Synthesis, stereochemistry, and solution dynamics of heterobimetallic complexes with metals connected by dithioxamides in k-S,S′ k-N,N′ binucleation mode. The molecular structure of [2-(diphenylphosphino)pyridine-Pt-C1-(μ-N,N′dibenzyldithioxhisamidato- K-S,S′-Pt-k-N,N′-Pd)(n3-allyl)Pd]

Article abstract of DOI:10.1021/om991008o

Dehydrohalogenation of dithioxamide complexes {(PN)ClPt(H₂R₂N₂C₂S ₂)+(Cl^-)} (PN = 2-(diphenylphosphino)pvridine; H₂R₂N₂C₂S₂ = secondary dithioxamides, H₂DTO, R = ethyl, 1; R = benzyl, 2; R = {S}-phenylethyl, 3) leads to the dithioxamidates [(PN)Cl]Pt(HR₂N₂C₂S₂)] (HR₂N₂C₂S₂^- = dialkyldithioxamidate, HDTO) 4-6, which can act as ligands (complexes as ligands).

Full text of DOI:10.1021/om991008o

2462
Organometallics 2000, 19, 2462-2469
Syn th esis, Ster eoch em istr y, a n d Solu tion Dyn a m ics of
Heter obim eta llic Com p lexes w ith Meta ls Con n ected by
Dith ioxa m id es in K-S,S′ K-N,N′ Bin u clea tion Mod e. Th e
Molecu la r Str u ctu r e of
[2-(Dip h en ylp h osp h in o)p yr id in e-P t-Cl-(µ-N,N′-
d iben zyld ith ioxbisa m id a to-K-S,S′-P t-K-N,N′-P d )(η3-a llyl)P d ]
Santo Lanza,* Giuseppe Bruno, Francesco Nicolo`, Archimede Rotondo,
Rosario Scopelliti, and Enrico Rotondo
Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica,
Universita` di Messina, Salita Sperone 31, Vill. S. Agata, 98166 Messina, Italy
Received December 20, 1999
Dehydrohalogenation of dithioxamide complexes {(PN)ClPt(H2R2N2C2S2)+(Cl-)} (PN )
2-(diphenylphosphino)pyridine; H2R2N2C2S2 ) secondary dithioxamides, H2DTO, R ) ethyl,
1; R ) benzyl, 2; R ) {S}-phenylethyl, 3) leads to the dithioxamidates [(PN)Cl]Pt(HR2N2C2S2)]
(HR2N2C2S2- ) dialkyldithioxamidate, HDTO) 4-6, which can act as ligands (complexes as
ligands). In fact, after deprotonation, they can easily promote chloro-bridge splitting reaction
of [Pd(η3-allyl)(µ-Cl)]2 leading to heterobimetallic complexes of formula [(PN)ClPt(µ-R2N2C2S2-
κ-S,S-Pt-κ-N,N-Pd)Pd(η3-allyl)]; R2N2C2S22- ) dialkyldithioxbisamidate, DTO; R ) ethyl, 7;
R ) benzyl, 8; R ) {S}-phenylethyl, 9. These complexes are chiral; hence, 7 and 8 have
been synthesized as racemates, and 9 as an equimolar diastereomeric mixture owing to the
optically pure {S}-phenylethyl substituent. Upon warming, 7 and 8 racemize, and 9
epimerizes. The isomerization processes may be explained by a mechanism that involves
(a) breaking of one of the two Pd-N bonds; (b) rotation around the remaining Pd-N bond;
(c) isomerization of the T-shaped intermediate; and (d) remaking of the Pd-N bond. The
solid structure of complex 8 has been determined by X-ray single-crystal diffraction analysis.
In tr od u ction
metals in an NS′-N′S binucleation mode.5 To the best
of our knowledge only one report has appeared concern-
ing dithioxamides in N,N′ cis-chelation mode,6 whereby
it deals with a trimetallic copper complex in which the
unusual coordination mode is reached owing to particu-
lar steric requirements of the dithioxamidic ligand.
By reacting a PtII ligand complex containing an S,S′-
chelated dithioxamide with a ruthenium p-cymene
dichloro dimer, we have recently obtained a binuclear
Pt-Ru complex with the metals connected by means of
a dithioxamide ligand in a κ-S,S′ Pt κ-N,N′ Ru coordina-
tion mode.7 This binuclear complex shows intrinsic
interest because it presents a unique example of a
bimetallic chiral axis. Its synthetic procedure is however
also interesting since it deals with an S,S′-coordinated
dithioxamide that is forced to link a second metal in an
N,N′-cis-coordination mode. In other words, the synthe-
sis of the referred bimetallic complexes has been achieved
according to the procedure of “complexes as ligands”.
Secondary dithioxamides are “exotic” ligands, for both
their versatility and multisite donor nature. Their
coordination chemistry is further complicated by the fact
that these ligands acting as neutral, monoanionic, or
dianionic species display rather flexible metal-ion
binding patterns.
Even though in neutral or monoanionic form dithiox-
amides generally chelate a single metal through sulfur
atoms,1 several examples of trans-S,S′ binucleation,2
S-monocoordination,3 and NS-N′S′ “exo” binucleation4
have been reported. In turn, a dianionic rubeanate
generally gives rise to oligonuclear or
polymeric systems in which the ligand coordinates
2-
R2N2C2S2
* To whom correspondence should be addressed. Fax: (090)393756.
E-mail: lanza@chem.unime.it.
(1) Antolini, L.; Fabretti, A. C.; Franchini, G.; Menabue, L.; Pella-
cani, G. C.; Desseyn, H. O.; Dommisse, R.; Hofmans, H. C. J . Chem.
Soc., Dalton Trans. 1987, 1921. Desseyn, H. O.; Van deer Veken, B.
J .; Hermann, M. A. Appl. Spectrosc. 1978, 32, 101. Rosace, G.; Bruno,
G.; Scolaro, M. L.; Nicolo`, F.; Sergi, S.; Lanza, S. Inorg. Chim. Acta
1993, 39, 208.
(2) (a) Drew, M. G. B.; Kisenyi, J . M.; Willey, G. R.; Wandiga, S. O.
J . Chem. Soc., Dalton Trans. 1984, 1717. (b) Baggio, R.; Garland. M.
T.; Perec, M. J . Chem. Soc., Dalton Trans. 1995, 987.
(3) Belicchi Ferrari, M.; Gasparri Fava, G.; Pelizzi, C.; Tarasconi,
P. Inorg. Chim. Acta 1985, 98, L49.
(5) (a) Veit, R.; Girerd, J . J .; Kahn, O.; Robert, F.; J eanin, Y.; El
Murr, N. Inorg. Chem. 1984, 23, 4448. (b) Ye, Q. Y.; Nakano, Y.;
Frauenhoff, G. R.; Whitcomb, D. R.; Tagusakawa, F.; Bush, D. H. Inorg.
