Preparation and reactivity of penta- And tetracoordinate platinum(II) hydride complexes with P(OEt)3 and PPh(OEt)2 phosphite ligandst

Article abstract of DOI:10.1039/b505453b

The pentacoordinate [PtH{P(OEt)₃}₄]BF₄ (1) hydride complex was prepared by allowing the tetrakis(phosphite) Pt{P(OEt) ₃}₄ to react with HBF₄·Et₂O at -80°C. Depending on the nature of the acid used, however, the protonation of the related Pt{PPh(OEt)₂}₄ complex yielded the pentacoordinate [PtH{PPh(OEt)₂}₄]BF₄ (3) or the tetracoordinate [PtH{PPh(OEt)₂}₃]Y (4) [Y = BF ₄^- (a), CF₃SO₃^- (b), Cl^- (c)] derivatives. Neutral PtHClP₂ (7, 8) [P = P(OEt)₃, PPh(OEt)₂] hydride complexes were prepared by allowing PtCl₂P₂ to react with NaBH₄ in CH ₃CN. The tetrakis(phosphite) [Pt{P(OEt)₃}4](BF ₄)₂ (2) derivative was also synthesised and then characterised spectroscopically and by an X-ray crystal structure determination. Reactivity with aryldiazonium cations of all the hydrides was investigated and found to proceed only with the PtHClP₂ complex to yield the aryldiazene [PtCl(ArN=NH)P₂]BF₄ [P = PPh(OEt)₂] derivative. The hydrazine [PtCl(NH₂NH₂){PPh(OEt) ₂}₂]BPh₄ complex was also prepared by allowing PtHClP₂ to react first with AgCF₃SO₃ and then with hydrazine. The Royal Society of Chemistry 2005.

Full text of DOI:10.1039/b505453b

View Article Online / Journal Homepage / Table of Contents for this issue
F U L L P A P E R
Preparation and reactivity of penta- and tetracoordinate platinum(II)
hydride complexes with P(OEt)3 and PPh(OEt)2 phosphite ligands†
Gabriele Albertin,*a Stefano Antoniutti,a Christian Busato,a Jesu´s Castrob and
Soledad Garcia-Fonta´na
a Dipartimento di Chimica, Universita` Ca’ Foscari di Venezia, Dorsoduro, 2137, 30123,
Venezia, Italy. E-mail: albertin@unive.it; Fax: +39 041 234 8917
b Departamento de Qu´ımica Inorga´nica, Universidade de Vigo, Facultade de Qu´ımica,
Edificio de Ciencias Experimentais, 36310, Vigo (Galicia), Spain
Received 18th April 2005, Accepted 7th June 2005
First published as an Advance Article on the web 21st June 2005
The pentacoordinate [PtH{P(OEt)3}4]BF4 (1) hydride complex was prepared by allowing the tetrakis(phosphite)
Pt{P(OEt)3}4 to react with HBF4·Et2O at −80 ◦C. Depending on the nature of the acid used, however, the
protonation of the related Pt{PPh(OEt)2}4 complex yielded the pentacoordinate [PtH{PPh(OEt)2}4]BF4 (3) or the
tetracoordinate [PtH{PPh(OEt)2}3]Y (4) [Y = BF4 (a), CF3SO3 (b), Cl− (c)] derivatives. Neutral PtHClP2 (7, 8)
[P = P(OEt)3, PPh(OEt)2] hydride complexes were prepared by allowing PtCl2P2 to react with NaBH4 in CH3CN. The
tetrakis(phosphite) [Pt{P(OEt)3}4](BF4)2 (2) derivative was also synthesised and then characterised spectroscopically
and by an X-ray crystal structure determination. Reactivity with aryldiazonium cations of all the hydrides was
−
−
=
investigated and found to proceed only with the PtHClP2 complex to yield the aryldiazene [PtCl(ArN NH)P2]BF4
[P = PPh(OEt)2] derivative. The hydrazine [PtCl(NH2NH2){PPh(OEt)2}2]BPh4 complex was also prepared by
allowing PtHClP2 to react first with AgCF3SO3 and then with hydrazine.
Introduction
Results and discussion
The chemistry of transition-metal hydrides continues to attract
considerable interest and a large number of complexes have been
reported in recent years.1 The ancillary ligands used to stabilise
this class of compounds involve mainly p-acceptor species such
as carbonyl, tertiary phosphine and cyclopentadienyl. However,
the use of phosphite ligands in hydride chemistry has received
little attention1,2 when compared to tertiary phosphines, whose
fundamental systematic study began in the 1950s.3,4 These
results are somewhat surprising, in view of the easy synthesis
of phosphite ligands,5 their good p-acceptor properties,6 and
the relevance of some phosphite complexes as catalysts for
hydrocyanation,7 alkene oligomerisation8 and isomerisation,9
and hydroformylation10 reactions.
Preparation of the hydrides
Tetrakis(phosphite)platinum(0), Pt{P(OEt)3}4,16 reacts with
HBF4·Et2O to give the pentacoordinate [PtH{P(OEt)3}4]BF4
(1) hydride complex, which was separated as white micro-
crystals and characterised (Scheme 1). In the presence of an
excess of HBF4·Et2O or by standing in solution, however, the
hydride (1) slowly decomposes to give the tetrakis(phosphite)
[Pt{P(OEt)3}4](BF4)2 (2) derivative.
Scheme 1 P = P(OEt)3; Reagents and conditions: (i) excess HBF4·Et2O
We are interested in the chemistry of classical and non-
classical transition-metal hydrides and have reported the syn-
thesis and the reactivity of several complexes of manganese,11
iron,12 and cobalt13 triads of the MH(CO)nP5−n (M = Mn,
or by standing in solution.
Different Brønsted acids such as CF3SO3H and HCl also react
with Pt{P(OEt)3}4 to give, in each case, the pentacoordinate
hydride cation 1+.
On the other hand, the outcome of the protonation reaction
of the related Pt(0) complex Pt{PPh(OEt)2}4 containing the
PPh(OEt)2 ligand depends on the nature of the acid used, as
shown in Scheme 2.
2
Re; n = 1–3), ReH3P4, ReH5P3, MXHP4, [MX(g -H2)P4]+
(M = Fe, Ru, Os; X = H, Cl, Br, N3), and [CoH2P4]+ [P =
P(OEt)3, PPh(OEt)2, PPh2OEt] type containing phosphites as
supporting ligands. Now we have extended these studies to
platinum(II) with the aim of testing whether hydride complexes
with P(OEt)3 and PPh(OEt)2 ligands can be prepared for this
metal as well. A glance through the literature, in fact, has
shown that the Pt(II) complexes with phosphite ligands are rather
few14–17 and the only reported hydrides are PtHCl{P(OMe)3}2,
PtHCl{PMe(OMe)2}2,15a the unstable14d PtHCl{P(OC6H4OMe-
2)3}2 and the cationic [PtH{P(OR)3}4]BF4 (R = Me, Et)
derivatives.15b It is therefore desirable to increase the knowledge
of this class of compounds, and in this paper we report the
synthesis and some reactivity of new penta- and tetracoordi-
nate platinum(II) hydride complexes containing P(OEt)3 and
PPh(OEt)2 as supporting ligands.
With both CF3SO3H and HCl the reaction proceeds to give
exclusively the cationic tetracoordinate [PtH{PPh(OEt)2}3]+ (4)
hydride complex, which was isolated with both the Cl− (4c)
−
and CF3SO3 (4b) anions in good yield and characterised. The
oxidative addition of H+ to the Pt(0) complex Pt{PPh(OEt)2}4
was followed by the dissociation of one phosphonite ligand to
give the tetracoordinate hydride derivatives 4. The reaction of
Pt{PPh(OEt)2}4 with HBF4·Et2O, on the other hand, gave a
mixture of the pentacoordinate [PtH{PPh(OEt)2}4]+ (3a) and
the tetracoordinate [PtH{PPh(OEt)2}3]+ (4a) hydride complexes,
which were not separated. Experiments, by fractional crystalli-
sation, gave solids only enriched in the tetracoordinate species.
