The reactivity of the dinuclear halo-bridged cycloplatinated complex [Pt(μ-Cl){(κ2-P,C)P(OC6H4)(OPh) 2}]2 towards neutral ligands

Article abstract of DOI:10.1016/j.jorganchem.2013.02.031

The reactivity of (cis- + trans-)[Pt(μ-Cl){(κ²-P,C) P(OC₆H₄)(OPh)₂}]₂ (1) towards several ligands L (L = RCN, P(OMe)₃, DMSO, NHEt₂, py, CO, C₂H₄, C₈

Full text of DOI:10.1016/j.jorganchem.2013.02.031

Journal of Organometallic Chemistry 733 (2013) 9e14
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
The reactivity of the dinuclear halo-bridged cycloplatinated complex [Pt(m-Cl)
{(
k
2-P,C)P(OC6H4)(OPh)2}]2 towards neutral ligands
*
Daniela Belli Dell’Amico , Luca Labella, Fabio Marchetti, Simona Samaritani
Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, 56126 Pisa, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
The reactivity of (cis- þ trans-)[Pt(
m-Cl){(k
2-P,C)P(OC6H4)(OPh)2}]2 (1) towards several ligands L (L ¼ RCN,
Received 21 December 2012
Received in revised form
19 February 2013
P(OMe)3, DMSO, NHEt2, py, CO, C2H4, C8H16) has been studied. Ethylene and 1-octene do not react while
the other reactions proceed with cleavage of the halide bridge and formation of one or both geometrical
isomers of [PtCl{(
some cases equilibrium reactions (L ¼ RCN, DMSO, CO, py) were observed. The structures of [SP4-3]-[PtCl
{(
2-P,C)P(OC6H4)(OPh)2}(S)DMSO] ([SP4-3]-4) and [SP4-4]-[[PtCl{( 2-P,C)P(OC6H4)(OPh)2}py] ([SP4-4]-
6) are reported.
k
2-P,C)P(OC6H4)(OPh)2}L] (2e8) depending on the nature of the entering ligand. In
Accepted 27 February 2013
k
k
Keywords:
Orthometalated platinum complexes
Bridge-splitting equilibrium
Ó 2013 Elsevier B.V. All rights reserved.
p-Acid ligands
Dinuclear platinum complexes
1. Introduction
expected to afford the mononuclear complexes [PtCl{(
P(OC6H4)(OPh)2}L] through the chloride bridge splitting of Eq. (1).
k
2-P,C)
Cyclometalated complexes have been successfully used in
organic synthesis, catalysis and photochemistry, so their chemistry
has attracted a considerable attention as evidenced by the number of
reviews on this topic [1]. In this field, platinum group metals have
been largely studied, especially palladium derivatives. Ortho-
metallated arylphosphite derivatives of palladium and platinum of
h
nꢀ
ꢁ
oi
2L þ Ptð
m
ꢀ ClÞ k2 ꢀ P; C PðOC6H4ÞðOPhÞ2
/
2
h
nꢀ
ꢁ
o i
(1)
2 PtCl k2 ꢀ P; C PðOC6H4ÞðOPhÞ2
L
This paper reports the reactions of 1 (as the mixture of its
geometrical isomers) with C2H4, C8H16 (1-octene), RCN (R ¼ Me, Et),
CO, Me2SO (DMSO), P(OMe)3, C5H5N (py) and NHEt2.
A few reactions do not proceed, some are well displaced to the
right, and others are easily reversed equilibria.
the type [M(m-Cl){(k
2-P,C)P(OC6H3X)(OR)2}]2 are known since the
seventies of last century [2] and recently, they have been successfully
used as catalysts in several organic reactions [3]. Moreover, their
synthesis and spectroscopic features have been re-examined [4,5]
and the crystal and molecular structure of trans-[Pt(
P(OC6H4)(OPh)2}]2 (trans-1) has been reported [5]. Furthermore, the
reactivities of -chloro bridged dinuclear cyclometalated Pd(II)
complexes [Pd{(4-R)C6H3CH]NeC6H3e2,6-iPr2}(
m-Cl){(k
2-P,C)
2. Results and discussion
m
[Pt(m-Cl){(k
2-P,C)P(OC6H4)(OPh)2}]2,1, is usually obtained [2,4,5]
as the mixture of its geometrical isomers, cis and trans, the latter
prevailing in both chloroform and toluene.
