Ni(acac)2/phosphine as an excellent precursor of nickel(0) for catalytic systems

Article abstract of DOI:10.1021/om1003732

The coordination of phosphine ligands to nickel acetylacetonate was studied in toluene solution, and the first X-ray structure of the unstable complex trans-[Ni(acac)₂(PMe₂Ph)₂] has been reported. A convenient procedure was developed to generate Ni(0) species in situ in solution from a Ni(acac)₂ precursor, and their application in catalysis was demonstrated. A study of the reaction mechanism has suggested that water may play an important role in the formation of zerovalent nickel species. The nature of the Ni(0) species was confirmed by trapping with Ph ₂S₂, and the structure of the resulting complexes trans-[Ni(SPh)₂L₂] was established by X-ray analysis for L = PMe₂Ph, PMePh₂, PBu₃.

Full text of DOI:10.1021/om1003732

5098 Organometallics 2010, 29, 5098–5102
DOI: 10.1021/om1003732
Ni(acac)2/Phosphine as an Excellent Precursor of Nickel(0) for
Catalytic Systems†
Valentine P. Ananikov,*,† Konstantin A. Gayduk,† Zoya A. Starikova,‡ and
Irina P. Beletskaya*,§
†Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, Moscow 119991,
Russia, ‡Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilova str. 28,
Moscow 119991, Russia, and §Chemistry Department, Lomonosov Moscow State University Vorob’evy gory,
Moscow 119899, Russia
Received April 30, 2010
The coordination of phosphine ligands to nickel acetylacetonate was studied in toluene solution,
and the first X-ray structure of the unstable complex trans-[Ni(acac)2(PMe2Ph)2] has been reported.
A convenient procedure was developed to generate Ni(0) species in situ in solution from a Ni(acac)2
precursor, and their application in catalysis was demonstrated. A study of the reaction mechanism
has suggested that water may play an important role in the formation of zerovalent nickel species. The
nature of the Ni(0) species was confirmed by trapping with Ph2S2, and the structure of the resulting
complexes trans-[Ni(SPh)2L2] was established by X-ray analysis for L = PMe2Ph, PMePh2, PBu3.
1. Introduction
rather complicated procedures for the preparation of highly
unstable unsaturated species PdLn (n=1-3). Not surpris-
ingly, a PdX2/L combination is now routinely utilized in
various catalytic reactions.2 The mechanism of this transfor-
mation has been thoroughly discussed and involves coordi-
nation of the phospine ligand to Pd followed by reduction of
the metal center.3
The increasing cost of Pd has stimulated a search for
reliable Ni alternatives for catalysis; moreover, in some cases
it was reported that Ni catalysts were more active than the Pd
analogues.1,4 In this regard, direct involvement of a readily
accessible and easy to handle Ni(II) precursor in the catalytic
reactions is a topic of much practical importance.5
In contrast to palladium, a similar procedure for in situ
generation of Ni(0) species from convenient Ni(II) precur-
sors has not been routinely applied. Although utilization of a
NiX2/L combination in catalytic reactions was reported, it
was accompanied by addition of special reducing agents
(diisobutylaluminium hydride (DIBAL), AlR3, NaBH4,
Zn, LiAlH4, etc.). Usage of such reducing agents to form
soluble metal complexes requires fine control of the reaction
conditions, since this may also lead to the formation of Ni
nanoparticles6 and may result in changing the nature of the
The development of Pd-catalyzed reactions has shown out-
standing growth, and the synthetic methods created have
attained widespread application in modern organic chemistry.1
The easy generation of Pd(0) species;an active form of the
catalyst;by in situ reduction of PdX2 salts is of great impor-
tance for the practical application of the catalytic reactions to
synthetic procedures. In fact, Pd(II) catalyst precursors usually
were reduced to Pd(0) by 1 equiv of phosphine ligand and
allowed controlled generation of coordination unsaturated (n=
1-3) and saturated (n = 4) PdLn species, depending on the
overall amount of the phosphine ligand L added to the reaction
(Scheme 1).
This simple in situ procedure in many cases avoided the
synthesis of air-sensitive PdL4 complexes and, especially,
† Part of the Dietmar Seyferth Festschrift.
*To whom correspondence should be addressed. V.P.A.: fax, þ7 499
1355328; e-mail, val@ioc.ac.ru. I.P.B.: fax, þ7 495 9393618; e-mail,
beletska@org.chem.msu.ru.
