Photochemical behavior of (diphosphine)(η2-tolane)Pt 0 complexes. Part A: Experimental considerations in solution and in the solid state

Article abstract of DOI:10.1039/b925562a

A series of various (diphosphine)(η²-tolane)Pt⁰ complexes exhibiting manifold substitution pattern of the tolane ligand (5a-g) and different rigid diphosphines defining various bite angles at the Pt center (9a-b) have been synthesized. All compounds were isolated and characterized by means of spectroscopic methods and additionally by X-ray structure determination (5a-e, 9a-b). In view of potential C_aryl-C_ethynyl bond activation, we investigated their photochemical behavior in the solid state as well as in solution by irradiating with sunlight. The reactivity towards C _aryl-C_ethynyl bond activation in the crystalline state and in solution is discussed in relation to substituents attached to the tolane ligand and on the extent of the torsion of its phenyl rings. Complexes 5a-c and 9a either bearing electron withdrawing bromides or possessing a large dihedral angle of the phenyl rings, showed selective oxidative addition of the C _aryl-C_ethynyl bond to the Pt center in the solid state, yielding complexes 6a-c and 10a, respectively. In contrast, 5d-f and 9b proved to be unreactive under similar conditions because of their electron donating methoxy groups as well as the reduced twisting of their phenyl or pyridyl moieties of the tolane ligands. Irradiation of complexes 5a and 5b with sunlight in solution revealed the formation of the appropriate C-Br activated compounds 7a and 7b along with 6a and 6b in a 1:1 mixture. The observed photochemical C_aryl-C_ethynyl bond activation is reversible under thermal conditions, regaining the appropriate Pt⁰ complexes by reductive elimination.

Full text of DOI:10.1039/b925562a

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www.rsc.org/dalton | Dalton Transactions
Photochemical behavior of (diphosphine)(g2-tolane)Pt0 complexes. Part A:
Experimental considerations in solution and in the solid state†
Thomas Weisheit,a Daniel Escudero,b Holm Petzold,c Helmar Go¨rls,a Leticia Gonza´lezb and
Wolfgang Weigand*a
Received 9th December 2009, Accepted 13th August 2010
DOI: 10.1039/b925562a
2
A series of various (diphosphine)(h -tolane)Pt0 complexes exhibiting manifold substitution pattern of
the tolane ligand (5a–g) and different rigid diphosphines defining various bite angles at the Pt center
(9a–b) have been synthesized. All compounds were isolated and characterized by means of
spectroscopic methods and additionally by X-ray structure determination (5a–e, 9a–b). In view of
potential Caryl–Cethynyl bond activation, we investigated their photochemical behavior in the solid state as
well as in solution by irradiating with sunlight. The reactivity towards Caryl–Cethynyl bond activation in
the crystalline state and in solution is discussed in relation to substituents attached to the tolane ligand
and on the extent of the torsion of its phenyl rings. Complexes 5a–c and 9a either bearing electron
withdrawing bromides or possessing a large dihedral angle of the phenyl rings, showed selective
oxidative addition of the Caryl–Cethynyl bond to the Pt center in the solid state, yielding complexes 6a–c
and 10a, respectively. In contrast, 5d–f and 9b proved to be unreactive under similar conditions because
of their electron donating methoxy groups as well as the reduced twisting of their phenyl or pyridyl
moieties of the tolane ligands. Irradiation of complexes 5a and 5b with sunlight in solution revealed the
formation of the appropriate C–Br activated compounds 7a and 7b along with 6a and 6b in a 1 : 1
mixture. The observed photochemical Caryl–Cethynyl bond activation is reversible under thermal
conditions, regaining the appropriate Pt0 complexes by reductive elimination.
has been reported.9,10 The determined metal–Caryl bond strength
Introduction
of the resulting product, which is significantly higher than that of
The activation of carbon–carbon bonds by using metal complexes
a metal–Calkyl bond, was supposed to be the driving force of these
in a homogeneous medium has attracted much interest particular
reactions.
in view of applications in petroleum chemistry.1–3 During the last
decades some examples for C–C bond activation by means of
However, beside the thermal activation of inactivated C–
C bonds, Jones et al. reported on the oxidative addition of
Pt0 complex fragments to the Caryl–Cethynyl bond of coordinated
diphenylacetylene derivatives (tolanes) via irradiating solutions
of these complexes with UV light.11,12 Interestingly, C–C bond
cleavage in this system is only observed under photochemical
conditions and not via thermal treatment of the Pt0 complexes.
Therefore, the framework of a tolane ligand coordinated to a
(diphosphine)Pt0 complex fragment is estimated to be a efficient
system for studying the driving force of this type of photochemical
C–C bond activation. In this context, Jones et al. investigated the
influence of the substitution pattern of the tolane ligand on the
photochemical reactivity of its appropriate platinum complex.12 It
was shown that stabilization of the addition products is achieved
when electron withdrawing groups were introduced and therefore,
the activation energy of the bond cleavage can be tuned by the
choice of the acetylenic ligand.
oxidative addition on a metal complex have been reported. Most
of them are driven by relief of ring strain2–4 in the corresponding
insertion products or the fact that the C–C bond is forced to react
with the metal center by proximity.3,5,6 On the other hand, only
a few examples for the activation of unstrained C–C bonds are
known so far.6,7 The principal reasons for this scarcity of examples
might be the more favorable C–H bond activation due to the higher
activation barrier of C–C bonds8 and the considerably increased
stability of the resulting metal-hydrogen bond in comparison
with the corresponding metal–carbon bond.9 However, C–C bond
cleavage also depends on the nature of the respective C–C bond.
Although Caryl–Caryl or Caryl–Calkyl bonds are generally stronger than
Calkyl–Calkyl bonds their activation by rhodium or iridium complexes
aInstitut fu¨r Anorganische und Analytische Chemie, Friedrich-Schiller-
Universita¨t Jena, August-Bebel-Str. 2, 07743, Jena, Germany. E-mail:
wolfgang.weigand@uni-jena.de; Fax: +49-3641-948102; Tel: +49-3641-
948160
Recently we could show that the aforementioned C–C bond
activation is not restricted to the solution state. By irradiating
2
crystals of (dppbe)(h -2,2¢-dibromotolane)Pt0 (1) with sunlight a
bInstitut fu¨r Physikalische Chemie, Friedrich-Schiller-Universita¨t Jena,
Helmholtzweg 4, 807743, Jena, Germany
highly selective insertion of the (dppbe)Pt moiety into the Caryl
–
Cethynyl bond was observed (Scheme 1).13 The different photochem-
cTU Chemnitz, Institut fu¨r Chemie, Straße der Nationen 62, 09111,
Chemnitz, Germany
2
istry of this complex compared to that of (dppbe)(h -tolane)Pt0
† CCDC reference numbers 743160 (for 5a), 743161 (for 5b), 743162 (for
5c), 743163 (for 5d), 743164 (for 5e), 743165 (for 6b), 743166 (for 7b),
743167 (for 9a) and 743269 (for 9b). For crystallographic data in CIF or
other electronic format see DOI: 10.1039/b925562a
was explained by remarkable differences in their calculated
UV/Vis spectra and electronic transitions included therein.13
A
conspicuous feature of 1 in the solid state is the twisting of
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The chemical shifts (51.3–52.6 ppm) as well as the 1JP,Pt coupling
constants (3063–3143 Hz) of 5a–g are in a narrow range, suggest-
ing only minor influence of the acetylene ligand on the electronic
nature of the Pt complex fragment. The purity and constitution
of 5a–g were confirmed by satisfying elemental analysis as well as
mass spectrometry. Additionally, the results of the X-ray structure
determination of 5a–e (Fig. 1) prove the proposed structures of
these complexes. Selected bond lengths and angles are summarized
in Table 1 and are comparable with those reported for related Pt0-
tolane complexes.11–15 The experimentally measured values are in
good agreement with the theoretically calculated ones (Table 1).
Noteworthy differences are only observed for torsion angles C(8)–
C(3)–C(9)–C(14), which are more sensitive to packing effects. The
arrangement of the ligands around the platinum center is distorted
square-planar for each complex. Due to the p back donation (dPt
Scheme 1 Selective C–C bond cleavage in the solid state via irradiation
2
of crystals of (dppbe)(h -2,2¢-dibromotolane)Pt0 with sunlight.
either phenyl groups of the tolane ligand against each other. Their
spatial orientation is caused by the repulsion of both ortho-bonded
bromine atoms.13 Additionally, the reported solid-state reaction of
1 might be explained by the electron-withdrawing nature of the
bromine atoms as well.
In order to study the effect of the spatial orientation of the
phenyl groups as well as the influence of attached electron donating
groups (EDGs) and electron withdrawing groups (EWGs), we
synthesized a series of novel (diphosphine)Pt0 complexes with
different tolane ligands. Hence, their photochemical behavior in
the solid state as well as in solution was paid main attention
to. A detailed discussion supported by density functional theory
(DFT) and time-dependent density functional theory (TD-DFT)
methods of the different reactivity will be given in part B.‡
*
→ p alkyne) the bond lengths C(1)–C(2) are significantly longer
than those reported for uncoordinated alkynes.16 Furthermore,
the decline of the angles C(1)–C(2)–C(3) and C(2)–C(1)–C(9),
compared to uncoordinated tolanes (180◦), is in good accordance
with the increased alkene character of the formerly alkynes. The
importance of the p back donation in these complexes was also
verified by means of natural-bond-order (NBO) calculations.17
As a consequence of the p back donation, the wave numbers
of the n(C C) are perspicuously shifted to smaller values for
coordinated alkynes.16
In continuation of the results achieved with 1, we first focused
on the photoreactions of 5a in the solid state and in solution.