However, comparison of the spectroscopic data of the mixture
of 3a and 4a with those of compounds 4b, 4c and with those of
1 strongly supports the presence of both the tetracoordinate
4a and pentacoordinate 3a species in the solid obtained in
† Electronic supplementary information (ESI) available: Hydrogen bond
parameters (Table S1); packing of the molecules in the cell (Fig. S1). See
http://dx.doi.org/10.1039/b505453b
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
D a l t o n T r a n s . , 2 0 0 5 , 2 6 4 1 – 2 6 4 9
2 6 4 1
©

View Article Online
and also accounts for the instability of 1 observed in solution
which yields the [Pt{P(OEt)3}4]2+ (2) species.
[PtHP4]+ ꢀ [PtHP3]+ + P
(1)
Decreasing the sample temperature below −30 ◦C does not
cause changes in the 31P spectra, which appear as sharp singlets
until −80 ◦C. Further lowering of the temperature causes a
broadening of the signals, which approach two multiplets at the
lowest attained temperature (−100 ◦C). These results suggest
that complex 1 undergoes a second dynamic process below
−30 ◦C involving intramolecular phosphite exchange. This
exchange is fast even at −100 ◦C, but should show that two
sets of signals are present in the low exchange limit process, in
agreement with either a trigonal-bipyramidal (TBP) or a square-
pyramidal (SP) geometry.
Unfortunately, these two multiplets are too broad at this
temperature to give any information on the geometry. The
31P spectrum of the related [PtH{P(OMe)3}4]+ cation, however,
shows two multiplets at −120 ◦C which are in a 1 : 3 ratio and
are consistent with a TBP structure with the hydride in an axial
position.15b A similar TBP geometry probably applies also for
our [PtH{P(OEt)3}4]+ (1) cation. The 1H NMR spectra parallel
the behaviour of the 31P one showing, between −30 and −80 ◦C,
a sharp quintet for the hydride signals, which broaden below
−80 ◦C and approach two multiplets at −100 ◦C.
Scheme 2 P = PPh(OEt)2.
the reaction with HBF4·Et2O. It could also be noted that the
pentacoordinate compound 3a, once formed, is fairly stable to
the loss of one phosphine and the enrichment in tetracoordinate
species 4a was observed only after several hours in solution.
The results of the protonation of the tetrakis(phosphite)
PtP4 complexes [P = P(OEt)3, PPh(OEt)2] giving penta- and/or
tetracoordinate hydride complexes may be explained taking into
account the different properties of both the phosphites and the
anions of the acids used. The protonation of PtP4 should give
the pentacoordinate [PtHP4]+ cation as the first formed product,
which can lose one phosphite ligand to yield the tetracoordinate
[PtHP3]+ cation. While with P(OEt)3 the dissociation of one
phosphite is probably very slow, and the pentacoordinate 1
was obtained in each case, with PPh(OEt)2 the influence of
Several examples of five-coordinate platinum(II) monohydride
complexes are reported in the relevant literature14b,20,21 and
the X-ray measurements of [PtHP4]BPh4 (P4 = 1,1,4,7,10,10-
hexaphenyl-1,4,7,10-tetraphosphadecane) show
a distorted
trigonal-bipyramidal structure in its solid state.21b Variable-
temperature NMR measurements of some of the other pen-
tacoordinate hydrides were interpreted20,21 on the basis of
the existence in solution of a distorted TBP geometry and
these precedents further support the hypothesis that a similar
geometry is present in solution also for our complex 1.
the anions does result. The Cl− and CF3SO3 anions, which
−
have good coordinating properties, may be in competition with
phosphite, as suggested by one referee, for the fifth coordination
site and favour the tetracoordinate [PtHP3]+X− species (X = Cl−,
The NMR spectra of the tetracoordinate [PtH{PPh(OEt)2}3]+
(4b a◦nd 4c) cation indicate that also this complex is fluxional. At
−70 C, however, the 31P{ H} spectra appear as a well-resolved
−
1
CF3SO3). With the poorly coordinating BF4 anion, instead,
both the penta- and tetracoordination are present.
AB2 multiplet which can be simulated with the parameters
reported in Table 1 and this indicates the presence of two
magnetically equivalent phosphonites and different from the
third. At the same temperature, in the proton spectra, the hydride
signal appears at −4.50 ppm as a AB2X (X = H) multiplet due to
the coupling with the phosphorus nuclei of the phosphonites. A
simulation, using an AB2X model, allowed the NMR parameters
to be determined. On the basis of these data,22 a square-planar
geometry (I) of the type of Scheme 2 can reasonably be proposed
for the tetracoordinate hydride complexes 4b and 4c.
Good analytical data were obtained for the new hydride
complexes 1 and 4, which are white solids stable in air and
in solutions of polar organic solvents where they behave as 1 : 1
electrolytes.19 The infrared and NMR data, reported in Table 1,
support the formulation of the complexes. [PtH{P(OEt)3}4]BF4
has been previously obtained15b from the reaction of [Pt(1-r,4,5-
g-C8H13)(cod)]BF4 (cod = cyclooctadiene) with P(OEt)3 and,
although the hydride signal was not detected in the proton NMR
spectra, the value of the 31P signal is the same as that of 1, in
agreement with a correct formulation of the compounds.
The IR spectrum of [PtH{P(OEt)3}4]BF4 (1) shows a weak
band at 2110 cm−1 attributed to m(PtH) of the hydride ligand.
The 1H NMR spectra confirm the presence of the hydride and
also show that the complex is fluxional. In fact, the broad
signal that appears at room temperature near −13.6 ppm
resolves into a sharp quintet at −30 ◦C with JPH of 56 Hz
and JPtH of 535 Hz due to the coupling of the hydride with
four equivalent phosphite ligands. The variable-temperature
The 1H NMR spectra of the mixture containing 4a and
3a show, in the hydride region at −70 ◦C, an AB2X (X =
H) multiplet centred to the same value of chemical shift of
the tetracoordinate 4b and 4c (−4.50 ppm) and a quintet at
−13.35 ppm (JPH = 47 Hz, JPtH = 535 Hz). The multiplet at
−4.50 ppm is simulable with the same parameters of 4b and
4c and is attributed to the tetracoordinate [PtH{PPh(OEt)2}3]+
(4a) cation, while the quintet at −13.35 ppm is attributable to
the pentacoordinate tetrakis(phosphonite) [PtH{PPh(OEt)2}4]+
1
1
31P{ H} NMR spectra, however, seem to suggest that the
hydride derivative. The 31P{ H} NMR spectra (Table 1) confirm
[PtH{P(POEt)3}4]BF4 (1) complex undergoes two dynamic
processes. At room temperature, in fact, a broad signal near
95 ppm appears, in which the coupling with the platinum nucleus
is lost. Decreasing the sample temperature causes a spectra
the presence of the two species 3a and 4a showing, besides the
AB2 multiplet of the [PtHP3]+ cation 4a, a singlet at 113 ppm
(JPtP = 3818 Hz) attributable to the pentacoordinate [PtHP4]+
cationic derivative 3a. Variable-temperature NMR spectra also
show, as for the related complex 1, that the pentacoordinate
[PtH{PPh(OEt)2}4]+ undergoes two dynamic processes. Above
◦
change until, at −30 C, a sharp singlet appears at 94.1 ppm,
with a platinum–phosphorus coupling of 3950 Hz. The loss of
the platinum–phosphorus coupling in the temperature range
between +20 and −30 ◦C may be interpreted on the basis
of a dynamic process involving intermolecular exchange with
free P(OEt)3. A dissociative mechanism of the type of eqn. (1)
may be proposed, which agrees with previous reports in the
literature20a,b on related pentacoordinate Pt(II) hydride species,
◦
−30 C, an intermolecular exchange via a dissociative mecha-
nism of the type of eqn. (1) is probably present. Below −30 ◦C,
a sharp singlet with Pt–P coupling was observed, which began
◦
to broaden near −80 C and approached to two multiplets at
◦
−100 C suggesting that a TBP geometry may be present also
for 3a at a very low temperature.
2 6 4 2
D a l t o n T r a n s . , 2 0 0 5 , 2 6 4 1 – 2 6 4 9

View Article Online
Table 1 Selected IR and NMR spectroscopic data for platinum complexes
1
1H NMRb,c
(J/Hz)
d
31P{ H} NMRb,d
Compound
IRa
Assgnt.
Assgnt.