m
-Cl)]2 (R ¼ H, OMe)
with mono-, bi- and tridentate ligands (aromatic N-heterocycles) [6]
and of the cycloplatinated dichloro-bridged complex of the 2-
tolylpyridine, [(2-Tolpy)Pt(m-Cl)]2, with monodentate ligands [7]
In the course of this work the reactions of 1 with a series of
neutral ligands have been studied. It was expected, as usual for
complexes with bridging halogens, that bridge cleavage occurred
with formation of one or both the geometrical isomers of the
have been recently studied. In view of the multidisciplinary inter-
est towards these derivatives and due to our previous experience in
the synthesis, characterization and reactivity of halo-bridged dinu-
clear platinum complexes [5,8], we have undertaken the study of the
reactions of 1 with several neutral ligands. Such reactions were
mononuclear complexes [PtCl{(k a
2-P,C)P(OC6H4)(OPh)2}L]. As
matter of fact, the complexes 2e7 were readily obtained (see
Scheme 1). Nevertheless, equilibrium reactions were observed not
only for the “weak” ligands RCN and DMSO, but also for the rela-
tively “robust” ligands CO and pyridine. Moreover, terminal alkenes
unexpectedly did not react.
* Corresponding author. Tel.: þ39 050 2219210; fax: þ39 050 2219246.
E-mail address: belli@dcci.unipi.it (D.B. Dell’Amico).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.02.031

10
D.B. Dell’Amico et al. / Journal of Organometallic Chemistry 733 (2013) 9e14
Scheme 1. Reactivity of 1 towards neutral ligands.
The reactions have been monitored by 31P and 195Pt NMR (see
Table 1).
A solution of 1 in MeCN at about 50 ꢁC yields [SP4-2]- and [SP4-
CO/alkylnitriles [9] and CO/alkenes [10] competition towards the
{PtCl2(CO)} fragment, showing that the coordination ability of
EtCN was similar to that of alkenes (1-octene, cyclohexene), ter-
minal alkene being slightly preferred. Surprisingly, no reaction
between 1 and C2H4 (PC H ¼ 1 atm, room temperature) in 1,2-
4]-2a. Similarly, the reaction of 1 with EtCN afforded the mixture of
the two geometrical isomers of 2b. Both 2a and 2b promptly release
the coordinated nitrile when the concentration of free nitrile de-
creases (Scheme 1) thus reverting to 1. 31P and 195Pt NMR data are
reported in Table 1. Although [SP4-2]-2b had been previously iso-
lated and structurally characterized in the solid state [5], its rapid
isomerisation in solution prevented the definition of its spectro-
scopic features, consequently the assignment of the signals to the
different isomers was not possible.
2
4
dichloroethane (1,2-DCE) was observed: 31P NMR spectra of the
mixture recorded after 1, 5, 12, 24 h showed no signals in addition
to those of the precursor. In order to force the reaction to the right
by increasing the alkene concentration without involving super-
atmospheric pressure, a liquid terminal alkene (1-octene) was
used. The reaction was carried out with a large excess of the
alkene with the addition of some 1,2-DCE to increase the solubility
of the metal complex.
In view of the reactivity with alkylnitrile reported above, we
expected 1 to react with ethylene with formation of [PtCl{(
k
2-P,C)
By monitoring the reaction by 31P NMR it was inferred that no
reaction occurred from room temperature to about 90 ꢁC. The {[PtCl
P(OC6H4)(OPh)2}(C2H4)], possibly through an equilibrium reac-
tion. Such a hypothesis stemmed from the results of studies on the
{(k
2-P,C)P(OC6H4)(OPh)2}]} fragment appears to prefer the chloro-
bridged dinuclear arrangement rather than the alkene coordination.
Unlike alkenes, CO reacted smoothly with 1. The resulting
product, 3, has already been reported in the literature and the
assignment of its geometry ([SP4-2], CO trans to C) was done on the
basis of the 31P- and 13C NMR parameters [4]. We have confirmed
that CO was absorbed by a solution of 1 in CH2Cl2 (PCO z 1 atm,
T ¼ 25 ꢁC) with the exclusive production of only one geometrical
isomer (Scheme 1), as inferred by monitoring the reaction via 31P
NMR [4]. In addition, 195Pt NMR spectra of the reaction mixture
were recorded immediately after the introduction of CO into the
reactor and regularly every 2 h for one day. Only one resonance was
observed (see Table 1). Consistently, the IR spectrum of the solution
showed only one CO stretching band at 2125 cme1. Thus, under CO
the system appears to contain only the complex [SP4-2]-3. How-
ever, it was observed that the evaporation of the solution at room
temperature under reduced pressure caused the release of CO with
formation of 1, thus proving that we were dealing with an easily
displaceable equilibrium reaction. In the platinum(II) chlor-
ocarbonyl chemistry, spontaneous dimerization in mild conditions
by release of CO and formation of chloride bridges are rare [11].
The reaction of 1 with neat DMSO rapidly led to a solution
containing only one isomer of the mononuclear product 4 (Scheme
Table 1
31P and 195Pt NMR data for 1 and [PtCl{(
k
2-P,C)P(OC6H4)(OPh)2}L].