Chem. 1991, 30, 1503.
(6) Veit, R.; Girerd, J . J .; Kahn, O.; Robert, F.; J eannin, Y. Inorg.
Chem. 1986, 25, 4175; J ournaux, Y.; Lloret, F.; Kahn, O. Inorg. Chem.
1990, 29, 3048.
(4) Girerd, J . J .; J eannin, S.; J eannin, Y.; Kahn, O. Inorg. Chem.
1978, 17, 3034.
(7) Lanza, S.; Bruno, G.; Nicolo`, F.; Scopelliti, R. Tetrahedron,
Asymmetry 1996, 7, 3347.
10.1021/om991008o CCC: $19.00 © 2000 American Chemical Society
Publication on Web 05/19/2000

Heterobimetallic Complexes with Metals
Organometallics, Vol. 19, No. 13, 2000 2463
Sch em e 1
This procedure to synthesize polymetallic complexes is
becoming more and more popular, but only a few
systematic syntheses have been to date described. One
of them, perhaps the most successful, exploits binucle-
ating ligands having equivalent coordination sites such
as bipyrimidine and related ligands.8 Another promising
procedure is based on coordinating properties of dipy-
ridilcatecolate (dpcat), which was detected by Balch as
a “dual chelating ligand” in 1975.9 Using dpcat as a dual
ligand, Pierpoint obtained a bimetallic complex10 whose
structure is similar to that of a Pt-Ru complex recently
reported by some of us7 and to the binuclear species 7,
8, and 9 described in this paper.
Pierpoint’s synthetic procedure seems to be of general
applicability and has been recently exploited by authors
interested in electrochemical11 and photochemical12
aspects of heterobimetallic complexes. Furthermore, the
formation of bi- and trimetallic complexes having dpcat
as the bridging ligand has been achieved with the
objective of constructing chain structures.13 These can
be regarded as multicomponent molecular systems and
represent an important evolution in the development
of molecular and supramolecular systems for catalysis,
light to chemical energy conversion, and molecular-
based devices.
Starting from this point, we wish to demonstrate that
dithioxamides, and likewise dpcat, can be advanta-
geously used to construct polymetallic systems by the
“complexes as ligands” procedure. Within the scope in
this paper we report the synthesis of binuclear com-
plexes obtained using the chloro-bridge dimer [Pd(η3-
allyl)(µ-Cl)]2 as a substrate for the platinum dithioxa-
midate complexes. Several considerations led us to
choose this organometallic substrate: first, the chem-
istry of PdII allyl complexes remains a widely studied
theme which finds many important applications in the
field of metal-promoted organic synthesis;14 second,
Pregosin’s fertile idea of NOE “reporter ligands” could
be applied to molecular systems such as II in order to
determine solution structure;15 and finally, the metal
coordination square planes in II when LnM is Pd(allyl)
are stereogenic. Hence, binucleating dithioxamides bear-
ing optically pure chiral substituents form diastereo-
mers suitable for the allyl isomerization study of chiral
chelate complexes, which is per se an interesting item.
Resu lts a n d Discu ssion
The synthetic way to bimetallic Pt-Pd complexes
starts from secondary dithioxamides as dithionic ligands,
which easily react with cis-[Pt(DMSO)PNCl2] to give
monochelate κ-S,S Pt ion pairs. These ion pairs can be
dehydrohalogenated and in the form of rubeanate
complexes quantitatively split the chloro-bridge dimer
[(η3-allyl)Pd(µ-Cl)]2 by means of the uncoordinated ni-
trogens (Scheme 1).
This synthetic procedure was previously followed by
us to obtain Pt-Ru bimetallic complexes7 and seems of
general applicability. In fact from our experiments the
capability of κ-S,S-coordinated dithioxamidate anions to
chelate MLn fragments after splitting [LnM(µ-Cl)]2
chloro-bridge dimers appears of widespread use. This
observation should be emphasized per se, since the
above synthetic procedure opens the way to a wide class
of heterobimetallic complexes in which a rigid hetero-
atomic planar spacer ensures the transmission of elec-
tronic effects between two metal centers rigidly con-
nected through the N,N and S,S donor sites of dithioxa-
midate anions.
(8) Balzani, V.; Campagna, S.; Denti, G.; J uris, A.; Serroni, S.;
Venturi, M. Acc. Chem. Res. 1998, 31, 26.
(9) Girgis, A. Y.; Sohn, Y. S.; Balch, A. L. Inorg. Chem. 1975, 14,
2327.
(10) Fox, G. A.; Bhattacharya, S.; Pierpont, C. G. Inorg. Chem. 1991,
30, 2895.
(11) Hill, P. L.; Lee, L. J .; Younkin, T. R.; Orth, S. D.; McElwee-
White, E. Inorg. Chem. 1997, 36, 5655.
(12) Paw, W.; Eisemberg, R. Inorg. Chem. 1997, 36, 2287.
(13) Bryngelson, P. A.; Haddad, T. S.; Doherty, N. M. Absract of
Papers, 21th National Meeting of the American Chemical Society, New
Orleans, LA, Spring 1996; American Chemical Society: Washington,
DC, 1996; INOR 38.
(14) Hayashi, T. In Catalytic Asymmetric Synthesis; Ojima, I., Ed.;
VCH: 1993; p 325. Trost, B. M. Angew. Chem. 1995, 107, 285.
(15) Albinati, A.; Kunz, R. W.; Amman, C. J .; Pregosin, P. S.
Organometallics 1991, 10, 1800.

2464 Organometallics, Vol. 19, No. 13, 2000
Lanza et al.
In addition, when [LnM(µ-Cl)]2 chloro-bridge dimers
are prochiral substrates, their splitting by means of
metal ligand complexes [LL′M′(Η-DTO-κ-S,S′)] leads to
binuclear species [LnM(µ-DTO)M′LL′], where both met-
als are stereogenic. We have demonstrated that in these
bimetallic complexes, when LnM ) [Ru(p-cymene)Cl]+
and LL′M′ ) [(PN)ClPt]+, the stereogenicity of both
platinum and ruthenium is fused in a bimetallic chiral
axis.7 When LnM ) [Pd(allyl)]+ and LL′M′ ) [(PN)-
ClPt]+, the stereochemistry of the resulting binuclear
complexes is slightly different, as it is described in the
next paragraph.
Ster eoch em istr y a n d Ster eoch em ica l Nota tion .
