn-
(s, NPPh3).
᎐
᎐
3
2
4
thesized in the same way as 2: [Pt(C–P)(NCMe)2][ClO4] (0.100
᎐
g, 0.147 mmol) was treated with Ph P᎐NC᎐N (0.088 g, 0.29
᎐
᎐
᎐
3
[PdCl(dmba)(N᎐CN᎐PPh )] 8. To
a
solution of [{Pd-
᎐
᎐
3
(µ-Cl)(dmba)}2] (0.100 g, 0.181 mmol) in CH2Cl2 (20 cm3) the
mmol) in CH2Cl2 to give 3 as a white solid, 0.117 g (66% yield)
(Found: C, 58.63; H, 3.85; N, 4.63. Calc. for C59H50ClN4O4P3Pt:
C, 58.93; H, 4.19; N, 4.66%). IR (ν/cmϪ1): 2228 (νNC). Mass
spectrum (FABϩ) [m/z, (%)]: 1102 (35%, Mϩ) and 800 (100,
[M Ϫ NCNPPh3]ϩ). 1H NMR (CDCl3, 213 K): δ 7.72–6.61 (m,
42H, Ph ϩ o-MeC6H4), 2.99, 2.77 (AB spin system, 2H, CH2Pt,
2JHH = 16.4 Hz), 2.45 and 2.10 (2s, 6H, 2o-MeC6H4). 31P-{1H}
NMR (CDCl3, 213 K): δ 29.52 (s, NPPh3), 28.06 (s, NPPh3) and
16.10 (s, C–P, 1JPt–P = 4551 Hz).
᎐
iminophosphorane Ph P᎐NC᎐N (0.109 g, 0.362 mmol) was
᎐
᎐
3
added, and the resulting solution stirred at room temperature
for 15 min. The solvent was evaporated to dryness and the
oily residue treated with Et2O (25 cm3), giving complex 8 as a
yellow solid, 0.170 g (81% yield) (Found: C, 57.88; H, 4.49; N,
7.19. Calc. for C28H27ClN3PPd: C, 58.15; H, 4.70; N, 7.26%).
IR (ν/cmϪ1): 2243 (νNC) and 305 (νPdCl). 1H NMR (CDCl3):
δ 7.70–7.52 (m, 15 H, Ph), 6.94–6.84 (m, 3H, C6H4), 6.69 (m,
1H, C6H4), 3.84 (d, 2H, CH2) and 2.84 (s, 6H, NMe2). 31P-{1H}
NMR (CDCl3): δ 26.78 (s, NPPh3).
᎐
[{Pd(dmba)(ì-N᎐CN᎐PPh )} ][ClO ] 4. Complex 4 was
synthesized in the same way as 2: [Pd(dmba)(NCMe)2][ClO4]
᎐
᎐
3
2
4 2
᎐
(0.084 g, 0.20 mmol) was treated with Ph P᎐NC᎐N (0.060 g,
᎐
᎐
3
᎐
[PtCl(C–P)(N᎐CN᎐PPh )] 9. To a suspension of [{Pt(µ-Cl)-
᎐
᎐
3
0.20 mmol) in CH2Cl2 to give 4 as a pale yellow solid, 0.104 g
(82% yield) (Found: C, 51.85; H, 4.17; N, 6.43. Calc. for C28-
H27ClN3O4PPd: C, 52.35; H, 4.23; N, 6.54%). IR (ν/cmϪ1):
2249 (νNC). Mass spectrum (FABϩ) [m/z, (%)]: 542 [100,
(M/2)ϩ]. ΛM/ΩϪ1 cm2 molϪ1 = 268 (5 × 10Ϫ4 M in acetone solu-
tion). 1H NMR (CDCl3, 223 K): δ 7.71–7.61 (m, 15 H, Ph), 6.94
(m, 1H, C6H4), 6.85 (m, 1H, C6H4), 6.72 (m, 2H, C6H4), 3.81
(s, 2H, CH2) and 2.72 (s, 6H, NMe2). 31P-{1H} NMR (CDCl3):
δ 29.16 (s, NPPh3).