This complex shows a torsion angle C(8)–C(3)–C(9)–C(14) (see
Table 1) of 30.7◦, which is remarkably smaller than that of 1,
promising decreased steric influence compared to 1. Nevertheless,
both bromine atoms in para-position should provide a comparable
electronic contribution to the reactivity as observed for 1. Indeed,
the irradiation of crystalline 5a with sunlight for 12 days resulted
in the selective conversion into a new unsymmetrical complex
Results and discussion
According to our previously reported synthesis of
(diphosphine)(nbe)Pt0 [nbe
=
norbornene] complexes,14 the
2
required (dppbe)Pt(h -tolane) complexes 5a–g were prepared
by reaction of (dppbe)PtCl2 (3) with sodium borohydride in
dichloromethane–ethanol and subsequent treatment with the
appropriate tolane derivative 4a–g (Scheme 2). Complexes 5a–g
were obtained analytically pure as yellow to orange solids via
crystallization by diffusion of pentane into concentrated toluene
or benzene solutions of the appropriate crude products. The
1
1
in 90% yield based on the 31P{ H} NMR data. Its 31P{ H} NMR
spectrum shows two doublets at 50.6 and 49.2 ppm along with 195Pt
1
satellites. The observed JP,Pt coupling constants (2467/1575 Hz)
1
31P{ H} NMR spectra of 5a–c and 5e–g revealed a singlet along
agree with the formation of the corresponding C–C activated
counterpart 6a (Scheme 3). Complex 6a was isolated by column
chromatography and obtained as pale yellow powder. Strong
absorption at n = 2112 cm-1 in the IR spectrum verifies the end-on
coordination of the alkyne ligand. The constitution and purity of
6a was unambiguously confirmed by mass spectrometry as well as
elemental analysis.
with the appropriate 195Pt satellites, pointing to their symmetrical
conformation. In contrast, the unsymmetrical complex 5d shows
an AB spin-system pattern in the 31P{ H} NMR spectrum,
1
consisting of two coinciding doublets together with 195Pt satellites.
‡ D. Escudero, T. Weisheit, W. Weigand and L. Gonza´lez, Photochemical
As expected, this selectivity vanishes when 5a is irradiated in
2
behavior of (diphosphine)(h -tolane)Pt0 complexes in solution and in
1
toluene solution. The 31P{ H} NMR spectrum of the reaction
the solid state; Part B: Theoretical part, Dalton Trans., 2010, 39, DOI:
mixture shows two AB spin systems with corresponding 195Pt
10.1039/B925928G.
2
Scheme 2 Synthesis of (dppbe)(h -tolane)Pt0 complexes 5a–g.
9494 | Dalton Trans., 2010, 39, 9493–9504
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◦
a
˚
Table 1 Selected bond lengths [A] and angles [ ] of complexes 5a–e and 9a–b. The corresponding calculated values are given in italics
5a
5b
5c
5d
5e
9a
9b
P(1)–Pt
2.2569(14)
2.333
2.2583(14)
2.335
2.027(6)
2.082
2.039(6)
2.084
2.2499(11)
2.333
2.2463(11)
2.325
2.049(4)
2.101
2.040(4)
2.089
2.2498(14)
2.324
2.2686(13)
2.331
2.064(6)
2.101
2.042(5)
2.090
2.2650(13)
2.335
2.2566(13)
2.333
2.030(5)
2.077
2.041(5)
2.081
2.2508(14)
2.333
2.2453(14)
2.328
2.041(5)
2.064
2.027(6)
2.079
2.2541(14)
2.319
2.2507(14)
2.315
2.047(6)
2.099
2.052(6)
2.102
2.2658(14)
2.344
2.2707(16)
2.348
2.045(6)
2.101
2.059(6)
2.103
P(2)–Pt
C(1)–Pt
C(2)–Pt
C(1)–C(2)
1.295(8)
1.312
1.302(6)
1.305
1.300(7)
1.304
1.293(8)
1.312
1.299(9)
1.314
1.288(8)
1.305
1.295(8)
1.306
P(1)–Pt–P(2)
C(1)–Pt–C(2)
C(1)–C(2)–C(3)
C(2)–C(1)–C(9)
C(8)–C(3)–C(9)–C(14)b
85.00(5)
85.0
37.1(2)
36.7
144.4(6)
146.7
145.9(6)
147.5
86.47(4)
85.7
37.13(18)
36.3
153.2(4)
149.8
149.0(4)
146.6
86.25(5)
85.7
36.9(2)
36.3
146.9(6)
150.1
141.2(5)
146.9
86.63(5)
84.8
37.0(2)
36.8
144.3(5)
145.1
143.4(5)
144.7
6.4(7)
87.28(5)
85.3
37.3(2)
37.0
144.0(6)
144.4
144.6(6)
144.9
88.10(5)
91.8
36.6(2)
36.2
149.1(6)
145.5
149.2(6)
148.4
102.79(5)
102.1
36.8(2)
36.2
145.5(6)
145.9
146.8(6)
146.0
30.7(6)
18.9
63.4(4)
92.2
71.0(6)
91.9
26.9(6)
7.3
121.9(6)
96.5
75.6(6)
72.5
3.6
a Theoretical values were calculated using the BP86/TZVP(ecp-mwb-60 for Pt) level. b Torsion angle between both phenyl groups of the appropriate
tolane ligand; for 5d this angle is defined as N(1)–C(3)–C(9)–C(10) and for 5e C(4)–C(3)–C(9)–N(2), respectively.
Fig. 1 Molecular structures of complexes 5a–e with thermal ellipsoids at 50% probability level. Hydrogen atoms and solvent molecules have been
omitted for clarity. The phenyl groups of the dppbe ligand are represented by their ipso-carbon atoms. Selected bond lengths and angles are summarized
in Table 1.
satellites, indicating the presence of two unsymmetrical complexes
in a 1 : 1 ratio, whereas one of them was identified as 6a and
the second complex showed resonances at 49.3 and 43.2 ppm
of irradiated samples of 5b and 5c revealed the conversion of
the starting materials to the appropriate C–C activated PtII coun-
terparts 6b and 6c (Scheme 3), indicated by two doublets along
1
1
with appropriate JP,Pt coupling constants of 1658 and 3988 Hz,
with 195Pt satellites, respectively (for 6b: 50.1/48.9 ppm, JP,Pt
=
respectively. The value of almost 4000 Hz points to the presence of
a bromine ligand trans to a phosphorous atom, as observed for the
C–Br activated counterpart of 1,13 hence the formation of complex
7a is likely (Scheme 4), but nevertheless attempts to isolate 7a by
column chromatography failed.
2474/1639 Hz and for 6c: 50.5/48.6 ppm, 1JP,Pt = 2469/1561 Hz).
Interestingly, after similar reaction periods 45% of 5b are converted
to 6b, but only 25% of 5c have been reacted to 6c. The torsion
angles of 5b and 5c have approximately the same value due to the
ortho-bonded methyl groups, which should provide a comparable
sterical contribution to the reactivity. However, methyl groups also
possess a marginal electron donating character, countervailing the
electron withdrawing properties of the bromine substituents in
These results show that the presence of the bromine moieties
at the coordinated tolane ligand mainly increases the reactivity
1
towards C–C bond activation. Indeed, the 31P{ H} NMR spectra
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Scheme 3 Selective formation of the C–C activated compounds 6a–c
2
by irradiation of the appropriate (dppbe)(h -tolane)Pt0 complexes with
sunlight.
Fig. 2 Molecular structure of 6b with thermal ellipsoids at 50% probabil-
ity level. Hydrogen atoms have been omitted for clarity. The phenyl groups
of the dppbe ligand are represented by their ipso-carbon atoms. Selected
◦
˚
bond lengths [A] and angles [ ]: P(1)–Pt 2.2761(14), P(2)–Pt 2.2709(14),
C(1)–Pt 2.022(6), C(10)–Pt 2.093(5), C(1)–C(2) 1.193(8), P(1)–Pt–P(2)
86.64(5), P(1)–Pt–C(1) 90.63(15), P(2)–Pt–C(10) 94.23(15), C(1)–Pt–C(10)
88.6(2), Pt–C(1)–C(2) 173.5(5).
Scheme 4 Irradiation of the bromo-substituted complexes in solution
results in the formation of the C–C activated compounds 6 and the C–Br
activated ones 7 in a 1 : 1 ratio.
5b, which might explain the reduced conversion of 5b and 5c in
comparison to 5a.
The reaction of 5b in toluene solution resulted in the formation
of two complexes in a 1 : 1 ratio, which were found to be the C–C
activated product 6b and the C–Br activated compound 7b, with
respect to the 31P{ H} NMR data of the crude product (Scheme 4).
1
Fig. 3 Molecular structure of 7b with thermal ellipsoids at 50%
probability level. Hydrogen atoms and solvent molecules have been
omitted for clarity. The phenyl groups of the dppbe ligand are
Column chromatography of the product mixture yielded both
complexes in analytical purity, which was verified by spectroscopic
1
methods and elemental analysis. The 31P{ H} NMR spectra of
˚
represented by their ipso-carbon atoms. Selected bond lengths [A]
6b and 7b revealed two doublets as well as the corresponding
195Pt satellites due to their unsymmetrical conformation (for 7b:
49.6/43.0 ppm, 1JP,Pt = 1684/4090 Hz). The 1JP,Pt values of 7b are
comparable to that of 7a, verifying the insertion of the (dppbe)Pt0
complex fragment into one of the C–Br bonds. The proposed
molecular structures of 6b and 7b are unambiguously confirmed
by the results of the X-ray structure determination (Fig. 2 and 3).
The arrangement of the ligands around the metal center is
slightly distorted from square planarity. The remarkably enlarged
bond length Pt–P(1) in comparison to Pt–P(2) in complex 7b can
be plausibly explained by the greater extent of the trans-influence
of the sp2 hybridized carbon atom. In contrast to the appropriate
and angles [◦]: P(1)–Pt 2.2806(19), P(2)–Pt 2.2082(17), C(1)–Pt
2.099(8), Pt–Br(1) 2.4679(8), C(8)–C(9) 1.176(10), P(1)–Pt–P(2) 87.62(6),
P(1)–Pt–Br(1) 90.35(5), P(2)–Pt–C(1) 93.02(19), C(1)–Pt–Br(1) 89.01(18),
C(4)–C(8)–C(9) 175.9(8).
75% compared with 25% in the respective experiment in the solid
state.
