Stereodiscrimination in Phosphanylthiolato Nickel(II) Complexes

Article abstract of DOI:10.1002/ejic.200300508

The presence of a stereogenic carbon centre (R or S) in the racemic ligand 1-(diphenylphosphanyl)propane-2-thiol induces a conformational preference (λ of δ) in the five-membered chelate ring of its 2:1 and 2:2 coordination compounds with Ni^II: the mononuclear trans-[Ni{SCH(CH₃)CH₂PPh₂-P,S}₂] (1) and the binuclear trans-[Ni{μ-SCH(CH₃)CH₂PPh ₂-P,S}(Cl)]₂ (2). Both complexes exist as mixtures of two diastereomers: racemic-trans (R_λ, R_λ, & and S_δ, S_δ) and meso-trans (R _λ, S_δ), in an equilibrium displaced towards the more stable isomer, the meso-trans for 1 (calculated ΔE = < -0.1 kcal·mol^-1) and the racemic-trans for 2 (calculated ΔE = -5.1 kcal·mol^-1). This phenomenon is especially evident for complex 2, in which an efficient chiral recognition between the two enantiomeric forms of the racemic ligand was observed. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.

Full text of DOI:10.1002/ejic.200300508

SHORT COMMUNICATION
Stereodiscrimination in Phosphanylthiolato Nickel(II) Complexes
Josep Duran,[a] Alfonso Polo,*[a] Julio Real,*[b] Jordi Benet-Buchholz,[c] Albert Poater,[a,d]
[a,d]
`
and Miquel Sola
Keywords: Nickel / P,S ligands / Conformation analysis / Chiral resolution / Density functional calculations
The presence of a stereogenic carbon centre (R or S) in the
racemic ligand 1-(diphenylphosphanyl)propane-2-thiol in-
duces a conformational preference (λ or δ) in the five-mem-
bered chelate ring of its 2:1 and 2:2 coordination compounds
with NiII: the mononuclear trans-[Ni{SCH(CH3)CH2PPh2-
P,S}2] (1) and the binuclear trans-[Ni{µ-SCH(CH3)CH2PPh2-
P,S}(Cl)]2 (2). Both complexes exist as mixtures of two dia-
stereomers: racemic-trans (Rλ, Rλ and Sδ, Sδ) and meso-trans
(Rλ, Sδ), in an equilibrium displaced towards the more stable
isomer, the meso-trans for (calculated ∆E = Ͻ −0.1
1
kcal·mol−1) and the racemic-trans for 2 (calculated ∆E = −5.1
kcal·mol−1). This phenomenon is especially evident for com-
plex 2, in which an efficient chiral recognition between the
two enantiomeric forms of the racemic ligand was observed.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2003)
Introduction
chelate rings are in a λ-conformation, and the two chelate
rings of the enantiomer are in a δ-conformation, we have
the racemic-trans complex and when each chelate ring is in
a different conformation, we have the meso-trans dia-
stereomer (see Scheme 1). These two stereoisomers can be
distinguished when a racemic chiral ligand is present, such
as in complex [Ni(SCH2CH2PMePh)2], which has a racemic
ligand chiral at the phosphorus centre. This compound ex-
ists in solution as a mixture of the racemic-trans and the
meso-trans forms that equilibrate slowly (t1/2 ca. 12 h)
through an intermolecular process to form a 1:1 mixture,
since the two diastereomers have very close energies.[4]
The reactivity of 2-phosphanylthiolato nickel() com-
plexes has been studied because of their relevance in S-alky-
lation/S-dealkylation reactions[1] and their applications in
desulfurisation technologies[2] and in understanding the
biological pathways of certain sulfur-containing metallo-