The bimetallic dialkyldithioxbisamidate complexes 7, 8,
and 9 are chiral: 7 and 8 were synthesized as racemic
mixture of enantiomers, 9 as a 1:1 mixture of diaster-
eomers owing to homochiral optically pure substituents
on amidic nitrogens. The molecular asymmetry arises
from the position of the η3-coordinated allyl moiety,
which is obliquely placed with respect to the metal
square planes, and from the different monodentate
substituents on platinum atom (PN and Cl). In this
asymmetric geometrical array, both palladium and
platinum are stereogenic. Although the species 7 and 8
contain two stereogenic centers, no more than two
enantiomers can be envisaged for each of them. Any
platinum substituent exchange affects the palladium
configuration and vice versa, causing interconvertion of
mutual enantiomers. This happens because the chirality
of the molecule can be seen to spread over the whole
coordination plane, which can be regarded as a plane
of chirality.
To designate the configuration at platinum in the
above planar chiral complexes, the stereonotation sys-
tem developed for use in the Chemical Abstract Service
registry system and in the Chemical Abstract Index16
cannot be used. In fact, the stereochemical descriptor
SP-4, which is the symmetry site term for square
planar, four-coordinate geometry, cannot be followed by
an additional digit since sulfur atoms on opposite side
with respect to monodentate ligands PN and Cl have
the same CIP priority. We suggest indicating the
enantiomers of the bimetallic Pt-Pd(allyl) complexes
by means of the direction C (clockwise) or A (anticlock-
wise) of the decreasing CIP priority sequence of the
monodentate ligands on platinum when the molecule
is viewed from the CH cusp of the allyl moiety:
F igu r e 1. Schematic draw of 9 with labeled hydrogens.
Ta ble 1. Selected NOE P er cen ta ge for 9
irradiated nucleous
H1s 9A
selected NOE
H1a 9A
percentage (%)
15
1
15
1
∼0
15
15
1
CH3 9A cis to P
H3a 9B
H3s 9B
CH3 9B trans to P
CH3 9B cis to P
H3a 9A
H3s 9A + H1s 9B
H1a 9B
CH3 9B cis to P
CH3 9A trans to P
H1s 9A
1
15
15
∼0
1
H1a 9A + H3a 9B
H3s 9B
CH3 (all resonances)
H
ortho (pyridine) 9A + 9B CH3 9A cis to P
CH3 9B cis to P
1
Thus complexes 7 and 8 can be termed as (A,C)-[(η3-
allyl)palladium(II)(µ-N,N′-(dialkyldithioxbisamidato-κ-
N,N′-Pd-κ-S,S′-Pt)(2-(diphenylphospino)pyridine)(chloro)-
platinum(II)], and diastereomers 9 as (A)- and (C)-[(η3-
allyl)palladium(II)(µ-(N,N′-{S}-diphenylethyldithi-
oxbis a m id a t o-κ-N ,N ′-P d -κ-S ,S ′-P t )(2-(d ip h en yl-
phospino)pyridine)(chloro)platinum(II)], respectively.
Solu tion Str u ctu r e of 9. In the absence of structural
data, spatial connectivity between ligands and three-
dimensional features of 9 could be investigated by NMR
spectroscopy exploiting mono- and bidimensional NOE
experiments. For this purpose it was necessary to
unambiguously assign the proton resonances with con-
ventional 1H and 13C 2-D homo- and heteronuclear
correlation techniques. On the basis of NMR consider-
ations it is impossible to say which diastereoisomer is
which, although, when resolved, the resonances of each
diastereoisomer (arbitrarily labeled respectively as 9A
and 9B) can be separately grouped.
The resonance frequencies of corresponding protons
in the two isomers are very close except for the allyl
groups whose chemical shifts are much more sensitive
to the relative orientation of the strictly close homochiral
substituents than to the geometrical disposition of the
peripheral phosphine. As a consequence, the H3s and
H3a (trans to P) resonances of diastereoisomer 9A
overlap, respectively, H1s and H1a (cis to P) resonances
of 9B, while, though both resolved, the resonances H1s
and H1a (cis to P) of 9A are very close respectively to
the H3s and H3a (trans to P) resonances of 9B (Figure
1).
Selected NOEs for the diastereomeric mixture are
reported in Table 1.
Eventhough selective irradiation of 9A with respect
to 9B resonances could never be totally achieved, the
results allowed us to draw some important conclusions.
The method adopted here is in agreement with the
IUPAC recommendation of using the symbols C or A to
designate chirality in systems other than tetrahedral
(T-4) or octahedral (OC-6).17
(16) Brown, M. F.; Cook, B. R.; Sloan, T. E. Inorg. Chem. 1978, 7,
1563. Sloan, T. E. Top. Stereochem. 1981, 12, 1.
(17) Nomenclature in Inorganic Chemistry, Recommendations; Black-
well: Oxford, U.K., 1990; Chapter 10.

Heterobimetallic Complexes with Metals
Organometallics, Vol. 19, No. 13, 2000 2465
First of all we can discriminate between methyl reso-
nances cis or trans to P of each diastereoisomer. Second
we can exploit the NOE between the methyls and the
syn-allyl proton resonances to discriminate between
allyl protons cis or trans to P of 9A and 9B.
Moreover it may be of interest that the NOE is
observed between DTO methyls and syn- but not anti-
allyl protons. Analogous selective NOEs for allyl deriva-
tives have been previously reported by Pregosin et al.
and have been attributed to CH syn twist toward the
metal out of the allyl plane.15,18 This distortion is rather
general in allyl complexes and has been observed in the
solid state both with X-rays19,20 and neutrons21 and has
also been theoretically rationalized.22
Solu tion Dyn a m ics of Com p lexes 7-9. Tempera-
1
ture produces important changes in H NMR spectra of
binuclear complexes. In fact the aliphatic DTO reso-
nances of 7 and 8, which appear at 298 K as a double
ABC3 in 7 and a double AB spin system in 8, above the
coalescence temperature, collapse, respectively, into two
A2B3 and two A2 spin systems. At the same time, the
allyl proton resonances of 7 and 8, which, in accordance
with the chemical unequivalence of the opposite termi-
nal atoms, show at room temperature resonances of an
ABCDE spin system, collapse in both complexes into an
A2B2C spin system. The high-temperature spectra are
thus consistent with a dynamic process which makes
the coordination plane of the metal a time-averaged
symmetry plane, thus rendering the geminal N-CH2
protons magnetically equivalent. The process also aver-
ages the resonances of the terminal allyl protons, but
not those of DTO substituents (cis and trans to P,
respectively).
Complex 9 shows at 298 K resonances of two diaste-
reoisomers, 9A and 9B, in 1:1 molar ratio. Accordingly
for each diastereoisomer two AB3 spin system for the
DTO aliphatic and two ABCDE spin systems for the
allyl protons are observed. The high-temperature spec-
trum of 9 shows the collapse of the four AB3 DTO
aliphatic resonances into two AB3 spin systems, while
the two ABCDE allyl protons collapse into two A2B2C
spin system with the C resonances overlapped (1,1′,2,2′-
tetracloroethane was necessary to monitor coalescence
and the high-temperature spectrum of 9; at room
temperature spectral features and isomerization rate of
9 in the two solvents are very similar).