195Pt 1JPePt/Hz Solvent
L
31P
/ppm
Ref.
d
d/ppm
trans-1
cis-1
2a
88.4
85.8
ꢀ4144 7760
ꢀ4038 7860
6700
CDCl3
CDCl3
MeCN
[4]
[4]
MeCN
EtCN
CO
100.5
94.6
101.2
95.8
This
work
This
work
This
work
This
work
This
work
This
work
[SP4-4]þ[SP4-2]
7469
2b
6750
6806
ꢀ4518 5949
MeNO2
CH2Cl2
DMSO
CDCl3
[SP4-4]þ[SP4-2]
[SP4-2]-3a
105.6
[SP4-3]-4
[SP4-3]-5a
DMSO
99.6
ꢀ4331 6681
P(OMe)3 128.8b ꢀ4547 3168b
105.7
95.4
6398
ꢀ4197 6602
ꢀ4128 7063
6501
[SP4-4]-6
[SP4-2]-6
7
[SP4-4]þ[SP4-2]
py
CDCl3
95.5
NHEt2
102.0
92.0
1,2-DCE This
work
7276
a
See also Ref. [4].
b
Coordinated P(OMe)3 (2JPeP 32 Hz).

D.B. Dell’Amico et al. / Journal of Organometallic Chemistry 733 (2013) 9e14
11
1), as revealed by 31P and 195Pt NMR spectra of the reaction mixture
Table 2
ꢁ
ꢀ
Selected bond lengths (A) and angles ( ) for [SP4-3]-4.
(see Table 1) recorded shortly after the addition. After 24 h, the
spectra were unchanged, showing that no isomerisation had
occurred. The product was recovered by evaporating the solvent
under vacuum at room temperature. The IR spectrum of the
product in the solid state showed a band at 1119 cmꢀ1, due to the SO
stretching vibration of coordinated DMSO. The position of this band
suggests that the sulfoxide is S-coordinated: in fact free DMSO
absorbs at 1050 cme1, while the band shifts to lower or higher
wavenumbers for the O- or S-coordinated ligand, respectively [12].
13C- and 1H NMR spectra confirmed this hypothesis. The resonances
of the sulphur-bonded carbon atom in dialkylsulfoxides are up- or
downfield shifted in the complexes with respect to the free ligand
when O- or S-coordination is adopted, respectively [13]. The 13C
NMR spectrum of our compound in CDCl3 showed the methyl
signal at 43.3 ppm, to be compared with 41.0 ppm of the free ligand
in the same solvent, which suggests S-coordination. Moreover, the
1H NMR spectrum of the complex (in CDCl3) showed a relatively
high coupling constant of the methyl protons with the active
Pt(1)eC(4)
Pt(1)eP(1)
C(4)ePt(1)eCl(1)
C(4)ePt(1)eP(1)
P(1)ePt(1)eCl(1)
2.041(3)
2.1578(9)
93.25(10)
81.88(10)
174.39(4)
Pt(1)eS(1)
Pt(1)eCl(1)
P(1)ePt(1)eS(1)
S(1)ePt(1)eCl(1)
C(4)ePt(1)eS(1)
2.3260(9)
2.3427(9)
96.38(3)
88.43(4)
177.94(10)
The platinum coordination is square planar with a maximum
deviation of 0.03 A. The orthometalation of a phenyl group of the
ꢀ
triphenylphosphite ligand produces a planar OPPtC2 five membered
ring. This feature is also observed in the other platinum orthome-
talated triarylphosphite structurally characterized [5,14]. Within the
five membered ring the greater lengths of the PteP and PteC bonds
with respect to the CeC and CeO ones causes a decrease of P(1)e
Pt(1)eC(4) angle from the ideal value for a pentagon (108ꢁ) to
about 82ꢁ. The narrowing of this angle is the more relevant devia-
tion from the ideal square coordination around the metal. While Pte
Cl, PteC and PteS bond lengths are as expected, PteP bond is
3
platinum nucleus (9.5 Hz), consistent with a JPteH of a S-coordi-
nated sulfoxide rather than with a 4JPteH of a O-coordinated ligand.
The NMR spectra of chloroform solution of 4 showed, besides the
product signals, additional resonances due to 1 and to free DMSO,
suggesting that the ligand is rather easily released. A confirm came
from the reaction of 1 with 2 equivalents of DMSO in CDCl3: NMR
spectra of the reaction mixture showed the presence of 1, 4 and free
DMSO, with about 20% of platinum in the form of 1. Moreover,
starting from chloroform solution of 4, complete conversion to 1
was obtained by operating under vacuum at about 90 ꢁC.
slightly shorter than the mean value, 2.23 A, normally found in
similar compounds, as results from a rapid survey on the CCDC
database [15].