Considering these previous observations, the question arises
whether the insertion of the Pt0 complex fragment into the
Caryl–Cethynyl bond occurs intramolecular or intermolecular in the
crystalline state. Taking a closer look to the arrangement of
2
the (diphosphine)(h -tolane)Pt0 complexes in the crystal ought
2
(dppbe)(h -tolane)Pt0 complex, the bond lengths C(1)–C(2) and
to be a simplified estimation concerning this problem. Fig. 4
exemplarily shows the alignment of 5a in the solid state. The
shortest distance between two platinum atoms of neighbouring
molecules of 5a (labeled as A and B) was determined to be
C(8)–C(9) in compounds 6b and 7b, respectively, are in the typical
range of carbon–carbon triple bonds. Furthermore, the end-
on coordination of the alkyne to the platinum atom in 6b is
underlined by the detected strong absorption at n = 2110 cm-1
in the corresponding IR spectrum.
˚
7.45 A. The tolane moiety of B, highlighted as purple triangle,
is evidently not directed to the Pt center of A, suggesting that
˚
Irradiation of a toluene solution of 5c with sunlight for
approximately 10 days, results in the selective formation of 6c. No
evidence for activation of the carbon–methyl bond was detected in
their distance is not significantly shorter than 7.45 A. Indeed,
approximated distances, calculated between the Pt atom of A and
˚
˚
one of the Cethynyl atoms of B, were found to be 7.07 A and 7.84 A,
respectively. Regarding that typically observed distances among
reactive centers in the course of photochemical reactions in the
1
the 1H and the 31P{ H} NMR spectra. The yield, calculated on the
1
basis of the 31P{ H} NMR spectrum, increases to approximately
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Scheme 5 Complexes 5d–g are non-reactive towards sunlight in the solid
state.
In order to study the influence of EDGs attached to the
tolane ligand, complexes 5f and 5g were placed in the sunlight
for photoreactions. However, neither 5f nor 5g showed any
rearrangement towards C–C or C–O bond activation with respect
1
to the 31P{ H} NMR spectroscopic data (Scheme 5). These results
Fig. 4 Section of the crystal-state arrangement of 5a. Platinum atoms
are depicted as green colored spheres. Intermolecular Pt ◊ ◊ ◊ Pt distances
are represented by dashed lines, whereas red lines exhibit a length of
approximately 10–13 A and the shortest contact (7.45 A) is emphasized by
a blue colored dashed line.
suggest an inhibition of C–C bond cleavage in the solid state
by the presence of EDGs on the tolane moiety. Furthermore, in
the case of 5f, this inhibition-effect seems to be stronger than a
potential C–C bond activation arising from the spatial orientation
of the phenyl rings, because its dihedral angle ought to be in the
same range as observed for the other complexes bearing ortho-
substituted tolanes. Single crystals of 5f and 5g were of poor
quality and not suitable for X-ray structure determination. Hence,
no information of the alignment of the phenyl groups in the solid
state is available. However, some information can be extracted
from the theoretical optimized geometries of 5f and 5g, which
predict C(8)–C(3)–C(9)–C(14) torsion angles of 72.2◦ and 20.1◦,
respectively. Due to its greater torsion angle, in comparison with
5g, we expect complex 5f to be prone in view of C–C bond
activation. Accordingly, the photolysis of 5f in toluene solution
resulted in the predominant formation of 6f, which was verified
by the presence of an AB spin system pattern accompanied
˚
˚
18
˚
solid state are generally in the range of 4 A, a bimolecular
reaction mechanism can be excluded. However, an intramolecular
attack of the (diphosphine)Pt moiety on the Caryl–Cethynyl bond after
a photo-excitation of 5a (see Part B‡) seems to be more plausible
due to the close proximity of the Pt atom to the regarded bond.
This might result in a reduced activation barrier for C–C bond
activation and explains the high selectivity in the solid state. The
determined intermolecular Pt ◊ ◊ ◊ Pt distances of complexes 5b–5g
and 9a–b are comparable to those of 5a. Therefore, an expansion of
the postulated mechanism of the solid state C–C bond activation
to these complexes ought to be justified.
On the contrary, the formation of the C–Br activated compound
7a via irradiating 5a in solution can be reasonably explained by a
“ring-walking” mechanism of the (diphosphine)Pt moiety along
the p-system of the tolane ligand as similarly described for bromo
substituted stilbene and azostilbene derivatives coordinated to a
(PEt3)2Ni19 as well as (PEt3)2Pt complex fragment.20
with 195Pt satellites (49.5/47.6 ppm, JP,Pt = 2473/1687 Hz) in
1
the 31P{ H} NMR spectrum. The reaction of 5g under similar
1
conditions revealed almost no conversion into the corresponding
insertion product 6g, based on the 31P{ H} NMR spectroscopic
1
data. However, attempts to isolate compounds 6f and 6g by means
of column chromatography failed.
The photochemical conversions of 5a–c to their C–C activated
counterparts suggest that the reactivity towards C–C bond cleav-
age in the solid state obviously depends on the electronic nature
of the used tolane ligand as well as on the spatial orientation
of its phenyl groups (for a detailed explanation see Part B‡). In
view of a minimization of potential steric influences, complexes
5d and 5e have been synthesized. The decreased steric bulkiness
of the pyridyl groups allows an almost coplanar arrangement in
the corresponding complexes, as reflected by the torsion angles
of 6.4◦ and 26.9◦ found for complexes 5d and 5e, respectively
(Table 1). Therefore, crystalline samples of 5d and 5e were
placed in the sunlight for approximately two weeks. After this
period, no obvious alterations of these samples were observed.
In order to investigate the influence of the bridging diphosphine
ligand on the reactivity, we focused on one tolane ligand (4c) and
synthesized two additional Pt0 complexes (9a–b) with diphosphine
ligands promising different bite angles P–Pt–P. Compounds 9a
and 9b were prepared by reduction of the appropriate PtII metal
precursor (8a–b) with sodium borohydride in dichloromethane–
ethanol solution and subsequent treatment with 4c (Scheme 6).
Diffusion of pentane into saturated benzene solutions of the crude
products afforded orange (9a) and pale yellow (9b) crystals in
analytical purity. The 31P{ H} NMR spectra of 9a and 9b show
1
a singlet with 195Pt satellites at 17.4 and 13.6 ppm, respectively.
Interestingly, the 1JP,Pt values increase with the corresponding bite
angles of the diphosphines. A similar correlation between these
values was already observed in related systems.14,21,22
1
Their 31P{ H} NMR spectra revealed the signals of the starting
material unchanged, indicating that no photoreaction occurred
(Scheme 5).
The molecular arrangements of 9a and 9b were unambiguously
confirmed by the results of the X-ray structure determination
(Fig. 5 and 6). Both complexes exhibit a distorted square-planar
coordination geometry. Selected bond lengths and angles are
summarized in Table 1 and comparable with those determined
The photolysis of 5d and 5e in solution resulted in the formation
of some unidentified side products. No signals assignable to the
corresponding C–C activated products have been detected in the
1
appropriate 31P{ H} NMR spectra.
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1
a photochemical induced reaction. Indeed, the 31P{ H} NMR
spectrum of this sample displayed full conversion of 9a to an
unsymmetrical complex characterized by two doublets at 11.9 and
9.0 ppm. The 1JP,Pt values (2427/1499 Hz) are comparable to those
determined for 6a–c, pointing to the formation of 10a (Scheme 7).
The IR spectrum of 10a shows strong absorption at n = 2112 cm-1,
typical for an end-on coordinated alkyne ligand. In contrast, a
crystalline sample of 9b, which was placed in sunlight for a similar
period, did not show any visible alterations as confirmed by the
1
unchanged 31P{ H} NMR spectrum.
2
Scheme 6 Synthesis of (diphosphine)(h -2,2¢-dimethyltolane)Pt0 com-
plexes 9a–b, bearing diphosphines with different bite angles.
Scheme 7 The dppn complex 9a shows light induced selective C–C bond
cleavage in the crystalline state as well as in solution.
The exposure of a toluene solution of 9a to the sunlight resulted
1
in the exclusive formation of 10a, as can be followed by 31P{ H}
1
NMR spectroscopy. On the contrary, the 31P{ H} NMR spectrum
of a solution of 9b, irradiated with sunlight for several days,
indicates almost no conversion of 9b except for a small amount
of the dioxidized phosphine ligand (33.0 ppm). On the one hand,
the differences in the reactivity of 9a/9b in solid state and solution
might be explained by the remarkably different torsion angles
of the phenyl rings of the coordinated 4c. On the other hand, a
clear trend in the relation between the phosphine chelate ring size
(and hence the bite angle P–Pt–P) and the reactivity is evident.
Whereas 5c and 9a, realizing 5- and 6-membered chelate rings,
respectively, and exhibiting relatively small P–Pt–P angles (86–
88◦), are reactive towards sunlight in the solid state and in solution,
9b proved to be unreactive under similar conditions, as mentioned
above. This complex exhibits a 7-membered chelate ring with an
appropriate P–Pt–P angle of almost 103◦. These miscellaneous
diphosphines are known to influence the electronic nature of
the appropriate Pt0 fragment,23 what might explain the different
reactivity of complexes 5c, 9a and 9b in the solid state and in
solution, respectively. A detailed discussion concerning the factors
influencing the reactivity is given in Part B.‡
Fig. 5 Molecular structure of 9a with thermal ellipsoids at 50% proba-
bility level. Hydrogen atoms and solvent molecules have been omitted for
clarity. The phenyl groups of the 1,8-bis(diphenylphosphanyl)naphthalene
ligand (dppn) are represented by their ipso-carbon atoms. Selected bond
lengths and angles are summarized in Table 1.
Generally, the described photochemically induced C–C bond
activation is thermodynamically uphill, hence the reactivity is
reversible under thermal conditions. In order to prove this
assumption for the specified complexes 5a–c, 5f and 9a, which
show C–C bond activation, their thermal induced back reactions
were investigated (for mechanistic DFT studies see Part B‡).