proteins.[3] However, less attention has been given to the
importance of the ligand-based stereoelectronic effects in
determining the coordination conformations around the
metal and the stereochemistries of these compounds.[4]
Thus, we decided to focus our attention on these particular
aspects. The bis(phosphanylthiolato)nickel() complexes
trans-[Ni(SCH2CH2PR2-P,S)2][4,5] exist as mixtures of dia-
stereomers because the five-membered chelate ring can ad-
opt two different conformations (λ and δ) and therefore is
able to form three optically isomeric complexes. When both
[a]
´
Departament de Quımica, Universitat de Girona,
Campus de Montilivi s/n, 17071 Girona, Spain
Fax: (internat.) ϩ34-9724-18150
E-mail: alfons.polo@udg.es
[b]
[c]
´
`
Departament de Quımica, Universitat Autonoma de Barcelona,
08193 Bellaterra, Spain
Fax: (internat.) ϩ34-9358-13101
E-mail: Juli.real@uab.es
Scheme 1. Stereoisomers of mononuclear five-membered ring
bis(phosphanylthiolato)nickel() complexes exemplified by com-
plex 1
Bayer AG, Bayer Industry Services, Analytics X-ray
Laboratory,
Geb. Q18, Raum 490, 51368 Leverkusen, Germany
Fax: (internat.) ϩ49-2143-050677
The same stereochemical analysis can be applied to the
2-phosphanylthiolato-bridged binuclear nickel() com-
plexes [Ni(µ-SCH2CH2PR2)(X)]2, which form bent syn-
endo-trans structures.[6,7] Theoretical studies have shown
that for this class of compounds the stabilisation of folded
structures with respect to the planar arrangement can be
E-mail: jordi.benet-buchholz.jb@bayerindustry.de
[d]
´
Institut de Quımica Computational, Universitat de Girona,
Campus de Montilivi s/n, 17071Girona, Spain
Fax: (internat.) ϩ34-9724-18356
E-mail: miquel@iqc.udg.es
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
Eur. J. Inorg. Chem. 2003, 4147Ϫ4151
DOI: 10.1002/ejic.200300508
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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`
J. Duran, A. Polo, J. Real, J. Benet-Buchholz, A. Poater, M. Sola
SHORT COMMUNICATION
ascribed to the pyramidalisation of the sulfur bridge com- tra all aliphatic carbon atoms appear as triplets owing to
pounded with a weak NiϪNi interaction. Furthermore, it virtual coupling with two equivalent mutually trans phos-
has been proposed that in a bent structure the chelate ring phorus nuclei (see Figure 1). According to the 31P{1H}
involving the bridging sulfur would be highly strained in NMR spectrum, bis-chelate 1 exists as a mixture of two
syn-exo or anti conformations.[7] As in the case of bis(phos- diastereomers: freshly prepared CDCl3 solutions of com-
phanylthiolato) complexes, the chelate chain introduces plex 1 show two resonances at δP ϭ 52.6 and 54.2 ppm in
some degree of structural variation, also producing the ra- about an 11:5 intensity ratio. The similar δP values point to
cemic-trans and meso-trans diastereomers (see Scheme 2). two diastereomers with the same configuration but differ-
Nevertheless, it should be noted that the anti conformation ent conformations.
of the bridging sulfur substituents would be necessary for
the meso-trans isomer to be formed and that, for this type
of complexes, the bent-anti structure has been observed
neither in the solid state nor in solution.