(1) (a) Negishi, E., Ed. Handbook of Organopalladium Chemistry for
Organic Synthesis; Wiley: New York, Chichester, 2002. (b) Togni, A.,
Gr€utzmacher, H., Eds.; Catalytic Heterofunctionalization; Wiley-VCH:
Weinheim, Germany, 2001. (c) Tsuji, J. Transition Metal Reagents and
Catalysts: Innovations in Organic Synthesis; Wiley: Chichester, 2000. (d)
Bhaduri, S. Homogeneous Catalysis: Mechanisms and Industrial Applica-
tions; Wiley-Interscience: New York, 2000. (e) Beller, M.; Bolm, C. Transi-
tion Metals for Organic Chemistry; Wiley-VCH: Weinheim, Germany,
1998. (f) Diederich, F., Stang, P. J., Eds. Metal-Catalyzed Cross-Coupling
Reactions; Wiley-VCH: Weinheim, Germany, 1998.
(2) Selected reviews: (a) Nolan, S. P.; Navarro, O. C-C Bond Formation
by Cross-Coupling. InComprehensive Organometallic Chemistry III; Mingos,
D. M. P., Crabtree, R. H., Eds.; Elsevier: Oxford, U.K., 2007; Vol. 11, pp 1-37.
(b) Beletskaya, I. P.; Cheprakov, A. V. Metal complexes as catalysts for C-C
cross-coupling reactions. In Comprehensive Coordination Chemistry II;
McCleverty, J. A., Meyer, T. J., Eds.; Elsevier: Oxford, U.K., 2004; Vol. 9,
pp305-368. (c) Miyaura, N. J. Organomet. Chem. 2002, 653, 54. (d) Kugami,
K.; Kosugi, M. Top. Curr. Chem. 2002, 219, 87. (e) Beletskaya, I. P.; Cheprakov,
A. V. Chem. Rev. 2000, 100, 3009. (f) Farina, V.; Krishnamurthy, V.; Scott, W. J.
The Stille Reaction. In Organic Reactions; Wiley: New York, 1997; Vol. 50.
(3) Clayden, N.; Greeves, N.; Warren, S.; Wothers, P. Organic
Chemistry; Oxford University Press: London, 2001; p 1322.
(4) (a) Ananikov, V. P.; Gayduk, K. A.; Beletskaya, I. P.; Khrustalev,
V. N.; Antipin, M. Yu. Chem. Eur. J. 2008, 14, 2420. (b) Ananikov, V. P.;
Orlov, N. V.; Beletskaya, I. P. Organometallics 2007, 26, 740. (c) Ananikov,
V. P.; Orlov, N. V.; Beletskaya, I. P. Organometallics 2006, 25, 1970.
(5) (a) Yamamoto, T.; Takamatsu, M.; Yamamoto, A. Bull. Chem.
Soc. Jpn. 1982, 55, 325. (b) Bontempelli, G.; Peccolo, R.; Daniele, S.; Ugo, P.
Inorg. Chim. Acta 1985, 99, 43. (c) Leadbeater, N. L. J. Org. Chem. 2001,
66, 7539.
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Rev. 2004, 104, 3893. (b) Jia, F.; Zhang, L.; Shang, X.; Yang, Y. Adv. Mater.