F igu r e 2. 2-D NOESY (EXSY) spectrum of 9 in 1,1′,2,2′-
tetrachloroethane at 298 K. The negative cross-peaks
shown in the whole spectrum are due to negative NOE.
Positive cross-peaks, very close to the diagonal, are evi-
denced by the expansions: (a) DTO methyls exchange; (b)
H3s 9A (trans to P)/H1s 9B (cis to P) exchange.
change; (ii) dissociation of the phosphine ligand, by the
lack of DTO proton exchange from cis to trans to P and
vice versa (phosphine dissociation has also been ex-
cluded on the basis of the absence of polarization
transfer from 195Pt satellites into the central peaks of
the 31P NMR spectrum); (iii) dissociation of [(PN)ClPt-
(H-DTO)] by the lack of polarization transfer from the
free metal ligand complex [(PN)ClPt(H-DTO)] to the
binuclear complexes 9. On the basis of conventional
wisdom, rotation of the π-allyl moiety can also be
excluded, believed “impossible” for palladium.23
The 2-D NOESY (EXSY) spectrum of 9 at 298 K sheds
light on the intimate nature of the dynamic process.
Figure 2 reports this spectrum together with a sche-
matic representation of the proton exchanges suggested
by its positive cross-peaks. Selective exchanges between
different but not within the same diastereoisomer are
observed.
In conclusion, if we assume that the allyl does not
rotate and that the phosphine and [(PN)ClPt(H-DTO)]
do not dissociate, all our observations may be accom-
modated with a mechanism that involves (a) dissociation
of one Pd-N bond; (b) rotation around the remaining
Pd-N bond; (c) isomerization of the T-shaped interme-
diate; and (d) remaking of the Pd-N bond (steps b and
c may be inverted). See Scheme 2.
According to this mechanism, the isomerization ex-
changes the position of the 1-3 allyl protons (from cis
to P in one diastereoisomer to trans to P in the other
and vice versa), but, of course, does not exchange the
position of DTO protons, which, upon isomerization,
retain their configuration with respect to P. This
hypothesis is supported by the fact that Pd-N bond
Some of the possible π-allyl complexes’ isomerization
pathways can be ruled out on the basis of our findings:
1
(i) η3-η isomerization, by the lack of syn-anti ex-
(18) Albinati, A.; Amman, C.; Pregosin, P. S.; Ruegger, H. Organo-
metallics 1990, 9, 1826-33.
(19) Gozum, J . E.; Pollina, D. M.; J ensen, J . A.; Girolami, G. S. J .
Am. Chem. Soc. 1988, 110, 2688.
(20) Faller, J . W.; Blankenship, C.; Whitmore, B. Inorg. Chem. 1985,
24, 4483.
(21) Goddard, R.; Kruger, C.; Mark, F.; Stansfield, R.; Zhang, X.
Organometallics 1985, 4, 285.
(22) Klark, T.; Rhode, C.; Schleier, P. R. Organometallics 1983, 2,
1344.
(23) Vrieze, K. In Dynamic Nuclear Magnetic Resonance Spectro-
scopy; J ackman, L. M., Cotton, F. A., Eds.; Academic Press: New York,
1975.

2466 Organometallics, Vol. 19, No. 13, 2000
Lanza et al.
Sch em e 2
Ta ble 2. Activa tion F r ee En er gy for th e
Ra cem iza tion P r ocess, ∆Gq, a n d Ch a r ton v
P a r a m eter s (See Text) for 7-9a
Ta ble 3. Cr ysta llogr a p h ic Da ta for Com p lex 8
formula
fw
C36H37ClN3O2S2PPdPt‚(CHCl3)
1091.05
orange, irregular
0.18 × 0.10 × 0.06
triclinic
P1h
11.648(3)
13.542(4)
15.046(4)
111.44(2)
108.48(2)
91.43(2)
2068(1)
∆Gq (kJ ‚mol-1
)
v
cryst form
cryst dimens, mm
cryst syst
space group
a, Å
complex
7, R ) ethyl
62.2
71.0
83.5
0.56
0.70
0.99
8, R ) benzyl
9, R ) phenylethyl
b, Å
c, Å
The linear regression analysis is ∆Gq ) 46v + 38, R2 ) 0.993;
a
P < 0.05.
R, deg
â, deg
γ, deg
breaking has been already invoked as an isomerization
source for other palladium allyl substrates.15,24
V, Å3
Z
2
A possible alternative isomerization pathway which
involves five-coordinate complexes seemed to us unlikely
in a poorly coordinating solvent like chloroform and in
the absence of coordinating species. We have also proved
that added water does not significantly alter the isomer-
ization rate. However the most convincing evidence
against pentacoordinate pseudorotation arises from the
lack of positive cross-peaks between the clearly resolved
methyl resonances observed in the EXSY spectrum of
the mononuclear complex [(η3-allyl)Pd({S}-phenyl-
ethyl)2HN2C2S2-κ-S,S-Pd]. Presumably in the latter case
the palladium sulfur bonds, differently from the weaker
Pd-N bonds of our binuclear complexes, do not break
precluding the dissociative mechanism. The contempo-
rary absence of syn-anti proton exchange for the latter
complex further supports that a high activation energy
hinders allyl movements in these substrates.
∆Gq values for both racemization and epimerization
processes have been measured and are reported in Table
2. As one can see, allyl pseudorotation is relatively fast
in 7 (R ) ethyl) and becomes increasingly slower in 8
(R ) benzyl) and in 9 (R ) phenylethyl). These results
indicate that the process is influenced by the nature of
alkyl substituents on amidic nitrogens: the bulkier and
F(000)
1064
1.752
4.247
0.71073 (Mo KR)
25
3-51
8211
7752
3987
176/515
0.051/0.102
0.113/0.133
0.791
F
calcd, g/cm3
µ, mm-1
λ (graphite monochromated), Å
T, °C
2θ range, deg
no. of data colld (2θ-ω)
no. of data refined (all)
no. of data with I g 2σ(I) (obs)
no. of restraints/params
Ra(obs/ all)
wR2b(obs/ all)
GOFc
largest diff peak and hole, e‚Å-3
1.609 and -1.302
R ) [∑||Fo| - |Fc||]/∑|Fo|. Rw ) [∑w(Fo - Fc2)2/∑w(Fo2)2]1/2
.
a
b
2
c GOF ) [∑w(Fo - Fc2)2/(Nobservns - Npar)]1/2
.