Spin system
A4
d (J/Hz)
[PtH{P(OEt)3}4]BF4 (1)
2110 m
m(PtH)
4.03 q
1.29 t
CH2
CH3
H−
CH2
CH3
H−
95 br
94.1 s
JPtP = 3950
e
A4
−13.6 s, br
3.90 qnte
1.24 t
−14.22 qnt
JPH = 56
JPtH = 535
[Pt{P(OEt)3}4](BF4)2 (2)
4.31 m
1.44 t
CH2
CH3
A4
88.0 s
JPtP = 3841
f
2058 m
m(PtH)
3.39 mf
1.24 t
−13.35 qnt
JPH = 47
JPtH = 535
3.96 mf
3.70 m
CH2
CH3
H−
A4
113 s
JPtP = 3818
f
AB2
dA 139.2
dB 128.4
JAB = 30
JPtPA = 2730
JPtPB = 3450
CH2
3.49 m
1.20 t
1.16 t
CH3
H−
AB2X spin system
(X = H)
dX −4.50
JAX = 207
JBX = 10.8
JPtH = 856
f
[PtH{PPh(OEt)2}3]CF3SO3 (4b)
2058 m
m(PtH)
3.86 mf
3.70 m
CH2
AB2
dA 139.0
dB 128.8
3.52 m
1.20 t
1.16 t
AB2X spin syst
(X = H)
dX −4.51
JAX = 207
JBX = 10.8
JPtH = 856
JAB = 30
CH3
H−
JPtPA = 2730
JPtPB = 3450
f
[PtH{PPh(OEt)2}3]Cl (4c)
2060 m
m(PtH)
3.86 mf
3.70 m
CH2
AB2
dA 139.2
dB 128.3
3.49 m
1.18 t
1.16 t
AB2X spin syst
(X = H)
dX − 4.50
JAX = 207
JBX = 10.8
JPtH = 856
JAB = 30
CH3
H−
JPtPA = 2730
JPtPB = 3450
trans-PtCl2{P(OEt)3}2 (5)
298 m
295 m
m(PtCl)
m(PtCl)
4.18 qnt
1.25 t
CH2
CH3
A2
A2
53.6 s
JPtP = 5694
trans-PtCl2{PPh(OEt)2}2 (6)
4.22 m
4.03 m
1.33 t
CH2
CH3
92.1 s
JPtP = 4828
trans-PtHCl{P(OEt)3}2 (7)
4.22 m
1.34 t
−16.54 t
JPH = 10
JPtH = 1248
CH2
CH3
H−
A2
A2
121.7 s
JPtP = 3785
trans-PtHCl{PPh(OEt)2}2 (8)
4.25 m
4.10 m
1.35 t
−16.24 t
JPH = 11
JPtH = 1273
CH2
137.4 s
JPtP = 3765
CH3
H−
D a l t o n T r a n s . , 2 0 0 5 , 2 6 4 1 – 2 6 4 9
2 6 4 3

View Article Online
Table 1 (Contd.)
1
1H NMRb,c
d (J/Hz)
31P{ H} NMRb,d
Compound
IRa
Assgnt.
Assgnt.
NH
Spin system
A2
d (J/Hz)
=
trans-[PtCl(C6H5N NH){PPh(OEt)2}2]BF4 (10a)
14.5 s, br
2JPtH = 84
4.20 m
110.0 s
JPtP = 3370
CH2
4.03 m
1.30 t
CH3
trans-[PtCl(C6H5N 15NH){PPh(OEt)2}2]BF4 (10a1)
14.54 d
NH
A2X
dA 110.0
=
1J15NH = 77
2JPtH = 84
4.22 m
(X = 15N)
JAX = 3.8
JPtP = 3370
CH2
4.05 m
1.30 t
14.2 s, br
2JPtH = 84
4.16 m
CH3
NH
=
trans-[PtCl(4-CH3C6H4N NH){PPh(OEt)2}2]BF4 (10b)
A2
110.2 s
JPtP = 3350
CH2
CH3
p-tol
CH3
phos
2.55 s
1.25 t
cis-[PtCl(NH2NH2){PPh(OEt)2}2]BPh4 (11)
3217 m
3163 m
m(NH)
5.18 brf
3.64 m
4.00 m
1.33 t
PtNH2
NH2
CH2
ABf
dA 84.7
dB 83.6
JAB = 21.4
JPtPA = 4462
JPtPB = 4765
CH3
1.18 t
a In KBr pellets. b In CD2Cl2 at 25 ◦C, unless otherwise noted. c Phenyl proton resonances omitted. d Positive shift downfield from 85% H3PO4. e At
−30 ◦C. f At −70 ◦C.
The easy synthesis of stable cationic platinum(II) hydride
complexes with P(OEt)3 and PPh(OEt)2 ligands prompted us
to extend the studies to the synthesis of related neutral hydride
complexes. The method we used for the successful synthesis is
shown in Scheme 3, and involves first the preparation of dichloro
PtCl2P2 (5, 6) complexes by treatment of dinitrile PtCl2(RCN)2
species with an excess of phosphite.
Chart 1
with two equivalent phosphite groups. In the temperature range
◦
between +20 and −80 C, the 31P{ H} NMR spectra appear as
a sharp singlet, in agreement with a trans geometry of type III
for the complexes. Values for 1JPtH of 1248 (7) and 1273 Hz (8) as
well as for JPtP of 3785 (7) and 3765 Hz (8) were also determined,
and fall within the range usually observed for tetracoordinate
Pt(II) hydrides.14,15
1
Reactivity studies involving the new hydrides 1, 3, 4 and 7,
8 with Brønsted acids were undertaken with the aim of testing
whether either the formation of dihydrogen complexes24 or the
oxidative addition of H+ could take place. The results show
that, while the cationic [PtHP4]+ and [PtHP3]+ complexes are
unreactive in the presence of an excess of HCl or HBF4·Et2O,
the neutral PtHCl{PPh(OEt)2}2 (8) hydride does react with an
excess of HCl to give the new hydride PtH2Cl2P2 (9) which is
rather unstable and was not isolated (Scheme 4).
Scheme 3 R = 4-CH3C6H4; P = P(OEt)3 (5, 7), PPh(OEt)2 (6, 8).
Reaction of the dichloro complexes 5, 6 with NaBH4 in
acetonitrile gives the final PtHClP2 (7, 8) hydride derivatives. The
use of CH3CN as a solvent, instead of the usual ethanol, is crucial
to the success of the synthesis. Otherwise, only traces of hydride
were observed. It can also be noted that the treatment of PtCl2P2
with NaBH4 does not give, under any conditions, formation of
dihydride PtH2P2 species, resulting the monohydride PtHClP2
the only product obtained.
The PtHCl{PPh(OEt)2}2 compound was isolated as a white
solid, while the related PtHCl{P(OEt)3}2 is an oily product at
room temperature. Both species 7 and 8 are stable in air and
in solutions of common organic solvents, where they behave as
non-electrolytes. The analytical and spectroscopic data (Table 1)
support the proposed formulation for both the chloro PtCl2P2
precursors and the PtHClP2 hydride derivatives. The IR spectra
of PtCl2P2 in the m(PtCl) region show only one band at 298 cm−1
for 5 and at 295 cm−1 for 6, suggesting that the two Cl− ligands
are in a mutually trans position. The 1H NMR spectra show the
signals of the phosphite ligands, while the 31P spectra between
+20 and −80 ◦C appear as a sharp singlet, in agreement with a
type II geometry (Chart 1).23
Scheme 4 P = PPh(OEt)2.
The reaction was followed by variable-temperature 1H and 31
P
NMR spectra and showed that the addition at −80 ◦C of HCl
to PtHCl{PPh(OEt)2}2 (8) caused the decrease of the hydride
resonance near −16 ppm and the appearance of a new broad
signal at −17.1 ppm (JPtH = 1196 Hz) attributed to the presence
of a new hydride species. T1 measurements of this signal gave a
T
1 min value of 240 ms, which indicates the presence of a classical
hydride ligand.25 Therefore, the protonation of PtHClP2 does
2
not take place at the H− giving a g -H2 complex of the type
The 1H NMR spectra of the hydride complexes PtHClP2 (7, 8)
show, in the high-field region, a well-resolved triplet at −16.57 (7)
and at −16.24 (8) ppm, attributed to the hydride ligand coupled
[PtCl(g -H2)P2]+, but seems to proceed through an oxidative
2
addition of HCl to the central metal to yield the PtH2Cl2P2 (9)
dihydride derivative. The progress of the protonation reaction
2 6 4 4
D a l t o n T r a n s . , 2 0 0 5 , 2 6 4 1 – 2 6 4 9

View Article Online
was monitored also by the 31P spectra and at −80 ◦C showed
the appearance of a new signal at 100.7 ppm (JPtP = 2170 Hz)
concurrent with the decrease of the singlet near 137 ppm of the
starting PtHClP2 complex, in agreement with the formation of
the new species 9. We also attempted to isolate this new hydride
in the solid state, but the solid obtained contained, beside some
decomposition products, the starting PtHClP2 (8) complex. The
addition of HCl is probably reversible and PtH2Cl2P2 can easily
lose HCl to give back the PtHClP2 derivative. We also studied the
protonation of 8 with HBF4·Et2O, but in this case several species
slowly formed and, among these, also the PtH2Cl2P2 derivative.