Therefore, toluene-d8 solutions of 5a–c, 5f and 9a where placed in
NMR tubes and exposed to sunlight. After 10 days the formation
Fig. 6 Molecular structure of 9b with thermal ellipsoids at 50% proba-
bility level. Hydrogen atoms and solvent molecules have been omitted for
clarity. The phenyl groups of the a,a¢-bis(diphenylphosphanyl)-o-xylene
[dpp(o-xyl)] ligand are represented by their ipso-carbon atoms. Selected
bond lengths and angles are summarized in Table 1.
for 5a–e, except the angles P(1)–Pt–P(2) which are predetermined
by the particular diphosphine. The torsion angle of the phenyl
rings of the tolane ligand in 9b was experimentally determined
to be 75.6◦, which is in good agreement with the theoretically
calculated value of 72.5◦ (Table 1) and thus, is comparable to that
in 5c. In contrast, the appropriate angle in 9a was found to be
significantly enlarged to 121.9◦.
1
of the corresponding PtII counterparts was confirmed by 31P{ H}
NMR spectroscopy and thereupon the NMR tubes were sealed
and placed in an oil bath at 100 ◦C. After 6 days a 31P{ H}
1
1
NMR spectrum of each sample was recorded. The 31P{ H} NMR
spectroscopic data of the experiments on 5c, 5f and 9a revealed
the quantitative re-conversion of the photochemically generated
PtII complexes 6c, 6f and 10a into the appropriate Pt0 complexes
(Scheme 8).
If crystals of 9a are irradiated with sunlight for two weeks,
smooth fading of the orange color was observed pointing to
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the C–C activated as well as the C–Br activated complexes 7a and
7b. The formation of 7a and 7b can be reasonably explained by a
“ring walking” mechanism of the Pt0 complex fragment on the p-
system of the ligand resulting in C–Br bond activation. However,
the highly selective formation of the C–C activated complexes in
the crystalline state might be caused by the close proximity of both
reactive sites of the appropriate complex. The observed C–C bond
cleavage proved to be reversible under thermal conditions, whereas
the insertion of the Pt0 complex fragment in the C–Br bonds turned
out to be irreversible, pointing to the thermal stability of complexes
7a and 7b, respectively.
In order to render the mechanism of this bond cleavage
in the crystalline state precisely, more information about the
excited states in the course of the reactions are indispensable.
Therefore, results of theoretical calculations on the UV-spectra of
2
Scheme 8 Photochemical C–C bond cleavage in (diphosphine)(h -
tolane)Pt0 complexes is reversible under thermal conditions.
If 1 : 1 mixtures of 6a and 7a as well as 6b and 7b, obtained
by irradiating solutions of 5a and 5b with sunlight, respectively,
2
the (diphosphine)(h -tolane)Pt0 complexes are presented in Part
B of this work,‡ which should substantiate the factors influencing
the different reactivity towards C–C bond cleavage.
are treated in a similar manner, the 31P{ H} NMR spectra only
1
revealed the re-conversion of 6a and 6b into 5a and 5b (Scheme 8),
whereas the signals of 7a and 7b remained unchanged. This
underlines the irreversible light induced oxidative addition of
the C–Br bond to the (diphosphine)Pt0 moiety in 5a and 5b,
respectively (Scheme 9). The irreversibility of the C–Br bond
activation reaction is addressed in Part B,‡ where mechanistic
DFT studies show that the appropriate backwards thermal
reductive elimination is thermodynamically uphill.
Experimental section
General considerations
Unless otherwise stated, all reactions were carried out under an
atmosphere of argon by using standard Schlenk techniques. All
chemicals were purchased from commercial suppliers and used
without further purification. The starting materials (dppbe)PtCl2
(3),24 (dppn)PtCl2 (8a),25 (dpp(o-xyl))PtCl2 (8b)26 as well as the
tolane derivatives 4d27 and 4e27 were prepared according to
literature procedures. Compounds 4a,28 4c,29 4f30 and 4g30 are
known from literature and were synthesized in a similar manner as
the synthesis of 4b described below. The determined spectroscopic
data are in good agreement with the reported ones. The NMR
spectra were recorded either with BRUKER AVANCE 400 or
BRUKER AVANCE 200 spectrometers at 27 ◦C. 1H NMR spectra
were calibrated using the signal of the residual non-deuterated
1
solvent, while 13C{ H} NMR spectra were measured using the
signal of the solvent as internal standard. 31P{ H} NMR spectra
1
Scheme 9 Complexes 7a and 7b are stable towards higher temperatures
and show no rearrangement to 5a and 5b, respectively.
were determined using 85% H3PO4 as external standard. The
assignment of the signals in the H and 13C{ H} NMR spectra
of compounds 5a–g and 9a–b was performed by means of two-
dimensional NMR methods (1H,1H-COSY, 1H,13C-HSQC and
1H,13C-HMBC). The protons as well as carbon atoms of the
appropriate tolane ligand are labeled according to Scheme 2,
whereas the signals of the ethynyl carbon atoms could not be
detected due to their low intensity. The complexity of the 1H
1
1
Conclusions
In summary, we were able to extend our previously reported
simple and straightforward synthesis of (diphosphine)(tolane)Pt0
complexes to a new series of complexes (5a–g and 9a–b), bearing
tolane ligands with manifold substituent patterns. Comparison
of their reactivity towards C–C bond activation showed that on
the one hand the spatial orientation of the phenyl rings of the
tolane ligand and on the other hand the electronic properties
of substituents attached to the tolane moiety influence the light
induced intramolecular oxidative addition of the Caryl–Cethynyl bond
to the Pt0 moiety in the crystalline state as well as in solution.
While compounds 5d–g, exhibiting either a relatively small twisting
of the phenyl or pyridyl rings of the tolane ligand or strong
EDGs, are unreactive towards sunlight, complexes 5a–c and 9a
could be selectively converted to the appropriate C–C activated
counterparts. Additionally, solution state photolysis of 5a and 5b,
bearing bromo substituted tolane ligands, leads to 1 : 1 mixtures of
1
and 13C{ H} NMR spectra of compounds 6a, 7a, 7b and 10a
disabled an exact assignment for most of the signals, even by
applying two-dimensional NMR methods. Mass spectra were
taken with a FINNIGAN MAT SSQ 710 mass spectrometer. IR
spectra were recorded with a PERKIN ELMER system 2000
FT-IR spectrometer. Elemental analyses were performed with
a Vario EL III CHNS (Elementaranalysen GmbH Hanau) as
single determinations. Melting points were determined using an
AXIOLAB microscope with a THMS 600 heating plate and are
uncorrected.
2,2¢-dimethyl-4,4¢-dibromotolane (4b). To a solution of 2-iodo-
5-bromotoluene (4.43 g, 14.9 mmol) in Et3N (40 mL) trimethylsi-
lylacetylene (1.48 g, 15.1 mmol), copper(I)iodide (117 mg,
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0.61 mmol) and (PPh3)2PdCl2 (126 mg, 0.18 mmol) were added,
whereupon the color of the solution turned to black and triethy-
lammoniumiodide began to precipitate. After stirring for 5 days
C6H4 of dppbe), 7.35 (m, 16 H, m-C6H5 and p-C6H5 of dppbe
and H-2/H-2¢ and H-6/H-6¢), 7.26 (m, 4 H, H-3/H-3¢ and H-
5/H-5¢); dC(100 MHz, CD2Cl2) 146.4 (m, ipso-C6H4 of dppbe),
135.5 (m, ipso-C6H5 of dppbe), 134.4 (m, C-1/C-1¢), 134.0 (m,
o-C6H4 of dppbe), 133.3 (m, o-C6H5 of dppbe), 132.3 (m, C-
2/C-2¢ and C-6/C-6¢), 131.5 (s, C-3/C-3¢ and C-5/C-5¢), 131.2
(s, m-C6H4 of dppbe), 130.3 (s, p-C6H5 of dppbe), 128.8 (m, m-
C6H5 of dppbe), 120.1 (s, C-4/C-4¢); dP(81 MHz, CD2Cl2) 51.17
R
the solid was filtered through Celiteꢀ and the residue was rinsed
with diethyl ether. The combined solvents were removed under
reduced pressure to give a dark oil which was distilled in vacuo
to give 2-trimethylsilylethynyl-5-bromotoluene31 as colorless oil.
(3.42 g, 88%); dH(200 MHz, CDCl3) 7.35–7.18 (m, 3 H), 2.37 (s,
3 H), 0.23 (s, 9 H); dC(50 MHz, CDCl3) 142.6 (s), 133.3 (s), 132.3
(s), 128.6 (s), 122.5 (s), 122.0 (s), 102.9 (s), 99.6 (s), 20.4 (s), 0.0 (s).
A solution of 2-trimethylsilylethynyl-5-bromotoluene (2.50 g,
9.34 mmol) in thf (30 mL) was cooled to -78 ◦C and tetra-n-
butylammoniumfluoride, dissolved in thf (20 mL), was added drop
wise. After warming to room temperature the yellow solution was
stirred over night. Then the solution was washed three times with
water, the phases were separated and the organic layer was dried
over Na2SO4. The solvent was removed under reduced pressure to
yield 2-ethynyl-5-bromotoluene as pale yellow oil. (1.70 g, 93%);
dH(200 MHz, CDCl3) 7.34–7.21 (m, 3 H), 3.28 (s, 1 H), 2.37 (s, 3
H); dC(50 MHz, CDCl3) 142.8 (s), 133.7 (s), 132.4 (s), 128.8 (s),
122.8 (s), 120.9 (s), 82.0 (s), 81.5 (s), 20.4 (s).
To a solution of 2-ethynyl-5-bromotoluene (1.70 g, 8.72 mmol)
in Et3N (40 mL) 2-iodo-5-bromotoluene (2.61 g, 8.80 mmol),
copper(I)iodide (113 mg, 0.59 mmol) and (PPh3)2PdCl2 (104 mg,
0.15 mmol) were added, whereas the color of the solution turned
black and triethylammoniumiodide began to precipitate. After
stirring for 5 days the solvent was removed in vacuo. The residue
was dissolved in CH2Cl2 and washed with water, saturated NH4Cl
solution and again water and dried over Na2SO4. After removing
the solvent the crude product was recrystallized from ethanol
to yield 4b as white solid (2.06 g, 65%). Mp: 119–120 ◦C;
dH(200 MHz, CDCl3) 7.41 (m, 2 H), 7.33–7.28 (m, 4 H), 2.48
(s, 6 H); dC(50 MHz, CDCl3) 141.9 (s), 133.1 (s), 132.5 (s), 128.9
(s), 122.4 (s), 122.0 (s), 92.3 (s), 20.7 (s); Anal. calcd. for C16H12Br2:
C 52.78, H 3.32, Br 43.89; Found: C 53.14, H 3.30, Br 43.72.