Figure 1. The aliphatic 13C{1H} NMR signals of complex 1 appear
as triplets owing to virtual coupling with 2 equiv. mutually trans
phosphorus nuclei
In keeping with the conformational analysis for com-
pound 1 (see Scheme 1), the preferred conformation for the
chiral chelate ring depends on the configuration at the
stereogenic carbon centre of the ligand.[10a] Thus, the ligand
Scheme 2. Stereoisomers of double 2-phosphanylthiolato-bridged
binuclear nickel() complexes with bent structures exemplified by
complex 2
with R configuration adopts the λ-conformation, which
places the substituent of the chelate ring in the equatorial
position. For the same reasons, the ligand with S configura-
tion adopts the δ-conformation. As a result of these confor-
mational preferences, complexes carrying two ligands with
the same configuration, trans-(R,R)-1 and trans-(S,S)-1 are
enantiomers (racemic-trans-1) giving a single 31P{1H}
NMR signal. The second resonance is then assigned to the
diastereomeric complex carrying one ligand in each con-
figuration, trans-(R,S)-1 (meso-trans-1). By comparison
with the related complex [Ni(SCH2CH2PMePh)2],[4] the
major signal could be initially assigned to the racemic-
trans-1 stereoisomer, which was claimed to be the kinetic
product. However, the intensity ratio of the 31P{1H} NMR
signals remains constant after 72 h at 50 °C. This behaviour
contrasts with that observed for other similar Group VIII
metal bis(phosphanylthiolato) complexes, in which the two
signals become equal after 24 h at room temperature. In the
For these reasons, we propose that the energy difference
between the racemic-trans and meso-trans diastereomers of
bis(phosphanylthiolato) complexes, and the strong tendency
of the phosphanylthiolato-bridged binuclear complexes to
adopt the folded syn-endo-trans conformation, could pro-
duce a chiral discrimination between the two enantiomeric
conformations of the five-membered chelate ring. In order
to demonstrate this hypothesis, we synthesised and charac-
terised the 2:1 and 1:1 coordination compounds of the ra-
cemic ligand 1-(diphenylphosphanyl)propane-2-thiol[8]
with nickel().
Results and Discussion
An alternative method to the literature procedures for the latter case the two diastereomers have very close ener-
syntheses of [Ni(SCH2CH2PPh2)2][5,9] and [Ni(µ- gies,[4,10a] suggesting that for complex 1 they have a slight,
[9]
SCH2CH2PPh2)(Br)]2 was applied to prepare the mono- but significant, difference in energy (experimental ∆E ഠ
nuclear bis-chelate trans-[Ni{SCH(CH3)CH2PPh2}2] (1) and 0.41 kcal·molϪ1). The BP86 energy calculations on complex
the binuclear trans-[Ni(µ-SCH(CH3)CH2PPh2)(Cl)]2 (2) 1 (see below) reveal that this energy difference is really small
complexes. Addition of a CH2Cl2 solution of two equiv. of (less than 0.1 kcal·molϪ1) and predict the stabilisation of
racemic 1-(diphenylphosphanyl)propane-2-thiol to a solu- the meso-trans-1 isomer over the racemic-trans-1, owing
tion of nickel chloride in methanol resulted in the formation most probably to the steric interactions between the pseudo-
of solid 1, which was isolated in 85 % yield. The same base- axial phenyl groups that are mutually syn in racemic-trans-
free procedure was used for 2, which was isolated in 80 % 1 and anti in meso-trans-1 (see Scheme 3).
yield upon addition of one equiv. of the racemic ligand and
Binuclear complex 2 adopts a bent syn-endo-trans confor-
mation in the solid state (see below) and shows a single,
precipitation with diethyl ether.[10]
The trans geometry of the mononuclear complex 1 was sharp resonance in the 31P{1H} NMR spectrum at δP
ϭ
determined by NMR analysis. In the 13C{1H} NMR spec- 36.3 ppm, both for freshly prepared and aged solutions,
4148
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Stereodiscrimination in Phosphanylthiolato Nickel(II) Complexes
SHORT COMMUNICATION
An XRD study was carried out on crystals of 2·CHCl3
(see Figure 3). The crystal structure contains only the ra-
cemic-trans-2 diastereomer and reveals an edge-sharing bi-
nuclear complex with square-planar coordination geometry
around the nickel atoms. The molecule adopts a folded syn-
endo-trans conformation (see Figure 3). Although the
NiϪS, NiϪP and NiϪCl distances are in the range ob-
served for the isostructural [Ni(µ-SCH2CH2PPh2)(X)]2
complexes (where X ϭ Cl, Br), the fold angle of the central
four-membered Ni2S2 cycle is appreciably greater (118.1 vs.