No compound was, however, isolated and characterised from
this reaction, owing to the instability at room temperature of the
former species and this prevents any proposal for the reaction
course.
onal crystal system, and the platinum atom of the cation and
the boron atom of the anion occupy special positions. In the
BF4 anion, the boron atom is on a four-fold axis (Wyckoff e
−
position). Two of the fluorine atoms are symmetry related and,
in addition, they are disordered over two positions, giving a
occupancy factor of 0.25 for each fluorine atom. For this reason,
the values obtained for distances and angles into the anion are
untrustworthy. Although the target of this study was the cation
[Pt{P(OEt)3}4]2+, some efforts were made to obtain better values
for the anion, but they were unsuccessful. The platinum atom
lies on a Wyckoff b position of the I4/m space group, on a
crystallographic 4/m symmetry site which relates only to one
of the four ligands. In the ligand, the phosphorus atom lies on
a symmetry plane, together with one of the oxygen atoms and
the a-carbon atom of an ethoxide group. The b-carbon of the
methyl group is disordered in two positions outside of the plane.
The other two ethoxide groups are also symmetry related.
The formation of a Pt(IV) hydride such as 9 instead of
2
a g -H2 complex in the protonation of the Pt(II) [PtHClP2]
˚
species is not surprising, in view of the known instability of
The four phosphorus atoms are at a distance of 2.3276(16) A
dihydrogen complexes with d8 configuration. Only recently some
from the platinum atom and, for symmetry reasons, the platinum
atom and the phosphorus atoms are in the same plane.
2
stable platinum(II) complexes with the g -H2 ligand have been
reported.24a,26 The behaviour of our PtHClP2 complex toward
the reaction with HCl is, therefore, in line with the properties
and the stability of dihydrogen derivatives.
The Pt–P distance is similar to that found in the closely
related square-planar tetracoordinated Pt(II) compounds [Pt-
{P(OMe)3}4](PF6)2 and [Pt(P(OH)(OMe)2)2(P(O)(OMe)2)2],17
16
27,28
˚
and slightly longer than 2.316 A.
Characterisation
of
[Pt{P(OEt)3}4](BF4)2
(2). The
white crystalline
It is noteworthy that the cation [Pt{P(OEt)3}4]2+ is less
distorted than the closely related [Pt{P(OMe)3}4]2+,21 in spite
of the bigger cone angle predicted for P(OEt)3.29
[Pt({P(OEt)3}4](BF4)2 (2) complex is
a
solid stable in air and in solutions of polar organic solvents
where it behaves as a 2 : 1 electrolyte.19 The complex was
characterised by analytical and spectroscopic data and by an
X-ray crystal structure determination. The NMR data also
indicate that in solution, as in a solid state, a square-planar
geometry is probably present. In the temperature range between
The presence of some CH · · · F hydrogen bond interactions,
˚
with distances C–F ranging from 2.15 to 2.35 A, between the
cation and the anion may contribute to the arrangement of ions
in the crystal lattice. A figure with the packing of the molecules
in the cell and the disorder occupancy of the fluorine atoms of
the anion can be found in the ESI.†
◦
+20 and −80 C, in fact, the 31P NMR spectrum appears as a
sharp singlet near 88 ppm (JPtP = 3841 Hz), in agreement with
the magnetic equivalence of the four phosphite ligands.
Reactions with aryldiazonium cations
Crystals of [Pt{P(OEt)3}4](BF4)2 were grown from an EtOH–
CH2Cl2 mixture, and the molecular structure of its cation
is shown in Fig. 1, drawn with thermal ellipsoids at 30%
probability level, together with the labelling scheme used.
[Pt{P(OEt)3}4](BF4)2 crystallises in the highly symmetric tetrag-
Our interest in the chemistry of “diazo” complexes30,31 prompted
us to explore the reactivity of the new platinum hydrides with
aryldiazonium cations with the aim of testing whether the
insertion reaction into the Pt–H bond can take place. The results
are reported in Scheme 5.
Scheme 5 Ar = C6H5 (a), 4-CH3C6H4 (b).
The hydrides PtHClP2 react with aryldiazonium cations to
+
=
give the aryldiazene [PtCl(ArN NH)P2] (10) cations which,
in the case of PPh(OEt)2, were isolated in the solid state and
characterised.
Crucial to the success of the synthesis are the use of an
equimolar amount of aryldiazonium salt and maintaining the
temperature near 5 ◦C. An excess of ArN2 or the use of
+
higher temperatures of reaction results in a high degree of
decomposition. At temperatures below 5 ◦C, however, the
reaction is rather slow and a long reaction time must be used.
Also the PtHCl{P(OEt)3}2 complex reacts with ArN2+ to give
the corresponding aryldiazene, but it is rather unstable even at
0 ◦C, and decomposes during the separation in its solid state.
Fig. 1 The cation [Pt{P(OEt)3}4]2+ drawn with 30% thermal el-
+
lipsoids probability. Only one of the disordered atoms is shown.
The easy reaction of PtHClP2 with ArN2 prompted us
◦
˚
Selected bond distances (A) and angles ( ), with standard deviations
in parentheses: Pt–P, 2.3276(16), P–O(1), 1.564(5); P–O(2), 1.565(4),
O(1)–C(11), 1.470(11); O(2)–C(21), 1.451(10); P–Pt–P1 90.0, P–Pt–P2
180.0; O(1)–P–O(2), 108.12(19). Symmetry transformations used to
generate equivalent atoms: 1 −z, −y, 1 − z; 2 −y, x, z.
to extend the studies to the cationic [PtHP3]+ and [PtHP4]+
derivatives. The results show that these cationic complexes do
not react with aryldiazonium cation and the starting hydride can
be recovered unchanged after 7 h of reaction (Scheme 5). This
D a l t o n T r a n s . , 2 0 0 5 , 2 6 4 1 – 2 6 4 9
2 6 4 5

View Article Online
unreactivity is not surprising due to the positive charge present in
the starting hydride complex, which makes the reaction between
two cationic species, in any case, very slow.
Aryldiazene complexes of Pt(II) were reported about
forty years ago,32 from the reaction of the triethylphosphine
complex PtHCl(PEt3)2 with aryldiazonium cations. Since this
pioneering result, however, no other data have been reported on
diazene complexes of this metal, whose “diazo” chemistry has
been scarcely developed32,33 compared to those of other transi-
tion metals.30 Its use as a precursor of the PtHCl{PPh(OEt)2}2
(8) hydride complex with PPh(OEt)2 phosphonite ligands allows
new aryldiazene complexes 10 to be prepared. This result also
highlights the important role of the PPh(OEt)2 group in the
stabilization of “diazo” complexes. As we have previously noted
with other central metals,31 the introduction of PPh(OEt)2 or
P(OEt)3 phosphites as ancillary ligands allows a rich and varied
“diazo” chemistry to be observed.
Scheme 7 P = PPh(OEt)2.
The platinum hydrazine complex 11 was isolated as a white
solid, stable in the air and in solutions of polar organic solvents,
where it behaves as a 1 : 1 electrolyte.19 The analytical and
spectroscopic data (Table 1) support the proposed formulation.
