Synthesis and Characterization of an Unusual Platinum(II) Alkene Complex with an η2-Arene Interaction

Article abstract of DOI:10.1021/om990272e

Dichloro(9,10-dihydro-9,10-ethenoanthracene)platinum(II) has been synthesized and characterized by NMR spectroscopy and X-ray crystallography. The crystal structure shows that the alkene fragment serves as an anchor to place one of the aromatic rings in close enough proximity for an η²-arene-platinum interaction. Thus, the ethenoanthracene functions as a bidentate ligand.

Full text of DOI:10.1021/om990272e

4558
Organometallics 1999, 18, 4558-4562
Syn th esis a n d Ch a r a cter iza tion of a n Un u su a l
P la tin u m (II) Alk en e Com p lex w ith a n η2-Ar en e
In ter a ction
Laura L. Wright,* Scott J . Moore, J ohn A. McIntyre, Sandra M. Dowling,
J ennifer D. Overcast, G. Robert Grisel, IV, Karen Konkel Nelson, and
Paula R. Rupert
Department of Chemistry, Furman University, Greenville, South Carolina 29613
William T. Pennington
Department of Chemistry, Clemson University, Clemson, South Carolina 29634
Received April 16, 1999
Dichloro(9,10-dihydro-9,10-ethenoanthracene)platinum(II) has been synthesized and char-
acterized by NMR spectroscopy and X-ray crystallography. The crystal structure shows that
the alkene fragment serves as an anchor to place one of the aromatic rings in close enough
proximity for an η2-arene-platinum interaction. Thus, the ethenoanthracene functions as
a bidentate ligand.
In tr od u ction
congestion is achieved as a result of the small bite angle
of the η3-allyl ligand. However, it is important to note
that the alkene-Pt bond distances are longer than those
reported in other platinum(II) complexes with styrene,
indicative of a weaker coordination of the styrene in this
complex. Since steric factors play such an important role
in the orientation of the ligand about the metal center,
it follows that a ligand which encounters severe steric
congestion when it coordinates in the normal upright
orientation might adopt an in-plane orientation. To
evaluate the feasibility of this premise, studies were
initiated using 9,10-dihydro-9,10-ethenoanthracene (1).
Platinum(II) alkene complexes are well-known orga-
nometallic species. The bonding of alkenes to a metal
center can be described qualitatively as donation of the
alkene π electrons into an empty orbital on the metal
with simultaneous back-donation of metal electrons into
the empty π* orbital of the alkene.1 In most square-
planar d8 metal alkene complexes the alkene is aligned
in an upright perpendicular orientation with respect to
the coordination plane.2 Hoffmann and co-workers have
performed calculations which indicate that this prefer-
ence is not due to electronic factors but instead is due
to the alkene avoiding steric interactions with the cis
ligands.3 Several examples have been reported in which
Pt(II) is bonded to an alkene that is actually aligned in
the in-plane orientation.4 Many of these examples of in-
plane alkenes that have been observed have the com-
mon feature of mutually perpendicular double bonds.
In these cases one double bond is coordinated in the
more common upright orientation while the other
double bond is forced to coordinate with the in-plane
orientation. In contrast, the lack of steric crowding in
the (η3-methylallyl)(triphenylphosphine)(styrene)plat-
inum(II) cation appears responsible for the ability of the
styrene to coordinate in a virtually in-plane orientation.5
According to Miki and co-workers, the lack of steric
If this ligand coordinates in the typical upright orienta-
tion, one of the ligand’s six-membered rings would be
placed in the same space as a substituent located in the
cis coordination site. Rotation of the alkene into the in-
plane orientation would alleviate the steric problems.
One of the six-membered rings would then be directed
above the coordination plane, while the other would be
directed away from the metal coordination sphere. The
reaction of ethenoanthracene with platinum(II) salts
and the characterization of the product obtained will
be described herein. Additional related studies with
allylbenzene and 1,4-dihydronaphthalene will also be
discussed.
