Efficient and convenient synthesis of β-vinyl sulfides in nickel-catalyzed regioselective addition of thiols to terminal alkynes under solvent-free conditions

Article abstract of DOI:10.1021/om051105j

A new nanosized catalytic system has been developed for convenient preparation of β-vinyl sulfides H₂C=C(SAr)R with high yields (79-98%) and excellent selectivity (>98:2). Inexpensive and easily available Ni(acac)₂ was used as catalyst precursor. Solvent-free conditions were combined with high atom efficiency of the ArSH addition reaction to terminal alkynes (HC=C-R) in order to create an environmentally friendly synthetic procedure. The mechanistic study has indicated that catalytic reaction takes place under heterogeneous conditions with alkyne insertion into the Ni-S bond as a key step.

Full text of DOI:10.1021/om051105j

1970
Organometallics 2006, 25, 1970-1977
Efficient and Convenient Synthesis of â-Vinyl Sulfides in
Nickel-Catalyzed Regioselective Addition of Thiols to Terminal
Alkynes under Solvent-Free Conditions
Valentine P. Ananikov,*,† Nikolay V. Orlov,† and Irina P. Beletskaya*,‡
Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, Moscow,
119991, Russia, and Chemistry Department, LomonosoV Moscow State UniVersity, Vorob’eVy gory,
Moscow, 119899, Russia
ReceiVed December 31, 2005
A new nanosized catalytic system has been developed for convenient preparation of â-vinyl sulfides
H2CdC(SAr)R with high yields (79-98%) and excellent selectivity (>98:2). Inexpensive and easily
available Ni(acac)2 was used as catalyst precursor. Solvent-free conditions were combined with high
atom efficiency of the ArSH addition reaction to terminal alkynes (HCtC-R) in order to create an
environmentally friendly synthetic procedure. The mechanistic study has indicated that catalytic reaction
takes place under heterogeneous conditions with alkyne insertion into the Ni-S bond as a key step.
(Scheme 1). The method is of particular importance since the
addition reaction proceeds in an atom-efficient manner without
waste. Under nucleophilic or free radical conditions anti-
Markovnikov products 3 and 4 were obtained.5 These conditions
are especially useful for the activated alkynes (R ) Ph, COOR′,
COR′, etc.), which smoothly react with thiols in high yields.
Regular unactiveted alkynes require longer reaction time or
heating.5
Markovnikov-type addition leading to â-vinyl sulfides 2 can
be achieved under transition metal-catalyzed conditions.6 Pal-
ladium-catalyzed ArSH addition to terminal alkynes was shown
to proceed with high regioselectivity and yields,7 although the
overall yield of 2 may not be high in some cases due to a
noncatalytic side reaction leading to 3 and 4 or isomerization
of 2 to internal alkenes 5 and 6 (Scheme 2). Very good yields
of 2 (70-85%) were achieved in Pd(OAc)2-catalyzed reactions
carried out for 16 h at 40 °C.7 Attempts to decrease reaction
time by increasing the temperature were unsuccessful, since the
amount of byproducts (3-6) dramatically increases at elevated
temperature.
1. Introduction
The application of vinyl sulfides in organic synthesis has
increased tremendously in recent years.1 The arylthio group
(ArS) can stabilize both negative and positive charges on
neighboring carbon atoms, therefore increasing the reactivity
of vinyl sulfides toward electrophilic and nucleophilic reagents.
Not surprisingly, vinyl sulfides became attractive reagents and
have been widely utilized in various synthetic reactions.1,2
Another very useful feature of vinyl sulfides concerns unique
selectivity-controlling properties of the sulfur atom in the
cyclization reactions.3 It was already shown that arylvinyl
sulfides are attractive reagents in [1+2], [2+2], [3+2], and
[4+2] cycloaddition reactions.3,4
A very useful practical method for the preparation of vinyl
sulfides involves addition of the S-H bond of thiols to alkynes
* To whom correspondence should be addressed. (V.P.A.) E-mail:
val@ioc.ac.ru. Fax:
+007 (495) 1355328. (I.P.B.) E-mail:
beletska@org.chem.msu.ru. Fax: +007 (495) 9393618.
† Zelinsky Institute of Organic Chemistry.
‡ Lomonosov Moscow State University.
(1) (a) McReynolds, M. D.; Dougherty, J. M.; Hanson, P. R. Chem. ReV.
2004, 104, 2239. (b) Zyk, N. V.; Beloglazkina, E. K.; Belova, M. A.;
Dubinina, N. S. Russ. Chem. ReV. 2003, 72, 769. (c) Sizov, A. Yu.;
Kovregin, A. N.; Ermolov, A. F. Russ. Chem. ReV. 2003, 72, 394. (d)
Mangini, A. Sulfur Rep. 1987, 7, 313. (e) Organic Sulfur Chemistry.
Theoretical and Experimental AdVances; Studies in Organic Chemistry.
V.19; Bernardi, F., Csizmadia, I. G., Mangini, A., Eds.; Elsevier: Amster-
dam, 1985. (f) Ager, D. J. Chem. Soc. ReV. 1982, 11, 493. (g) Block, E.
Reactions of Organosulfur Compounds; Academic Press: New York, 1978.
(2) See, for example: (a) Muraoka, N.; Mineno, M.; Itami, K.; Yoshida,
J.-I. J. Org. Chem. 2005, 70, 6933. (b) Aucagne, V.; Lorin, C.; Tatibouet,
A.; Rollin, P. Tetrahedron Lett. 2005, 46, 4349. (c) Woodland, C. A.;
Crawley, G. C.; Hartley, R. C. Tetrahedron Lett. 2004, 45, 1227. (d) Farhat,
S.; Marek, I. Angew. Chem., Int. Ed. 2002, 41, 1410. (e) Marciniec, B.;
Chadyniak, D.; Krompiec, S. J. Mol. Catal. A 2004, 224, 111. (f) Su, M.;
Yu, W.; Jin, Z. Tetrahedron Lett. 2001, 42, 3771. (g) Lee, Y. R.; Kim, N.
S.; Kim, B. S. Tetrahedron Lett. 1997, 38, 5671. (h) Andres, D. F.; Dietrich,
U.; Laurent, E. G.; Marquet, B. S. Tetrahedron 1997, 53, 647. (i) Krief,
A.; Kenda, B.; Remacle, B. Tetrahedron Lett. 1995, 36, 7917. (j) Andres,
D. F.; Laurent, E. G.; Marquet, B. S.; Benotmane, H.; Bensadat, A.
Tetrahedron 1995, 51, 2605. (k) Backvall, J.-E.; Ericsson, A. J. Org. Chem.