2
more electron-withdrawing the substituents, the slower
the isomerization rates. This suggests that rather than
the Pd-N bond rupture, the rate-determining step of
the process is the rotation around the residual Pd-N
bond subsequent to the Pd-N bond rupture (fast reverse
ring closure could minimize the kinetic effects of Pd-N
bond rupture if DTO rotation and T-shaped intermedi-
ate isomerization were relatively slow). Accordingly ∆Gq
significantly correlates with Charton’s v values, param-
eters that correctly describe the internal rotation barrier
in racemization of substituted biphenyl substrates.26
Cr ysta l Str u ctu r e of 8. The crystallographic cell
contains two molecules simulating a center of symmetry
(24) Gogol, A.; Ornebro, J .; Grennberg, H.; Backball, J . E. J . Am.
Chem. Soc. 1994, 116, 3631.

Heterobimetallic Complexes with Metals
Organometallics, Vol. 19, No. 13, 2000 2467
142(1)°). The H-Pt distance is significantly longer than
the value we have reported in an analogous platinum-
chloroform interaction;28 this is probably due to the
hindrance of the 2-(diphenylphosphino)pyridine ligand,
which points the pyridine ring toward CHCl3.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. Secondary dithioxamides were
synthesized according to Hurd.29 cis-[Pt(Me2SO)2Cl2]30 and cis-
[(PN)(Me2SO)PtCl2]31 were prepared following reported pro-
cedures. Other chemicals were commercially available and
used as purchased.
1H, 13C, and 31P NMR spectra were obtained on a Bruker
ARX-300; external standards were SiMe4 for 13C and 1H and
85% H3PO4 for 31P. Coupling constants are reported in hertz,
and chemical shifts in ppm assuming positive shifts downfield
in all cases.
Free activation energies, ∆Gq, were calculated in kJ mol-1
from the equation ∆Gq ) 8.31T[23.76 + ln(T/2π∆ν)]; Τ )
coalescence temperature; ∆ν ) frequency difference (Hz) of
coalesced resonances taken from the temperature frozen
spectrum.
F igu r e 3. View of the asymmetric unit with atom-
numbering scheme and thermal ellipsoids at 40% prob-
ability, while H size is arbitrary. The split conformations
are represented by dashed-bond/shaded-ball, while the Pt‚
‚‚H interaction is represented by a shaded line. [Pt-S(1)
) 2.312(3); Pt-S(2) ) 2.258(3); Pt-P ) 2.262(3); Pt-Cl(1)
) 2.333(3); Pd-C(19) ) 2.070(17); Pd-C(18B) ) 2.09(4);
Pd-C(18A) ) 2.15(2); Pd-C(17) ) 2.139(13); Pd-N(2) )
2.095(9); Pd-N(1) ) 2.096(9); C(1)-C(2) ) 1.506(15) Å and
S(1)-C(1)-C(2)-S(2) ) -1.1(12); S(2)-Pt-P ) 92.95(11);
S(2)-Pt-S(1) ) 89.44(10); P-Pt-Cl(1) ) 90.98(11); S(1)-
Pt-Cl(1) ) 86.65(11); C(19)-Pd-N(2) ) 106.0(6); N(2)-
Pd-N(1) ) 78.7(4); N(1)-Pd-C(17) ) 106.5(6)°].
Gen er a l P r oced u r e for th e P r ep a r a tion of Ion P a ir
Dith ioxa m id e Com p lexes {(P N)ClP t(H2R2N2S2C2)+, (Cl-)
} (R ) Eth yl, 1; R ) Ben zyl, 2; R ) {S}-P h en yleth yl, 3). A
1 mmol sample of cis-[Pt(Me2SO)(PN)Cl2] (prepared in situ by
mixing 1 mmol of cis-[Pt(Me2SO)2Cl2] and 1 mmol of PN) in
the minimum amount of chloroform (∼10 mL) was reacted
with a stoichiometric amount of H2R2N2C2S2. The solution
turned red and was allowed to stand at room temperature for
0.5 h. After this time to the concentrated solution petroleum
ether 40-60 was added (∼50 mL). From the solution the
{((PN)ClPt(H2R2N2C2S2))+, (Cl-)} ion pair immediately pre-
cipitated as magenta powders, which were separated from the
uncolored supernatant and air-dried. Yields were higher than
90%.
evidenced by the diffraction data statistics and con-
firmed by the difficult model refinement. Due to the
pseudo-symmetry effects, the crystal packing is better
described in the centrosymmetric space group P1h by
using a unique independent disordered molecular unit.
The ligand asymmetries appear as a molecular confor-
mational disorder which causes the large thermal
parameters of the benzyl substituents and the splitting
of one ring orientation in the 2-(diphenylphosphino)-
pyridine ligand. The complex flattening is determined
by the planar DTO bridge chelating the “hard” palla-
dium(II) via N atoms and the “soft” platinum(II) via the
S atoms on the mean plane in whose respect the benzyl
fragments are on opposite sides (Figure 3). By consider-
ing the allyl as a “short bite” chelating ligand, the PdII
coordination might be considered a distorted square-
planar geometry with the allyl central C(18) atom split
symmetrically with respect to the coordination plane
(50% of occupancy), as usually observed in analogous
complexes.27 The PtII atom adopts a regular square-
planar geometry similar to that we have already re-
ported for the analogous Pt-Ru complex.7 However the
crystal packing reveals an axial hydrogen interaction
of the platinum with the cocrystallized chloroform
molecule in the same asymmetric unit (Pt‚‚‚H(38) )
3.275(1) Å, Pt‚‚‚C(38) ) 4.09(1) Å, Pt‚‚‚H(38)-C(38) )
{((P N)ClP t(H2(C2H5)2N2S2C2))+, (Cl-)} (1). 1H NMR (300.13
MHz, CDCl3, 298 K): 13.14 (br s, 2H, NH); 8.82 (m, 1H, pyrH-
6); 8.11 (m, 1H, pyrH-3); 7.78-7.28 (m, 12H, ArH and pyrH);
3.83 (q, 3J H-H ) 7.3, 2H, NCH2); 3.34 (q,3J H-H) 7.3, 2H, NCH2);
3
3
1.50 (t, J H-H ) 7.3, 3H, CH3); 1.33 (t, J H-H ) 7.3, 3H, CH3).
13C{1H} NMR (75.47 MHz, CDCl3, 298 K): 150-124 (17C, ArC
and pyrC); 44.5 (1C, NCH2); 44.1 (1C, NCH2); 11.7 (1C, CH3);
11.4 (1C, CH3). 31P{1H} NMR (121.49 MHz, CDCl3, 298 K):
13.2(1J Pt-P ) 3320, Pt-P). Anal (%) Calcd for C23H26N3PS2-
Cl2Pt: C, 39.15; H, 3.71; N, 5.96; S, 9.09; Cl, 10.05. Found: C,
38.98; H, 3.68; N, 6.03; S, 9.32; Cl 9.87.