(C–P)}2] (0.100 g, 0.094 mmol) in 20 cm3 of CH2Cl2 the imino-
᎐
phosphorane Ph P᎐NC᎐N (0.057 g, 0.19 mmol) was added.
᎐
᎐
3
The original suspension gradually dissolved and after 30
min stirring at room temperature a colorless solution was
obtained. The solvent was then evaporated to dryness and
the residue washed with Et2O (25 cm3), giving complex 9 as a
white solid which was collected and air dried, 0.124 g (79%
yield) (Found: C, 57.39; H, 4.02; N, 3.28. Calc. for C40-
H35ClN2P2Pt: C, 57.45; H, 4.22; N, 3.35%). IR (ν/cmϪ1): 2233
(νNC) and 292 (νPtCl). 1H NMR (CDCl3, 213 K): δ 7.65–6.66 (m,
27H, Ph ϩ o-MeC6H4), 3.42, 3.33 (AB spin system, 2H, CH2Pt,
2JHH = 16.7 Hz), 2.59, 2.31 (2s, 6H, 2o-MeC6H4). 31P-{1H}
NMR (CDCl3, 213 K): δ 27.07 (s, NPPh3) and 19.00 (s, C–P,
1JPtP = 4743 Hz).
᎐
[Pd(dmba)(N᎐CN᎐PPh ) ][ClO ] 5. Complex 5 was syn-
thesized in the same way as 2: [Pd(dmba)(NCMe)2][ClO4]
᎐
᎐
3
2
4
᎐
(0.200 g, 0.474 mmol) was treated with Ph P᎐NC᎐N (0.286 g,
᎐
᎐
3
0.948 mmol) in CH2Cl2 to give 5 as a white solid, 0.307 g (69%
yield) (Found: C, 58.90; H, 4.18; N, 7.08. Calc. for C47-
H42ClN5O4P2Pd: C, 59.76; H, 4.48; N, 7.41%). IR (ν/cmϪ1):
2211 (νNC). Mass spectrum (FABϩ) [m/z, (%)]: 844 (60, Mϩ). 1H
NMR (CDCl3): δ 7.69–7.55 (m, 30H, Ph), 6.88–6.80 (m, 3H,
C6H4), 6.56 (m, 1H, C6H4), 3.79 (s, 2H, CH2) and 2.52 (s, 6H,
NMe2). 31P-{1H} NMR (CDCl3): δ 26.60 and 26.41 (2s, NPPh3).
Crystallography
Data collection. Crystals of complex 1 of adequate quality
for X-ray purposes were grown from slow diffusion of n-hexane
into a CH2Cl2 solution of 1 kept at Ϫ30 ЊC. An orange crystal
was mounted on a quartz fiber and covered with epoxy. Normal
procedures were used on a Enraf-Nonius CAD4 diffractometer
for the determination of the unit cell constants and for the
measurement of intensity data. After preliminary indexing and
transformation of the cell to a conventional setting, axial
photographs were taken of the a, b and c axes to verify the Laue
symmetry and lattice dimensions. Accurate unit cell dimensions
were determined from 25 centered reflections in the range
22.4 ≤ 2θ ≤ 31.2Њ. For intensity data collection, ω–2θ scans were
used with ∆ω = 1.12 ϩ 0.35tan θ. Three monitor reflections
were measured after 3 h of beam time, and the orientation of
the crystal was checked after every 400 intensity measurements.
Absorption corrections27 were based on azimuthal scans of
11 reflections, 4 of which had the Eulerian angle χ near 90Њ.
The other reflections used for this purpose had their bisecting-
position χ values distributed in the range 12–70Њ.
᎐
[Pd(dmba)(PPh )(N᎐CN᎐PPh )][ClO ] 6. To a solution of
᎐
᎐
3
3
4
[Pd(dmba)Cl(PPh3)] (0.100 g, 0.186 mmol) in THF (20 cm3),
AgClO4 (0.038 g, 0.19 mmol) was added. The resulting sus-
pension was stirred in the dark at room temperature for
20 min and then filtered. To the freshly obtained solution of
[Pd(dmba)(THF)(PPh3)][ClO4] (0.186 mmol) the iminophos-
᎐
phorane Ph P᎐NC᎐N (0.056 g, 0.19 mmol) was added and the
᎐
᎐
3
resulting solution stirred at room temperature for 15 min.