(1) (a) Dewar, M. J . S. Bull. Soc. Chim. Fr. 1951, 18, C79. (b) Chatt,
J .; Duncanson, L. A. J . Chem. Soc. 1953, 2939. (c) Dewar, M. J . S.;
Ford, G. P. J . Am. Chem. Soc. 1979, 101, 783.
(2) Lukehart, C. M. Fundamental Transition Metal Organometallic
Chemistry; Brooks/Cole: Monterey, CA, 1985.
(3) Albright, T. A.; Hoffmann, R.; Thibeault, J . C.; Thorn, D. L. J .
Am. Chem. Soc. 1979, 101, 3801.
(4) (a) Wright, L. L.; Wing, R. M.; Rettig; M. F.; Wiger, G. R. J . Am.
Chem. Soc. 1980, 102, 5949. (b) Wright, L. L.; Wing, R. M.; Rettig, M.
F. J . Am. Chem. Soc. 1982, 104, 610. (c) Rakowsky, M. H.; Woolcock,
J . C.; Wright, L. L.; Green, D. B.; Rettig, M. F.; Wing, R. M.
Organometallics 1987, 6, 1211.
Resu lts a n d Discu ssion
The synthesis of the platinum(II) ethenoanthracene
complex was carried out by reacting Zeise’s dimer with
a stoichiometric amount of ethenoanthracene in a
toluene-ether solvent mixture to yield a bright orange
(5) Miki, K.; Kai, Y.; Kasai, N.; Kurosawa, H. J . Am. Chem. Soc.
1983, 105, 2482.
10.1021/om990272e CCC: $18.00 © 1999 American Chemical Society
Publication on Web 09/28/1999

A Pt(II) Alkene Complex with an η2-Arene Interaction
Organometallics, Vol. 18, No. 22, 1999 4559
crystalline solid. A comparison of the 1H NMR spectrum
of the complex with that of the free ethenoanthracene
indicates clearly that the ethenoanthracene coordinates
to the metal via the ethene fragment. The multiplet
corresponding to the alkene protons was shifted from
7.40 to 5.50 ppm and displayed coupling to 195Pt. The
protons on the bridgehead carbons shift slightly from
5.50 to 5.65 ppm upon coordination of the ligand to the
metal. The hydrogens on the aromatic rings of the free
ligand display characteristic quartets at 6.78 and 7.32
ppm. In the complex these quartets split into two sets
of quartets, giving a total of four resonances attributed
to the aromatic hydrogens located at 7.65, 7.50, 7.35,
and 7.15 ppm. This is consistent with a breaking of the
symmetry of the organic fragment such that the two
aromatic rings are no longer equivalent. The 13C NMR
spectrum provides more information about the manner
in which the symmetry has been altered.
F igu r e 1. ORTEP drawing of dichloro(9,10-dihydro-9,10-
ethenoanthracene)platinum(II) showing 35% probability
thermal ellipsoids and atom labeling.
The 13C NMR spectrum of free ethenoanthracene
shows five resonances. Upon coordination to platinum
eight resonances are present and dramatic changes in
chemical shifts are observed. The resonances assigned
to the bridging ethene carbons shift from 139 to 75 ppm,
Ta ble 1. Cr ysta l Da ta for C16H12Cl2P t‚0.5CHCl3
formula
fw
C16H12Cl2Pt‚0.5CHCl3
529.96
cryst syst
space group
a, Å
b, Å
c, Å
monoclinic
Cc (No. 9)
7.969(2)
17.898(5)
22.897(9)
98.57(3)
3229(2)
8
a shift of 64 ppm, and display coupling to 195Pt (J Pt,C
)
151 Hz). Prior to coordination the quaternary carbons
are equivalent and appear at 146 ppm. Upon coordina-
tion they split into two resonances, one at 146 ppm and
one at 100 ppm. This dramatic shift of one of the
quaternary carbons was unexpected. The remaining
carbons of the aromatic rings which originally gave rise
to two resonances appear as four resonances in the
complex. Upon inspection of these NMR data it became
apparent that the structure of the material isolated was
not the expected in-plane-coordinated ethenoanthracene.