1994, 59, 5850. (l) Magnus, P.; Quagliato, D. J. Org. Chem. 1985, 50,
1621. (m) Trost, B. M.; Lavoie, A. C. J. Am. Chem. Soc. 1983, 105, 5075.
(n) Wenkert, E.; Ferreira, T. W. J. Chem. Soc., Chem. Commun. 1982, 840.
(o) Grobel, B.-T.; Seebach, D. Synthesis 1977, 357.
(4) For representative examples see (and references therein): (a) Bruck-
ner, R.; Huisgen, R. Tetrahedron Lett. 1990, 31, 2561. (b) Singleton, D.
A.; Church, K. M. J. Org. Chem. 1990, 55, 4780. (c) Sugimura, H.; Osumi,
K. Tetrahedron Lett. 1989, 30, 1571. (d) Gupta, R. B.; Franck, R. W.; Onan,
K. D.; Soll, C. E. J. Org. Chem. 1989, 54, 1097. (e) Weber, A.; Sabbioni,
G.; Galli, R.; Stampfli, U.; Neuenshwander, M. HelV. Chim. Acta 1988,
71, 2026. (f) Tsuge, O.; Kanemasa, S.; Sakamoto, K.; Takenaka, S. Bull.
Chem. Soc. Jpn. 1988, 61, 2513. (g) Pabon, R. A.; Bellville, D. J.; Bauld,
N. L. J. Am. Chem. Soc. 1984, 106, 2730.
(5) (a) Kondoh, A. K.; Takami, K.; Yorimitsu, H.; Oshima, K. J. Org.
Chem. 2005, 70, 6468. (b) Trofimov, B. A. Curr. Org. Chem. 2002, 6,
1121. (c) Benati, L.; Capella, L.; Montevecchi, P. C.; Spagnolo, P. J. Chem.
Soc., Perkin Trans. 1995, 1035. (d) Back, T. G.; Krishna, M. V. J. Org.
Chem. 1988, 53, 2533. (e) Ichinose, Y.; Wakamatsu, K.; Nozaki, K.;
Birbaum, J.-L.; Oshima, K.; Utimoto, K. Chem. Lett. 1987, 1647. (f)
Trofimov, B. A. Russ. Chem. ReV. 1981, 50, 138. (g) Truce, W. E.; Tichenor,
G. J. W. J. Org. Chem. 1972, 37, 2391. (h) Truce, W. E.; Heine, R. F. J.
Am. Chem. Soc. 1957, 79, 5311.
(6) (a) Beller, M.; Seayad, J.; Tillack, A.; Jiao, H. Angew Chem., Int.
Ed. 2004, 43, 3368. (b) Alonso, F.; Beletskaya, I. P.; Yus, M. Chem. ReV.
2004, 104, 3079. (c) Kondo, T.; Mitsudo, T. Chem. ReV. 2000, 100, 3205.
(d) Ogawa, A. J. Organomet. Chem. 2000, 611, 463. (e) Han, L.-B.; Zhang,
C.; Yazawa, H.; Shimada, S. J. Am. Chem. Soc. 2004, 126, 5080.
(7) (a) Ogawa, A.; Ikeda, T.; Kimura, K.; Hirao, T. J. Am. Chem. Soc.
1999, 121, 5108. (b) Kuniyasu, H.; Ogawa, A.; Sato, K.; Ryu, I.; Kambe,
N.; Sonoda, N. J. Am. Chem. Soc. 1992, 114, 5902.
(3) Yamazaki, S. J. Synth. Org. Chem. 2000, 58, 50.
10.1021/om051105j CCC: $33.50 © 2006 American Chemical Society
Publication on Web 03/10/2006

Synthesis of â-Vinyl Sulfides Catalyzed by Ni
Organometallics, Vol. 25, No. 8, 2006 1971
Table 2. Ni(acac)2-Catalyzed PhSH Addition to 1-Heptyne at
Different Temperaturesa
Scheme 1
yield,c %
2:5+6:3+4
entry
conditionsb
1
2
3
4
5
6
80 °C, 10 min
40 °C, 10 min
25 °C, 10 min
10 °C, 10 min
10 °C, 20 min
10 °C, 90 min
28:61:10
81:4:4
72:3:3
34:3:0
67:9:0
84:15:0
Scheme 2
a See Schemes 1 and 2 for the reactions (R ) C5H11). b Using 2 mmol
of PhSH, 1 mmol of 1-heptyne, and 2 mol % of Ni(acac)2 in a sealed tube
with stirring (solvent-free). c Determined by NMR.
Table 1. PhSH Addition to 1-Heptyne Catalyzed by Various
Metal Complexesa
observed after 30 min (Table 1, entry 2). Under solvent-free
conditions 35% conversion was found within the same time
period (Table 1, entry 3), which corresponds to a 1.5-fold
reaction rate enhancement. Most likely, the rate enhancement
originates from the concentration effect.9 In both cases, in THF
solution and under solvent-free conditions, Markovnikov-type
product 2 was formed (Table 1, entries 2 and 3). The complete
conversion of the alkyne under solvent-free conditions was
observed after ca. 12 h (cf. ca. 16 h in THF; Table 1, entry 1).
Therefore, excluding solvent provides not only ecological and
economical benefits but also an additional advantage of shorten-
ing the reaction time.
At the next stage we searched for a replacement of the
palladium catalyst. Surprisingly, nickel complexes have shown
desired catalytic activity under the studied mild conditions. The
rather poor catalytic activity of Ni(OAc)2 (2% of 2) was
significantly improved (55% of 2) by using NiCp2 as a catalyst
(Table 1, entries 4 and 5, respectively). Utilizing Ni(acac)2 leads
to 99% alkyne conversion after 30 min at 40 °C (Table 1, entry
6). It is important to point out that Ni(acac)2 provides better
overall selectivity than Pd(OAc)2. The yield of Markovnikov
product 2 was 89% and 80% for Ni(acac)2 and Pd(OAc)2,
respectively (Table 1, entries 6 and 1). The other acetylacetonate
compounds, Cu(acac)2, Co(acac)2, and VO(acac)2, did not show
significant catalytic activity (<1% yield of 2). Interesting to
note, using Pd(acac)2 as a catalyst did not lead to a noticeable
improvement over the Pd(OAc)2; similar yields and selectivity
were observed. Therefore, nickel acetylacetonate is the catalyst
of choice for the studied reaction due to its remarkable efficiency
and selectivity.
alkyne
conversion,c % 2:5+6:3+4
yields,c %
entry
catalyst
conditionsb
1
2
3
4
5
6
Pd(OAc)2 THF, 40 °C, 16 h
Pd(OAc)2 THF, 40 °C, 30 min
Pd(OAc)2 40 °C, 30 mind
Ni(OAc)2 40 °C, 30 mind
99
24
35
28
65
99
80:19:0
24:0:0
29:6:0
2:0:26
55:8:2
89:5:5
Ni(Cp)2
40 °C, 30 mind
Ni(acac)2 40 °C, 30 mind
a See Schemes 1 and 2 for the reactions (R ) C5H11). b Using 2 mmol
of PhSH, 1 mmol of 1-heptyne, and 2 mol % of the catalyst in a sealed
tube with stirring. c Determined by NMR. d Solvent-free.