ꢀ
The reaction of 1 with P(OMe)3 has already been reported and
the assignment of the product geometry, [SP4-2], i.e. with P(OMe)3
trans to C, has been proposed on the basis of NMR data [4].
We have confirmed that by reacting 1 with the stoichiometric
amount of P(OMe)3 in CDCl3 only one isomer of 5 is obtained,
corresponding to that reported in the literature [4], as inferred by
comparison of the NMR data (see Table 1). To compare this reaction
with the others discussed so far, we controlled the possibility to
convert 5 to 1 by operating under vacuum at relatively high tem-
perature (up to 120 ꢁC, a temperature higher than the b.p. of
P(OMe)3). In the course of these experiments 5 remained un-
changed and no formation of 1 was noticed. At variance with the
other mononuclear complexes 2e4, the trimetylphosphite complex
[SP4-2]-5 appears to be stable with respect to ligand release, in
spite of the strong trans-effect of the aryl group [16].
X-Ray diffraction studies on single crystals of 4 confirmed that
the complex contained S-coordinated DMSO and allowed to define
the geometry around platinum as [SP4-3], i.e. with S trans to C (see
Fig. 1). Selected bond lengths and angles are reported in Table 2.
By monitoring the reaction of 1 with the stoichiometric
amount of pyridine (in CDCl3) via 31P NMR, the disappearance of
the precursor was observed and the mixture of the two geomet-
rical isomers of 6 [Scheme 1] was obtained. The molar ratio be-
tween the two isomers was constant with time, thus preventing
the possibility to detect the kinetic product. The reaction can be
reversed by operating under vacuum at relatively high tempera-
tures (T ¼ 60e90 ꢁC).
Single crystals of [SP4-2]-6 separated out from 1,2-DCE/pentane
(v/v ¼ 1) and the molecular and crystal structure of the complex
was studied by X-Ray diffraction methods. Fig. 2 shows a view of
the molecular structure and selected bond lengths and angles are
reported in Table 3.
A comparison with the molecular structure of [SP4-3]-4 shows
that the substitution of the DMSO with the pyridine leaves unal-
tered the coordination geometry around the metal. Due to the
different encumbrance of the coordinated pyridine with respect to
DMSO the C6H5 groups of the phosphite are differently oriented.
The assignment of the NMR signal to the two geometrical iso-
mers of 6 was achieved by recording a 31P NMR spectrum of a
freshly prepared solution (CDCl3) of [SP4-2]-6: the spectrum
showed the resonance at 96.0 ppm (1JPePt ¼ 7063 Hz) only. After a
few hours, the equilibrium mixture of the two isomers was present.
When 1 was treated with the stoichiometric amount of NHEt2 in
1,2-DCE as solvent, a 31P NMR spectrum, recorded 30 min after
the amine addition, showed the absence of the signals due to the
precursor and the presence of two resonances attributable to the
Fig. 1. View of the molecular structure [SP4-3]-4. Thermal ellipsoids are at 30%
probability.

12
D.B. Dell’Amico et al. / Journal of Organometallic Chemistry 733 (2013) 9e14
On the other hand, the complexes with the other ligands, 2
(L ¼ RCN), 3 (L ¼ CO), 4 (L ¼ DMSO), 6 (L ¼ Py) were found to revert
to 1, their stability depending on the nature of L increasing in the
order: RCN < CO < DMSO < py.
It is known that alkylnitriles and dialkylsulphoxide are easily
displaceable ligands, commonly used for this reason also in catal-
ysis [17]. Although CO and pyridine are not usually so easily dis-
placed, we have to conclude that their bond to platinum is not
sufficiently strong to prevent (when the free ligand concentration
decreases) the shift to the left side of the entropically disfavoured
equilibrium 1. On the other hand, the more basic NHEt2 [18] and the
trimethylphosphite produce more stable complexes, so that reac-
tion 1 becomes irreversible.
3. Experimental section
3.1. General comments
All manipulations were performed under a dinitrogen atmo-
sphere, if not otherwise stated. Solvents and liquid reagents were
dried according to reported procedures [19].
1H-, 13C-, 31P and 195Pt NMR spectra were recorded with a Bruker
“Avance DRX 400” spectrometer, in CDCl3 solution if not otherwise
stated. Chemical shifts were measured in ppm (d) from TMS by re-
Fig. 2. View of the molecular structure of [SP4-2]-6. Thermal ellipsoids are at 30%
probability. The less populated position of the disordered phenyl group has been
omitted for clarity.
sidual solvent peaks for 1H and 13C, from aqueous (D2O) H3PO4 (85%)
for 31P and from aqueous (D2O) hexachloroplatinic acid for 195Pt. A
sealed capillary containing C6D6 was introduced in the NMR tube to
lock the spectrometer when non-deuterated solvents were used.