Instead, the ethenoanthracene seemed to be coordinat-
ing as a bidentate ligand (2).
â, deg
V, Å3
Z
D
calcd, g cm-3
2.18
9.35
µ, mm-1
transmissn coeff
no. of obsd data
R(Fo)a
0.75/0.96
2179
0.0590
Rw(Fo)b
0.0800
a
b
R ) ∑||Fo| - |Fc||/∑|Fo|. Rw ) [∑w(|Fo| - |Fc|)2/∑w(Fo)2]1/2
.
Ta ble 2. Bon d Len gth s (Å)
Pt(1)-Cl(1)
Pt(1)-C(1)
Pt(1)-C(11)
C(1)-C(2)
2.326(10)
2.13(4)
2.33(2)
1.43(5)
1.42(4)
1.50(4)
1.33(4)
1.41(5)
1.39(4)
1.56(4)
1.50(4)
1.42(4)
1.35(5)
Pt(1)-C1(2)
Pt(1)-C(2)
Pt(1)-C(16)
C(1)-C(10)
C(3)-C(16)
C(4)-C(9)
2.270(9)
2.10(3)
2.34(3)
1.50(4)
1.57(4)
1.44(4)
1.39(5)
1.39(5)
1.49(3)
1.42(4)
1.40(5)
1.37(4)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(5)-C(6)
C(6)-C(7)
C(7)-C(8)
C(8)-C(9)
C(9)-C(10)
C(11)-C(12)
C(12)-C(13)
C(14)-C(15)
C(10)-C(11)
C(11)-C(16)
C(13)-C(14)
C(15)-C(16)
To clarify the structure of this new material, a single-
crystal X-ray diffraction study was performed. X-ray-
quality crystals were obtained by slow evaporation of a
chloroform solution of the complex. The molecular
structure determined clearly shows that the complex is
not a dimer in which the ligand is monodentate. Instead,
the ethenoanthracene coordinates in a bidentate fashion
through the C1-C2 bond as expected and through the
C11-C16 bond in one of the arene rings, as shown in
Figure 1. The bidentate nature of the coordination
requires the orientation of the coordinated double bond
to be upright and not the anticipated in-plane orienta-
tion.
The complex crystallizes in the space group Cc with
two independent molecules related by a pseudo-inver-
sion center with one solvent molecule (CHCl3) per
asymmetric unit which breaks the symmetry. Crystal-
lographic data are tabulated in Table 1, and selected
bond distances are provided in Table 2. The two
molecules differ slightly in structure, but they have the
same key features. By focusing on one of these mol-
ecules, it is possible to gain some insight into the
relative strengths of the metal-ligand interactions. The
bond length for the platinum to the midpoint of the C1-
C2 double bond is 1.98(4) Å. In comparison, the bond
distance from the midpoint of the C11-C16 bond of the
aromatic ring to the platinum atom is 2.22(4) Å. This
difference in bond lengths reflects a difference in the
relative strengths of interaction with the metal such
that the C1-C2 double bond is coordinating more
strongly to the metal. This qualitative analysis of the
bonding interactions can be extended further. Viewing
the complex from above the coordination plane, as
shown in Figure 2, reveals further information about
the arene-platinum interaction. The coordinated aro-
matic ring appears to have bent back from the metal
center. The aromatic rings in this ligand are normally
coplanar with the bridgehead carbons, as observed in

4560 Organometallics, Vol. 18, No. 22, 1999
Wright et al.
Upon analysis of the structure of this complex, it was
of interest to see if other arenes could be bound to Pt-
(II) in a similar fashion. Allylbenzene was considered a
promising candidate for further work, since it has the
same relative distance between the arene ring and the
alkene fragment. A direct reaction between allylbenzene
and Na2[PtCl4] was carried out, yielding Na[PtCl3(η2-
CH2dCHCH2C6H5)] (3). This is a simple Zeise’s salt type
Figu r e 2. Top view of dichloro(9,10-dihydro-9,10-ethenoan-
thracene)platinum(II).
the uncoordinated portion of the complex. The coordina-
tion of the aromatic ring bends the ring back 11° away
from the normal orientation. This is clear evidence of π
back-bonding between the metal and the coordinated
aromatic ring carbons. This loss of planarity upon
coordination has been well-documented for metal alkene
complexes.6
product with the alkene portion coordinated to the Pt
and the arene uncoordinated.