100.7Ϫ104.1°), increasing the NiϪNi distance from
2.681Ϫ2.695 to 2.906 A. The reason for this geometrical
alteration must be attributed to the presence of the substitu-
ent in the chelate chain, because there are no other struc-
tural changes. In complex 2, the requirement to locate the
methyl group in the equatorial position increases the bend-
ing of the tertiary carbon atom away from the SϪS hinge
(33.6 vs. 27.1Ϫ27.8°) and, since this bending is related to
the arching of the Ni2S2 group,[7] the central core must un-
fold.
Scheme 3. The pseudo-axial phenyl groups of the trans-bis(2-di-
phenylphosphanylthiolato)nickel() complexes are mutually syn in
the stereoisomers carrying both chelate rings in the same confor-
mation (λ, λ or δ, δ) and anti in the stereoisomer with one chelate
ring in each conformation (λ, δ)
[6]
˚
pointing to the presence of only one of the possible dia-
stereomers. It is noteworthy that in the 13C{1H} NMR spec-
trum of binuclear 2, two of the aromatic carbon atoms (Co
and Cm) show two signals each, and all are pseudo-triplets
(see Figure 2). The doubling of these signals is assigned to
the different surroundings of each phenyl ring in the same
diphenylphosphanyl group, while the fine splitting could be
ascribed to a somewhat surprisingly similar coupling to
both phosphorus nuclei generated by the PϪNiϪNiϪP
connection, a special case of the known phenomenon of
virtual coupling.[7]
Figure 2. Two of the aromatic 13C{1H} NMR signals of complex
2 appear as pseudo-triplets (Co and Cm), probably owing to a
PϪNiϪNiϪP coupling; complex 2 is not soluble enough to obtain
quality signals for the quaternary carbon atoms, but an unfolded
doublet of doublets can be glimpsed in the spectral trace
Figure 3. ORTEP plot (50 %) of complex 2, hydrogen atoms are
˚
omitted; selected distances (A) and angles (°): Ni1ϪNi2 2.9065(4),
Ni1ϪS1 2.1556(6), Ni1ϪS2 2.2244(7), Ni1ϪP1 2.1705(7), Ni1ϪCl1
2.1910(7), Ni2ϪS1 2.2081(7), Ni2ϪS2 2.1558(7), Ni2ϪP2
2.1559(7), Ni2ϪCl2 2.1811(7), S1ϪC14 1.841(3), C13ϪC14
1.531(4), C14ϪC15 1.516(4), P1ϪC13 1.834(3), S2ϪC29 1.854(3),
C28ϪC29 1.520(4), C29ϪC30 1.521(4), P2ϪC28 1.833(3),
S1ϪNi1ϪP1 87.99(3), P1ϪNi1ϪCl1 95.22(3), S1ϪNi1ϪS2
The conformational analysis of complex 2 shows, as in
the case of 1, that ligands with R and S configuration adopt
λ and δ conformations, respectively, thereby placing the
chelate chain substituent in the equatorial position. Thus,
two diastereomeric forms of 2 could exist (racemic-trans-2
and meso-trans-2: see Scheme 2), but only one of them was
observed in solution. The BP86 energy calculations on com-
plex 2 (see below) gave an energy difference of 5.1
kcal·molϪ1 between the racemic-trans-2 and the meso-trans-
2 isomers, in agreement with an equilibrium strongly dis-
placed towards the racemic-trans-2 diastereomer (exper-
imental ∆E Ն 2.3 kcal·molϪ1).[11] Furthermore, the mini-
mum in energy for the meso-trans-2 isomer represents a
folded syn-endo-trans structure with one of the chelate chain
79.51(2),
Cl1ϪNiϪS2
97.74(3),
S2ϪNi2ϪP2
88.29(3),
P2ϪNi2ϪCl2 92.58 (3), S2ϪNi2ϪS1 79.81(3), Cl2ϪNi2ϪS1 99.15
(3),
Ni1ϪS1ϪNi2
83.52(2),
C14ϪS1ϪNi1
105.94(8),
C14ϪS1ϪNi2 112.74(9), Ni2ϪS2ϪNi1 83.13(2), C29ϪS2ϪNi2
105.38(8), C29ϪS2ϪNi1 112.77(9).