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r
pubs.acs.org/Organometallics
Published on Web 06/30/2010
2010 American Chemical Society

Article
Organometallics, Vol. 29, No. 21, 2010 5099
Scheme 1. In Situ Generation of Pd(0) Catalyst Active Form
Scheme 2. Formation of Ni0Ln Species and Trapping with
Diphenyl Disulfide
catalytic system.7 Another drawback of this methodology
can considerably limit the scope of the catalytic system: as a
typical example, the reagents for catalyst activation listed
above readily react with functional groups in the substrates
(carbonyl groups, etc.). In spite of the great practical im-
portance of in situ generation of Ni(0) species for homo-
geneous catalysis applications, a mechanistic picture has not
been addressed so far.8
Recently we have found that Ni(acac)2 is an excellent
catalyst precursor for the catalytic reactions of carbon-
heteroatom bond formation.4,9 An active form of the cata-
lyst was generated directly in a catalytic system containing
phosphine ligands without addition of any dedicated re-
agents. Interestingly, Ni(acac)2 was found to be a better
catalyst precursor compared to NiCl2 or Ni(OAc)2.10
These results are unusual, since reduction of the metal
center with phosphines requires coordination of the phos-
phine ligand as the first necessary step. At the moment no
structures for the [Ni(acac)2(PR3)n] complexes have been
reported, in sharp contrast with the case for other NiX2
salts, where numerous [NiX2(PR3)2] derivatives have been
prepared and characterized.11 It was even assumed that
Ni(acac)2 does not coordinate phosphines and only in a
few studies was coordination proposed on the basis of
spectral and electrochemical measurements.12
2. Results and Discussion
First, we explored the possibility of coordination of phos-
phine ligands with nickel acetylacetonate. After several
attempts under different reaction conditions we have found
that phosphine ligands coordinate to the nickel center
(Scheme 2). A complex with 2 equiv of the PMe2Ph ligand
was isolated at -17 °C, and the structure of trans-[Ni(acac)2-
(PMe2Ph)2] (1a) was determined by X-ray analysis (Figure 1).13
Complex 1a possessed an elongated-octahedral coordination
geometry with the metal-phosphorus bond length Ni-P =
˚
2.440 A. The Ni-O distances between the metal and acac
˚
ligands, 2.028 and 2.045 A, were slightly longer as compared to
oxygen coordination in the bis(acetylacetonato)nickel dietha-
nol complex Ni(acac)2(EtOH)2, 1.997 and 2.026 A.14 In com-
˚
plex 1a the Ni-P distance was shorter and the Ni-O distances
were longer compared to those in the trans-[Ni(1-C6H5-3-CF3-
˚
acac)2(PPh3)2] complex, where Ni-P = 2.552 A and Ni-O =
2.011 and 2.013 A.
12c
˚
The complex was stable in the solid state at low tempera-
ture, while an attempt to increase the temperature to room-
temperature conditions or to dissolve the complex in organic
solvents afforded quick decomposition. Poor stability in
solution and in the solid state is the likely reason, which
precluded isolation of the complex in previous studies.
We have studied the decomposition pathways of complex
1a and have found that it either underwent a back-reaction to
a mixture of Ni(acac)2 and PMe2Ph or afforded formation
of new metal species, according to 31P NMR. The formation
of new species provided some evidence for possible genera-
tion of Ni(0). However, rather broad signals observed in the
31P NMR spectrum did not allow unambiguous identifi-
cation of the products. In agreement with earlier studies, the
NMR data for M0Ln compounds in solution may not be
characteristic, due to the dynamic nature of the system caused
by ligand dissociation and the formation of series of species.15
A better way to identify Ni(0) species in solution is to trap
them with an oxidative addition reaction and detect the forma-
tion of a well-defined metal complex, which gives an unambi-
guous NMR spectrum. In our case we proposed trapping with di-
phenyl disulfide in order to form a stable Ni(SPh)2L2 complex.16
To examine the reliability of the Ph2S2 trapping, first we
In the present study we have addressed the questions of
whether Ni(acac)2 can be reduced by phosphine ligands to
generate Ni(0) species and what is the pathway of this
transformation. The metal complexes were detected in solu-
tion by NMR, the key species were isolated, and their
structures were determined by X-ray analysis. Finally, the
performances of directly added Ni0(COD)2 catalyst and
Ni(0) species generated in situ from NiII(acac)2 were compared
in selected catalytic reactions.
(7) Reviews about the interplay of homogeneous and heterogeneous
pathways in catalysis: (a) Ananikov, V. P.; Gayduk, K. A.; Beletskaya,
I. P. Nanotechnol. Russ. 2010, 5, 1. (b) Pachon, L. D.; Rothenberg, G. Appl.
Organomet. Chem. 2008, 22, 288. (c) Phan, N. T. S.; Sluys, M. V. D.; Jones, C. W.
Adv. Synth. Catal. 2006, 348, 609. (d) de Vries, J. G. Dalton Trans. 2006, 421.
(8) Redox processes with nickel are more complicated (compared to
palladium) due to the possible involvement of Ni(I) and Ni(III) species.