The solvent was evaporated to dryness and the oily residue
treated with Et2O (25 cm3), giving complex 6 as a white solid,
0.143 g (85% yield) (Found: C, 60.77; H, 4.29; N, 4.65. Calc.
for C46H42ClN3O4P2Pd: C, 61.07; H, 4.68; N, 4.64%). IR
(ν/cmϪ1): 2239 (νNC). Mass spectrum (FABϩ) [m/z (%)]: 804 (40,
Mϩ), 542 (45, [M Ϫ PPh3]ϩ) and 502 (100, [M Ϫ NCNPPh3]ϩ).
1H NMR (CDCl3): δ 7.74–7.29 (m, 30 H, Ph), 6.96 (d, 1H,
3
3
C6H4, JHH = 6.5), 6.80 (t, 1H, C6H4, JHH = 7.2), 6.34 (t, 1H,
C6H4, JHH = 7.2), 6.19 (t, 1H, C6H4, JHH ≈ 4JPH = 6.8), 4.00
(d, 2H, CH2, 4JPH = 1.9) and 2.50 (d, 6H, NMe2, 4JPH = 2.6 Hz).
31P-{1H} NMR (CDCl3): δ 42.11 (s, Pd–PPh3) and 27.69 (s,
NPPh3).
Structure solution and refinement. The structure was solved
and developed by Patterson and Fourier methods.28 All non-
hydrogen atoms were assigned anisotropic displacement
parameters. The hydrogen atoms of the aromatic carbon atoms
3
3
J. Chem. Soc., Dalton Trans., 1998, 3745–3750
3749

View Article Online
Table 2 Crystal data and structure refinement for complex 1
18, 3307 and refs. therein; P. Dapporto, G. Denti, G. Dolcetti
and G. Ghedini, J. Chem. Soc., Dalton Trans., 1983, 779; M. J.
Fernández, J. J. del Val, L. A. Oro, F. Palacios and J. Barluenga,
Polyhedron, 1987, 6, 1999; K. V. Katti and R. G. Cavell, Inorg.
Chem., 1989, 28, 413; Organometallics, 1989, 8, 2147; K. V. Katti,
R. J. Batchelor, F. W. B. Einstein and R. G. Cavell, Inorg. Chem.,
1990, 29, 808; P. Imhoff, C. J. Elsevier and C. H. Stam, Inorg. Chim.
Acta, 1990, 175, 209; P. Imhoff, R. van Asselt, C. J. Elsevier,
M. C. Zoutberg and C. H. Stam, Inorg. Chim. Acta, 1991, 184,
73; K. V. Katti and R. G. Cavell, Organometallics, 1991, 10, 539;