{(P N)ClP t(H2(C7H7)2N2S2C2)+, (Cl-)} (2). 1H NMR (300.13
MHz, CDCl3, 298 K): 13.69 (br s, 2H, NH); 8.79 (m, 1H, pyrH-
6); 8.11 (m, 1H, pyrH-3); 7.84-7.08 (m, 22H, ArH and pyrH);
4.94 (s, 2H, NCH2); 4.48 (s, 2H, NCH2). 13C{1H} NMR (75.47
MHz, CDCl3, 298 K): 150.5-125.0 (29C, ArC and pyrC); 51.9
(1C, NCH2), 51.6 (1C, NCH2). 31P{1H} NMR (121.49 MHz,
CDCl3, 298 K): 13.1 (1J Pt-P ) 3313, Pt-P). Anal (%) Calcd for
C
33H30N3PS2Cl2Pt: C, 47.77; H, 3.64; N, 5.06; S, 7.73; Cl, 8.55.
Found: C, 48.10; H, 3.56; N, 4.98; S, 7.41; Cl, 8.61.
{(P N)ClP t(H2({S}-CHCH3P h )2N2S2C2)+, (Cl-)} (3). 1H
NMR (300.13 MHz, CDCl3, 298 K): 13.89 (br s, 2H, NH); 8.77
(m, 1H, pyrH-6); 8.11 (m, 1H, pyrH-3); 7.79-7.06 (m, 22H, ArH
and pyrH); 5.34 (q,3J ) 6.6, 1H, NCHPh); 5.22 (q,3J H-H ) 6.6,
3
1H, NCHPh); 1.91 (d,3J H-H ) 6.6, 3H, CH3); 1.79 (d, J H-H
)
6.6, 3H, CH3). 13C{1H} NMR (75.47 MHz, CDCl3, 298 K):
(25) Thorn, D. L.; Hoffmann, R. J . Am. Chem. Soc. 1978, 99, 2079.
Tatsumi, K.; Hoffmann, R.; Yamamoto, A.; Stille, J . K. Bull. Chem.
Soc. J pn. 1981, 54, 1857.
(26) Charton, M.; Charton, B. J . Am. Chem. Soc. 1975, 97, 6472.
Roussel, C.; Lide´n, A.; Chanon M.; Metzger, J .; Sandstro¨m, J . J . Am.
Chem. Soc. 1976, 98, 2847, and references therein. Charton, M. J . Org.
Chem. 1977, 42, 2528.
(28) Lanza, S.; Bruno, G.; Nicolo`, F. Acta Crystallogr., Sect. C 1990,
46, 765.
(29) Hurd, R. N.; De La Mater J .; McEleheny, G. C.; Tuner, R. J .;
Wallingford, V. H. J . Org. Chem. 1961, 26, 3980.
(30) Kukushkin, Y. N.; Viaz’mesnkii Y. E.; Zorina, L. I. Russ. J .
Inorg. Chem. 1968, 835.
(27) Schaffner, S.; Macko, L.; Neuburger, M. Zehnder, M. Helv.
Chim. Acta 1997, 80, 463.
(31) Arena, C. G.; Ciani, G.; Drommi, D.; Faraone, F.; Proserpio, D.
M.; Rotondo, E. J . Organomet. Chem. 1994, 71, 848.

2468 Organometallics, Vol. 19, No. 13, 2000
Lanza et al.
3
151.0-124.0 (29C, ArC and pyrC); 60.3 (2C, NCHPh); 21.8 (1C,
CH3); 21.6 (1C, CH3). 31P{1H} NMR (121.49 MHz, CDCl3, 298
K): 13.5 (1J Pt-P ) 3307, Pt-P). Anal (%) Calcd for C35H34N3-
PS2Cl2Pt: C, 49.01; H, 4.00; N, 4.90; S, 7.48; Cl, 8.27. Found:
C, 49.13; H, 4.10; N, 5.12; S, 7.32; Cl, 8.05.
13.8, J H-H ) 6.8, 2H, NCH2 trans to P, part AB of ABC3);
3 3
1.15 (t, J H-H ) J H-H ) 6.8, 3H, CH3 trans to P, part C3 of
ABC3); 0.95, (t, J H-H ) 3J H-H ) 6.8, 3H, CH3 cis to P, part C3
3
of ABC3); 5.42 (m, 1H, central-allyl, CH); 3.52 (m, 3J H-H ) 6.9,
1H, syn-allyl CHH); 3.50 (m, 3J H-H ) 6.9, 1H, syn-allyl CHH);
2.91 (m,3J H-H ) 12.7, 1H, anti-allyl CHH); 2.89, (m, J H-H
)
3
Gen er a l P r oced u r e for th e P r ep a r a tion of Dith ioxa -
m id a to Com p lexes [(P N)ClP t(HR2N2S2C2)] (R ) Eth yl, 4;
R ) Ben zyl, 5; R ) {S}-P h en yleth yl, 6). A 200 mg sample
of sodium bicarbonate was added to 1 mmol of the above ion
pairs dissolved in the minimum amount of chloroform (∼20
mL). The magenta solution immediately turned to orange;
after 0.5 h of stirring, the sodium bicarbonate was removed
by filtration and the orange solution was concentrated to a
small volume (∼1 mL). [(PN)ClPt(HR2N2C2S2)] complexes 4-6
precipitated as orange powders, which were collected and air-
dried. Yields were higher than 90%.
12.7, 1H, anti-allyl CHH). 13C{1H} NMR (75.47 MHz, CDCl3,
3
298 K): 190.8 (d, J C-P ) 11, 1C, CS trans to P); CS 190.3 (d,
3J C-P ) 2, 1C, CS cis to P); 154.6 -124.3 (17C, ArC and pyrC);
115.5 (1C, central-allyl CH); 58.0 (1C, allyl CH2); 57.9 (1C, allyl
CH2); 52.8 (1C, NCH2); 52.1 (1C, NCH2); 13.0 (1C, CH3); 12.7
(1C, CH3). 31P{1H} NMR (121.49 MHz, CDCl3, 298 K): 17.3
(1J Pt-P ) 3267, Pt-P). Anal (%) Calcd for C26H29N3PS2-
ClPdPt: C, 38.33, H, 3.59; N, 5.16; S, 7.83; Cl, 4.30. Found:
C, 38.61; H, 3.71; N, 5.25; S, 8.05; Cl, 4.52.