Representative studies: (a) Koola, J. D.; Kochi, J. K. Inorg. Chem. 1987, 26,
908. (b) Amatore, C.; Jutand, A.; Mottier, L. J. Electroanal. Chem. 1991, 306,
125. (c) Baidya, N.; Olmstead, M. M.; Mascharak, P. K. J. Am. Chem. Soc. 1992,
114, 9666. (d) James, T. L.; Cai, L. S.; Muetterties, M. C.; Holm, R. H. Inorg.
Chem. 1996, 35, 4148. (e) Lin, X.; Phillips, D. L. J. Org. Chem. 2008, 73, 3680.
(f) Ghosh, M.; Weyherm€uller, T.; Wieghardt, K. Dalton Trans. 2010, 39, 1996.
(9) (a) Ananikov, V. P.; Gayduk, K. A.; Beletskaya, I. P.; Khrustalev,
V. N.; Antipin, M. Yu. Eur. J. Inorg. Chem. 2009, 1149. (b) Beletskaya,
I. P.; Ananikov, V. P. Eur. J. Org. Chem. 2007, 3431.
(13) A detailed list of geometric parameters is provided in the
Supporting Information.
(14) Pfluger, C. E.; Burke, T. S.; Bednowitz, A. L. J. Cryst. Mol.
Struct. 1973, 3, 181.
(10) Better solubility in organic systems can be one of the advantages
(15) The equilibrium ML4 T ML3 þ L T ML2 þ 2L usually takes
place in solution and may result in a poorly defined NMR spectrum with
multiple (broad) signals: (a) Mann, B. E.; Musco, A. J. Chem. Soc.,
Dalton Trans. 1975, 1673. (b) Coulson, D. R. Inorg. Synth. 1990, 28, 1990.
(c) Tolman, C. A.; Seidel, W. C.; Gosser, L. W. J. Am. Chem. Soc. 1974, 96,
43. (d) Ittel, S. D. Inorg. Synth. 1990, 28, 98. (e) The presence of the
paramagnetic species could be another reason for the broad signals.8a-f
(16) Diphenyl disulfide was much more efficient for trapping Ni(0)
species in comparison to the dialkyl disulfide nBu2S2. Single crystals of
of nickel acetylacetonate.
(11) Cambridge Structural Database, release 2010, Cambridge, U.K.,
2010.
(12) (a) Nesmeyanov, A. N.; Isaeva, L. S.; Morozova, L. N.; Petrovskii,
P. V.; Tumanskii, B. L.; Lokshin, B. V.; Klemenkova, Z. S. Inorg. Chim.
Acta 1980, 43, l. (b) Pozdeeva, A. A.; Popod'ko, N. R.; Tolstikov, G. A.;
Dzhemilev, U. M.; Kolosnitsyn, V. S.; Zhdanov, S. I. Russ. Chem. Bull. Int.Ed.
1986, 35, 2412 and references therein. The complex can be stabilized by
introducing electron-withdrawing groups on the acac ligand; see: (c) Dickman,
M. H. Acta Crystallogr. 2001, E57, m220.
n
1a were obtained from the solution containing Bu2S2, which was not
coordinated to the metal center.

5100 Organometallics, Vol. 29, No. 21, 2010
Ananikov et al.
Figure 1. X-ray molecular structures of trans-[Ni(acac)2(PMe2Ph)2] (1a), trans-[Ni(SPh)2(PMe2Ph)2] (2a), trans-[Ni(SPh)2(PMePh2)2]
(2b), and trans-[Ni(SPh)2(PBu3)2] (2c).
studied the reaction with a well-known zerovalent nickel
complex;bis(cyclooctadiene)nickel (Scheme 2). A clean re-
action was observed in toluene at 40 °C; a yellow solution of
Ni(COD)2 immediately turned brown upon addition of the
phosphine ligand and Ph2S2. The oxidative addition reaction
was carried out with three different phosphine ligands;
PMe2Ph, PMePh2, and PBu3;and formation of a single
complex was identified in the 31P NMR in each case with
>80% yield. Complexes 2a-c were isolated from the toluene
solution as crystalline products, and the structures were
determined by X-ray analysis (Figure 1). A typical square-
planar geometry was adopted in the complexes with a trans
arrangement of the ligands and the distances Ni-P = 2.203-
bond angles P-Ni-P=180.0° and S-Ni-S=180.0° were
observed in both complexes. Complex 2b crystallized with a
syn orientation of the phenyl rings around the plane contain-
ing the metal and heteroatoms; the bond angles P-Ni-P=
169.3° and S-Ni-S=175.5° were observed in the complex.