Upon treatment of 3 with 1 equiv of pyridine, trans-
(pyridine)(η2-allylbenzene)dichloroplatinum(II) (4) is iso-
lated. The elemental analysis is consistent with this
The 13C NMR data can now be reevaluated in light
of this monomeric structure. The shift of one of the
quaternary aromatic carbons now is completely under-
standable. Upon coordination to the platinum it shifts
toward TMS by 46 ppm. The ethene carbons (C1-C2)
shift by 64 ppm toward TMS. These shifts are as
expected for an η2 bonding interaction with substantial
π back-bonding. The magnitudes of the shifts provide
additional direct evidence of the relative bonding inter-
actions for the two portions of the ligand with the
platinum. The smaller change in chemical shift of the
quaternary carbons of the aromatic ring demonstrates
that the bond between C11 and C16 has not been
altered as much by bonding to the metal as has the C1-
C2 bond, again indicative of a weaker Pt-arene bonding
interaction.
This η2-arene coordination is unusual. Most examples
of arene coordination to transition metals involve η6
coordination, as in (arene)Cr(CO)3 complexes, or η2
coordination with at least one of the coordinating
carbons being unsubstituted.7 What we have observed
seems to be equivalent to the η2 coordination of a
tetrasubstituted alkene. Complexes with tetrasubsti-
tuted alkenes have been of interest but have rarely been
isolated in stable form. The preference of this particular
ligand to coordinate in a bidentate η4 manner is most
likely due to increased stability of the upright perpen-
dicular orientation of the C1-C2 bond. Rather than
coordinate in the less favorable in-plane orientation, one
of the aromatic rings coordinates to the metal, and this
cleaves the chloride bridges. Thus, in this situation the
alkene fragment serves as an anchor to place the
aromatic ring in close enough proximity to allow for a
binding interaction.
formulation, as is the 1H NMR spectrum. Again the
alkene portion shows three unique resonances in the
spectrum, and each is coupled to the 195Pt. Both allylic
protons are clearly visible in the spectrum, as are the
aromatic protons. Attempts to remove the pyridine from
4 and open up a coordination site for the arene to bond
to yielded a white solid. The same white solid was
isolated from the direct reaction of allylbenzene with
1
Zeise’s dimer. The H NMR spectrum of this material
shows that the alkene portion of the molecule is
coordinated, as evidenced by the 195Pt coupling. In 3 and
4 the aromatic resonances are all at chemical shifts
greater than 7.2 ppm, but in this new material the
aromatic resonances are shifted to 6.8 ppm. The two
allylic protons are still visible in the spectrum, indicat-
ing that this material is not an η3-allyl complex. When
the 13C NMR spectrum was acquired, only seven reso-
nances were observed. The three carbons of the allyl
fragment are easily identifiable at 93, 64, and 39 ppm,
with the resonances at 93 and 64 ppm showing 195Pt
coupling, but there are only four aromatic carbons in
the spectrum. The quaternary carbon at 148 ppm shows
weak Pt coupling, and one of the other aromatic carbon
resonances also shows weak Pt coupling, but with only
four aromatic resonances the arene cannot be coordinat-
ing in a simple static η2 manner.
Casas et al.7c have observed similar NMR behavior
in a platinum(II) complex of 2-benzylpyridine. In their
complex, the nitrogen of the pyridine serves as the
anchor for an arene so that it is capable of binding as
an η2-arene. Their crystal structure shows that the
arene is bound as a weak η2-arene in the solid state,
but in solution they have observed a fluxional behavior
such that both ortho carbon atoms of the arene display
(6) Ittel, S. D.; Ibers, J . A. Adv. Organomet. Chem. 1976, 14, 33.