An excellent study of the catalytic S-H bond addition to
alkynes made by A. Ogawa, N. Sonoda, et al. has proven the
great potential of transition metal catalysis in the synthesis of
â-vinyl sulfides.6,7 The synthetic procedures reported so far were
designed for small-scale synthesis resulting in ∼0.2-0.3 g of
product 2 and required chromatography at the purification stage.
The increasing cost of palladium-based catalysts imposes
significant limits to synthetic utilization of â-vinyl sulfides
prepared in that way. Recently we have suggested NiCl2 as a
catalyst precursor for alkyne hydrothiolation.8 However, this
methodology again was proven to be useful only for the
reactions on a 1 mmol scale (<0.3 g of product). Therefore,
there is an obvious lack of practical method for the preparation
of â-vinyl sulfides on a synthetic scale. On the other hand,
â-vinyl sulfides are of particular importance for metathesis and
cyclization reactions, the synthesis of biologically active
compounds, and the development of new materials.1-4
In the present study we report a new method for a convenient
and efficient synthesis of â-vinyl sulfides, which meets the
following criteria: (1) easily scalable procedure suitable for the
preparation of 0.5-50 g of product; (2) inexpensive and easily
available Ni catalyst; (3) avoidance of chromatography at the
purification stage; (4) high efficiency of catalysis and short
reaction time; (5) high selectivity with minimal amount of
byproducts; (6) solvent-free conditions.
In addition to the catalytic Markovnikov-type reaction, two
side reactions could take place in the studied system: (1)
noncatalytic addition leading to compounds 3 and 4 (Scheme
1) and (2) isomerization of product 2 to compounds 5 and 6
(Scheme 2). This is a common problem of transition metal-
catalyzed H-E bond addition to alkynes.6,7,10 Our study of the
Ni-catalyzed reaction has shown that reaction temperature and
amount of catalyst are the key factors that need to be optimized
to reduce the contribution of the side reactions.
2. Results and Discussion
To find optimal conditions, we varied the reaction temperature
in the range 10-80 °C (Table 2) and the amount of catalyst in
the range 0.5-5 mol % (Table 3). The noncatalytic addition
leading to 3 and 4 was facilitated at elevated temperature (Table
2, entries 1-3). The selectivity of the catalytic reaction
decreased from 25.0 at 25 °C to 8.9 at 80 °C.11 More
At first we tested whether solvent-free conditions provide an
advantage for the studied addition reaction. For this purpose
we have selected a known procedure with Pd(OAc)2 catalyst
developed for THF solution.7 In the model reaction of PhSH
addition to 1-heptyne 99% conversion of the alkyne was
observed after 16 h at 40 °C (Table 1, entry 1). This result is in
good agreement with literature data.7 For a proper comparison
the experiments with shorter reaction time (30 min) have been
carried out. In THF solution 24% conversion of the alkyne was
(9) For a related discussion of rate enhancement in the catalytic C-E
(E ) S, Se) bond formation reaction under solvent-free conditions see:
Ananikov, V. P.; Beletskaya, I. P. Org. Biomol. Chem. 2004, 2, 284.
(10) Ananikov, V. P.; Malyshev, D. A.; Beletskaya, I. P.; Aleksandrov,
G. G.; Eremenko, I. L. J. Organomet. Chem. 2003, 679, 162.
(11) The selectivity of the addition reactions is reflected by the ratio of
catalytic and noncatalytic products (2+5+6)/(3+4).
(8) Ananikov, V. P.; Malyshev, D. A.; Beletskaya, I. P.; Aleksandrov,
G. G.; Eremenko, I. L. AdV. Synth. Catal. 2005, 347, 1993.

1972 Organometallics, Vol. 25, No. 8, 2006
AnanikoV et al.
Table 3. Ni(acac)2-Catalyzed PhSH Addition to 1-Heptyne
with Different Amounts of Catalysta
as OH, OMe, and MeCOO (entries 2-10; Table 4). In the
developed catalytic system even the activated alkyne 1i (phe-
nylacetylene) reacts with benzenethiol in a Markovnikov
manner, producing vinyl sulfides in 82% yield and 73:27
selectivity. This result is superior to the NiCl2 catalyst (yield
27%, selectivity 3:10)8 reported earlier. Except for phenylacety-
lene, in all other cases the catalytic reactions lead to â-vinyl
sulfides with excellent regioselectivity (Table 4). Compounds
2c-2h, without allylic hydrogen, did not isomerize under the
studied conditions (see Scheme 2).
Ni(acac)2,
mol %
alkyne
yields,c %
2:5+6:3+4
entry
conditionsb
conversion,c %
1
2
3
4
5.0
2.0
1.0
0.5
25 °C, 30 min
25 °C, 30 min
25 °C, 30 min
25 °C, 30 min
99
89
74
26
75:19:4
80:5:4
60:7:7
23:7:3
a See Schemes 1 and 2 for the reactions (R ) C5H11). b Using 2 mmol
of PhSH, 1 mmol of 1-heptyne, and Ni(acac)2 in a sealed tube with stirring
(solvent-free). c Determined by NMR.
The developed synthetic procedure can be very easily scaled
for the synthesis of various amounts of products (Table 5). The
same yields and selectivity were obtained in the catalytic
reactions performed with 5, 10, 100, and 300 mmol of the initial
alkyne, which corresponds to 0.8-49.0 g of the isolated product
(Table 5, entries 1-4).
We have found that the rate of the catalytic reaction was
greatly decreased by traces of water. To verify this observation,
we have undertaken a comparative study of Ni(acac)2-catalyzed
PhSH addition to 1a in the presence and in the absence of added
water. Particularly, 15 mol % of water significantly suppressed
the catalytic reaction: 41% yield was observed after 10 min of
reaction time, compared to 81% yield (entry 2, Table 2)
observed after the same time without water addition. To
eliminate the reproducibility problem, freshly dried Ni(acac)2
should be used and the alkynes should be stored under molecular
sieves.