Computational Results
The reported calculations were carried out by using the
substituents in the equatorial position and the other in the Amsterdam density functional (ADF2002.03) program
axial. This result is in agreement with the instability of the system, developed by Baerends et al.[12Ϫ14] The numerical
bent anti conformations predicted for this type of com- integration scheme employed was that of te Velde and
plex.[7]
Baerends.[15] An uncontracted triple-ζ basis set[16] was used
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J. Duran, A. Polo, J. Real, J. Benet-Buchholz, A. Poater, M. Sola
SHORT COMMUNICATION
for describing the 3s, 3p, 3d, 4s, and 4p orbitals of nickel. phosphanylthiolato complexes of NiII are in agreement with
For carbon (2s,2p), phosphorus (3s,3p), sulfur (3s,3p), and the experimentally observed racemic-trans/meso-trans ratios
hydrogen (1s), double-ζ basis sets[16] were employed and and are responsible for the chiral recognition between the
augmented by an extra polarisation function. Electrons in two enantiomeric forms of the racemic ligand. This
lower shells were treated within the frozen core approxi- phenomenon is especially important in the binuclear com-
mation.[13a] A set of auxiliary s, p, d, f, and g functions,[17] plex 2, in which a destabilised anti conformation of the
centred in all nuclei, was introduced in order to fit the mo- bridging sulfurs would be necessary in order for the meso-
lecular density and Coulomb potential accurately in each trans isomer to be stable.
SCF cycle. Both geometry optimisations and energy evalu-
ations have been fully carried out within a generalised
gradient approximation (GGA) that includes a GGA ex-
change and correlation corrections of Becke[18] and Per-
Experimental Section
dew (BP86).[19]
In order to validate the method, the XRD data of com-
plex 2 was geometrically optimised by excluding the solvent
molecules. The results show good agreement between the
experimental and theoretical data. The experimental and
theoretical bond lengths and angles differ by less than 0.08
General Remarks: The complexes were synthesised using standard
Schlenk techniques under nitrogen atmosphere. The solvents were
dried by standard methods and distilled and deoxygenated before
use. The C, H and S analyses were carried out using a CarloϪErba
microanalyser. CDCl3 for NMR measurements was dried over mo-
lecular sieves. Proton NMR spectra were recorded at 200 MHz on
a Bruker DPX-200 spectrometer. Peak positions are relative to
tetramethylsilane as internal reference. 31P{1H} NMR spectra were
recorded on the same instrument operating at 81.0 MHz. Chemical
shifts are relative to external 85 % H3PO4 and downfield values are
reported as positive. 13C{1H} NMR spectra were recorded on the
same instrument operating at 50.3 MHz. Chemical shifts are rela-
tive to tetramethylsilane as internal reference.
˚
A and 3.6°, respectively. The standard deviations for the
˚
selected distances and angles listed in Figure 3 were 0.04 A
and 2.1°, respectively, which confirm the validity of the
chosen computational method.
All the experimental compounds were analysed compu-
tationally. It was found experimentally that both mononu-
clear and binuclear species are diamagnetic. For this reason,
optimisations were carried out for neutral closed-shell sing-
let ground-state structures. However, since it has been found
that the triplet state is close in energy to the singlet state,
or it can be even more stable than the singlet state, we
checked the relative stability of both states for all com-
pounds by optimising the triplet state. In all cases the triplet
state geometry presented a higher energy, indicating that
the singlet states are the most favourable. This is in agree-
ment with the sharp peaks in the NMR spectra. The differ-
ence between these two states is around 20 kcal·molϪ1
[Ni{SCH(CH3)CH2PPh2-P,S}2] (1): 1-(diphenylphosphanyl)pro-
pane-2-thiol (205.4 mg, 0.79 mmol) in CH2Cl2 (1 mL) was added
to a solution of NiCl2·6H2O (75.1 mg, 0.316 mmol) in methanol
(2 mL) under a nitrogen atmosphere to produce a green precipitate.