The π-π stacking interaction between the phenyl rings was
present in the crystal of 2b, and this was the likely reason for
the change of the SPh group alignment.
This trapping procedure was applied to Ni(0) species
generated from Ni(acac)2 in toluene solution (Scheme 2).
The formation of complexes 2a-c was observed in the
studied reactions as detected with NMR. Identical 31P
and 1H spectra were recorded for the complexes 2a-c
obtained from Ni(COD)2 and Ni(acac)2, thus confirming
the generation of zerovalent nickel species from nickel
acetylacetonate.
2.215 A and Ni-S = 2.217-2.233 A.13 In complexes 2a,c the
phenyl rings of the SPh groups possessed an anti orientation
around the plane containing the metal and heteroatoms; the
˚
˚

Article
Organometallics, Vol. 29, No. 21, 2010 5101
Scheme 3. Generation of Ni(0) Species in the Presence of Water
the product was formed in excellent yield (99%) with excep-
tional selectivity (>99/1). The isolated yield of 4 after
purification with rapid flash chromatography was 85-87%.
Generation of zerovalent nickel species in situ resulted
in a high-performance catalytic procedure as good as that
involving bis(cyclooctadiene)nickel. As already outlined,
Ni(acac)2 is much cheaper and easier to handle (all manipula-
tions were carried out in air), while Ni(COD)2 is extremely
air sensitive and requires a glovebox.
Scheme 4. Catalytic Stereoselective Addition of Diphenyl
Disulfide to 3-Hexyne
In conclusion, we have shown that a phosphine ligand can
coordinate with nickel acetylacetonate and Ni(0) species can
be smoothly generated in situ in solution. The nature of the
Ni(0) species was confirmed by trapping experiments, and
the structures of the resulting nickel complexes were estab-
lished. It is important to generate Ni(0) for homogeneous
catalysis by utilizing an additional amount of the phosphine
ligand without using other reducing agents, which may alter
the properties of the catalytic system. The replacement of
Ni(0) with a readily available and stable catalyst precursor
also has important practical advantages for developing cost-
efficient synthetic procedures.
It is interesting to consider the mechanistic pathway of
in situ generation of Ni(0) species. Carrying out the reac-
tion with a Ni(acac)2 H2O salt and PMe2Ph ligand under
3
1H NMR monitoring revealed the release of acacH.17 The
formation of OdPMe2Ph (3) was detected by 31P NMR and
was proven by X-ray analysis.18 In the presence of water the
reduction of Ni(II) to Ni(0) was accompanied by the oxida-
tion of the phosphine ligand and transfer of the hydrogen
atoms from water to the acac ligand (Scheme 3).
3. Experimental Section
3.1. General Procedures. All manipulations with Ni(COD)2
were carried out in a glovebox under an argon atmosphere;
manipulations with Ni(acac)2 were carried out by the usual
technique in air. Unless otherwise noted, Ni(acac)2 was dried
under vacuum (0.1-0.05 Torr, 60 °C, 30 min) before use.
Solvents were purified according to published methods. The
reactions were carried out in PTFE screw-capped tubes or
flasks. NMR measurements were performed using Bruker
AVANCE 500 and 600 MHz spectrometers. The spectra were
processed on a Linux workstation using the TOPSPIN software
package.
The same outcome was observed on carrying out the
reaction with Ni(acac)2 in the dried solvent;complexes
2a-c were formed after reaction with Ph2S2. However, the
1
release of free acacH was not observed in H NMR. The
presence of 3 was detected by 31P NMR, indicating that
oxygen abstraction from the acac ligand took place. Since no
1H NMR signals of acac residues or products of their
transformation were resolved, we can propose that in the
absence of water reduction of Ni(acac)2 was accompanied by
decomposition of the acetylacetonate ligand. The result is
quite comparable with the reported reaction on reduction of
Pd(OAc)2 with phosphine ligands (PR3), which led to the
formation of OdPR3 (via oxygen abstraction) and Ac2O.3 In
the case of acetylacetone dimerization of the residues should
be considered unlikely.