In addition to the synthetic part it was very interesting to
reveal the mechanism of the chemical reactions in the developed
catalytic system. The plausible mechanism of the hydrogen-
element (H-E) bond addition to alkynes may involve either an
external nucleophile attack to the coordinated triple bond or an
insertion reaction into the metal-element bond (Scheme 3).6 If
a terminal alkyne is involved in the reaction (R′ ) H, Scheme
3), exactly the same â-substituted vinylic compounds may be
formed as final products for both mechanisms. Therefore, on
the basis of the product structure it is impossible to distinguish
the mechanisms of the addition reaction. However, if an internal
alkyne is involved, nuleophilic attack leads to trans-isomer 7,
while cis-isomer 8 is formed as a result of an insertion reaction
(Scheme 3).15
To reveal the mechanism of the reaction, we have performed
catalytic PhSH addition to 3-pentyn-1-ol (Scheme 4). In this
case four products could be expected: compounds 9 and 10 if
insertion reaction takes place and compounds 11 and 12 if
nucleophilic attack is involved. After 8 h of reaction 86%
conversion of the alkyne has been observed. Compounds 9 and
10 were formed with 1:1 ratio and 42% yield each; only trace
amounts of 11 and 12 were detected (<2%). This experiment
clearly indicates that insertion reaction is the key step of the
C-S bond formation in the studied catalytic cycle.16
complicated behavior was observed for the isomerization
reaction. The minimum amount of byproducts 5 and 6 within
the reasonable conversion of the alkyne was detected ap-
proximately in the middle of the studied temperature range. The
higher the reaction temperature, the greater the yield of
isomerization products (cf. entries 1-3, Table 2). At 80 °C
internal alkenes 5 and 6 are the major reaction products with
61% yield (Table 2, entry 1). On the other hand, longer reaction
time at lower temperature also increases the contribution of the
isomerization process (cf. entries 4-6, Table 2).12 Finally, the
temperature range 25-40 °C seems to be the most favorable
for the studied model reaction in order to minimize the yield of
the byproducts.
Using 2 mol % of the catalyst seems to be the most
appropriate for the addition reaction (Table 3, entry 2). Decreas-
ing the amount of catalyst slows the rate of the reaction (Table
3, entries 2-4). As has been discussed already, the contribution
of the isomerization reaction may significantly increase at longer
reaction time. On the other hand, increasing the amount of
catalyst facilitates the isomerization reaction (entry 1, Table 3)
due to contribution of the metal-catalyzed pathway.12 Therefore,
2 mol % of the Ni catalyst can be accepted as a reasonable
estimation (entry 2, Table 3).
Despite the common side reactions (noncatalyzed addition
and isomerization, see discussion above), a specific feature of
the nickel complexes is high activity in oligo- and polymeri-
zation. The key step of the oligo- and polymerization reactions
is alkyne insertion into the metal-carbon bond, which proceeds
easily for nickel compounds.13 If a 1.0:1.0 ratio of the alkyne
and PhSH was used in the reaction, about 10-12% of the alkyne
was converted to oligomers, as evidenced by 1H NMR, and with
a 1.0:0.5 ratio of the alkyne and PhSH, an even larger amount
of the oligomers was detected (15-25%). However, we have
found that this side reaction can be suppressed by an excess of
PhSH. With a 1.0:2.0 ratio of the alkyne and PhSH the amount
of oligomers was below detectable limit of 1H NMR. Unreacted
benzenethiol can be easily recovered in the product purification
stage and reused in the reaction. Unless otherwise noted, the
1.0:2.0 ratio of alkyne:ArSH was employed throughout this
article.
Under the optimized conditions (2 mol % of Ni(acac)2, 40
°C, 2:1 ratio of PhSH:alkyne, solvent-free) the addition reaction
proceeded with high selectivity and yields for various alkynes
and arylthiols (Table 4). Functional group-substituted alkynes
react slower compared to hexyne-1 (entry 1, Table 4). In some
cases heating at 60 °C is required to achieve high product yields
(entries 4, 5, 7, 9, 10; Table 4). It is important to point out that
the catalyst can tolerate typical organic functional groups such
Another question concerns the nature of the catalyst in the
studied system. It has been shown that H-E and E-E bond (E
) S, Se) activation by transition metal complexes may produce
mononuclear, dinuclear, or polymeric species.10,17,18 In all
(14) The E/Z ratio of anti-Markovnikov isomers was in the range 2:1-
1:1. This suggests a radical nature of the side reaction.
(15) In Scheme 3 “E” means element (not electrophile) as usually
accepted in the literature concerning E-H and E-E bond addition to
unsaturated molecules (see reviews6a-d). Trans and cis notations indicate
the position of the R and R′ groups.
(16) Longer heating at 40 °C resulted in isomerization of initially formed
compounds 9 and 10 to 11 and 12. Decrease in intensity of 1H NMR signals
of 9 and 10 was accompanied with simultaneous increase in intensity of
corresponding signals of 11 and 12. Therefore, 9 and 10 are the kinetic
products of the syn-addition reaction.
(12) It was shown that the isomerization reaction may proceed under
transition metal-catalyzed, radical or photochemical conditions (refs 7 and
9). Therefore, different isomerization mechanisms may play the dominant
role depending on reaction conditions and amount of catalyst.
(13) Jolly, P. W.; Wilke, G. The Organic Chemistry of Nickel; Academic
Press: New York, 1974.

Synthesis of â-Vinyl Sulfides Catalyzed by Ni
Organometallics, Vol. 25, No. 8, 2006 1973
Table 4. Ni-Catalyzed ArSH Addition to Various Alkynesa
a Using 20 mmol of PhSH, 10 mmol of alkyne and 2 mol % of the catalyst under solvent free conditions (see experimental part for details). b After
washing and filtering of crude mixture (see experimental part for details). c The regioselectivity of the addition reaction (the ratio of Markovnikov: anti-
Markovnikov products).14
catalytic reactions discussed in the present study (Table 4) an
insoluble dark brown polymer [Ni(SAr)2]n was formed, as
confirmed by elemental analysis. The important point is whether
this polymer is an active catalyst or the major contribution to
the product formation makes the remaining metal complex
soluble in the liquid phase. To reveal the nature of the catalyst,
we have performed a comparative study of two model reactions.
The first reaction was performed using a 2:1 ratio of PhSH:1a
(18) (a) Hannu-Kuure, M. S.; Wagner, A.; Bajorek, T.; Oilunkaniemi,
R.; Laitinen, R. S.; Ahlgren, M. Main Group Chem. 2005, 4, 49. (b) Hannu-
Kuure, M. S.; Paldan, K.; Oilunkaniemi, R.; Laitinen, R. S.; Ahlgren, M.
J. Organomet. Chem. 2003, 687, 538. (c) Oilunkaniemi, R.; Laitinen, R.
S.; Ahlgren, M. J. Organomet. Chem. 2001, 623, 168. (d) Dey, S.; Jain, V.
K.; Varghese, B. J. Organomet. Chem. 2001, 623, 48. (e) Oilunkaniemi,
R.; Laitinen, R. S.; Ahlgren, M. J. Organomet. Chem. 1999, 587, 200. (f)
Nakanishi, I.; Tanaka, S.; Matsumoto, K.; Ooi, S. Acta Crystallogr., Sect.