[(P N)ClP t (µ-N,N′-(C7H 7)2N2S2C2K-S,S′-P t K-N,N′-P d )-
(η3-a llyl)P d ] (8). 1H NMR (300.13 MHz, CDCl3, 298 K): 8.76
(m, 1H, pyrH-6); 8.55 (m, 1H, pyrH-3); 7.60-7.00 (m, 22 H,
ArH and pyrH); 5.10 (AB q,1J ) 15, 2H, NCH2 cis to P); 4.55
(AB q, 1J ) 15, 2H, NCH2 trans to P); 4.90 (m, 1H, central-
[(P N)ClP t(H(C2H5)2N2S2C2)] (4). 1H NMR (300.13 MHz,
CDCl3, 298 K): 8.74 (m, 1H, pyr H-6) 8.39 (m, 1H, pyrH-3);
3
7.87-7.27 (m, 12H, ArH and pyrH); 3.71 (q, J H-H ) 7.3, 2H,
3
3
NCH2) 3.28 (q, J H-H ) 7.3, 2H, NCH2); 1.34 (t, J H-H ) 7.3,
3H, CH3); 1.17 (t, J H-H ) 7.3, 3H, CH3). 13C{1H} NMR (75.47
allyl CH); 3.10 (m, J H-H ) 5.8, 1H, syn-allyl CH H trans to
3
3
3
3
MHz, CDCl3, 298 K): 186.8 (d, J C-P ) 3, 1C); 172.9 (d, J C-P
) 11, 1C, CS trans to P); 150.5-124.9 (17C, ArC and pyrC);
45.3 (1C, NCH2); 41.8 (1C, NCH2); 14.5 (1C, CH3); 13.1 (1C,
CH3). 31P{1H} NMR (121.49 MHz, CDCl3, 298 K): 16.6 (1J Pt-P
) 3408, Pt-P). Anal(%) Calcd for C23H25N3PS2ClPt: C, 41.29;
H, 3.77; N, 6.28; S, 9.58; Cl, 5.30. Found: C, 41.15; H, 3.67;
N, 6.11; S, 9.62; Cl, 5,47.
P); 2.86 (m, 3J H-H ) 5.8, 1H, syn-allyl CH H cis to P); 2.29 (m,
3J H-H ) 12, 1H, anti-allyl CHH cis to P); 2.24 (m,3J H-H ) 12,
1H, anti-allyl CHH trans to P). 13C{1H} NMR (75.47 MHz,
3
CDCl3, 298 K): 192.2 (d, J C-P ) 2, 1C, CS cis to P); 192.1
(d,3J C-P ) 10, 1C, CS trans to P); 150.1-123.0, 29C, ArC and
pyrC); 60.7 (1C, NCH2 cis to P); 60.1 (1C, NCH2 trans to P);
114.7 (1C, central-allyl CH); 59.1 (1C, allyl CH2 cis to P); 58.8
1C, allyl CH2 trans to P). 31P{1H} NMR (121.49 MHz, CDCl3,
[(P N)ClP t(H(C7H7)2N2S2C2)] (5). 1H NMR (300.13 MHz,
CDCl3, 298 K): 8.76 (m, 1H, pyrH-6); 8.39 (m, 1H, pyrH-3);
7.86-7.08 (m, 22H, ArH and pyrH); 4.84 (s, 2H, NCH2); 4.40
(s, 2H, NCH2). 13C{1H} NMR (75.47 MHz, CDCl3, 298 K): 188.0
1
298 K): 17.1 (Pt-P, J Pt-P ) 3272). Anal (%) Calcd for
C36H33N3PS2ClPdPt: C, 46.05; H, 3.55; N, 4.48; S, 6.82; Cl,
3.73. Found: C, 46.16; H, 3.61; N, 4.51; S, 6.70; Cl, 3.57.
[(P N)ClP t(µ-N,N′-({S}-d ip h en yleth yl)d ith ioxa m id a toK-
3
3
(d, J C-P ) 3, 1C, CS cis to P); 185.4 (d, J C-P ) 8, 1C, CS
trans to P); 150.1-124.5 (29 C, ArC and pyrC); 54.5 (1C,
NCH2); 51.0 (1C, NCH2). 31P{1H} NMR (121.49 MHz, CDCl3,
298 K): 16.2 (1J Pt-P ) 3400, Pt-P). Anal (%) Calcd for
S,S′-P t K-N,N′-P d ) (η3-a llyl)P d ] (9). H NMR (300.13 MHz,
1
CDCl3, 298 K): 8.67 (m, 1 H, pyrH-6); 8.46 (m, 1H, pyr H-3);
7.00-7.70 (m, 22 H, ArH and pyrH 9A a n d 9B); 5.85 (q,3J H-H
) 6.6, 0.5H, NCHPh cis to P 9A); 5.81 (q,3J H-H ) 6.6, 0.5H,
NCHPh cis to P 9B); 5.14 (q,3J H-H ) 6.6, 0.5H, NCHPh trans
to P 9A); 5.10 (q, J H-H ) 6.6, 0.5H, NCHPh trans to P 9B);
4.46 (m, 1H, central-allyl CH 9A a n d 9B); 3.15 (m, J H-H
C
33H29N3PS2ClPt: C, 49.97; H, 3.68; N, 5.30; S, 8.08; Cl, 4.47.
Found: C, 50.15; H, 3.76; N, 5.08; S, 8.23; Cl, 4.58.
[(P N)ClP t(H({S}-CHCH3P h )2N2S2C2)] (6). 1H NMR (300.13
MHz, CDCl3, 298 K): 8.74 (m, 1H, pyrH-6); 8.43 (m, 1H, pyrH-
3
3
)
3
3
3); 7.88-7.10(m, 22H, ArH and pyrH); 5.42 (q, J H-H ) 6.6,
6.7, 0.5H, syn-allyl CHH cis to P 9A); 3.06 (m, J H-H ) 6.7,
0.5H, syn-allyl CHH trans to P 9B); 2.49 (m, J H-H ) 6.6, 1H,
1H, NCHPh); 4.74 (q, 3J H-H ) 6.6, 1H, NCHPh); 1.64 (d, 3J H-H
3
) 6.6, 3H, CH3); 1.40 (d, 3J H-H ) 6.6, 3H, CH3). 13C{1H} NMR
syn-allyl CHH overlapped cis to P 9A and trans to P 9B); 2.24
(m, 1H, anti-allyl CHH overlapped trans to P 9B and cis to P
9A); 1.33 (m partially obscured by the methyls, 0.5H, anti-
allyl CHH cis to P 9A); 1.28 (m partially obscured by the
methyls, 0.5H, anti-allyl CHH trans to P 9B); 1.53 (d, 3J )
3
(75.47 MHz, CDCl3, 298 K): 186.5 (d, J C-P ) 3, 1C, CS cis to
3
P); 177,8 (d, J C-P ) 9, 1C, CS trans to P); 149.0-124.3 (29C,
ArC and pyrC); 58.8 (1C, NCHPh); 56.4 (1C, NCHPh); 22.2
(1C, CH3); 20.9 (1C, CH3). 31P{1H} NMR (121.49 MHz, CDCl3,
298 K): 13.5 (1J Pt-P ) 3307, Pt-P). Anal (%) Calcd for C35H33N3-
PS2ClPt: C, 52.12; H, 4.17; N, 5.11; S, 7.80; Cl, 4.31. Found:
C, 51.93; H, 4.20; N, 5.14; S, 7.66; Cl, 4.05.