(7) (a) Browning, J .; Green, M.; Penfold, B. R.; Spencer, J . L.; Stone,
F. G. A. J . Chem. Soc., Chem. Commun. 1973, 31. (b) Sweet, J . R.;
Graham, W. A. G. Organometallics 1983, 2, 135. (c) Casas, J . M.;
Fornies, J .; Martin, A.; Menjon, B. Organometallics 1993, 12, 4376.
(d) Li, C.-S.; J ou, D.-C.; Cheng, C.-H. Organometallics 1993, 12, 3945.
(e) Liu, C.-H.; Li, C.-S.; Cheng, C.-H. Organometallics 1994, 13, 18.

A Pt(II) Alkene Complex with an η2-Arene Interaction
Organometallics, Vol. 18, No. 22, 1999 4561
weak coupling to the platinum. Cheng et al.7d,e have also
found a similar situation with a palladium complex. In
their work they have found that an η2-aryl group is able
to rotate in a manner such that it slips between two
limiting η2-arene orientations. While our system uses
a different functional group to anchor the arene in the
vicinity of the platinum, it likely uses the same types
of motions. The added degree of rotational freedom
between the alkene and arene fragments present in
allylbenzene gives rise to the different coordination
geometry that it adopts, as compared to that of the
ethenoanthracene complex.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. Zeise’s salt9 and Zeise’s dimer8
were prepared using standard literature methods. 9,10-Dihy-
dro-9,10-ethenoanthracene was provided by Steve Ittel, Cen-
tral Research and Development, E. I. DuPont de Nemours and
Co. All other alkenes were used as received (Aldrich). Elemen-
tal analyses were performed by Midwest Micro Laboratory.
NMR spectra were measured at 300 MHz (1H) and 75 MHz
(13C), and coupling constants are reported in hertz.
Dich lor o(9,10-d ih yd r o-9,10-et h en oa n t h r a cen e)p la t -
in u m (II)‚0.5(tolu en e) (2). To 0.315 g (0.536 mmol) of [(C2H4)-
PtCl2]2 (Zeise’s dimer) dissolved in 25 mL of diethyl ether and
5 mL of toluene was added 0.219 g (1.073 mmol) of 9,10-
dihydro-9,10-ethenoanthracene. The solution was stirred vig-
orously under N2 for 6 h. Upon concentration of the resulting
solution, a bright orange solid was produced. Filtration yielded
0.46 g of the desired product with 0.5 equiv of toluene
In an effort to remove this flexiblility and isolate an
analogue of 2, 1,4-dihydronaphthalene (5) was reacted
with Pt(II). When Zeise’s dimer was reacted with 1,4-
1
cocrystallized for an 85% yield. H NMR (CDCl3): δ 7.65 (m,
2 H), 7.50 (m, 2 H), 7.35 (m, 2 H), 7.15 (s, toluene C6H5-),
7.20 (m, 2 H), 5.60 (m, H3 and H10), 5.50 (m, J Pt,H ) 95, H1
and H2), 2.38 (s, toluene -CH3). 13C NMR (CDCl3): δ 146 (C4,
C9), 135, 131, 127, 124, 100 (C11, C16), 75 (J Pt,C ) 151, C1,
C2), 52 (C3, C10). IR (Nujol): 3069, 1595, 1584, 1530, 1488,
1355, 1301, 1294, 1192, 1178, 1158, 1111, 1084, 1023, 984, 975,
948,928, 781, 767, 756, 740, 720, 701, 622 cm-1. Anal. Calcd
for C19.5H16Cl2Pt: C, 45.36; H, 3.10; Cl, 13.74; Pt, 37.79.