FTIR spectra in the solid state were recorded with a PerkineElmer
“Spectrum One” spectrometer, with the ATR technique. FTIR
spectra in solution were recorded with a PerkineElmer “Spectrum
100” spectrometer. Intensity of bands: w ¼ weak, m ¼ medium,
s ¼ strong. A 0.1 mm cell supplied with CaF2 windows was used.
Elemental analyses (C, H, N) were performed at Dipartimento di
Scienze e Tecnologie Chimiche, Università di Udine. The products
undergoing conversion to 1 under vacuum were not analysed.
two geometrical isomers of 7 (Scheme 1): the ratio between the
main signal (101.9 ppm) and the other (92.1 ppm) was 93:7. After
24 h, a new 31P NMR spectrum presented the same signals but the
ratio was changed to 40:60. Therefore, the kinetic product of the
reaction, associated to the resonance at 101.9 ppm, slowly iso-
merises until the equilibrium mixture is obtained. A strong trans-
effect is associated with both triarylphosphite and aryl ligands [13];
thus, it is not easy to predict the geometry of the kinetic product by
exploiting this effect. Nevertheless, we suggest that the kinetic
product is the [SP4-2] isomer where NHEt2 is trans to C. Our pro-
posal is supported by the finding that the reactions of 1 with CO,
DMSO, P(OMe)3 (Scheme 1) afford the isomer with L trans to C
(products 3, 4, 5, respectively), as observed immediately after the
reagent mixing, corresponding to the fast formation of the ther-
modynamic product.
In summary, the reactions of 1 with the carbon-based ligands
CO, C2H4, 1-octene, the group 15 ligands MeCN, EtCN, Py, NHEt2,
P(OMe)3 and with DMSO have been examined. For each ligand
except alkenes, chloro-bridge cleavage was observed. Of the two
possible geometrical isomers both were obtained with the
nitrogen-based ligands, while only the isomers with L trans to C
were observed with the ligands CO, P(OMe)3 and the S-ligated
{Pt(
m
k
-Cl)[(k2-P,C)P(OC6H4)(OC6H5)2]}2, 1, [PtCl{( 2-P,C)P(OC6H4)(O-
Ph)2}(EtCN)], 2b, [PtCl{(
k
2-P,C)P(OC6H4)(OPh)2}(CO)], 3, and [PtCl{(k2
-
P,C)P(OC6H4)(OPh)2}(P(OMe)3)], 5, were prepared according to the
literature [4,5].
3.2. Reaction of 1 with alkenes (ethylene and 1-octene)
In a 50 mL reactor, 193.0 mg (1.8 ꢂ 10e1 mmol) of 1 were treated
with C2H4 (P ¼ 1 atm) in 1,2-DCE. No gas uptake was observed. A 31
P
NMR spectrum of the yellow solution recorded after 24 h stirring
showed only the signals due to 1. From the reaction mixture 1 was
recovered unchanged.
In a 25 mL reactor 152.9 mg (1.4 ꢂ 10e1 mmol) of 1 were sus-
pended in a mixture of 1-octene (7.0 mL) and 1,2-DCE (2.0 mL). The
suspension was stirred at room temperature (48 h). A 31P NMR
spectrum showed the signals due to 1 only. The suspension, heated
at 90 ꢁC, turned into a yellow solution. A 31P NMR spectrum of the
solution showed the signals due to 1 only.
DMSO. It is reasonable to suggest that ligands with a strong
character prefer the position trans to the good -donor C- rather
than to the -acid P coordination site of the orthometalated
p-acid
s
p
phosphite. Moreover, only the products obtained with NHEt2, 7, and
P(OMe)3, 5, turned out to be stable in solution in the absence of the
free ligand even in vacuo at relatively high temperature (30e90 ꢁC).
3.3. Formation of [PtCl{(k
2-P,C)P(OC6H4)(OPh)2}(DMSO)], 4
In a 50 mL Schlenk tube, 5 mL of DMSO were added to 92.4 mg
(8.5 ꢂ 10e2 mmol) of 1. A yellow solution was obtained. NMR
spectra were recorded on the reaction mixture. 31P NMR: 99.6 (1JPe
Table 3
ꢁ
ꢀ
Selected bond lengths (A) and angles ( ) for [SP4-2]-6.
¼ 6681 Hz) ppm; 195Pt NMR: e4331 (d, 1JPteP ¼ 6681 Hz) ppm.