1
(s with 195Pt satellites, JP,Pt = 3087 Hz); n(KBr)/cm-1 3052 (s),
1736 (s, n(C C)), 1629 (s), 1482 (vs), 1434 (vs), 1389 (m), 1097
(vs) 1067 (s), 1008 (s), 826 (s), 745 (s), 694 (vs), 669 (s), 548
(vs), 527 (s); m/z (DEI) 976 (2%, [M]+), 896 (2, [M – Br]+), 721
(30, [(dppbe)PtBr]+), 641 (10, [(dppbe)Pt]+), 336 (23, [4a]+); Anal.
calcd. for C44H32Br2P2Pt: C 54.06, H 3.30, Br 16.35; Found C
54.30, H 3.51, Br 16.01.
[(dppbe)(g2-2,2¢-dimethyl-4,4¢-dibromotolane)Pt0] (5b). Com-
pound 3 (175 mg, 0.25 mmol) was reacted with 4b (89 mg,
0.24 mmol) to yield 5b (111 mg, 45%) as yellow crystals.
Mp: >230 ◦C; dH(400 MHz, CD2Cl2) 7.81 (m, 2 H, o-C6H4
of dppbe), 7.50 (m, 10 H, m-C6H4 and o-C6H5 of dppbe), 7.36
(m, 4 H, p-C6H5 of dppbe), 7.29 (m, 8 H, m-C6H5 of dppbe),
7.22 (s, 2 H, H-3/H-3¢), 7.00 (m, 4 H, H-5/H-5¢ and H-6/H-6¢),
1.96 (s, 6 H, CH3); dC(100 MHz, CD2Cl2) 146.4 (m, ipso-C6H4
of dppbe), 138.7 (m, C-2/C-2¢), 137.0 (m, C-1/C-1¢), 135.8 (m,
ipso-C6H5 of dppbe), 134.1 (m, o-C6H4 of dppbe), 133.1 (m, o-
C6H5 of dppbe), 132.6 (s, C-6/C-6¢), 132.1 (s, C-3/C-3¢), 131.2 (s,
m-C6H4 of dppbe), 130.1 (s, p-C6H5 of dppbe), 128.7 (m, m-C6H5
of dppbe), 128.2 (s, C-5/C-5¢), 119.3 (s, C-4/C-4¢), 21.0 (s, CH3);
dP(81 MHz, CD2Cl2) 51.59 (s with 195Pt satellites, 1JP,Pt = 3143 Hz);
n(KBr)/cm-1 3052 (m), 2930 (w), 1763 (m, n(C C)), 1625 (m),
1475 (s), 1434 (s), 1188 (m), 1097 (s), 891 (m), 745 (m), 694 (vs), 549
(vs), 527 (vs), 507 (s); m/z(DEI) 1006 (2%, [M]+), 923 (2, [M – Br]+),
721 (6, [(dppbe)PtBr]+), 641 (2, [(dppbe)Pt]+), 485 (1, [(dppbe)Pt –
2¥Ph]+), 364 (3, [4b]+); Anal. calcd. for C46H36Br2P2Pt: C 54.94, H
3.61, Br 15.89; Found C 55.16, H 3.69, Br 16.01.
General procedure for the syntheses of the (diphosphine)
(g2-tolane)Pt0 complexes
[(dppbe)(g2-2,2¢-dimethyltolane)Pt0]
(5c). Compound
3
(129 mg, 0.18 mmol) was reacted with 4c (37 mg, 0.18 mmol) to
The appropriate (diphosphine)PtCl2 was suspended in CH2Cl2
(12 mL) and ethanol (3 mL) in a Schlenk flask. To this suspension
NaBH4 (50 mg, 1.06 mmol) was added and stirred for 6 h at rt.
During this period the mixture became yellow to orange in color
and the (diphosphine)PtCl2 dissolved. Water (5 mL) was added to
the mixture and after diminishing of the hydrogen evolvement the
phases were separated using a pipette and the appropriate tolane
ligand was added to the organic layer in equimolar ratio. This
solution was stirred over night. After removing the solvent under
reduced pressure, the residue was dissolved in a small amount of thf
and this solution was filtered through a silica gel charged pipette.
The solvent was evaporated and the yellow to orange colored
crude product was dissolved in toluene or benzene (3 mL). Pure
complexes were obtained by slow diffusion of pentane into these
solutions.
yield 5c (113 mg, 74%) as orange crystals.
Mp: 132 ◦C (dec.); dH(400 MHz, CD2Cl2) 7.81 (m, 2 H, o-C6H4
of dppbe), 7.52 (m, 8 H, o-C6H5 of dppbe), 7.45 (m, 2 H, m-C6H4
of dppbe), 7.34 (m, 4 H, p-C6H5 of dppbe), 7.28 (m, 8 H, m-C6H5
of dppbe), 7.15 (d, 3JH,H = 7.6 Hz, 2 H, H-6/H-6¢), 7.07 (d, 3JH,H
=
7.2 Hz, 2 H, H-3/H-3¢), 6.98 (t, 3JH,H = 7.2 Hz, 2 H, H-4/H-4¢ or
H-5/H-5¢), 6.91 (t, 3JH,H = 7.2 Hz, 2 H, H-4/H-4¢ or H-5/H-5¢),
2.01 (s, 6 H, CH3); dC(100 MHz, CD2Cl2) 146.7 (m, ipso-C6H4 of
dppbe), 137.8 (m, C-2/C-2¢), 136.6 (m, C-1/C-1¢), 136.2 (m, ipso-
C6H5 of dppbe), 134.1 (m, o-C6H4 of dppbe), 133.2 (m, o-C6H5
of dppbe), 131.3 (s, C-6/C-6¢), 131.0 (s, m-C6H4 of dppbe), 129.9
(s, p-C6H5 of dppbe), 129.4 (s, C-3/C-3¢), 128.6 (m, m-C6H5 of
dppbe), 125.9 (s, C-4/C-4¢ or C-5/C-5¢), 125.2 (s, C-4/C-4¢ or
C-5/C-5¢), 21.2 (s, CH3); dP(81 MHz, CD2Cl2) 52.05 (s with 195Pt
satellites, 1JP,Pt = 3138 Hz); n(KBr)/cm-1 3052 (s), 2922 (m), 1778
(m, n(C C)), 1753 (m), 1625 (s), 1481 (s), 1434 (vs), 1096 (s), 759
(s) 694 (vs), 547 (vs), 527 (vs); m/z(DEI) 847 (100%, [M]+), 641
(60, [(dppbe)Pt]+), 486 (10, [(dppbe)Pt - 2¥Ph]+), 205 (20, [4c]+);
Anal. calcd. for C46H38P2Pt: C 65.17, H 4.52; Found C 64.88, H
4.46.
[(dppbe)(g2-4,4¢-dibromotolane)Pt0]
(5a). Compound
3
(142 mg, 0.20 mmol) was reacted with 4a (66 mg, 0.20 mmol) to
yield 5a (83 mg, 40%) as orange crystals.
Mp: 127 ◦C (dec.); dH(400 MHz; CD2Cl2) 7.77 (m, 2 H, o-C6H4
of dppbe), 7.59 (m, 8 H, o-C6H5 of dppbe), 7.48 (m, 2 H, m-
9500 | Dalton Trans., 2010, 39, 9493–9504
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OCH3); dP(81 MHz, CD2Cl2) 51.68 (s with 195Pt satellites, 1JP,Pt
[(dppbe)(g2-1-phenyl-2-(2-pyridyl)acetylene)Pt0] (5d). Com-
pound 3 (112 mg, 0.16 mmol) was reacted with 4d (29 mg,
0.16 mmol) to yield 5d (54 mg, 49%) as yellow crystals.
=
3107 Hz); n(KBr)/cm-1 3052 (s), 2935 (m), 2830 (m), 1785 (m,
n(C C)), 1625 (s), 1587 (s), 1571 (s), 1481 (vs), 1433 (vs), 1241
(vs), 1181 (s), 1096 (vs), 1027 (s), 747 (vs), 695 (vs), 548 (vs), 526
(vs), 507 (vs); m/z(DEI) 879 (1%, [M]+), 641 (3, [(dppbe)Pt]+),
485 (2, [(dppbe)Pt - 2¥Ph]+), 238 (100, [4f]+); Anal. calcd. for
C46H38O2P2Pt · 0.5 C7H8: C 64.21, H 4.57; Found C 63.98, H 4.81.
Mp: 138 ◦C (dec.); dH(400 MHz, CD2Cl2) 8.61 (d, 3JH,H = 4.2 Hz,
1 H, H-5), 7.99 (d, 3JH,H = 7.0 Hz, 2 H, H-2¢/H-6¢), 7.79 (m, 2 H,
o-C6H4 of dppbe), 7.67 (m, 8 H, o-C6H5 of dppbe), 7.48 (m, 2 H,
m-C6H4 of dppbe), 7.33 (m, 13 H, m-C6H5 and p-C6H5 of dppbe
and H-3), 7.25 (d, 3JH,H = 7.7 Hz, 1 H, H-2), 7.16 (m, 3 H, H-3¢,
H-4¢ and H-5¢), 6.97 (m, 1 H, H-4); dC(100 MHz, CD2Cl2) 154.6
(m, C-1), 149.8 (s, C-5), 146.4 (m, ipso-C6H4 of dppbe), 136.2 (s,
C-3), 135.5 (m, ipso-C6H5 of dppbe), 134.0 (m, o-C6H4 of dppbe
and C-1¢), 133.4 (m, o-C6H5 of dppbe), 132.7 (m, C-2¢ and C-6¢),
131.1 (s, m-C6H4 of dppbe), 130.2 (s, p-C6H5 of dppbe), 128.7 (m,
m-C6H5 of dppbe), 128.3 (s, C-3¢ and C-5¢), 127.4 (s, C-2), 127.2
(s, C-4¢), 120.4 (s, C-4); dP(81 MHz, CD2Cl2) 51.28 (d with 195Pt
[(dppbe)(g2-4,4¢-dimethoxytolane)Pt0] (5g). Compound
3
(140 mg, 0.20 mmol) was reacted with 4g (46 mg, 0.20 mmol) to
yield 5g (68 mg, 39%) as orange crystals.