C 1994, C50, 58. (g) Zanella, R.; Ros, R.; Graziani, M. Inorg. Chem. 1973,
12, 2736.
(17) (a) Ananikov, V. P.; Kabeshov, M. A.; Beletskaya, I. P.; Khrustalev,
V. N.; Antipin, M. Yu. Organometallics 2005, 24, 1275. (b) Ananikov, V.
P.; Beletskaya, I. P.; Aleksandrov, G. G.; Eremenko, I. L. Organometallics
2003, 22, 1414. (c) Ananikov, V. P.; Kabeshov, M. A.; Beletskaya, I. P.;
Aleksandrov, G. G.; Eremenko, I. L. J. Organomet. Chem. 2003, 687, 451.

1974 Organometallics, Vol. 25, No. 8, 2006
AnanikoV et al.
Table 5. Catalytic Benzenethiol Addition to 1c at Different
Scalesa
Scheme 5
entry
alkyne,b mmol
yield,c %
amount of product,c g
1
2
3
4
5
10
100
300
82
81
82
84
0.8
1.6
15.9
49.0
a A detailed description of the experiments is given in the Experimental
Section. b Initial amount of alkyne. c After washing and filtering of the crude
mixture (see Experimental Section for details).
Scheme 3
Scheme 6
smoothly increased, while no product formation was observed
in the second reaction (Table 6). The results clearly indicate
that polymeric metal species represent an active form of the
catalyst in the studied system. The contribution of the remaining
metal complex available in the liquid phase is negligible.
The plausible catalytic reaction mechanism is shown in
Scheme 5. It involves alkyne insertion as a key C-S bond
formation step and polymeric nickel species as an active form
of the catalyst. The mechanism also explains the observed
dependence of the product yield on the alkyne:PhSH ratio.
Trapping intermediate complex 14 with PhSH leads to product
formation and suppresses alkyne insertion into the Ni-C bond
of 14.
Scheme 4
To confirm the proposed mechanism, we have performed a
series of stoichiometric reactions (Scheme 6). The polymeric
compound [Ni(SPh)2]n has been isolated in 95% yield after the
reaction of Ni(acac)2 with PhSH. According to the elemental
analysis, both acac ligands were substituted with PhS groups
(see Experimental Section for details). This reaction corresponds
to stage (a) of the catalytic cycle (Scheme 5). Isolated polymeric
compound [Ni(SPh)2]n reacted with alkyne in the presence of
PhSH, leading to the expected Markovnikov-type product in
95% yield (Scheme 6).19 The reaction corresponds to stages (b)
and (c) of the catalytic cycle (Scheme 5).
In addition to the stoichiometric reactions, the isolated
polymeric compound was successfully utilized in the catalytic
reaction. Using the isolated Ni compound as a catalyst (2 mol
%) in the PhSH addition reaction to 1c the complete conversion
of the alkyne and 98:2 selectivity were observed after 30 min
at 40 °C (see Experimental Section for details). The same results
were observed using Ni(acac)2 as the initial form of the catalyst
(entry 3, Table 4).
Table 6. Catalytic PhSH Addition to 1a in the Presence and
in the Absence of the Solid Phase
relative yield of 2a,a %
entry
time, min
heterogeneous reaction
without solid phaseb
1
2
3
60
180
300
36
58
70
0
0
0
a Reaction mixtures stirred for 30 min were used as a reference point
(see Experimental Section for details). b The precipitate was removed by
centrifugation.
with 2 mol % Ni(acac)2 in THF solution. The heterogeneous
mixture was stirred at 40 °C for 30 min and used in NMR
monitoring without further treatment. This experiment was
designed as a model of the typical catalytic procedure employed
in the present study. The second reaction was performed with
the same amounts of reagents and catalyst, but the solid phase
was removed by centrifugation. Both reactions were investigated
with 1H NMR monitoring (Table 6). Under heterogeneous
conditions (the first reaction) the yield of the product was
It was impossible to characterize polymeric compound [Ni-
(SPh)2]n by NMR, since it was insoluble in common organic
solvents. To investigate the structure and morphology of the
Ni species, we have carried out light microscopy and scanning
(19) In agreement with proposed mechanism, no reaction took place in
the absence of PhSH.

Synthesis of â-Vinyl Sulfides Catalyzed by Ni
Organometallics, Vol. 25, No. 8, 2006 1975
3. Conclusions
In the present article we describe a new catalytic system for
highly regioselective arylthiol addition to terminal alkynes
resulting in selective formation of â-vinyl sulfides. The catalytic
reaction is based on the inexpensive and easily available
compound nickel acetylacetonate as a catalyst precursor.
In the developed system atom economy of the addition
reaction is combined with ecological and economical benefits
of the solvent-free methodology in agreement with green
chemistry requirements. To minimize solvent waste, chroma-
tography was avoided in the product purification stage. The
developed synthetic procedure can be easily scaled-up to prepare
up to 50 g of products with high selectivity.
Figure 1. Size distribution of [Ni(SPh)2]n particles determined by
It is very important to note that nickel provides useful
replacement for palladium catalysts. Moreover, the nickel-based
catalyst is more efficient and selective. The mechanistic
investigations revealed that alkyne insertion into the Ni-S bond
is a key step of the catalytic cycle. The [Ni(SAr)2]n species
represent an active form of the catalyst, which is built from
nanosized structural units.
light microscopy.
Further studies concerning the application of nickel-catalyzed
reactions in carbon-element bond formation as well as structural
studies of the catalyst are in progress.
3. Experimental Section
3.1. General Procedures. Unless otherwise noted, the synthetic
work was carried out under an argon atmosphere. The alkynes 1e,21
1f,22 1g,23 and 1h23 were prepared according to published proce-
dures. Other reagents were obtained from Acros and Lancaster and
used as supplied (checked by NMR before use). Ni(acac)2 was dried
under vacuum (0.005-0.02 Torr, 60 °C, 30 min) before use.
Solvents were purified according to published methods.
Figure 2. SEM images of catalyst particle (A) and magnified
central region of this particle (B). Particle size is 6.5 × 8.2 µm
(largest dimensions), particle area is 30.7 µm2, and Feret diameter
is 6.2 µm.
All NMR measurements were performed using a three-channel
Bruker DRX-500 spectrometer operating at 500.1 and 125.8 MHz
for 1H and 13C nuclei, respectively. The spectra were processed on
a Silicon Graphics workstation using the XWINMR software
package. All 2D spectra were recorded using an inverse triple
1
resonance probehead with an active shielded Z-gradient coil. H
and 13C chemical shifts are reported relative to the corresponding
solvent signals used as internal reference. Estimated errors in the
1
yield determination by H NMR are <2% (Tables 1-3, 6).