3.2. Synthesis of trans-[Ni(acac)2(PMe2Ph)2] (1a). Ni(acac)2
(2.0 ꢀ 10-4 mol, 51.4 mg), 0.75 mL of toluene, and PMe2Ph
(6.0 ꢀ 10-4 mol, 82.9 mg) were stirred until a homogeneous brown
solution was formed (ca. 1-3 min).20 A 3 mL portion of hexane
was added to the mixture, which was then cooled to -17 °C. Blue
crystals precipitated from the mixture over 5 h (50% yield).
3.3. Synthesis of trans-[Ni(SPh)2(L)2] (2a-c). Ni(COD)2
(2.0 ꢀ 10-4 mol, 53.4 mg) and 0.6 mL of toluene were stirred
until a light yellow solution was obtained. The phosphine ligand
(6.0 ꢀ 10-4 mol) was added to the solution, and the mixture was
stirred for 1 min. Ph2S2 (2.0 ꢀ 10-4 mol, 43.7 mg) was added to
the mixture, which was then heated to 40 °C for 1 h. The mixture
turned dark brown. The solvent was slowly evaporated at room
temperature for a few days, and dark crystals were obtained
(ca. 60% yield).
Therefore, depending on the presence of water, two dif-
ferent pathways may operate in the system when reduction of
Ni(II) to Ni(0) occurs in solution. In either case generation of
zerovalent nickel species took place smoothly and formation
of product 2 was observed. This preliminary evidence on the
involvement of water could be of great importance in con-
sidering catalytic reactions. In a typical catalytic reaction a
small amount of the metal complex is utilized in comparison
to the other reagents and reduction of Ni(II) may be assisted
by traces of water.
To reveal the efficiency of in situ generated zerovalent
nickel species in catalysis, we have studied the catalytic
addition of Ph2S2 to the triple bond of alkynes. The catalytic
reaction is known to proceed with involvement of Ni(0)
species and takes place with high stereoselectivity, producing
only the Z isomer.19 Under the same conditions the reaction
was carried out using two catalytic systems based on Ni-
(COD)2 and Ni(acac)2 (Scheme 4). In both catalytic systems
1
trans-[Ni(SPh)2(PMe2Ph)2] (2a). H NMR (C6D6; δ, ppm):
1.37 (12H, s), 6.97 (6H, m), 7.30 (m, 6H), 7.58 (4H, m), 7.80 (4H,
m). 31P{1H} NMR (C6D6; δ, ppm): -7.9. Anal. Calcd for
C28H32NiP2S2: C, 60.78; H, 5.83; Ni, 10.61; S, 11.59. Found:
C, 60.50; H, 6.01; Ni, 10.72; S, 11.33.
1
trans-[Ni(SPh)2(PMePh2)2] (2b). H NMR (C6D6; δ, ppm):
1.60 (6H, s), 6.91 (10H, m), 7.30 (5H, m), 7.62 (5H, m). 31P{1H}
NMR (C6D6; δ, ppm): -26.4. Anal. Calcd for C38H36NiP2S2: C,
67.37; H, 5.36; Ni, 8.66; S, 9.47. Found: C, 67.59; H, 5.62; Ni,
8.40; S, 9.16.
trans-[Ni(SPh)2(PBu3)2] (2c). 1H NMR (C6D6; δ, ppm; J, Hz):
0.86 (18H, t, J = 7.5), 1.27 (12H, m), 1.62 (12H, br m), 1.70
(12H, br m), 6.95 (2H, t, J = 7.4) 7.10 (4H, t, J = 7.3), 8.30 (4H,
(17) The observed signals were compared with the spectrum of an
authentic sample.
(18) The crystal structure of OdPMe2Ph (3) is reported in the
Supporting Information.
(19) Ananikov, V. P.; Gayduk, K. A.; Orlov, N. V.; Beletskaya, I. P.;
Khrustalev, V. N.; Antipin, M. Yu. Chem. Eur. J. 2010, 16, 2063.
(20) As an experiment to demonstrate the trapping inefficiency of
dibutyl disulfide, nBu2S2 (2.0 ꢀ 10-4 mol, 35.7 mg) was added to the
solution at this stage and the mixture stirred for 10 min. Single crystals of
1a were obtained in the presence of nBu2S2 in the same yield.