The IR spectra show two slightly broad medium-intensity
bands at 3217 and 3163 cm−1 attributed to m(NH) of the
hydrazine ligand. The presence of the NH2NH2 group, however,
is confirmed by the 1H NMR spectra, which show, besides
the signals of the phosphine and the BPh4 anion, two slightly
broadened multiplets at 5.18 and 3.64 ppm, due to the NH2
group of the hydrazine. Integration of the signals, decoupling
experiments, and the COSY spectrum support the proposed
attribution. Furthermore, the presence of two NH2 signals
=
The aryldiazene complexes [PtCl(ArN NH)P2]BF4 (10) were
isolated as yellow or orange solids, which are moderately stable
in a solution of polar organic solvents, where they behave as 1 : 1
electrolytes.19 The analytical and spectroscopic data (Table 1)
support the proposed formulation. The presence of the diazene
1
suggests also the presence of a g -coordination for the hydrazine
1
ligand is confirmed by the H NMR spectra which show the
ligand.
characteristic NH signal as a slightly broad singlet at 14.5 (10a)
In the temperature range between +20 and −80 ◦C the
1
and at 14.2 ppm (10b) with 2JPtH of 84 Hz.
31P{ H} NMR spectra appear as an AB multiplet which can
Further support for this attribution comes from the pro-
be easily simulated with the parameters reported in Table 1. On
the basis of these data a cis geometry like V can be reasonably
proposed for the hydrazine complex 11 (Chart 3).
ton NMR spectra of the labelled [PtCl(C6H5N 15NH)P2]BF4
=
(10a1) complex, which show the diazene signal as a doublet
1
15
at 14.54 ppm with
J
of 77 Hz, in agreement with the
NH
proposed◦formulation.34 In the temperature range between +20
and −80 C the 31P NMR spectra of the aryldiazene complexes
15 31
10a and 10b appear as a sharp singlet, while a doublet (J
=
N
P
3.8 Hz) can be observed in the spectrum of the labelled complex
10a1 due to the coupling of the phosphorus nuclei with the
15N diazenic nitrogen atom. On the basis of these data, a
trans geometry of type IV may reasonably be proposed for the
aryldiazene derivatives 10 (Chart 2).
Chart 3
Conclusions
In this report we describe the synthesis of new penta- and tetra-
coordinate cationic hydride complexes of Pt(II) of the [PtHP4]+
and [PtHP3]+ types containing the ethoxyphosphines P(OEt)3
and PPh(OEt)2 as ancillary ligands. The preparation and
the crystal structure determination of the tetrakis(phosphite)
[Pt{P(OEt)3}4](BF4)2 derivative are also reported. Neutral
Chart 2
=
PtHClP2 hydride complexes [P PPh(OEt)2 and P(OEt)3] can
be obtained from the dichloro PtCl2P2 precursors and their
reaction with aryldiazonium cation allowed the new aryl-
Reaction with H2 (1 atm) of the aryldiazene derivatives 10 was
extensively studied to test whether the formation of a hydrazine
complex32 can take place. At room temperature, no reduction
was observed (Scheme 6) and the starting complex could be
recovered unchanged after 10 h of reaction. Increasing the re-
action temperature or time produced only some decomposition
and no evidence of the formation of hydrazine was detected.
=
diazene [PtCl(ArN NH)P2]BPh4 complexes to be prepared.
The hydrazine [PtCl(NH2NH2){PPh(OEt)2}2]BPh4 derivative
was, instead, obtained using the dichloro PtCl2P2 as a precursor.
Experimental
General information
All synthetic work was carried out in an appropriate atmosphere
(Ar, N2) using standard Schlenk techniques or a vacuum
atmosphere dry-box. Once isolated, the complexes were found
to be relatively stable in air, but were stored in an inert
atmosphere at −25 ◦C. All solvents were dried over appropriate
drying agents, degassed on a vacuum line, and distilled into
vacuum-tight storage flasks. K2PtCl4 was prepared as previously
reported.35 Phosphonite PPh(OEt)2 was prepared by the method
of Rabinowitz and Pellon,36 while P(OEt)3 was an Aldrich
product purified by distillation under nitrogen. Diazonium salts
were prepared in the usual way.37 The labeled diazonium tetraflu-
Scheme 6 P = PPh(OEt)2.
Hydrazine complexes of Pt(II) of the [PtCl(NH2NH2)P2]BPh4
type (11), however, were obtained following a different method
(Scheme 7) involving the reaction of the PtCl2P2 complex with
AgCF3SO3. The resulting triflate complex PtCl(j1-OSO2CF3)P2
(not isolated) reacts with an excess of hydrazine to give the
[PtCl(NH2NH2)P2]+ cation, which was isolated as its BPh4 salt
and characterised.
The triflate complex PtCl(j1-OSO2CF3)P2 was also treated
with different hydrazines, such as CH3NHNH2 and PhNHNH2,
but in these cases only intractable mixtures of products were
obtained. It seems that only with NH2NH2 can a pure and
isolable complex be prepared.
15
oroborate [C6H5N≡ N]BF4 was prepared from Na15NO2 (99%
enriched, CIL) and aniline. Hydrazine, NH2NH2, was prepared
by decomposition of hydrazine cyanurate (Fluka) following
the reported method.38 Other reagents were purchased from
2 6 4 6
D a l t o n T r a n s . , 2 0 0 5 , 2 6 4 1 – 2 6 4 9

View Article Online
commercial sources in the highest available purity and used
as received. Infrared spectra were recorded on Nicolet Magna
750 FT-IR or Perkin-Elmer Spectrum One spectrophotometer.
NMR spectra (1H, 31P) were obtained on AC200 or AVANCE
300 Bruker spectrometers at temperatures between −90 and
+30 ◦C, unless otherwise noted. 1H spectra are referred to
for about 30 min. A white solid separated out, which was filtered
off, washed with Et2O and dried under vacuum. The solid
resulting was a mixture of the two hydrides 3a and 4a (ratio
about 2 : 3), which were not separated.
[PtH{PPh(OEt)2}3]CF3SO3 (4b).
A
slight excess of
1
internal tetramethylsilane; 31P{ H} chemical shifts are reported
CF3SO3H (0.11 mmol, 10 lL) was added to a solution of
Pt{PPh(OEt)2}4 (0.10 g, 0.10 mmol) in Et2O (5 mL) cooled to
−80 ◦C. The reaction mixture was brought to room temperature
and stirred for 30 min. A white, gummy product separated out,
which was collected and crystallised from CH2Cl2 (1 mL) and
diethyl ether (8 mL); yield ≥65%.
with respect to 85% H3PO4, with downfield shifts considered
positive. The COSY, HMQC and HMBC NMR experiments
were performed using their standard programs. The SwaN-
MR software package39 was used to treat NMR data. The
conductivity of 10−3 mol dm−3 solutions of the complexes in
CH3NO2 at 25 ◦C were measured with a Radiometer CDM 83.
C31H46F3O9P3PtS (939.77): calc. C 39.62, H 4.93, S 3.41; found
C 39.55, H 5.06, S 3.28%. KM = 80.2 X−1 mol−1 cm2.
[PtH{PPh(OEt)2}3]Cl (4c). A slight excess of HCl (1.1 mL
of 0.1 M solution in Et2O, 0.11 mmol) was added to a solution
of Pt{PPh(OEt)2}4 (0.10 g, 0.10 mmol) in Et2O (5 mL) cooled to
−80 ◦C. The reaction mixture was brought to room temperature
and stirred for 1 h. A white solid separated out, which was filtered
off and dried under vacuum; yield ≥70%. C30H46ClO6P3Pt
(826.15): calc. C 43.62, H 5.61, Cl 4.29; found C 43.55, H 5.60,
Cl 4.14%. KM = 89.6 X−1 mol−1 cm2.
Synthesis of complexes
The nitrile complex cis-PtCl2(4-CH3C6H4CN)2 was prepared
following the method previously reported.40
Pt{PPh(OEt)2}4 and Pt{P(OEt)3}4. The complexes were
prepared by a modification of the method used for the P(OEt)3
derivative.18 An excess of NaBH4 (2 g, 53 mmol) in ethanol
(35 mL) was added to a suspension of K2PtCl4 (2 mmol, 0.83 g)
in ethanol (25 mL) containing an excess of the appropriate
phosphine (10 mmol). The reaction mixture was refluxed for
4 h and then the solvent removed under reduced pressure. From
the red–brown solid obtained the complex was extracted with
five 10-mL p◦ortions of a mixture of benzene and petroleum
ether (50–60 C) (ratio 1 : 1). The extracts were evaporated to
dryness and the oil obtained treated with ethanol (15 mL). By
slow cooling of the resulting solution, white microcrystals of
the complex separated out, which were filtered off and dried
under vacuum; yield about 45% for Pt{PPh(OEt)2}4, 55% for
Pt{P(OEt)3}4.
trans-PtCl2{P(OEt)3}2 (5). An excess of P(OEt)3 (4 mmol,
0.66 mL) was added to a solution of cis-PtCl2(4-CH3C6H4CN)2
(0.5 g, 1 mmol) in 40 mL of CH2Cl2 and the reaction mixture was
stirred for 24 h. The solvent was removed under reduced pressure
to give an oil which was treated with ethanol (5 mL). By cooling
of the resulting solution, a gummy product was obtained, which
was separated and kept at −25 ◦C; yield ≥70%.