3.2. General Synthetic Procedure for 2a-2k. The alkyne (1.0
× 10-2 mol) was added to Ni(acac)2 (2.0 × 10-4 mol) and stirred
at room temperature until a uniform green suspension was formed
(ca. 5-10 min). PhSH (2.0 × 10-2 mol) was added to the stirred
mixture at ∼5 °C (water/ice bath). The stirring was continued for
an additional 10 min, and the color of the suspension changed from
green to dark. The reaction was carried out at 40-60 °C under
stirring until complete conversion of the alkyne (small aliquots were
taken from the mixture and checked by 1H NMR). See Table 4 for
details about reaction time and temperature.24
Figure 3. SEM images of two different catalyst particles: (A)
particle size 2.4 × 2.4 µm (largest dimensions), particle area 3.6
µm2, Feret diameter 2.1 µm; (B) Feret diameter 380 nm.
electron microscopy (SEM) studies. The distribution of particle
sizes determined by light microscopy in solution is shown in
Figure 1. About 75% of observed particles were 0.5-2.0 µm
in size. The unsymmetrical form of the distribution curve
indicates the tendency for particle adhesion and a noticeable
amount of larger particles of 4.5-8.5 µm size were also detected
(∼10%). The SEM study has indicated that both larger and
smaller particles have the same structure and consist of
nanosized building units. Examples of 6.2 and 2.1 µm particles
are shown in Figure 2 and Figure 3A, respectively. Analysis of
the SEM images gave the typical size of the unit of 300 ( 90
nm. An example of the individual nanosized unit is shown in
Figure 3B. Therefore, the size of the building unit is close to
the upper range observed in nanocatalytic systems.20 We believe
that the nanosized structure of the catalyst is a key factor
responsible for high activity of the Ni complexes.
The reaction mixture was filtered through Celite using CH2Cl2
as an eluent (40 mL). Then 20 mL of hexane was added to the
(20) Typically accepted range of particles sizes for the nanocatalytic
systems is 1-100 nm; see reviews: (a) Love, J. C.; Estroff, L. A.; Kriebel,
J. K.; Nuzzo, R. G.; Whitesides, G. M. Chem. ReV. 2005, 105, 1103. (b)
Buchachenko, A. L. Russ. Chem. ReV. 2003, 72, 375. (c) Bukhtiyarov, V.
I.; Slin’ko, M. G. Russ. Chem. ReV. 2001, 70, 147.
(21) Wagner, C. E.; Shea, K. J. Org. Lett. 2004, 313.
(22) Scott, L. T.; DeCicco, G. J.; Hyun, J. L.; Reinhardt, G. J. Am. Chem.
Soc. 1985, 107, 6546.
(23) Chakraborti, A. K.; Sharma, L.; Gulhane, R.; Shivani. Tetrahedron
2003, 59, 7661.
(24) Catalyst activity depends on the amount of water in the reaction
mixture. NMR monitoring (or GC) is the easiest way to determine
appropriate reaction time.

1976 Organometallics, Vol. 25, No. 8, 2006
AnanikoV et al.
mixture after filtration, and remaining PhSH was removed by
extraction with 25 mL of aqueous NaOH (5 M).25 The organic layer
was dried over Na2SO4, and the solvent was removed under reduced
pressure. The products were obtained as light brown oils (92-95%
purity as confirmed by NMR). Highly pure, colorless products were
obtained after distillation in a vacuum (98+% as confirmed by
NMR).
The products H2CdC(SPh)-(CH2)3-CH3 (2a),26 H2CdC(SPh)-
C(CH3)2OH (2c),7b and H2CdC(SPh)-Ph (2k),27 were identified
according to the published data. The data for the other compounds
are given below.
(m, 2H). 13C{1H} NMR (126 MHz; CDCl3; δ, ppm): 26.41, 50.69,
77.94, 109.48, 128.33, 129.24, 132.89, 135.08, 153.66. Anal. Calcd
for C12H16OS: C 69.19; H 7.74; S 15.39. Found: C 68.89; H 7.75;
S 15.10. Mass spectrum (EI): m/e 208 (M+ 9%).
2-(Phenylthio)-2-(1-methoxycyclohexyl)-1-ethene, H2CdC-
(SPh)-C6H11(OCH3) (2h): light brown liquid, 85% (2.11 g); yield
after distillation 65% (1.61 g), bp 71-73 °C, 5.0 × 10-3 Torr,
1
colorless oil. H NMR (500 MHz; CDCl3; δ, ppm; J, Hz): 1.24
(m, 2H), 1.50-1.69 (m, 8H), 3.18 (s, 3H), 4.62 (s, 1H), 5.21 (s,
1H), 7.20-7.38 (m, 3H), 7.50 (m, 2H). 13C{1H} NMR (126 MHz;
CDCl3; δ, ppm): 21.78, 25.78, 34.08, 49.63, 78.55, 110.07, 127.11,
129.24, 135.17, 133.08, 153.68, 128.08. Anal. Calcd for C15H20-
OS: C 72.53; H 8.12; S 12.91. Found: C 72.21; H 7.82; S 13.15.
Mass spectrum (EI): m/e 248 (M+ 3%).
2-(Phenylthio)hexene, H2CdC(SPh)-CH2-CH2-CH2-CH3
(2a): light brown oil, 79% (1.52 g); yield after distillation 58%
(1.12 g), bp 39-42 °C, 1.5 × 10-2 Torr, colorless oil.
2-(Phenylthio)-4-hydroxy-1-butene, H2CdC(SPh)-CH2-
CH2-OH (2b): light brown oil, 93% (1.68 g); yield after distillation
2-(Phenylthio)-3-acetoxy-3-methyl-1-butene, H2CdC(SPh)-
C(OOC-CH3)(CH3)2 (2i): light brown liquid, 96% (2.27 g); yield
after distillation 79% (1.87 g), bp 91 °C, 3.0 × 10-2 Torr, colorless
oil. 1H NMR (500 MHz; DMSO-d6; δ, ppm; J, Hz): 1.60 (s, 6H),
1.97 (s, 3H), 4.59 (s, 1H), 5.37 (s, 1H), 7.38-7.45 (m, 5H). 13C-
{1H} NMR (126 MHz; DMSO-d6; δ, ppm): 21.18, 26.54, 80.99,
110.36, 128.03, 129.09, 131.66, 133.27, 150.53, 168.39. Anal. Calcd
for C13H16O2S: C 66.07; H 6.82; S 13.57. Found: C 66.30; H 7.10;
S 13.24. Mass spectrum (EI): m/e 236 (M+ 39%).