The precipitate was washed with hexane yielding complex 1
(155.1 mg, 80 %). 1H NMR (200 MHz, CDCl3, TMS): δ ϭ 1.31 (d,
3
3J ϭ 6.4 Hz, 2.72 H, CH3 racemic-trans-1); 1.40 (d, J ϭ 6.2 Hz, 6
2
H, CH3 meso-trans-1); 2.33 (tt, 2J ϭ Ϫ13.4, 3J ϭ 13.4, JH,P
ഠ
2.8 Hz, 2 H, CH2ax. meso-trans-1); 2.47 (ddt, 2J ϭ Ϫ13.1, 3J ϭ
10.1, JH,P ഠ 3.0 Hz, 0.92 H, CH2ax. racemic-trans-1); 2.6Ϫ3.0 (m,
2
5.8 H, CH2 equiv., CH, meso-trans-1 and racemic-trans-1); 7.1Ϫ8.3
(racemic-trans-1 22.2 kcal·molϪ1
;
meso-trans-1 21.4
(m, 29 H, Har) ppm. 13C{1H} NMR (50.3 MHz, CDCl3, TMS):
kcal·molϪ1; racemic-trans-2 19.4 kcal·molϪ1; meso-trans-2
δ ϭ 25.10 (t, JC,P ϭ 9.0 Hz, CH3 meso-trans-1); 26.08 (t, JC,P
ϭ
21.6 kcal·molϪ1).
7.4 Hz, CH3 racemic-trans-1); 36.37 (t, JC,P ϭ 12.3 Hz, CH meso-
trans-1); 37.22 (t, JC,P ϭ 14.4 Hz, CH racemic-trans-1); 46.51 (t,
JC,P ϭ 18.5 Hz, CH2 meso-trans-1); 47.44 (t, JC,P ϭ 18.2 Hz, CH2
racemic-trans-1); 128.5Ϫ129.2 (m, Cm meso-trans-1 and racemic-
trans-1); 129.2Ϫ132.3 (m, Ci meso-trans-1 and racemic-trans-1);
130.66 (s, Cp meso-trans-1); 130.79 (s, Cp racemic-trans-1); 131.23
(s, CЈp racemic-trans-1); 131.41 (s, CЈp meso-trans-1); 132.85 (t,
JC,P ϭ 5.4 Hz, C0 meso-trans-1); 133.41 (t, JC,P ϭ 5.6 Hz, C0 ra-
cemic-trans-1); 134.58 (t, JC,P ϭ 6.1 Hz, CЈ0 racemic-trans-1);
135.10 (t, JC,P ϭ 6.1 Hz, CЈ0 meso-trans-1) ppm. 31P{1H} NMR
(81 MHz, CDCl3, H3PO4): δ ϭ 52.56 (s, 1P, meso-trans-1); 54.23
(s, 0.46P, racemic-trans-1) ppm. C30H32NiP2S2 (577.4): calcd. C
62.41, H 5.59, S 11.11; found C 62.22, H 5.70, S 10.99 %.
Energy calculations predicted a slight stabilisation, by
less than 0.1 kcal·molϪ1, of the meso-trans-1 isomer relative
to the racemic-trans-1, showing that the two isomers have
similar energies, in line with the fact that experimentally the
two isomers are present as final products. On the other
hand, the energy calculations on complex 2 gave an energy
difference of 5.1 kcal·molϪ1 between the racemic-trans-2
and the meso-trans-2 isomers, in agreement with an equilib-
rium strongly displaced towards the racemic-trans-2 dia-
stereomer (experimental ∆E Ն 2.3 kcal·molϪ1).[11]
We also attempted to optimise an anti conformation for
the binuclear complex, but the optimisation process evolved
towards the racemic-trans-2 species, as the anti confor-
mations are even less stable than the syn ones because of
the steric requirements of the ligands.