Pt
Pt(1)eC(7)
Pt(1)eP(1)
C(7)ePt(1)eCl(1)
C(7)ePt(1)eP(1)
P(1)ePt(1)eCl(1)
2.018(3)
2.1424(8)
93.85(8)
81.68(8)
175.54(3)
Pt(1)eN(1)
Pt(1)eCl(1)
P(1)ePt(1)eN(1)
N(1)ePt(1)eCl(1)
C(7)ePt(1)eN(1)
2.131(2)
2.3411(7)
97.18(7)
87.27(7)
176.60(10)
The solution was evaporated to dryness: the pale yellow solid
residue was stored in vials under dinitrogen (about 84% yield). The
product was contaminated by 1. 31P NMR (CDCl3): 98.4 (1JPe
¼ 6629 Hz) ppm due to 4, 88.4 (1JPePt ¼ 7760 Hz) and 85.8
Pt

D.B. Dell’Amico et al. / Journal of Organometallic Chemistry 733 (2013) 9e14
13
2
(1JPePt ¼ 7860 Hz) ppm due to 1; 1H NMR (CDCl3): 8.05 (d, 1H, Pte
NeCH2eCH3, JHeH ¼ 7.0 Hz) ppm; 31P NMR (CDCl3): 92.1 (1JPe
2
3
CeCH, JHeH ¼ 7.4 Hz, JHePt ¼ 52.2 Hz), 7.40e6.89 (m, 13H, aro-
matic protons), 2.95 (s, 6H, coordinated DMSO CH3, 3JHePt ¼ 9.5 Hz),
2.66 (s, free DMSO CH3, about 15% with respect to the coordinated
DMSO signal), and minor signals due to 1; 13C NMR (CDCl3): 158.0,
150.2, 135.8, 129.9, 128.7, 126.1, 123.0, 121.4, 111.2 (aromatic nuclei),
43.3 (coordinated DMSO), 41.0 (free DMSO) and minor signals
due to 1.
¼ 7292 Hz) ppm. IR (ATR, selected bands): 3210 m, 1587 m,
Pt
1486 s,1435 m,1380 m,1209 m,1163 ms,1110 m,1062 m,1026 s, 948
ms, 926 ms, 889 ms, 806 s, 764 ms, 751 ms, 687 m cme1
.
3.6. Attempted thermal conversion of [PtCl{(k
2-P,C)P(OC6H4)(OPh)2}
(P(OMe)3)], 5, to 1
2
3
1H NMR (d6-DMSO): 7.74 (d, 1H, PteCeCH, JHeH ¼ 7.7 Hz, JHe
A solution of [PtCl{(k
2-P,C)P(OC6H4)(OPh)2}(P(OMe3))], 5, was
¼ 47.8 Hz), 7.44e6.89 (m, 13H). 13C NMR (d6-DMSO): 158.3,
Pt
prepared by reacting 1 with P(OMe)3 (molar ratio 1:2) in CDCl3. The
solution was treated under vacuum at 60 ꢁC. The colourless residue
was dissolved in CDCl3 and the 31P NMR spectrum of the solution
149.8, 136.0 (2JCeP ¼ 89 Hz), 135.9, 130.9, 129.1, 127.0, 123.0, 121.5,
111.6. IR (ATR, selected bands): 1585 m, 1483 s, 1174 ms, 1155 s,
1119 s, 1022 s, 938 ms, 900 ms, 803 s, 786 s, 767 s, 748 f, 726 m,
showed the signals to [PtCl{(k
2-P,C)P(OC6H4)(OPh)2}(P(OMe)3)]
686 s cme1
.
only. The same result was obtained by analogous treatments car-
ried out at 90 ꢁC and at 120 ꢁC.
When chloroform solutions of 4 were evaporated to dryness at
about 60 ꢁC under stirring, the 31P NMR recorded on CDCl3 solu-
tions of the residue showed extensive or even complete conversion
of 4 to 1.
3.7. Conversion of [PtCl{(k
2-P,C)P(OC6H4)(OPh)2}(CO)], 3, to 1
A solution of 3 obtained by reacting 1 with CO (P ¼ 1 atm) in a
1:1 mixture of CH2Cl2 and heptane was evaporated to dryness
under vacuum at room temperature. The colourless residue was
dissolved in CDCl3 and the 31P NMR of the resulting solution
showed the signals attributed to 1 only.
3.4. Preparation of [PtCl{(k
2-P,C)P(OC6H4)(OPh)2}py], 6
In a NMR tube, 40.3 mg (3,73 ꢂ 10e2 mmol) of 1, 1.0 mL of CDCl3
and 6
m
L (7.5 ꢂ 10e2 mmol) of pyridine were introduced. NMR
spectra were recorded. 31P NMR: 95.4 (1JPePt ¼ 6602 Hz), 95.5 (1JPe
¼ 7063 Hz) ppm. 195Pt NMR (CDCl3): e4128 (d, 1JPteP ¼ 7063 Hz),
Pt
e4197 (d, 1JPteP ¼ 6602 Hz) ppm. Crystals of [SP4-2]-6 (see X-ray
diffraction) were obtained by slow diffusion of pentane vapours
into the solution. 31P NMR on a freshly prepared CDCl3 solution of
[SP4-2]-6 showed the signal at 95.5 ppm (1JPePt ¼ 7063 Hz) only.