◦
Mp: >230 C; dH(400 MHz, CD2Cl2) 7.79 (m, 2 H, o-C6H4 of
dppbe), 7.65 (m, 8 H, o-C6H5 of dppbe), 7.48 (m, 6 H, m-C6H4 of
dppbe and H-2/H-2¢ and H-6/H-6¢), 7.34 (m, 12 H, m-C6H5 and
p-C6H5 of dppbe), 6.68 (m, 4 H, H-3/H-3¢ and H-5/H-5¢), 3.76
(s, 6 H, OCH3); dC(100 MHz, CD2Cl2) 158.5 (s, C-4/C-4¢), 146.9
(m, ipso-C6H4 of dppbe), 136.0 (m, ipso-C6H5 of dppbe), 134.0 (m,
o-C6H4 of dppbe), 133.4 (m, o-C6H5 of dppbe), 132.4 (s, C-2/C-2¢
and C-6/C-6¢), 131.0 (s, m-C6H4 of dppbe), 130.1 (s, p-C6H5 of
dppbe), 128.7 (m, m-C6H5 of dppbe), 128.0 (m, C-1/C-1¢), 113.8
(s, C-3/C-3¢ and C-5/C-5¢), 55.6 (s, OCH3); dP(81 MHz, CD2Cl2)
51.63 (s with 195Pt satellites, 1JP,Pt = 3065 Hz); n(KBr)/cm-1 3052 (s),
2954 (m), 2834 (m), 1743 (m, n(C C)), 1601 (s), 1506 (vs), 1481
(s), 1435 (vs), 1285 (s), 1242 (vs), 1180 (s), 1097 (s), 1028 (s), 831
(s), 747 (s), 694 (vs), 669 (s), 546 (vs), 526 (vs), 506 (s); m/z(DEI)
879 (1%, [M]+), 641 (3, [(dppbe)Pt]+), 486 (1, [(dppbe)Pt - 2¥Ph]+),
238 (100, [4g]+); Anal. calcd. for C46H38O2P2Pt: C 62.80, H 4.35;
Found C 62.46, H 4.36.
1
2
satellites, JP,Pt = 3063 Hz, JP,P = 55.1 Hz), 51.25 (d with 195Pt
satellites, 1JP,Pt = 3079 Hz, 2JP,P = 55.1 Hz); n(KBr)/cm-1 3051 (s),
1736 (s, n(C C)), 1629 (s), 1579 (vs), 1555 (m), 1482 (s), 1435 (vs),
1424 (vs), 1097 (vs), 759 (s), 694 (vs), 669 (s), 548 (vs), 527 (vs);
m/z(FAB in nba) 821 (80%, [M]+), 641 (65, [(dppbe)Pt]+), 561 (55,
[(dppbe)Pt – Ph]+), 485 (75, [(dppbe)Pt - 2¥Ph]+; Anal. calcd. for
C43H33NP2Pt · C4H8O: C 63.22, H 4.63, N 1.57; Found C 63.26, H
4.67, N 1.56.
[(dppbe)(g2-1,2-bis(2-pyridyl)acetylene)Pt0] (5e). Compound 3
(133 mg, 0.19 mmol) was reacted with 4e (34 mg, 0.19 mmol) to
yield 5e (75 mg, 49%) as yellow crystals.
Mp: 165 ◦C (dec.); dH(400 MHz, CD2Cl2) 8.53 (m, 2 H, H-
3
5/H-5¢), 7.96 (d, JH,H = 7.8 Hz, 2 H, H-2/H-2¢), 7.84 (m, 2 H,
[(dppn)(g2-2,2¢-dimethyltolane)Pt0]
(9a). Compound
8a
o-C6H4 of dppbe), 7.74 (m, 8 H, o-C6H5 of dppbe), 7.49 (m, 4 H,
m-C6H4 of dppbe and H-3/H-3¢), 7.33 (m, 12 H, m-C6H5 and p-
C6H5 of dppbe), 7.01 (m, 2 H, H-4/H-4¢); dC(100 MHz, CD2Cl2)
153.5 (m, C-1/C-1¢), 149.7 (s, C-5/C-5¢), 146.5 (m, ipso-C6H4 of
dppbe), 136.1 (s, C-3/C-3¢), 135.9 (m, ipso-C6H5 of dppbe), 134.2
(m, o-C6H4 of dppbe), 133.5 (m, o-C6H5 of dppbe), 131.1 (s, m-
C6H4 of dppbe), 130.1 (s, p-C6H5 of dppbe), 128.6 (m, m-C6H5
of dppbe), 127.4 (m, C-2/C-2¢), 121.0 (s, C-4/C-4¢); dP(81 MHz,
CD2Cl2) 52.60 (s with 195Pt satellites, 1JP,Pt = 3108 Hz); n(KBr)/cm-1
3049 (s), 1736 (s, n(C C)), 1628 (m), 1579 (vs), 1556 (s), 1481
(s), 1461 (vs), 1434 (vs), 1425 (vs), 1272 (m), 1097 (s), 781 (s),
744 (s), 694 (vs), 549 (vs), 527 (vs); m/z(FAB in nba) 822 (25%,
[M]+), 641 (15, [(dppbe)Pt]+), 561 (15, [(dppbe)Pt – Ph]+), 485 (40,
[(dppbe)Pt - 2¥Ph]+), 408 (40, [(dppbe)Pt - 3¥Ph]+); Anal. calcd.
for C42H32N2P2Pt: C 61.39, H 3.93, N 3.41; Found C 61.54, H 3.81,
N 3.35.
(235 mg, 0.31 mmol) was reacted with 4c (64 mg, 0.31 mmol) to
yield 9a (175 mg, 63%) as orange crystals.
◦
3
Mp: 106 C (dec.); dH(400 MHz, CD2Cl2) 8.02 (dd, JH,H
=
8.0 Hz, 4JH,H = 1.2 Hz, 2 H, H-4 and H-5 of dppn), 7.46 (m, 2 H,
H-2 and H-7 of dppn), 7.39 (t, 3JH,H = 7.5 Hz, 2 H, H-3 and H-6
of dppn), 7.14 (m, 12 H, o-C6H5 and p-C6H5 of dppn), 7.02 (m, 8
3
H, m-C6H5 of dppn), 6.94 (m, 2 H, H-6/H-6¢), 6.88 (dt, JH,H
=
7.4 Hz, 4JH,H = 1.5 Hz, 2 H, H-5/H-5¢), 6.73 (m, 2 H, H-3/H-3¢),
6.70 (m, 2 H, H-4/H-4¢), 1.98 (s, 6 H, CH3); dC(50 MHz, CD2Cl2)
139.1 (m, C-8a of dppn), 136.9 (m, C-2 and C-7 of dppn and
C-2/C-2¢), 136.2 (m, ipso-C6H5 of dppn), 135.9 (m, C-1 and C-8
of dppn and C-1/C-1¢), 133.6 (m, o-C6H5 of dppn), 132.8 (s, C-4
and C-5 of dppn), 130.0 (s, C-3/C-3¢), 129.3 (s, p-C6H5 of dppn),
128.2 (m, m-C6H5 of dppn), 127.8 (m, C-4a of dppn), 125.2 (m,
C-3 and C-6 of dppn and C-4/C-4¢ and C-5/C-5¢), 21.2 (s, CH3);
dP(81 MHz, CD2Cl2) 17.43 (s with 195Pt satellites, 1JP,Pt = 3049 Hz);
n(KBr)/cm-1 3053 (s), 2952 (m), 2919 (m), 1775 (s, n(C C)),
1751 (s, n(C C)), 1595 (s), 1479 (vs), 1455 (s), 1434 (vs), 1313
(m), 1182 (m), 1093 (vs), 875 (m), 824 (m), 772 (vs), 744 (vs), 693
(vs), 587 (vs), 519 (vs), 495 (vs); m/z(FAB in nba) 898 (2%, [M]+),
691 (6, [(dppn)Pt]+), 535 (4, [(dppn)Pt - 2¥Ph]+); Anal. calcd. for
C50H40P2Pt · C5H12: C 68.10, H 5.40; Found C 67.91, H 5.25.
[(dppbe)(g2-2,2¢-dimethoxytolane)Pt0] (5f). Compound
3
(129 mg, 0.18 mmol) was reacted with 4f (43 mg, 0.18 mmol) to
yield 5f (54 mg, 34%) as yellow crystals.
Mp: 183 ◦C (dec.); dH(400 MHz, CD2Cl2) 7.79 (m, 2 H, o-C6H4
of dppbe), 7.60 (m, 8 H, o-C6H5 of dppbe), 7.45 (m, 2 H, m-C6H4
of dppbe), 7.29 (m, 12 H, m-C6H5 and p-C6H5 of dppbe), 7.11
(m, 2 H, H-6/H-6¢), 7.07 (t, 3JH,H = 7.2 Hz, 2 H, H-4/H-4¢), 6.77
3
3
(d, JH,H = 8.4 Hz, 2 H, H-3/H-3¢), 6.67 (t, JH,H = 7.2 Hz, 2 H,
H-5/H-5¢), 3.43 (s, 6 H, OCH3); dC(100 MHz, CD2Cl2) 157.6 (s,
C-2/C-2¢), 146.9 (m, ipso-C6H4 of dppbe), 136.3 (m, ipso-C6H5 of
dppbe), 134.0 (m, o-C6H4 of dppbe), 133.3 (m, o-C6H5 of dppbe),
133.1 (s, C-6/C-6¢), 130.9 (s, m-C6H4 of dppbe), 129.9 (s, p-C6H5
of dppbe), 128.6 (m, m-C6H5 of dppbe), 127.1 (s, C-4/C-4¢), 126.6
(m, C-1/C-1¢), 119.8 (s, C-5/C-5¢), 110.0 (s, C-3/C-3¢), 55.0 (s,
[(dpp(o-xyl))(g2-2,2¢-dimethyltolane)Pt0] (9b). Compound 8b
(140 mg, 0.19 mmol) was reacted with 4c (40 mg, 0.19 mmol)
to yield 9b (63 mg, 38%) as pale yellow crystals.