Found: C, 45.97; H, 3.11; Cl, 13.92; Pt, 38.0.
dihydronaphthalene, a product with an empirical for-
mula of PtCl2(C10H10)‚0.5(toluene) was isolated. Unfor-
tunately this material was insoluble in CDCl3, CD2Cl2,
and d6-acetone and falls apart in DMSO. We were thus
unable to characterize this material by NMR spectro-
scopy, nor were we able to obtain crystals. If the ligand
is bound in a bidentate manner, compound 6 could be
formed. On the other hand, if this is a dimeric structure,
Sod iu m (η2-a llylben zen e)tr ich lor op la tin a te(II) (3). To
a solution of 0.474 g (1.08 mmol) of Na2[PtCl4]‚4H2O dissolved
in 30 mL of n-propanol was added 0.60 mL (4.5 mmol) of
allylbenzene. The solution was covered, allowed to stand
overnight, and then filtered to remove the insoluble NaCl
byproduct. The filtrate was concentrated almost to dryness.
Upon addition of hexanes a yellow solid precipitated. Filtration
1
yielded 0.37 g of the desired product for a 77% yield. H NMR
(d6-acetone): δ 7.45 (d, 2H), 7.30 (t, 2H), 7.20 (t, 1H), 5.05 (m,
J Pt,H ) 66, 1H), 4.30 (d, J Pt,H ) 66, 1H), 4.14 (d, J Pt,H ) 81,
1H), 3.53 (dd, 1H), 3.10 (dd, 1H). IR (Nujol): 1630, 1010, 740,
695, 595 cm-1. Anal. Calcd for NaPtCl3C9H10: C, 24.40; H, 2.28.
Found: C, 24.13; H, 2.31.
we may have isolated a simple Zeise’s dimer analogue
with the 1,4-dihydronaphthalene coordinated as an η2-
alkene (compound 7). Without NMR or X-ray evidence
tr a n s-Dich lor o(η2-a llylb en zen e)(p yr id in e)p la t in u m -
(II) (4). To a solution of 0.278 g (0.628 mmol) of Na[PtCl3(η2-
C9H10)] in 15 mL of H2O was added 51 µL (0.634 mmol) of
pyridine. A light yellow solid precipitated. The product was
collected by filtration to give 0.25 g of product for an 86% yield.
Occasionally the initial product of the reaction was a viscous
oil. In these cases the H2O was decanted off and hexanes were
added to the oil. Stirring for about 30 min usually produced
the desired yellow solid in comparable yields. 1H NMR
(CDCl3): δ 8.80 (d, J Pt,H ) 30, 2H), 7.88 (t, 2H), 7.13-7.48 (m,
6H), 5.85 (m, J Pt,H ) 60, 1H), 4.85 (d, J Pt,H ) 60, 1H), 4.74 (d,
J Pt,H ) 60, 1H), 3.70 (dd, 1H), 3.36 (dd, 1H). IR (Nujol): 1607,
1244, 1217, 1155, 1106, 1066, 1017, 996, 765, 690 cm-1. Anal.
Calcd for C14H15NCl2Pt: C, 36.28; H, 3.27; N, 3.03. Found: C,
36.37; H, 3.26; N, 3.02.
At t em p t ed Syn t h esis of Dich lor o(η4-a llylb en zen e)-
p la tin u m (II). 1. Using the method of Busse et al.,8 a solution
of 31 mg (0.067 mmol) of trans-dichloro(η2-allylbenzene)-
(pyridine)platinum(II) in 10 mL of diethyl ether was added to
1.5 g (55 mequiv) of Dowex 50W-8X ion-exchange resin in a
50 mL Erlenmeyer flask. After it was stirred vigorously for 1
h, the solution was filtered. The resin was washed twice with
5 mL portions of ether. The combined filtrate and washes were
treated with 1.5 g of fresh resin and stirred for 1 h. The
mixture was again filtered, and the resin was washed as above.
The combined filtrate and washes were treated a third time
with 1.5 g of fresh resin. The final combined filtrate and
washes were dried over Na2SO4 and then evaporated to
it is not possible to distinguish between the two struc-
tures. Thus, while 1,4-dihydronaphthalene does form a
complex with platinum(II), 9,10-dihydro-9,10-ethenoan-
thracene is the only ligand that we have been able to
show definitively to form a simple η2-arene complex.