1
70% (1.26 g), bp 75-77 °C, 1.0 × 10-2 Torr, colorless oil. H
NMR (500 MHz; CDCl3; δ, ppm; J, Hz): 1.97 (s, 1H), 2.48 (dt, J
) 7.3, J ) 0.8, 2H), 3.77 (t, J ) 7.3, 2H), 5.00 (s, 1H), 5.24 (d, J
) 0.8, 1H), 7.25-7.35 (m, 3H), 7.43 (m, 2H). 13C{1H} NMR (126
MHz; CDCl3; δ, ppm): 39.56, 60.74, 115.07, 127.97, 129.16,
132.41, 133.13, 142.16. Anal. Calcd for C10H12OS: C 66.63; H
6.71; S 17.79. Found: C 66.56; H 6.86; S 17.73. Mass spectrum
(EI): m/e 180 (M+ 37%).
2-(Phenylthio)-3-acetoxy-3-methyl-1-pentene, H2CdC(SPh)-
C(OOC-CH3)(CH3)-CH2-CH3 (2j): light yellow liquid, 98%
(2.45 g); yield after distillation 87% (2.18 g), bp 93-97 °C, 3.0 ×
2-(Phenylthio)-3-hydroxy-3-methyl-1-butene, H2CdC(SPh)-
C(CH3)2OH (2c): light brown liquid, 80% (1.55 g); yield after
distillation 55% (1.07 g), bp 65-66 °C, 7.0 × 10-3 Torr, colorless
oil.
1
10-2 Torr, colorless oil. H NMR (500 MHz; CDCl3; δ, ppm; J,
Hz): 0.90 (t, 3H, J ) 7.5), 1.70 (s, 3H), 1.94 (m, 1H), 2.03 (m,
1H), 2.05 (s, 3H), 4.67 (s, 1H), 5.26 (s, 1H), 7.31-7.36 (m, 3H),
7.49 (m, 2H). 13C{1H} NMR (126 MHz; CDCl3; δ, ppm): 7.98,
21.97, 23.04, 32.34, 85.04, 110.54, 128.34, 129.24, 132.51, 134.72,
150.56, 169.58. Anal. Calcd for C14H18O2S: C 67.16; H 7.25; S
12.81. Found: C 67.07; H 7.27; S 12.74. Mass spectrum (EI): m/e
250 (M+ 59%).
2-[(p-Methylphenyl)thio]-3-hydroxy-3-methyl-1-butene, H2Cd
C(p-MeC6H4S)-C(CH3)2OH (2d): brown liquid, 90% (1.87 g);
yield after distillation 56% (1.17 g), bp 75-80 °C, 9.0 × 10-3 Torr,
colorless oil. 1H NMR (500 MHz; CDCl3; δ, ppm; J, Hz): 1.51 (s,
6H), 2.29 (br s, 1H), 2.34 (s, 3H), 4.60 (s, 1H), 5.37 (s, 1H), 7.14
(m, 2H), 7.36 (m, 2H). 13C{1H} NMR (126 MHz; CDCl3; δ,
ppm): 21.08, 29.63, 73.80, 108.79, 129.50, 130.01, 134.09, 138.22,
155.55. Anal. Calcd for C12H16OS: C 69.19; H 7.74; S 15.39.
Found: C 69.20; H 7.79; S 15.03. Mass spectrum (EI): m/e 208
(M+ 60%).
2-(Phenylthio)-2-phenyl-1-ethene, H2CdC(SPh)-Ph (2k): light
brown liquid, 82% (1.74 g); yield after distillation 50% (1.06 g),
bp 87-89 °C, 3.0 × 10-2 Torr, colorless oil.
3.3. Synthetic Procedure at Different Scales. The same general
synthetic procedure has been used (see 3.2) with the following
amounts of reagents: alkyne (5.0 × 10-3 mol), Ni(acac)2 (1.0 ×
10-4 mol), and PhSH (1.0 × 10-2 mol) for 5 mmol scale reaction
(Table 5, entry 1); alkyne (0.1 mol), Ni(acac)2 (2.0 × 10-2 mol),
and PhSH (0.2 mol) for 100 mmol scale reaction (Table 5, entry
3); alkyne (0.3 mol), Ni(acac)2 (6.0 × 10-2 mol), and PhSH (0.6
mol) for 300 mmol scale reaction (Table 5, entry 4).
2-[(p-Chlorophenyl)thio]-3-hydroxy-3-methyl-1-butene, H2Cd
C(p-ClC6H4S)-C(CH3)2OH (2e): light brown liquid, 81% (1.85
g); yield after distillation 61% (1.40 g), bp 96-100 °C, 1.0 × 10-3
1
Torr, colorless oil. H NMR (500 MHz; DMSO-d6; δ, ppm; J,
Hz): 1.35 (s, 6H), 4.55 (s, 1H), 5.45 (s, 1H), 7.41-7.46 (m, 4H).
13C{1H} NMR (126 MHz; DMSO-d6; δ, ppm): 29.16, 71.91,
109.48, 128.94, 132.28, 132.49, 134.27, 154.83. Anal. Calcd for
C11H13ClOS: C 57.76; H 5.73; S 14.02; Cl 15.50. Found: C 57.71;
H 5.68; S 13.92; Cl 15.40. Mass spectrum (EI): m/e 228 (M+ 92%).
2-(Phenylthio)-3-hydroxy-3-methyl-1-pentene, H2CdC(SPh)-
C(OH)(CH3)-CH2-CH3 (2f): light brown liquid, 96% (2.0 g);
yield after distillation 76% (1.58 g), bp 73-75 °C, 1.0 × 10-2 Torr,
colorless oil. 1H NMR (500 MHz; CDCl3; δ, ppm; J, Hz): 0.90 (t,
J ) 7.3, 3H), 1.46 (s, 3H), 1.72-1.87 (m, 2H), 2.03 (br s, 1H),
4.70 (s, 1H), 5.38 (s, 1H), 7.28-7.37 (m, 3H), 7.50 (m, 2H). 13C-
{1H} NMR (126 MHz; CDCl3; δ, ppm): 8.13, 27.50, 33.95, 76.41,
110.41, 128.12, 129.23, 133.22, 134.05, 153.50. Anal. Calcd for
C12H16OS: C 69.19; H 7.74; S 15.39. Found: C 68.91; H 7.87; S
15.45. Mass spectrum (EI): m/e 208 (M+ 20%).
3.4. PhSH Addition to 3-Pentyn-1-ol (Scheme 4). The alkyne
(2.0 × 10-3 mol) was added to Ni(acac)2 (4.0 × 10-5 mol) and
stirred at room temperature until a uniform green suspension was
formed (ca. 5-10 min). PhSH (4.0 × 10-3 mol) was added to the
stirred reaction mixture at ca. 5 °C (water/ice bath). The stirring
was continued for an additional 10 min, and the color of the
suspension changed from green to dark. The reaction was carried
out at 40 °C under stirring. The structure of the products was
determined with 2D COSY, NOESY, HMQC, and HMBC NMR
experiments.