C12H30Cl2O6P2Pt (598.31): calc. C 24.09, H 5.05, Cl 11.85;
found C 23.78, H 5.16, Cl 11.77%.
trans-PtCl2{PPh(OEt)2}2 (6). An excess of PPh(OEt)2
(2 mmol, 0.4 mL) was added to a solution of cis-PtCl2(4-
CH3C6H4CN)2 (0.5 g, 1 mmol) in 40 mL of CH2Cl2 and the
reaction mixture was stirred for 24 h. The solvent was removed
under reduced pressure to give an oil which was triturated with
ethanol (5 mL). A white solid slowly separated out, which was
filtered off and crystallised from CH2Cl2 and ethanol; yield
≥90%.
Pt{PPh(OEt)2}4: C40H60O8P4Pt (987.89): calc. C 48.63, H 6.12;
found C 48.72, H 6.24%. 1H NMR (CD2Cl2), d: 7.30–7.00 m (20
H, Ph), 3.52 m, 3.27 m (16 H, CH2), 0.95 t (24 H, CH3). 31P{ H}
1
NMR (CD2Cl2), d: 137.2 s, JPtP = 4694.
Pt{P(OEt)3}4: C24H60O12P4Pt (859.72): calc. C 33.53, H 7.03;
1
found C 33.67, H 7.11%. H NMR (C6D6), d: 4.12 m (24 H,
CH2), 1.27 t (36 H, CH3). 31P{ H} NMR (C6D6), d: 126.6 s,
1
C20H30Cl2O4P2Pt (662.40): calc. C 36.27, H 4.56, Cl 10.70;
found C 36.19, H 4.60, Cl 10.49%.
JPtP = 5387.
[PtH{P(OEt)3}4]BF4 (1). Tetrafluoroboric acid (0.11 mmol,
16 lL of a 54% solution of HBF4 in Et2O) was added to a
solution of Pt{P(OEt)3}4 (86 mg, 0.10 mmol) in Et2O (5 mL)
trans-PtHCl{P(OEt)3}2 (7). To
a solution of trans-
PtCl2{P(OEt)3}2 (5) (185 mg, 0.31 mmol) in 5 mL of CH3CN
cooled to −196 ◦C was added, by cannula, a solution of NaBH4
(6 mg, 0.16 mmol) in CH3CN (10 mL). The reaction mixture
was brought to room temperature, stirred for 4 h, and then
the solvent removed under reduced pressure. The hydride was
extracted from the oil obtained with five 5-mL portions of a
mixture of benzene and petroleum ether (bp 50–60 ◦C) (ratio
1 : 1). The extracts were evaporated to dryness to give an oil
which was treated with benzene (1 mL) and diethyl ether (5 mL).
By cooling of the resulting solution to −25 ◦C, a pale-yellow
solid separated out, which was filtered off. At room temperature,
however, it turns into an oil; yield ≥65%.
◦
cooled to −80 C. The reaction mixture was brought to room
temperature and stirred for about 1 h. A white solid slowly
separated out which was filtered off, washed with Et2O and
dried under vacuum; yield ≥80%.
C24H61BF4O12P4Pt (947.53): calc. C 30.42, H 6.49; found C
30.62, H 6.53%. KM = 91.7 X−1 mol−1 cm2.
[Pt{P(OEt)3}4](BF4)2 (2).
A
solution of the [PtH-
{P(OEt)3}4]BF4 (1) compound (0.200 g, 0.21 mmol) in 10 mL of
CH2Cl2 was stirred at room temperature for 24 h. The solvent
was removed under reduced pressure to give an oil which was
treated with ethanol (2 mL) containing a slight excess of NaBF4
(0.25 mmol, 27 mg). The addition of diethyl ether (10 mL) to the
resulting solution caused the separation of a white solid which
was filtered off and crystallised from CH2Cl2 and diethyl ether;
yield ≥35%.
trans-PtHCl{PPh(OEt)2}2 (8). This complex was prepared
exactly like the related complex 7, but adding NaBH4 in 1 : 1
ratio to the trans-PtCl2{PPh(OEt)2}2 (6) precursor; yield ≥70%.
C20H31ClO4P2Pt (627.95): calc. C 38.25, H 4.98, Cl 5.65; found
C 38.41, H 4.94, Cl 5.80%.
C24H60B2F8O12P4Pt (1033.32): calc. C 27.90, H 5.85; found C
28.05, H 5.91%. KM = 177 X−1 mol−1 cm2.
=
trans-[PtCl(ArN NH){PPh(OEt)2}2]BF4 (10) (Ar = C6H5
a, 4-CH3C6H4 b). In a 25-mL three-necked round-bottomed
flask were placed equimolar amounts of PtHCl{PPh(OEt)2}2
(8) (200 mg, 0.32 mmol) and the appropriate aryldiazonium
[PtH{PPh(OEt)2}4]BF4 (3a) and [PtH{PPh(OEt)2}3]BF4 (4a).
A slight excess of HBF4·Et2O (0.11 mmol, 16 lL of a 54%
solution in Et2O) was added to a solution of Pt{PPh(OEt)2}4
(0.10 g, 0.10 mmol) in Et2O (5 mL) cooled to −80 ◦C. The
reaction mixture was brought to room temperature and stirred
−
[ArN≡N]+BF4 salt (0.32 mmol). The flask was cooled to
−196 ◦C and dichloromethane (10 mL) slowly added. The
reaction mixture was brought to 5 ◦C and stirred at this
temperature for 30 min. The solvent was removed under reduced
D a l t o n T r a n s . , 2 0 0 5 , 2 6 4 1 – 2 6 4 9
2 6 4 7

View Article Online
pressure to give a brown oil which was triturated with Et2O
(5 mL). A yellow–orange solid slowly separated out which was
filtered off and dried under vacuum; yield ≥70%.
Acknowledgements
The financial support of MIUR (Rome), PRIN 2004, is grate-
fully acknowledged. We thank Daniela Baldan for technical
assistance.
10a: C26H36BClF4N2O4P2Pt (819.88): calc. C 38.09, H 4.43, N
3.42, Cl 4.32; found C 37.86, H 4.47, N 3.55, Cl 4.15%. KM
=
90.5 X−1 mol−1 cm2.
10b: C27H38BClF4N2O4P2Pt (833.90): calc. C 38.89, H 4.59, N
References
3.36, Cl 4.25; found C 39.04, H 4.67, N 3.20, Cl 4.38%. KM
=
88.3 X−1 mol−1 cm2.
1 (a) A. Dedieu, Transition Metal Hydrides, Wiley-VCH, New York,
1992; (b) M. Peruzzini and R. Poli, Recent Advances in Hydride
Chemistry, Elsevier, Amsterdam, 2001.
2 (a) S. Sabo-Etienne and B. Chaudret, Chem. Rev., 1998, 98, 2077–
2091; (b) M. A. Esteruelas and L. A. Oro, Chem. Rev., 1998, 98,
577–588.
3 C. A. McAuliffe and W. Levason, Phosphine, Arsine and Stibine
Complexes of Transition Elements, Elsevier, Amsterdam, 1979.
4 (a) F. R. Hatley, in Comprehensive Organometallic Chemistry, ed.
G. Wilkinson, F. G. A. Stone and E. W. Abel, Pergamon, Oxford,
1982; (b) R. M. Roundhill, in Comprehensive Coordination Chem-
istry, ed. G. Wilkinson and J. A. McCleverty, Pergamon, Oxford,
1987.
5 W. Gerrard and H. R. Hudson, Organophosphorus Compounds, ed.
G. M. Kosolapoff and L. Maier, Wiley, New York, 1973.
6 (a) C. A. Tolman, Chem. Rev., 1977, 77, 313–348; (b) M. M. Rahman,
H.-Y. Liu, K. Eriks, A. Prock and W. P. Giering, Organometallics,
1989, 8, 1–7.