5102 Organometallics, Vol. 29, No. 21, 2010
Ananikov et al.
d, J = 7.3). 31P{1H} NMR (C6D6; δ, ppm): -1.4. Anal. Calcd
for C36H64NiP2S2: C, 63.43; H, 9.46; Ni, 8.61; S, 9.41. Found: C,
63.65; H, 9.70; Ni, 8.31; S, 9.19.
3.4. NMR Monitoring of Formation of 2a-c. Ni(acac)2 (1.0 ꢀ
10-4 mol, 25.7 mg) and 0.5 mL of toluene-d8 were transferred to
the NMR tube, followed by addition of the phosphine ligand
(3.0 ꢀ 10-4 mol) and Ph2S2 (1.0 ꢀ 10-4 mol, 21.8 mg). The
mixture was heated to 40 °C for 1 h and shaken. The solution
turned to dark brown. The 1H and 31P NMR spectra were
recorded directly for the mixture.
Bruker SMART 1000 CCD area detector at 120 K (1a, 2c), using
˚
graphite-monochromated Mo KR radiation (λ = 0.710 73 A).
Experimental data have been corrected for absorption effects
with the SADABS program.22
The structures were solved by direct methods and refined by
the full-matrix least squares method against F2 in the anisotropic
(for non-hydrogen atoms) approximation. All hydrogen atoms
were placed in geometrically calculated positions and refined in
the isotropic approximation in the riding model. All calculations
were performed using the SHELXTL software.23
3.5. Catalytic Procedure for the Stereoselective Addition of
Diphenyl Disulfide to 3-Hexyne.19 3.5.1. Reaction with Nickel
Acetylacetonate Catalyst Precursor. Ni(acac)2 (3.0 ꢀ 10-5 mol,
7.7 mg), Ph2S2 (1.0 ꢀ 10-3 mol, 218.3 mg), PMePh2 (3.0 ꢀ 10-4
mol, 60.0 mg), and toluene (0.5 mL) were placed in a reaction
vessel and stirred at room temperature until a homogeneous
brown solution was formed (ca. 1-3 min). 3-Hexyne (1.5 ꢀ 10-3
mol, 123.2 mg) was added to the solution, and the reaction was
carried out at 100 °C for 8 h with stirring. An excess of the
phosphine ligand was utilized to maintain homogeneous reac-
tion conditions. After completion of the reaction the products
were purified by dry column flash chromatography on silica
(hexanes/toluene).21 After drying under vacuum the pure pro-
Crystallographic data and refinement parameters for com-
pounds 1a and 2a-c, crystal packing and geometric para-
meters for the complexes, and details of the X-ray study of
compound 3 are provided in the Supporting Information.
Molecular structures for compounds 1a and 2a-c are shown
in Figure 1.
Crystallographic data for the structures reported in this study
have been deposited with the Cambridge Crystallographic Data
Centre as supplementary CCDC files 775145 (1a), 775146 (2a),
775147 (2b), 775148 (2c), and 775149 (3).
Acknowledgment. The research work was supported
by the Russian Foundation for Basic Research (Project
No. 10-03-00370), Research Grant MD-4831.2009.3, and
Program No. 1 of the Division of Chemistry and Material
Sciences of the RAS.
ducts were obtained. Compound 4 was identified by 1H and 13
C
NMR according to the published data, and the elemental
analysis was carried out to confirm purity (agreed within 0.1%
with previously published data).19
3.5.2. Reaction with Bis(Cyclooctadiene) Nickel Catalyst. The
procedure was the same as that above using Ni(COD)2 instead
of Ni(acac)2.
3.6. Description of the X-ray Study. Single-crystal X-ray
diffraction experiments were carried out with a Bruker APEX2
1000 CCD area detector at 100 K (2b) and 150 K (2b) and with a
Supporting Information Available: Tables, figures, and CIF
files giving details of the X-ray structure analysis of compounds
1a, 2a-c, and 3 and geometric parameters. This material is
available free of charge via the Internet at http://pubs.acs.org.
(22) Sheldrick, G. M., SADABS; Bruker AXS Inc.: Madison, WI
53719, 1997.
(21) (a) Pedersen, D. S.; Rosenbohm, C. Synthesis 2001, 2431. (b)
Harwood, L. M. Aldrichim. Acta 1985, 18, 25.
(23) Sheldrick, G. M. SHELXTL-97, Version 5.10; Bruker AXS Inc.,
Madison, WI 53719.