3
6.6 (1.5H, CH3 cis to P 9A); 1.44 (d, J ) 6.6, 1.5H, CH3 cis to
3
P 9B); 1.33 (d, J H-H ) 6.6, 1.5H, CH3 trans to P 9A); 1.23 (d,
3J H-H ) 6.6, 1.5H, CH3 trans to P 9B). 13C{1H} NMR (75.47
MHz, CDCl3, 298 K): 190.8 (d,3J C-P)10, 0.5C, CS trans to P
Gen er a l P r oced u r e for th e P r ep a r a tion of Bin u clea r
Dith ioxbisa m id a to Com p lexes [(P N)ClP t(µ-R2N2S2C2-K-
S,S-P t-K-N,-P d )P d (η3-C3H5)] (η3-C3H5 ) η3-Allyl; R ) Eth -
yl, 7; R ) Ben zyl, 8; R ) {S}-P h en yleth yl, 9). A 1 mmol
sample of [Pd(η3-C3H5)(µ-Cl)]2 was dissolved in about 30 mL
of a 70:30 v/v chloroform/methanol mixture and reacted with
a half molar quantity of [(PN)ClPt(HR2N2S2C2)] complexes.
The solution, which turned deep red, was allowed to stand for
2 h. The solvents were removed and the crude products,
redissolved in the minimum amount of chloroform (about 10
mL), placed on an alumina column, and equilibrated with light
petroleum. The desired products were collected as orange
eluates and concentrated to a small volume (about 1 mL). By
adding petroleum ether 40-60 (about 30 mL), bimetallic
complexes precipitated as orange powders. Yields were higher
than 80%.
3
9A); 190.4 (d, J C-P ) 10, 0.5C, CS trans to P 9B); 190.1 (d,
3J C-P ) 3, 0.5C, CS cis to P 9A); 189.8 (d, J C-P)3, 0.5C, CS
3
cis to P 9A); 150.0-125.0 (29C, ArC and pyrC); 60.5 (1C,
NCHPh cis to P overlapped 9A a n d 9B); 59.9 (1C, NCHPh
trans to P overlapped 9A a n d 9B); 111.9 (1C, central-allyl CH);
58.7 (1C, allyl CH2 cis to P overlapped 9A a n d 9B); 57.9 (1C,
allyl CH2 trans to P overlapped 9A a n d 9B); 18.5 (0.5C, CH3
cis to P, 9A); 17.4 (0.5C, CH3 cis to P 9B); 18.3 (0.5C, CH3
trans to P 9A); 17.2 (0.5C, CH3 trans to P 9B). 31P{1H} NMR
1
(121.49 MHz, CDCl3, 298 K): 17.5 (0.5P, J Pt-P ) 3273, Pt-
1
P); 17.4 (0.5P, J Pt-P ) 3273, Pt-P). Anal (%) Calcd for
C
38H37N3PS2ClPdPt: C, 46.20; H, 3.86; N, 4.35; S, 6.62; Cl,
3.62. Found: C, 46.42; H, 3.71; N, 4.21; S, 6.56; Cl, 3.41.
X-r a y Cr ysta llogr a p h ic Stu d ies of 8. Diffraction data of
a suitable crystal were collected at room temperature on a
Siemens P4 automatic four-circle diffractometer by using
graphite-monochromated Mo KR radiation. Lattice parameters
were obtained from least-squares refinement of the setting
angles of 35 reflections with 11° e 2θ e 30°. No sign of crystal
deterioration was revealed during the data collection. The
[(P N)ClP t(µ-N,N′-(C2H5)2N2S2C2-K-S,S′-P tK-N,N′-P d )(η3-
a llyl)P d ] (7). 1H NMR (300.13 MHz, CDCl3, 298 K): 8.68 (m,
1H, pyr H-6); 8.47(m, 1H, pyrH-3); 7.80÷7.13, (12 H, ArH and
2
3
pyrH); 5.39 (m, 1H, allyl CH); 4.81 (dq, J H-H ) 13.8, J H-H
)
)
2
6.8, 2H, NCH2 cis to P, part AB of ABC3); 3.38 (dq, J H-H

Heterobimetallic Complexes with Metals
Organometallics, Vol. 19, No. 13, 2000 2469
reflection intensities, collected by variable speed ω-2θ scan
technique, were evaluated by a profile fitting among 2θ shell
procedure32 and then corrected for Lorentz-polarization ef-
fects. An absorption correction was applied by fitting a pseudo-
ellipsoid to the azimutal scan data of 20 high ø reflections33
(Rint a/ p ) 12.7/3.9%, Tmin/max ) 0.51/1.00). Data reduction has
been performed with the SHELXTL-PLUS system.34
geometry and the H isotropic displacement parameter depend-
ing on the parent atom X. The refinement, with all non
hydrogen atoms anisotropic and minimizing the function ∑w-
(Fo2 - Fc2)2, was carried out with the full-matrix least-squares
technique, based on all independent F2, with SHELXL97.35 The
final weighting scheme was w-1 ) [σ2(Fo)2 + (0.0238(Fo
+
2
2Fc ))2]. A parameter for extinction correction was included into
the last refinement cycles and assumed the final value 1.9(2)
× 10-3. In the last difference Fourier map the significant den-
sity residuals were up to 1.56 e Å-3 at 1 Å from the Pt atom.
Final geometrical calculations and drawings were carried
out with the PARST program36 and the XPW utility of the
Siemens package, respectively.
2
The statistics |E2 - 1| ) 0.807 (expected 0.736 for non- and
0.968 for centrosymmetric packing) pointed to the acentric
arrangement. However each attempt to complete/refine the
crystal modeling in P1 was unsuccessful due to the very large
correlation between the two molecules into the cell. Therefore
the crystal structure was solved by the standard Patterson
method and subsequently completed by a combination of least-
squares technique and Fourier syntheses in the centrosym-
metric space group P1h, treating the conformational disorder
by suitable restraints. H atoms were included in the refine-
ment in the “riding model” method with the X-H bond
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal-
lographic data and data collection details, atomic coordinates,
thermal displacement parameters, bond lengths and angles,
hydrogen atom coordinates, and torsion angles for 8. This
material is available free of charge via the Internet at
http://pubs.acs.org.
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