Mp: 203 ◦C (dec.); dH(400 MHz, CD2Cl2) 7.60 (m, 8 H, o-C6H5
of dpp(o-xyl)), 7.36 (m, 4 H, p-C6H5 of dpp(o-xyl)), 7.29 (m, 8 H,
3
m-C6H5 of dpp(o-xyl)), 6.93 (d, JH,H = 7.5 Hz, 2 H, H-6/H-6¢),
3
4
6.81 (dt, JH,H = 7.3 Hz, JH,H = 1.7 Hz, 2 H, H-5/H-5¢), 6.74
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1
by 31P{ H} NMR spectroscopy. After completion of the reaction
(m, 2 H, m-C6H4 of dpp(o-xyl)), 6.63 (m, 2 H, H-4/H-4¢), 6.60
(m, 2 H, H-3/H-3¢), 6.25 (m, 2 H, o-C6H4 of dpp(o-xyl)), 4.13
(m, 4 H, PCH2), 1.82 (s, 6 H, CH3); dC(100 MHz, CD2Cl2) 137.4
(m, C-2/C-2¢), 136.8 (m, ipso-C6H5 of dpp(o-xyl)), 135.9 (m, C-
1/C-1¢), 134.8 (s, ipso-C6H4 of dpp(o-xyl)), 133.7 (m, o-C6H5 of
dpp(o-xyl)), 131.2 (s, o-C6H4 of dpp(o-xyl)), 129.9 (s, p-C6H5 of
dpp(o-xyl)), 129.6 (s, C-3/C-3¢), 129.1 (s, C-6/C-6¢), 128.2 (m,
m-C6H5 of dpp(o-xyl)), 126.1 (s, m-C6H4 of dpp(o-xyl)), 125.3 (s,
C-5/C-5¢), 124.8 (s, C-4/C-4¢), 38.9 (m, PCH2), 21.0 (s, CH3);
dP(81 MHz, CD2Cl2) 13.58 (s with 195Pt satellites, 1JP,Pt = 3449 Hz);
n(KBr)/cm-1 3053 (s), 2943 (m), 2916 (m), 1779 (s, n(C C)), 1754
(m, n(C C)), 1595 (s), 1480 (vs), 1455 (s), 1435 (vs), 1183 (m),
1096 (vs), 1027 (m), 863 (s), 837 (s), 763 (vs), 742 (vs), 695 (vs), 503
(vs); m/z(FAB in nba) 876 (1%, [M]+), 669 (4, [(dpp(o-xyl))Pt]+);
Anal. calcd. for C48H42P2Pt · C6H6: C 67.99, H 5.07; Found C
67.52, H 5.38.
10a was ob◦tained as yellow powder (88 mg, 90%).
Mp: 175 C (dec.); dH(400 MHz, CD2Cl2) 8.08 (d, 3JH,H = 8.0 Hz,
2 H, H-4 and H-5 of dppn), 7.62–7.41 (m, 8 H, H-2, H-3, H-6
and H-7 of dppn), 7.37–7.16 (m, 10 H), 7.06 (m, 2 H), 7.01–6.79
(m, 6 H), 6.73 (m, 3 H), 6.60 (m, 2 H), 6.42 (m, 1 H), 2.40 (s, 3
H, CH3), 1.88 (s, 3 H, CH3); dC(100 MHz, CD2Cl2) 159.7 (m),
143.1 (m), 138.9 (s), 138.5 (s), 136.4 (m including 2 different C-
atoms), 135.1 (s), 134.7 (m including 2 different C-atoms), 134.2 (m
including 2 different C-atoms), 133.7 (m including 2 different C-
atoms), 131.5 (s), 130.7 (s), 130.2 (s), 128.9 (m), 128.5 (m including
3 different C-atoms), 127.8 (m), 125.7 (m), 124.9 (m including 2
different C-atoms), 123.8 (m), 121.3 (s), 26.9 (s, CH3), 20.1 (s,
CH3); dP(81 MHz, CD2Cl2) 11.92 (d with 195Pt satellites, JP,Pt
=
1
2427 Hz, 2JP,P = 34 Hz), 8.98 (d with 195Pt satellites, 1JP,Pt = 1499 Hz,
2JP,P = 34 Hz); n(KBr)/cm-1 3052 (s), 2982 (m), 2916 (m), 2112 (s,
n(C C)), 1595 (s), 1573 (m), 1480 (vs), 1435 (vs), 1329 (s), 1314
(s), 1185 (s), 1158 (s), 1096 (vs), 878 (m), 824 (s), 771 (vs), 743 (vs),
693 (vs), 585 (vs), 524 (vs), 499 (vs); m/z(DEI) 897 (10%, [M]+),
691 (20, [(dppn)Pt]+), 206 (100, [4c]+); Anal. calcd. for C50H40P2Pt
· 0.25 CH2Cl2: C 65.67, H 4.44; Found C 65.90, H 4.57.
Irradiation experiments in the solid state
2
In a sample vial the appropriate (diphosphine)(h -tolane)Pt0
complex was placed in the sunlight for the stated periods. From
time to time the vial was turned to ensure constant irradiation
conditions. A portion of each sample was dissolved in benzene-d6
1
and a 31P{ H} NMR spectrum was recorded to survey the result
Irradiation experiments in solution
of the experiment.
The appropriate (diphosphine)(h -tolane)Pt0 complex was dis-
2
5a. Complex 5a (11 mg, 0.011 mmol) was irradiated with
solved in toluene and put in a round bottom flask. These solutions
were irradiated with sunlight for the stated periods and the
reaction progress was checked by TLC. After completion of the
reactions the solvent was removed under reduced pressure and the
residue was worked up by column chromatography to isolate the
corresponding products. In the case of 5c, 5g, 5f and 9a, this work
up procedure failed.
sunlight for approximately 12 days. Integration of the signals in
1
the corresponding 31P{ H} NMR spectrum revealed nearly 90%
conversion of 5a to 6a.
dP(81 MHz, C6D6) 51.17 (s with 195Pt satellites, 1JP,Pt = 3102 Hz,
1
2
residual 5a), 50.59 (d with 195Pt satellites, JP,Pt = 2467 Hz, JP,P
=
=
1
2
3.2 Hz, 6a), 49.23 (d with 195Pt satellites, JP,Pt = 1575 Hz, JP,P
3.2 Hz, 6a).
5a. A solution of 5a (120 mg, 0.123 mmol) in toluene (60 mL)
was irradiated with sunlight for approximately 30 days. After
removing the solvent the residue was chromatographed on silica
gel using dichloromethane–hexane (2/1) → dichloromethane as
eluent to yield 6a (45 mg, 37%) as pale yellow powder.
5b. Complex 5b (16 mg, 0.016 mmol) was irradiated with
sunlight for approximately 10 days. Integration of the signals in the
1
corresponding 31P{ H} NMR spectrum revealed 45% conversion
of 5b to 6b.
dP(81 MHz, C6D6) 51.77 (s with 195Pt satellites, 1JP,Pt = 3132 Hz,
◦
Mp: 158 C (dec.); dH(400 MHz, CD2Cl2) 7.75 (m, 5 H), 7.67
1
2
residual 5b), 50.22 (d with 195Pt satellites, JP,Pt = 2454 Hz, JP,P
=
=
(m, 1 H), 7.54–7.42 (m, 11 H), 7.34 (m, 8 H), 7.20 (m, 2 H), 7.05
(m, 1 H), 6.97 (m, 2 H), 6.81 (m, 2 H); dC(100 MHz, CD2Cl2)
155.2 (m), 139.8 (m), 134.4 (m), 134.1 (m, including 3 different C-
atoms), 132.8 (s), 132.5 (m, including 2 different C-atoms), 131.9
(s), 131.2 (m, including 2 different C-atoms), 130.0 (m), 129.6
(s), 129.0 (m, including 2 different C-atoms), 119.0 (s), 116.8 (s);
dP(81 MHz, CD2Cl2) 50.33 (d with 195Pt satellites, 1JP,Pt = 2493 Hz,
1
2
3.0 Hz, 6b), 48.89 (d with 195Pt satellites, JP,Pt = 1615 Hz, JP,P
3.0 Hz, 6b).
5c. Complex 5c (13 mg, 0.015 mmol) was irradiated with
sunlight for approximately 11 days. Integration of the signals in the
1
corresponding 31P{ H} NMR spectrum revealed 25% conversion
of 5c to 6c.
dP(81 MHz, C6D6) 52.38 (s with 195Pt satellites, 1JP,Pt = 3149 Hz,
2JP,P = 4.0 Hz), 49.01 (d with 195Pt satellites, 1JP,Pt = 1603 Hz, 2JP,P
=
1
2
residual 5c), 50.50 (d with 195Pt satellites, JP,Pt = 2469 Hz, JP,P
=
=
4.0 Hz); n(KBr)/cm-1 3054 (m), 2112 (s, n(C C)), 1620 (w), 1581
(w), 1481 (vs), 1468 (s), 1435 (vs), 1210 (m), 1185 (m), 1114 (s),
1100 (vs), 1069 (s), 1003 (vs), 824 (s), 799 (s), 745 (s), 693 (vs),
670 (s), 551 (vs), 532 (vs), 506 (s); m/z(DEI) 977 (0.1%, [M]+),
897 (0.05, [M – Br]+), 721 (1, [(dppbe)PtBr]+); Anal. calcd. for
C44H32Br2P2Pt: C 54.06, H 3.30, Br 16.35; Found C 54.27, H 3.38,
Br 16.76.
1
2
2.8 Hz, 6c), 48.57 (d with 195Pt satellites, JP,Pt = 1561 Hz, JP,P
2.8 Hz, 6c).
2
5d–g and 9b. The appropriate (diphosphine)(h -tolane)Pt0
complex (12 mg, 0.012–0.015 mmol) was irradiated with sunlight
1
for approximately 14 days. The corresponding 31P{ H} NMR
spectrum showed only the resonances of the starting material.
No evidence for C–C bond activation was observed in any case.