In conclusion, the ethenoanthracene is unusual in
that it does coordinate in an η4 fashion, using the alkene
fragment to anchor the arene in place. This allows for
the ethenoanthracene to function as a bidentate ligand
with the equivalent of an η2 tetrasubstituted alkene. We
believe the specific locked conformation of the ethenoan-
thracene may be necessary for this unusual type of η2-
arene coordination.
(8) Busse, P. J .; Greene, B.; Orchin, M. Inorg. Synth. 1980, 10, 181.

4562 Organometallics, Vol. 18, No. 22, 1999
Wright et al.
dryness, yielding a tacky dark orange solid. Extraction of this
material with ether and subsequent evaporation of the ether
yielded a white solid in very low yield.
metry, that the chloroform molecule be disordered about a
symmetry element, or that an additional chloroform molecule
be present. Translation of the origin, such that the ap-
proximate inversion center in the space group Cc coincides
with any of the real inversion centers of the space group C2/c
(e.g. 0.25, 0.25, 0 or 0, 0, 0) does not move the chloroform
molecule to any symmetry site. There is also no evidence of
any disorder involving the chloroform molecule. A systematic
search for vacant cavities within the unit cell, using a modified
(W. R. Schiedt and local) version of the program CAVITY,10
revealed no significant holes within which a missing chloro-
form molecule could lie. The largest cavity found was ap-
proximately 4.6 Å across at its maximum dimension. By
comparison, the cavity occupied by the chloroform molecule
in this structure has a maximum dimension of about 7.8 Å.
Additional evidence for the choice of space group lies in the
chemically reasonable structure observed for both molecules
of the complex. The severe distortion from idealized geometries
of chemically equivalent groups often observed for centrosym-
metric structures refined in acentric space groups11 is not seen.
Final verification of the choice comes from a comparison of
final residuals for models refined in the two enantiomeric
settings for space group Cc. One model gives residuals of R )
0.0590, Rw ) 0.0800, and S ) 1.49; the model generated by
reversing the signs of all atomic coordinates gives R ) 0.0618,
Rw ) 0.0856, and S ) 1.59. The reported values of the atomic
coordinates and all derived parameters correspond to the
model giving significantly lower residuals.
2. Allylbenzene (0.207 mL, 1.56 mmol) was slowly added to
a solution of Zeise’s dimer (0.459 g, 0.780 mmol) in 40 mL of
diethyl ether. The resulting solution was stirred under a very
slow stream of N2 gas until the solution volume was reduced
to 10 mL. The reaction vessel was then sealed and allowed to
stand for 16 h. Upon further concentration and cooling, a light
tan solid was produced. The product was collected by filtration
and washed three times with small portions of ether. A white
solid (0.125 g) was isolated. Additional small amounts of this
product could be obtained upon evaporation of the filtrate. 1H
NMR (CDCl3): δ 6.91 (d, 3H), 6.81 (m, 2H), 5.12 (m, J Pt,H
)
88, 1H), 4.27 (t, J Pt,H ) 88, 1H), 3.96 (d, 1H), 3.82 (d, 1H), 2.65
(d, J Pt,H ) 125, 1H). 13C NMR (CD2Cl2): δ 148 (J Pt,C ) 75),
131, 126, 124 (J Pt,C ) 46), 93 (J Pt,C ) 264), 64 (J Pt,C ) 225), 39.
IR (Nujol): 3039, 1579, 1238, 1165, 1112, 1049, 1031, 1009,
943, 901, 822, 740, 665 cm-1. Anal. Calcd for C9H10Cl2Pt: C,
28.12; H, 2.62; Cl, 18.46; Pt, 50.80. Found: C, 31.86; H,2.61;
Cl, 9.71.
Dich lor o(1,4-d ih yd r on a p h t h a len e)p la t in u m (II)‚0.5-
(tolu en e). To 0.315 g (0.536 mmol) of [(C2H4)PtCl2]2 (Zeise’s
dimer) dissolved in 25 mL of diethyl ether and 5 mL of toluene
was added 2.068 g (15.9 mmol) of 1,4-dihydronaphthalene. The
solution was stirred vigorously under N2 for 6 h. Upon
concentration of the resulting solution, a bright orange solid
was produced. Filtration yielded 0.110 g of a product with an
empirical formula consistent with the desired product with 0.5
equiv of toluene cocrystallized for a 23% yield. IR (Nujol):
1649, 1194, 1018, 959, 890, 836, 724, 665 cm-1. Anal. Calcd
for C13.5H14Cl2Pt: C, 36.66; H, 3.19; Cl, 16.03; Pt, 44.13.