7 (a) C. A. Tolman, R. J. McKinney, W. C. Seidal, J. D. Druline
and W. R. Stevens, Adv. Catal., 1985, 33, 1; (b) R. J. McKinney
and D. C. Roe, J. Am. Chem. Soc., 1986, 108, 5167–5173; (c) J. E.
Ba¨ckvall and O. S. Andell, Organometallics, 1986, 5, 2350–2355;
(d) I. Mamalis, A. F. Noels, E. Puentes, R. Warin, P. Teyssie´, A. J.
Hubert, J. Grandjean, R. Hubin and D. Y. Waddan, J. Catal.,
1986, 102, 357; (e) M. Hodgson, D. Parker, R. J. Taylor and G.
Ferguson, Organometallics, 1988, 7, 1761–1766; (f) G. D. Fallon,
N. J. Fitzmaurice, W. R. Jackson and P. Perlmutter, J. Chem. Soc.,
Chem. Commun., 1985, 4–5.
trans-[PtCl(C6H5N 15NH){PPh(OEt)2}2]BF4 (10a1). This
=
complex was prepared in exactly the same way as the related un-
15
−
labelled compound 10a using [C6H5N≡ N]+BF4 as a reagent;
≥65%.
cis-[PtCl(NH2NH2){PPh(OEt)2}2]BPh4 (11). In a 25-mL
three-necked round-bottomed flask were placed equimolar
amounts of PtCl2{PPh(OEt)2}2 (6) (200 mg, 0.30 mmol) and
silver triflate AgCF3SO3 (77 mg, 0.30 mmol). Dichloromethane
(15 mL) was added into the flask and the reaction mixture
was stirred in the dark for 24 h. After filtration to remove the
AgCl, the solution was cooled to −196 ◦C and then an excess of
NH2NH2 (16 lL, 0.50 mmol) added. The reaction mixture was
brought to room temperature and stirred for 8 h. The solvent
was removed under reduced pressure to give an oil which was
treated with ethanol (3 mL) containing an excess of NaBPh4
(0.151 g, 0.44 mmol). A white solid slowly separated out which
was filtered off and crystallised from CH2Cl2 and ethanol; yield
≥70%.
C44H54BClN2O4P2Pt (978.22): calc. C 54.02, H 5.56, N 2.86,
Cl 3.62; found C 53.88, H 5.64, N 2.93, Cl 3.50%. KM = 53.9
X−1 mol−1 cm2.
8 (a) R. Taube and J. P. Gehrke, J. Organomet. Chem., 1987, 327,
419–427; (b) R. Taube and J. P. Gehrke, J. Organomet. Chem., 1987,
328, 393–401; (c) P. Benn, P. W. Jolly, R. Mynott, B. Raspel, G.
Schenker, K. P. Schick and G. Schroth, Organometallics, 1985, 4,
1945–1953; (d) R. Benn, B. Bu¨ssemeier, S. Holle, P. W. Jolly, R.
Mynott, I. Tkatchenko and G. Wilke, J. Organomet. Chem., 1985,
279, 63–86.
Protonation reactions
The protonation reactions of PtHClP2 complexes was studied
1
by H and 31P NMR measurements at variable temperatures
between −80 and +20 ◦C. A typical experiment involved the
addition of 30–40 mg of the appropriate hydride PtHClP2 in a
screw-cap NMR tube placed in a Vacuum Atmosphere dry-box.
CD2Cl2 (0.5 mL) was added, the solid was dissolved, and the
tube sealed by a screw cap. Incremental amounts of HCl (2 M
solution in Et2O) or HBF4·Et2O were added by microsyringe to
9 (a) R. B. King and S. Ikai, Inorg. Chem., 1979, 18, 949–954; (b) A.
Vassilian and J. C. Bailar, Jr., J. Catal., 1980, 62, 389–395.
10 (a) M. Cattelani, G. P. Chiusoli, G. Salerno and F. Dellatomasina,
J. Organomet. Chem., 1978, 146, C19–C22; (b) H. Takaya, M.
Yamakaua and R. Noyori, Bull. Chem. Soc. Jpn., 1982, 55, 582;
(c) H. Kurosawa and M. Emoto, Chem. Lett., 1985, 1161; (d) B.
◦
the NMR tube cooled to −80 C, which was then transferred
into the probe pre-cooled to −80 ◦C.
˚
Akermark, K. Zetterberg, S. Hansson, B. Krakenberger and A.
Vitagliano, J. Organomet. Chem., 1987, 335, 133–142.
Crystal structure determination of [Pt{P(OEt)3}4](BF4)2 (2)
11 (a) S. Garcia-Fonta´n, A. Marchi, L. Marvelli, R. Rossi, S. Antoniutti
and G. Albertin, J. Chem. Soc., Dalton Trans., 1996, 2779–2785; (b) G.
Albertin, S. Antoniutti, M. Bettiol, E. Bordignon and F. Busatto,
Organometallics, 1997, 16, 4959–4969; (c) G. Albertin, S. Antoniutti,
S. Garcia-Fonta´n, R. Carballo and F. Padoan, J. Chem. Soc., Dalton
Trans., 1998, 2071–2081; (d) G. Albertin, S. Antoniutti, A. Bacchi
and B. Fregolent, Eur. J. Inorg. Chem., 2004, 1922–1938.
The data collection was taken on a SIEMENS Smart CCD area-
detector diffractometer with graphite-monochromated Mo-Ka
radiation at −100 ◦C. Absorption correction was carried out
using SADABS.41
The structure of [Pt{P(OEt)3}4](BF4)2 was solved by direct
methods and refined by full-matrix least-squares based on
F2, using the SHELX-97 package program.42 Non-hydrogen
atoms were refined with anisotropic displacement parameters.
Hydrogen atoms were included in idealised positions and refined
using a constrained model. Atomic scattering factors and
anomalous dispersion corrections for all atoms were taken from
International Tables for X-ray Crystallography.43
12 (a) G. Albertin, S. Antoniutti, E. Bordignon and M. Pegoraro,
J. Chem. Soc., Dalton Trans., 2000, 3575–3584; (b) G. Albertin, S.
Antoniutti and M. Bortoluzzi, Inorg. Chem., 2004, 43, 1328–1335;
(c) G. Albertin, S. Antoniutti, A. Bacchi, C. D’Este and G. Pelizzi,
Inorg. Chem., 2004, 43, 1336–1349; (d) G. Albertin, S. Antoniutti and
S. Pizzol, J. Organomet. Chem., 2004, 689, 1639–1647.
13 (a) G. Albertin, S. Antoniutti, P. Amendola and E. Bordignon,
J. Chem. Soc., Dalton Trans., 1990, 2979–2984; (b) G. Albertin, S.
Antoniutti, E. Bordignon and F. Menegazzo, J. Chem. Soc., Dalton
Trans., 2000, 1181–1189.
14 (a) N. Ahmad, E. Ainscough, T. A. Janas and S. D. Robinson,
J. Chem. Soc., Dalton Trans., 1973, 1148–1150; (b) A. Albinati, P. S.
Pregosin and H. Ru¨egger, Inorg. Chem., 1984, 23, 3223–3229; (c) M. J.
Baker, K. N. Harrison, A. G. Orpen, P. G. Pringle and G. Shaw,
J. Chem. Soc., Dalton Trans., 1992, 2607–2614; (d) A. Crispini, K. N.
Harrison, A. G. Orpen, P. G. Pringle and J. R. Wheatcroft, J. Chem.
Soc., Dalton Trans., 1996, 1069–1076, and references therein.
15 (a) W. R. Meyer and L. M. Venanzi, Angew. Chem., Int. Ed., 1984,
23, 529–530; (b) M. Green, D. M. Grove, J. L. Spencer and F. G. A.
Stone, J. Chem. Soc., Dalton Trans., 1977, 2228–2234.
Crystal data and structure refinement for 2: empirical for-
mula, C24H60B2F8O12P4Pt; formula weight, 1033.31; tempera-
˚
ture, 173(2) K; wavelength, 0.71073 A; crystal system, tetrago-
nal; space group, I4/m; unit cell dimensions: a = 10.6494(16),
˚
b = 10.6494(16), c = 18.205(4) A; Z = 2; absorption coefficient,
3.639 mm−1; reflections collected, 6872; independent reflections,
1287 (Rint = 0.0500); reflections observed (>2r), 1282; final R
indices [I > 2r(I)], R1 = 0.0342, wR2 = 0.0838; R indices (all
data), R1 = 0.0344 wR2 = 0.0839.