K. V. Katti, B. D. Santarsiero, A. A. Pinkerton and R. G. Cavell,
Inorg. Chem., 1993, 32, 5919; M. S. Balakrishna, B. D. Santarsiero
and R. C. Cavell, Inorg. Chem., 1994, 33, 3079; M. W. Avis, K Vrieze,
H. Kooijman, N. Veldman, A. Spek and C. J. Elsevier, Inorg. Chem.,
1995, 34, 4092; A. Mahieu, A. Igau, J. Jaud and J. P. Majoral,
Organometallics, 1995, 14, 944; W. K. Holley, G. E. Ryschkewitsch,
A. E. Koziol and G. J. Palenik, Inorg. Chim. Acta, 1995, 239,
171; J. Li, R. McDonald and R. G. Cavell, Organometallics, 1996,
15, 1033; M. W. Avis, K. Vrieze, J. M. Ernsting, C. J. Elsevier,
N. Veldman, A. Spek, K. V. Katti and C. L. Barnes, Organo-
metallics, 1996, 15, 2376; D. M. Hankin, A. A. Danopoulos,
G. Wilkinson, T. K. N. Sweet and M. B. Hursthouse, J. Chem. Soc.,
Dalton Trans., 1996, 4063; M. W. Avis, C. J. Elsevier, N. Veldman,
H. Kooijman and A. L. Spek, Inorg. Chem., 1996, 35, 1518; R. W.
Reed, B. Santarsiero and R. G. Cavell, Inorg. Chem., 1996, 35, 4292;
J. Li, A. A. Pinkerton, D. C. Finnen, M. Kummer, A. Martin,
F. Wiesemann and R. G. Cavell, Inorg. Chem., 1996, 35, 5684;
J. Vicente, M. T. Chicote, M. A. Beswick and M. C. Ramírez de
Arellano, Inorg. Chem., 1996, 35, 6592; M. W. Avis, M. E. van der
Boom, C. J. Elsevier, W. J. J. Smeets and A. L. Spek, J. Organomet
Chem., 1997, 527, 263; R.-Z. Ku, D.-Y. Chen, G.-H. Lee, S.-M. Peng
and S.-T. Liu, Angew. Chem., Int. Ed. Engl., 1997, 36, 2631.
11 S. Bittner, M. Pomerantz, Y. Assaf, P. Krief, S. Xi and M. K.
Witczak, J. Org. Chem., 1988, 53, 1.
Formula
Formula weight
C38H30Cl2N4P2Pd
781.90
Crystal system
Space group
Monoclinic
P21/n
a/Å
b/Å
c/Å
9.5452(7)
12.9923(5)
13.8799(7)
93.862(6)
1717.4(2)
2
β/Њ
V/Å3
Z
Dc/Mg mϪ3
1.512
0.823
µ/mmϪ1
Reflections collected
Unique reflections
Data/restraints/parameters
Goodness of fit
Final R1, wR2 indices [I > 2σ(I)]
T/K
3226
3022, Rint = 0.0399
3022/0/214
1.045
0.0349, 0.0937
150(2)
λ(Mo-Kα)/Å
0.71073
were constrained to idealized geometries and the isotropic dis-
placement parameter of each of these hydrogen atoms was
set to a value of 1.2 times the equivalent isotropic displace-
ment parameter of its parent carbon atom. The data-to-
parameter ratio in the final refinement was 14.1. The structure
2
was refined on Fo , and all reflections were used in the least-
squares calculations.29 The residuals and other pertinent
parameters are summarized in Table 2. Crystallographic
calculations were done on a Local Area VAXCluster computer
(VAX/VMS V5.5-2). Data reduction was done by the program
XCAD4B.30
12 G. K. Anderson and M. Lin, Inorg. Synth., 1990, 28, 60.
13 J. Forniés, A. Martín, R. Navarro, V. Sicilia and P. Villarroya,
Organometallics, 1996, 15, 1826.
CCDC reference number 186/1184.
14 W. A. Herrmann, C. Brossmer, K. Öfele, C.-P. Reisinger,
T. Priermeier, M. Beller and H. Fischer, Angew. Chem., Int. Ed.
Engl., 1995, 34, 1844; L. R. Falvello, J. Forniés, A. Martín,
R. Navarro, V. Sicilia and P. Villarroya, Inorg. Chem., 1997, 36, 6166.
15 P. Villarroya, Ph. D. Thesis, University of Zaragoza, 1998.
16 J. Forniés, R. Navarro and V. Sicilia, Polyhedron, 1988, 7, 2659.
17 A. J. Deeming, I. P. Rothwell, M. B. Hursthouse and L. New,
J. Chem. Soc., Dalton Trans., 1978, 1490.
See http://www.rsc.org/suppdata/dt/1998/3745/ for crystallo-
graphic files in .cif format.
Acknowledgements
We thank the Dirección General de Enseñanza Superior
(Spain) for financial support (Projects PB95-0792 and PB95-
0003-C02-01) and Professor J. Forniés for his invaluable
logistical support.
18 A. C. Cope and E. C. Friedrich, J. Am. Chem. Soc., 1968, 90,
909.
19 A. G. Orpen, L. Brammer, F. H. Allen, O. Kennard, D. G. Watson
and R. Taylor, J. Chem. Soc., Dalton Trans., 1989, S1.
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