Both isomers were observed (31P NMR) after 48 h.
3.8. Crystal structure of complexes [SP4-3]-4 and [SP4-2]-6
The X-ray diffraction experiments were carried out at room
temperature (T ¼ 293 K) by means of a Bruker Smart Breeze CCD
diffractometer operating with graphite-monochromated Mo-Ka
radiation. The sample of [SP4-3]-4 was sealed in a glass capillary
under N2 atmosphere, while that of [SP4-2]-6 was glued at the end
of a glass fibre. The intensities were corrected for Lorentz and
polarisation effects and for absorption by means of a multi-scan
method [20]. Some relevant crystal parameters are listed in Table 4.
The structure solution of [SP4-3]-4 has been obtained by the
automatic direct methods contained in SHELXS97 [21]. The
hydrogen atoms have been introduced in calculated positions and
have been refined following the method of riding motion. The final
refinement cycles gave the reliability factors listed in Table 4.
A solution of 6 in chloroform was subjected to evacuation at
60 ꢁC and the resulting residue was dissolved in CDCl3. In the 31P
NMR spectrum, besides the resonances due to the two isomers of 6,
a minor signal at 88.2 ppm was observed, due to 1. The sample was
treated a second time under vacuum at a higher temperature
(90 ꢁC). The residue was dissolved in CDCl3 and a 31P NMR spectrum
showed a nearly quantitative conversion to 1.
3.5. Preparation of [PtCl{(k
2-P,C)P(OC6H4)(OPh)2}(NHEt2)], 7
In a 50 mL reactor 141.9 mg (1.31 ꢂ10e1 mmol) of 1 were reacted
with 30
m
L of NHEt2, (2.90 ꢂ 10e1 mmol) in 1,2-DCE as solvent
Table 4
(5 mL). A pale yellow solution was obtained. After 40 min stirring, a
Crystal data and selected structure refinements details.
31P NMR spectrum was recorded: 102.0 (main signal, JPe
1
Compound
[SP4-3]-4
[SP4-2]-6
¼ 6501 Hz), 92.0 (1JPePt ¼ 7276 Hz) ppm, integral ratio 93:7. Af-
Pt
ter 24 h stirring, a new 31P NMR spectrum was recorded: 102.0 (1JPe
Chemical formula
Formula mass (g mole1
Crystal system
C20H20ClO4PPtS
617.93
Monoclinic
P21/c(n. 14)
9.449(2)
16.028(3)
15.245(3)
105.921(3)
2220.3(8)
4
C23H19ClNO3PPt
618.90
)
1
¼ 6501 Hz), 92.0 (main signal, JPePt ¼ 7276 Hz) ppm, integral
Pt
Monoclinic
P21/n(n. 14)
9.6272(2)
15.1925(4)
15.2288(4)
98.0390(10)
2205.49(9)
4
ratio 40:60. The solution was evaporated to dryness under vacuum
and the pale-yellow residue was dissolved in toluene (5 mL) and
heptane (2 mL) was added to the solution. After 3 d, the micro-
crystalline solid which precipitated out was collected by filtration.
A second crop of crystals was obtained from the filtrate. Both
fractions were washed with heptane and dried under vacuum. The
two fractions showed analogous analytical results. Anal. Calcd for
C23H19ClNO3PPt: C, 43.1; H, 4.1; N, 2.3. Found C, 43.2; H, 4.2; N, 2.1.