CCDC reference number 269224.
See http://dx.doi.org/10.1039/b505453b for crystallographic
data in CIF or other electronic format.
16 Q.-B. Bao, S. J. Geib, A. L. Rheingold and T. B. Brill, Inorg. Chem.,
1987, 26, 3453–3458.
2 6 4 8
D a l t o n T r a n s . , 2 0 0 5 , 2 6 4 1 – 2 6 4 9

View Article Online
17 J. M. Solar, R. D. Rogers and W. R. Mason, Inorg. Chem., 1984, 23,
373–377.
18 (a) L. Malatesta and C. Cariello, J. Chem. Soc., 1958, 2323; (b) M.
Meier and F. Basolo, Inorg. Synth., 1972, 13, 112.
19 W. J. Geary, Coord. Chem. Rev., 1971, 7, 81–122.
20 (a) A. D. English, P. Meakin and J. P. Jesson, J. Am. Chem. Soc., 1976,
98, 422–436; (b) J. W. Ellis, K. N. Harrison, P. A. T. Hoye, A. G. Orpen,
P. G. Pringle and M. B. Smith, Inorg. Chem., 1992, 31, 3026–3033;
(c) A. Handler, P. Peringer and E. P. Mu¨ller, J. Organomet. Chem.,
1991, 412, 451–456; (d) V. De Felice, M. L. Ferrara, A. Panunzi and
F. Ruffo, J. Organomet. Chem., 1992, 439, C49–C51.
21 (a) P. Bru¨ggeller, Inorg. Chem., 1990, 29, 1742–1750; (b) W. Lin, S. R.
Wilson and G. S. Girolami, Inorg. Chem., 1997, 36, 2662–2669.
22 The NMR data of the complexes 4b and 4c are very similar, indicating
that the influence of the anion is negligible.
31 (a) G. Albertin, S. Antoniutti, A. Bacchi, E. Bordignon, G. Pelizzi
and P. Ugo, Inorg. Chem., 1996, 35, 6245–6253; (b) G. Albertin,
S. Antoniutti, A. Bacchi, E. Bordignon, F. Busatto and G. Pelizzi,
Inorg. Chem., 1997, 36, 1296–1305; (c) G. Albertin, S. Antoniutti, E.
Bordignon and S. Pattaro, J. Chem. Soc., Dalton Trans., 1997, 36,
4445–4453; (d) G. Albertin, S. Antoniutti, A. Bacchi, E. Bordignon,
P. M. Dolcetti and G. Pelizzi, J. Chem. Soc., Dalton Trans., 1997, 36,
4435–4444; (e) G. Albertin, S. Antoniutti, A. Bacchi, G. B. Ballico, E.
Bordignon, G. Pelizzi, M. Ranieri and P. Ugo, Inorg. Chem., 2000, 39,
3265–3279; (f) G. Albertin, S. Antoniutti, A. Bacchi, E. Bordignon,
M. T. Giorgi and G. Pelizzi, Angew. Chem., Int. Ed., 2002, 41, 2192–
2194; (g) G. Albertin, S. Antoniutti, A. Bacchi, M. Boato and G.
Pelizzi, J. Chem. Soc., Dalton Trans., 2002, 41, 3313–3320; (h) G.
Albertin, S. Antoniutti, M. Bortoluzzi, J. Castro-Fojo and S. Garcia-
Fonta´n, Inorg. Chem., 2004, 43, 4511–4522.
23 The related PtCl2{P(OPh)3}2 complex shows trans geometry (see ref.
32 (a) G. W. Parshall, J. Am. Chem. Soc., 1965, 87, 2133–2136; G. W.
Parshall, J. Am. Chem. Soc., 1967, 89, 1826; (b) S. D. Ittel and J. A.
Ibers, J. Am. Chem. Soc., 1974, 96, 4804–4809; (c) S. Krogsrud and
J. A. Ibers, Inorg. Chem., 1975, 14, 2298–2300.
33 (a) S. Cenini, R. Ugo and G. La Monica, J. Chem. Soc. A, 1971,
3441–3446; (b) U. Croatto, L. Toniolo, A. Immirzi and G. Bombieri,
J. Organomet. Chem., 1975, 102, C31–C33; (c) R. A. Henderson,
J. Chem. Soc., Dalton Trans., 1985, 2067–2077; (d) V. L. Frost and
R. A. Henderson, J. Chem. Soc., Dalton Trans., 1985, 2059–2065.
34 (a) K. R. Laing, S. D. Robinson and M. F. Uttley, J. Chem. Soc.,
Dalton Trans., 1973, 2713–2722; (b) J. A. Carrol, D. Sutton and Z.
Xiaoheng, J. Organomet. Chem., 1983, 244, 73–86.
14a).
24 (a) G. J. Kubas, Metal Dihydrogen and r-Bonded Complexes, Kluwer,
New York, 2001; (b) P. G. Jessop and R. H. Morris, Coord. Chem.
Rev., 1992, 121, 155–284; (c) D. M. Heinekey and W. J. Oldham, Jr.,
Chem. Rev., 1993, 93, 913–926; (d) R. H. Crabtree, Angew. Chem.,
Int. Ed. Engl., 1993, 32, 789–805.
25 (a) D. G. Hamilton and R. H. Crabtree, J. Am. Chem. Soc., 1988,
110, 4126–4136; (b) M. T. Bautista, K. A. Earl, P. A. Maltby, R. H.
Morris, C. T. Schweitzer and A. Sella, J. Am. Chem. Soc., 1988, 110,
7031–7036; (c) P. J. Desrosiers, L. Cai, Z. Lin, R. Richards and J.
Halpern, J. Am. Chem. Soc., 1991, 113, 4173–4184.
26 (a) D. G. Gusev, J. U. Notheis, J. R. Rambo, B. E. Hauger, O.
Eisenstein and K. G. Caulton, J. Am. Chem. Soc., 1994, 116, 7409–
7410; (b) M. D. Butts, B. L. Scott and G. J. Kubas, J. Am. Chem.
Soc., 1996, 118, 11831–11843; (c) A. Vigalok, Y. Ben-David and D.
Milstein, Organometallics, 1996, 15, 1839–1844.
27 Value estimated as an average of the Pt–P distance of 40 complexes.
They were retrieved from the Cambridge Crystallographic Data
Center data base on the basis of square-planar mononuclear Pt(II)
complexes with four P donor ligands (core PtP4).
35 G. B. Kauffman and L. A. Teter, Inorg. Synth., 1963, 7, 240–241.
36 R. Rabinowitz and J. Pellon, J. Org. Chem., 1961, 26, 4623–
4626.
37 A. I. Vogel, Practical Organic Chemistry, Longmans, Green and Co,
New York, 3rd edn., 1956.
38 E. Nachbaur and G. Leiseder, Monatsh. Chem., 1971, 102, 1718–
1723.
39 G. Balacco, J. Chem. Inf. Comput. Sci., 1994, 34, 1235–1241.
40 D. Fraccarollo, R. Bertani, M. Mozzon, U. Belluco and R. A.
Michelin, Inorg. Chim. Acta, 1992, 201, 15–22.
41 G. M. Sheldrick, SADABS. An empirical absorption correction
program for area detector data, University of Go¨ttingen, Germany,
1996.
28 T. Mizuta, A. Okano, T. Sasaki, H. Nakazawa and K. Miyoshi, Inorg.
Chem., 1997, 36, 200–203.
29 K. A. Bunten, L. Chen, A. L. Ferna´ndez and A. J. Poe¨, Coord. Chem.
Rev., 2002, 233–234, 41–51.
30 (a) For diazo complexes, see: D. Sutton, Chem. Rev., 1993, 93, 995–
1022; (b) H. Kisch and P. Holzmeier, Adv. Organomet. Chem., 1992,
34, 67–109; (c) H. Zollinger, Diazo Chemistry II, VCH, Weinheim,
Germany, 1995.
42 G. M. Sheldrick, SHELX-97. Program for the solution and refinement
of crystal structures, University of Go¨ttingen, Germany, 1997.
43 International Tables for X-ray Crystallography, Kluwer, Dordrecht,
1992, Vol. C.
D a l t o n T r a n s . , 2 0 0 5 , 2 6 4 1 – 2 6 4 9
2 6 4 9