Found: C, 36.76; H, 3.13; Cl, 15.85.
Structure solution, refinement, and calculation of derived
results were performed using the SHELXTL12 package of
computer programs. Neutral atom scattering factors were
those of Cromer and Waber,13 and the real and imaginary
anomalous dispersion corrections were those of Cromer.14
X-r a y Cr ysta l Str u ctu r e of Dich lor o(9,10-d ih yd r o-9,-
10-eth en oa n th r a cen e)p la tin u m (II). An orange crystal of
C16H12Cl2Pt‚0.5CHCl3 was mounted on a thin glass fiber for
data collection. Single-crystal intensity measurements were
made at 21 ( 1 °C using ω-2θ scans (2θmax ) 45°) on a Nicolet
R3mV diffractometer with graphite-monochromated Mo KR
radiation (λ ) 0.710 73 Å). Of the 5489 reflections measured
(-h,(k,(l), 2321 were unique (Rint ) 0.066) and 2179 were
observed (I > 3σ(I)). The data were corrected for Lorentz and
polarization effects. The structure was solved by the Patterson
method, expanded by standard difference Fourier searches,
and refined by using full-matirix least-squares techniques. All
heavy atoms other than those of the olefinic ligand were
refined anisotropically; the latter were refined isotropically.
Ack n ow led gm en t. Funding for this work was pro-
vided in part by the donors of the Petroleum Research
Fund, administered by the American Chemical Society,
the National Science Foundation, and The Duke En-
dowment. Sincere gratitude is also extended to Dr. Steve
Ittel for his generous and insightful input on this
project.
Su p p or tin g In for m a tion Ava ila ble: Tables containing
complete crystallographic data, atomic coordinates for all non-
hydrogen atoms and equivalent isotropic thermal parameters,
all bond lengths and angles, anisotropic thermal parameters,
and hydrogen atom coordinates and thermal parameters,
ORTEP diagrams for both molecules one and two, and a
description of the data collection and refinement. This material
is available free of charge via the Internet at http://pubs.acs.org.
Hydrogen atoms were included at idealized positions (dC-H
0.96 Å) with a refined isotropic group thermal parameter (UH
)
) 0.07(2) Å2).
The compound crystallized in the monoclinic space group
Cc with eight molecules per unit cell. In addition, the unit cell
contains four chloroform solvent molecules. Two independent
molecules of the platinum complex within the asymmetric unit
are related by a pseudo-inversion center, and there are no
significant differences in the bonding parameters or conforma-
tions of the two molecules. It is the presence of only one solvent
molecule in the asymmetric unit which breaks the symmetry
and prevents crystallization in the centrosymmetric space
group C2/c. A centrosymmetric packing would require that the
chloroform molecule have crystallographically imposed sym-
OM990272E
(9) Chock, P. B.; Halpern, J .; Paulik, F. E. Inorg. Synth. 1975, 14,
90.
(10) Basso, R.; Guista, A. D. J . Appl. Crystallogr. 1977, 10, 496.
(11) Marsh, R. E.; Schomaker, V. Inorg. Chem. 1979, 18, 299.
(12) Sheldrick, G. M. SHELXTL, Crystallographic Computing Sys-
tem; Nicolet Instruments Division, Madison, WI, 1986.
(13) Cromer, D. T.; Waber, J . T. International Tables for X-ray
Crystallography; Kynoch Press: Birmingham, England, 1974; Vol. IV,
Table 2.2B.
(14) Cromer, D. T. International Tables for X-ray Crystallography;
Kynoch Press: Birmingham, England, 1974; Vol. IV, Table 2.3.1.