Space group
ꢀ
a (A)
ꢀ
b (A)
ꢀ
c (A)
b
(ꢁ)
3
ꢀ
Volume (A )
Z
Temperature
296(2)
1.849
6.628
3.89e32.73
27,746
296(2)
1.864
6.580
3.00e36.53
27,268
Density (calculated)/g cmꢀ3
)
Absorption coefficient (mmꢀ1
(ꢁ) Min Max
)
First fraction: 1H NMR (CDCl3): 8.24 (d, 1H, PteCeCH, JHe
3
q
¼ 50 Hz), 7.48e6.89 (m, 13H, aromatic protons), 3.26e3.02 (m,
Pt
Reflections collected
5H, NH and NeCH2), 1.21 (t, 6H, NeCH2eCH3, 2JHeH ¼ 7.4 Hz) ppm;
Independent reflections [Rint
]
8148 [0.0265]
8148/0/255
0.0506, 0.0275
0.0654, 0.0571
0.987
10,551 [0.0221]
10551/0/236
0.0695, 0.0328
0.0994, 0.0841
0.892
31P NMR (CDCl3): 101.0 (1JPePt ¼ 6516 Hz) and 92.1 (main signal, 1JPe
Data/restraints/parameters
a
Rall, Rgt
¼ 7330 Hz) ppm, integral ratio 20:80; IR (ATR, selected bands):
Pt
wR(F2o)all, wR(Fo2)gt
a
3299 mw, 3210 w, 1597 m, 1585 m, 1484 s, 1435 m, 1381 m, 1209 m,
1172 s, 1155 s, 1110 m, 1062 m, 1026 m, 1006 m, 950 s, 924 ms, 889
ms, 803 s, 764 m, 749 s, 687 s cme1. Second fraction: 1H
NMR (CDCl3): 8.24 (d, 1H, PteCeCH, 2JHeH ¼ 8.5 Hz 3JHePt ¼ 50 Hz),
7.38e6.90 (m, 13H), 3.21e2.99 (m, 5H, NH and NeCH2), 1.21 (t, 6H,
Goodness-of-fit a
a
½
2
R ¼ SrrFor e rFcrr/SrFor; R(F2o) ¼ [S[w(Fo2 e Fc2)2 ]/S[ w(Fo2)2]] ; w ¼ 1/[
s
(F2o) þ (AQ)2 þ BQ] where Q ¼ [MAX(Fo2,0) þ 2Fc2]/3; Goodness-of-fit ¼ [S [w(Fo2
e
F2c)2]/(N e P)] , where N, P are the numbers of observations and parameters,
½
respectively.

14
D.B. Dell’Amico et al. / Journal of Organometallic Chemistry 733 (2013) 9e14
(f) J.A.G. Williams, Chem. Soc. Rev. 38 (2009) 1783e1801;
The structure solution of [SP4-2]-6 has been obtained by the
(g) M. Albrecht, Chem. Rev. 110 (2010) 576e623.
automatic direct methods contained in SIR92 program [22]. During
the first stages of the refinement the thermal ellipsoids of a phenyl
group of the phosphine appeared excessively elongated with a
disposition suggesting the presence of disorder in the position of
this moiety. This phenyl group was then introduced in the model as
distributed in two different positions, fixing to one the total occu-
pancy of the site. After the introduction of the hydrogen atoms in
calculated positions, the refinement was completed. The disor-
dered phenyl groups were refined with a fixed idealized geometry
and with isotropic thermal parameters. The distribution on the two
positions refined to an almost statistical value: 0.54 and 0.46,
respectively. The more relevant reliability parameters of the
refinement are listed in Table 4. In addition to the aforementioned
software, other control calculations and preparation of publication
material were performed with the programs contained in the suite
WINGX [23].
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Acknowledgement
[9] D. Belli Dell’Amico, F. Calderazzo, L. Carbonaro, L. Labella, S. Libri, F. Marchetti,
Inorg. Chim. Acta 360 (2007) 3765e3770.
[10] D. Belli Dell’Amico, R. Bini, F. Calderazzo, L. Carbonaro, L. Labella, A. Vitullo,
Organometallics 24 (2005) 4427e4431.
[11] V.K. Jain, L. Jain, Coord. Chem. Rev. 249 (2005) 3075e3197 (and references
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[12] P. Goggin, in: G. Wilkinson, R.D. Gillard, J.A. McCleverty (Eds.), Comprehensive
Coordination Chemistry, 2, Pergamon Press, Oxford, 1987, pp. 487e503.
[13] J.D. Fotheringham, G.A. Healt, A.J. Linsady, T.A. Stephenson, J. Chem. Res. 3
(1986) 82e83.
The Ministero dell’Università
e della Ricerca Universitaria
(MIUR), Progetti di Ricerca di Rilevante Interesse Nazionale (PRIN
2009) is gratefully acknowledged for financial support. Thanks are
due to Chimet S.p.A., Ie52041 Badia al Pino (Arezzo), for a loan of
platinum. The authors wish to thank Professor Fausto Calderazzo
(Professor Emeritus, Università di Pisa) for useful discussions.
Appendix A. Supplementary Material
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R.L. Wingad, Dalton Trans. (2009) 7796e7804.
[15] F.H. Allen, Acta Crystallogr. B58 (2002) 380e388.
CCDC 916573 and 916574 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via www.
ccdc.cam.ac.uk/data_request/cif.
[16] a) R.G. Wilkins, Kinetics and Mechanism of Reactions of Transition Metal
Complexes, WCH Verlagsgesellschaft, Weinheim and WCH Publishers, Inc.,
New York, 1991 (and references therein);
b) L.M. Tobe, J. Burgess, Inorganic Reaction Mechanisms, Longman, New York,
1999 (and references therein).
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[20] G.M. Sheldrick, SADABS, Program for Empirical Absorption Correction, Uni-
versity of Göttingen, Germany, 1996.
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