5b. A solution of 5b (237 mg, 0.236 mmol) in toluene (60 mL)
was irradiated with sunlight for approximately 21 days. After
removing the solvent the residue was chromatographed on silica
gel using dichloromethane–hexane (2/1) → dichloromethane as
9a. Orange crystals of 9a (98 mg, 0.110 mmol) were placed
in a sample vial and irradiated as described above for 50 days to
ensure full conversion into 10a. The reaction progress was checked
9502 | Dalton Trans., 2010, 39, 9493–9504
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©

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Table 2 Crystal data and refinement details for the X-ray structure determinations
Compound
Formula
5a
5b
5c
5d
5e
6b
7b
9a
9b
C44H32Br2P2Pt C46H36Br2P2Pt C46H38P2Pt C43H33NP2Pt C42H32N2P2Pt C46H36Br2P2Pt C46H36Br2P2Pt, C50H40P2Pt, C48H42P2Pt,
C4H8O
1077.70
-90(2)
Monoclinic
P21/n
15.3444(5)
15.6009(3)
21.3260(6)
C6H6
C6H6
Fw/g mol-1
977.55
-90(2)
1005.60
-90(2)
Orthorhombic Triclinic
847.79
-90(2)
820.73
-90(2)
821.73
-90(2)
1005.60
-90(2)
975.96
-90(2)
Triclinic
953.95
-90(2)
Triclinic
T/◦C
Crystal system Triclinic
Triclinic
Triclinic
Triclinic
¯
¯
¯
¯
¯
¯
¯
Space group
P1
Pbca
P1
P1
P1
P1
P1
P1
˚
a/A
10.7128(4)
11.4086(4)
16.6238(6)
100.791(2)
96.609(2)
20.5293(3)
16.4027(2)
23.2611(3)
90
11.1682(5)
12.2745(5)
15.0911(7)
79.550(2)
69.759(2)
69.043(2)
11.3596(4)
11.5124(3)
14.0287(5)
71.401(2)
83.585(2)
88.476(2)
8.9010(4)
11.0800(6)
19.0760(7)
103.772(3)
96.509(2)
107.308(2)
8.9257(2)
11.2405(4)
20.9629(8)
11.8366(5)
12.6126(5)
15.7836(9)
102.484(2)
107.407(3)
95.895(3)
11.6006(5)
12.9579(5)
15.4685(5)
91.791(2)
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
78.7990(10) 90
83.363(2)
69.013(2)
90
90
111.085(2)
90
107.389(2)
103.098(2)
107.566(2)
3
˚
V/A
1870.52(12) 7832.85(18) 1808.67(14) 1727.8(1)
2
1.736
60.03
1709.75(14) 1923.84(11) 4763.4(2)
2
1.596
42.3
12065
2159.55(18) 2148.93(14)
2
1.501
33.61
15004
Z
8
2
2
2
4
2
r/g cm-3
1.705
57.37
48171
1.557
40
12759
1.578
41.85
12393
1.736
58.4
13479
1.503
47.24
31984
1.474
33.76
15688
m/cm-1
Measured data 11771
Data with
I > 2s(I)
6807
6750
6772
6421
6139
6971
7025
7358
7398
Unique data/Rint 7820/0.0485 8934/0.0822 8218/0.0447 7859/0.0494 7769/0.0502 8752/0.0332 10847/0.0669 9765/0.0365 9765/0.0470
wR2 (all data, on 0.1268
0.0775
0.0902
0.0912
0.0996
0.0962
0.1483
0.1090
0.1226
F2)a
R1 (I > 2s(I))a 0.0482
0.0349
1.036
0.0451
1.020
0.0420
1.018
0.0470
1.060
0.0426
1.008
0.0534
1.004
0.0469
1.023
0.0526
1.011
sb
1.048
-3
˚
Res. dens./e A
Absorpt. method NONE
CCDC No. 743160
1.396/-1.646 1.298/-1.458 1.471/-1.288 1.078/-1.469 1.094/-1.133 1.318/-1.457 1.476/-1.506 1.530/-1.432 1.657/-1.741
NONE
743161
NONE
743162
NONE
743163
NONE
743164
NONE
743165
NONE
743166
NONE
743167
NONE
743269
2
2
a Definition of the R indices: R1 = (R||Fo| - |Fcꢀ)/R|Fo|; wR2 = {R[w(Fo - Fc2)2]/R[w(Fo2)2]}1/2 with w-1 = s (Fo2) + (aP)2+bP; P = [2Fc2 + Max(Fo2]/3;
b s = {R[w(Fo - Fc2)2]/(No - Np)}
.
2
1/2
eluent to yield 6b (60 mg, 25%) as white powder and 7b (57 mg,
24%) as yellow crystals.
(d with 195Pt satellites, 1JP,Pt = 4090 Hz, 2JP,P = 3.5 Hz); n(KBr)/cm-1
3053 (m), 2973 (m), 2868 (m), 2205 (m, n(C C)), 1631 (m), 1573
(s), 1484 (vs), 1435 (vs), 1190 (s), 1100 (vs), 881 (s), 816 (s), 746
(s), 693 (vs), 671 (s), 560 (vs), 533 (vs), 505 (vs); m/z(DEI) 1006
(2%, [M]+), 924 (3, [M –Br]+), 721 (40, [(dppbe)PtBr]+), 641 (10,
[(dppbe)Pt]+), 283 (80, [4b – Br]+); Anal. calcd for C46H36Br2P2Pt
· 2 C4H8O: C 56.41, H 4.56, Br 13.90; Found C 56.84, H 4.49, Br
14.03.
6b. Mp: >230 ◦C; dH(400 MHz, CD2Cl2) 7.84 (m, 2 H), 7.77
(m, 1 H), 7.66 (m, 5 H), 7.56–7.38 (m, 12 H), 7.24 (m, 2 H), 7.12
3
4
(s, 1 H), 7.02 (dd, JH,H = 8.2 Hz, JH,H = 1.9 Hz, 1 H), 6.92 (m,
4 H), 6.83 (m, 1 H), 6.73 (m, 1 H), 1.94 (s, 3 H, CH3), 1.93 (s,
3 H, CH3); dC(100 MHz, CD2Cl2) 147.3 (m), 141.8 (m), 138.3
(m), 134.4 (m, including 3 different C-atoms), 133.8 (m), 132.7
(m, including 3 different C-atoms), 131.8 (m, including 2 different
C-atoms), 131.1 (m), 129.1 (m, including 2 different C-atoms),
128.7 (m), 128.2 (s), 126.5 (m), 118.4 (s), 116.9 (s), 25.9 (s, CH3),
20.6 (s, CH3); dP(81 MHz, CD2Cl2) 50.08 (d with 195Pt satellites,
Crystal structure determinations
The intensity data for the compounds were collected on a Nonius
KappaCCD diffractometer using graphite-monochromated Mo-
Ka radiation. Data were corrected for Lorentz and polarization
effects but not for absorption effects.32,33 The structures were
solved by direct methods (SHELXS)34 and refined by full-matrix
1JP,Pt = 2474 Hz, 2JP,P = 4.0 Hz), 48.86 (d with 195Pt satellites, 1JP,Pt
=
1639 Hz, 2JP,P = 4.0 Hz); n(KBr)/cm-1 3053 (s), 2950 (w), 2110 (s,
n(C C)), 1619 (m), 1472 (vs), 1435 (vs), 1187 (s), 1100 (vs), 1028
(s), 865 (m), 839 (m), 815 (m), 745 (s), 693 (vs), 670 (s), 552 (vs),
532 (vs), 506 (vs); m/z(DEI) 1006 (2%, [M]+), 924 (4, [M – Br]+),
721 (35, [(dppbe)PtBr]+), 641 (12, [(dppbe)Pt]+), 487 (4, [(dppbe)Pt
– 2¥Ph]+), 364 (4, [4b]+); Anal. calcd. for C46H36Br2P2Pt: C 54.94,
H 3.61, Br 15.89; Found C 55.28, H 3.59, Br 15.31.
least squares techniques against Fo (SHELXL-97) (Table 2).35
2
All hydrogen atoms were included at calculated positions with
fixed thermal parameters. All non-disordered non-hydrogen atoms
were refined anisotropically.35 Diamond 3.0b as well as POV-
Ray 3.6.1c were used for structure representations. CCDC-
743160 (for 5a), -743161 (for 5b), -743162 (for 5c), -743163
(for 5d), -743164 (for 5e), -743165 (for 6b), -743166 (for 7b), -
743167 (for 9a) and -743269 (for 9b) contain the supplementary
crystallographic data for this paper.† These data can be obtained
free of charge from the Cambridge Crystallographic Centre via
www.ccdc.cam.ac.uk/data_request/cif.
◦
7b. Mp: 151 C (dec.); dH(400 MHz, CD2Cl2) 7.76 (m, 4 H),
7.63 (m, 1 H), 7.51 (m, 11 H), 7.38 (m, 10 H), 7.29 (m, 2 H), 6.98 (m,
2 H), 6.80 (d, 3JH,H = 7.0 Hz, 1 H), 2.45 (s, 3 H, CH3), 2.13 (s, 3 H,
CH3); dC(100 MHz, CD2Cl2) 136.5 (m), 142.2 (m), 139.0 (m), 138.1
(m), 135.4 (m), 134.0 (m, including 5 different C-atoms), 133.1 (s),
132.6 (m), 131.6 (m), 131.3 (s), 130.1 (m), 128.9 (m, including 3
different C-atoms), 123.6 (s), 121.5 (s), 117.0 (m), 95.6 (s, C C),
89.5 (s, C C), 21.0 (s, CH3), 20.7 (s, CH3); dP(81 MHz, CD2Cl2)
49.64 (d with 195Pt satellites, 1JP,Pt = 1684 Hz, 2JP,P = 3.5 Hz), 43.01
Computational details
See part B.‡
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The Royal Society of Chemistry 2010
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Acknowledgements
The donation of K2PtCl4 by the Heraeus GmbH is gratefully
acknowledged by the authors. Additionally, we thank the students
A. Pospiech and M. Assmann for preparing the phosphane
ligands as well as some tolanes. Financial support from the Carl–
Zeiss Stiftung (D.E.) is also acknowledged. Finally, we thank the
reviewers for their valuable comments and suggestions.
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9504 | Dalton Trans., 2010, 39, 9493–9504
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