[Ni{µ-SCH(CH3)CH2PPh2-P,S}(Cl)]2 (2): 1-(diphenylphosphanyl)-
propane-2-thiol (88.1 mg, 0.338 mmol) in CH2Cl2 (1 mL) was ad-
ded to a solution of NiCl2·6H2O (80.5 mg, 0.338 mmol) in meth-
anol (2 mL) under a nitrogen atmosphere. The green precipitate
obtained had redissolved after 3 h stirring, yielding a brown solu-
tion. The product was crystallised by addition of diethyl ether to
afford complex 2 as brown crystals (91.3 mg, 80 %). 1H NMR
Conclusion
(200 MHz, CDCl3, TMS): δ ϭ 1.34 (d, 3J ϭ 8.0 Hz, 6 H, CH3);
In conclusion, the calculated energy differences between
the racemic-trans and meso-trans diastereomers of these 2.34 (td, J ϭ Ϫ13.7, 3J ϭ 13.7, 2JH,P ϭ 6.4 Hz, 2 H, CH2ax.); 2.63
2
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Eur. J. Inorg. Chem. 2003, 4147Ϫ4151

Stereodiscrimination in Phosphanylthiolato Nickel(II) Complexes
SHORT COMMUNICATION
(ddpseudo-t, 2J ϭ Ϫ13.7, 3J ϭ 4.5, 2JH,P ഠ 4.4 Hz, 2 H, CH2 equiv.);
3.24 (m, 2 H, CH); 7.2Ϫ8.4 (m, 20 H, Har) ppm. 13C{1H} NMR
(50.3 MHz, CDCl3, TMS): δ ϭ 22.96 (m, CH3); 39.16 (pseudo-t,
J ഠ 3.0 Hz, CH); 44.97 (d, 1JC,P ϭ 38.8 Hz, CH2); 128.80 (pseudo-
[1]
[2]
J. S. Kim, J. H. Reibenspies, M. Y. Darensbourg, J. Am. Chem.
Soc. 1996, 118, 4115Ϫ4423.
D. A. Vicic, W. D. Jones, J. Am. Chem. Soc. 1999, 121,
7606Ϫ7617.
3
3
t, JC,P ϭ 5.2 Hz, Cm); 128.95 (pseudot, JC,P ϭ 5.2 Hz, CЈm);
[3] [3a]
L. C. Myers, M. P. Terranova, A. E. Ferentz, G. Wagner,
1
4
130.12 (dd, JC,P ϭ 6.7, JC,Pഠ3.1 Hz, Ci); 131.09 (dd, 1JC,P ϭ 5.6,
4JC,P ഠ 3.0 Hz, CЈi); 131.84 (s, Cp); 133.14 (pseudo-t, JC,P ഠ 4.9 Hz,
Co); 133.63 (pseudo-t, JC,P ഠ 5.1 Hz, Co) ppm. 31P{1H} NMR
(81 MHz, CDCl3, H3PO4): δ ϭ 36.28 (s) ppm. C30H32Cl2Ni2P2S2
(707.0): calcd. C 50.97, H 4.56, S 9.07; found C 50.66, H 4.69, S
8.93 %.
[3b]
G. L. Verdine, Science 1993, 261, 1164Ϫ1167.
T. Ohkubo,
H. Sakashita, T. Sakuma, M. Kainosho, M. Sekiguchi, K. Mo-
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Received July 25, 2003
Acknowledgments
This work was financially supported by the DGESIC, projects
PB98-0913-C02, BQU2002-04070-C02 and BQU2002-04112-
C02-02. M. S. would like to thank the DURSI (Generalitat de
Catalunya) for financial support through the Distinguished Univer-
sity Research Promotion, 2001.
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www.eurjic.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4151