3.5. Catalytic PhSH Addition to 1a in the Presence and in
the Absence of Solid Phase. Reaction in the Presence of the
Solid Phase. The alkyne 1a (0.082 g, 1.0 × 10-3 mol) and THF
(0.5 mL) were added to Ni(acac)2 (0.005 g, 2.0 × 10-5 mol) and
stirred until a homogeneous green solution was formed (ca. 5-10
min). PhSH (0.220 g, 2.0 × 10-3 mol) was added to the stirred
solution at ca. 5 °C (water/ice bath), and stirring was continued
for an additional 10 min. The color of the solution changed from
green to dark and an insoluble dark brown precipitate was formed.
The reaction was carried out with stirring at 40 °C and monitored
2-(Phenylthio)-3-methoxy-3-methyl-1-butene, H2CdC(SPh)-
C(OCH3)(CH3)2 (2g): yellow liquid, 84% (1.75 g); yield after
distillation 76% (1.58 g), bp 65-68 °C, 5.0 × 10-3 Torr, colorless
1
oil. H NMR (500 MHz; CDCl3; δ, ppm; J, Hz): 1.49 (s, 6H),
3.23 (s, 3H), 4.58 (s, 1H), 5.20 (s, 1H), 7.31-7.39 (m, 3H), 7.50
(25) Unreacted PhSH can be easily recovered from the water phase by
addition of aqueous HCl and extraction with hexane.
(26) Fiandanese, V.; Marchese, G.; Naso, F.; Ronzini, L. Synthesis 1987,
1034.
1
(27) Labiad, B.; Villemin, D. Synthesis 1989, 143.
with H NMR (Table 6).

Synthesis of â-Vinyl Sulfides Catalyzed by Ni
Organometallics, Vol. 25, No. 8, 2006 1977
Reaction in the Absence of the Solid Phase. The alkyne 1a
(0.082 g, 1.0 × 10-3 mol) and THF (0.5 mL) were added to Ni-
(acac)2 (0.005 g, 2.0 × 10-5 mol) until a homogeneous green
solution was formed (ca. 5-10 min). PhSH (0.220 g, 2.0 × 10-3
mol) was added to the stirred solution at ca. 5 °C (water/ice bath),
and stirring was continued for an additional 10 min. The color of
the solution changed from green to dark, and an insoluble dark
brown precipitate was formed. The temperature was increased to
40 °C, and stirring was continued for 5 min. The precipitate was
removed by centrifugation (6000 rpm, 15 min). The reaction was
(acac)2 (0.093 g, 3.6 × 10-4 mol) and stirred until a homogeneous
green solution was formed (ca. 5-10 min). PhSH (3.98 g, 3.6 ×
10-2 mol) was added to the stirred solution at ca. 5 °C (water/ice
bath), and stirring was continued for an additional 10 min. The
color of the solution changed from green to dark and an insoluble
dark brown precipitate was formed. The reaction mixture was heated
at 40 °C for 30 min, followed by adding 10 mL of toluene and
washing with 20 mL of aqueous NaOH (5 M) to remove unreacted
PhSH. The suspension of the precipitate in toluene was used in the
light microscopy study. For the SEM study the precipitate was dried
in a vacuum.
1
carried out with stirring at 40 °C and monitored with H NMR
(Table 6).
General Comments. Image processing, object analysis, size
determination, and statistical analysis were performed using the
UTHSCSA ImageTool 3.0 program.
3.6. Preparation of [Ni(SPh)2]n (Scheme 6). PhSH (7.7 × 10-3
mol) was added to Ni(acac)2 (1.1 × 10-3 mol) at ca. 5 °C (water/
ice bath), leading to the formation of dark brown suspension. The
suspension was stirred for 10 min at ca. 5 °C (all manipulations
were carried out in air). The precipitate was separated by centrifu-
gation (6000 rpm, 15 min), washed with hexane (3 × 5 mL) and
THF (3 × 5 mL), and dried in a vacuum. Yield: 95% (0.29 g) of
a dark brown solid. Anal. Calcd for C12H10NiS2: C 52.03; H 3.64;
Ni 21.19; S 23.15. Found: C 52.22; H 3.79; Ni 21.07; S 22.90.
3.7. Reaction of [Ni(SPh)2]n with Alkyne (Scheme 6). The
alkyne 1c (2.0 × 10-3 mol), PhSH (2.0 × 10-3 mol), and THF
(0.5 mL) were added to [Ni(SPh)2]n (1.0 × 10-3 mol) and stirred
at 40 °C until complete conversion of the alkyne (∼45 min) as
confirmed by NMR.
Light Microscopy. The analysis was performed in a 10 µm ×
10 µm sample area containing 358 particles. The particles were
classified into 11 groups according to the occupied area. The
distribution of the particles in each group (mean Feret diameter29
in µm and percentage): 0.32, 0.8%; 0.39, 6.7%; 0.53, 12.3%; 0.74,
14.5%; 1.03, 19.0%; 1.39, 15.9%; 2.01, 13.1%; 2.92, 7.8%; 4.41,
4.7%; 6.04, 3.4%; 8.46, 1.7% (for graphical representation see
Figure 1).
SEM Study. The sizes of 300 ( 90 nm were determined for 50
building units selected at random. Examples of SEM images are
shown in Figures 2 and 3, and an example of an individual structural
unit is represented in Figure 3B.
3.8. Catalytic Reaction Using [Ni(SPh)2]n as a Catalyst. The
alkyne 1c (1.0 × 10-3 mol) was added to [Ni(SPh)2]n (2.0 × 10-5
mol) and stirred at room temperature until a uniform dark brown
suspension was formed (ca. 5-10 min). PhSH (2.0 × 10-3 mol)
was added to the stirred reaction mixture at ca. 5 °C (water/ice
bath), and stirring was continued for 10 min. The reaction was
Acknowledgment. The work was supported by the Russian
Foundation for Basic Research (Projects No. 04-03-32501 and
05-03-34888) and the Division of Chemistry and Material
Sciences of the Russian Academy of Sciences (under the
program “Theoretical and Experimental Investigation of the
Nature of Chemical Bond and Mechanisms of the Most
Important Chemical Reactions and Processes”).
1
carried out with stirring at 40 °C and monitored with H NMR
until complete conversion of the alkyne (∼30 min).
3.9. SEM and Light Microscopy Studies.28 Sample Prepara-
tion. The alkyne 1i (1.84 g, 1.8 × 10-2 mol) was added to Ni-
OM051105J
(28) In the studied system particle size and distribution depend on the
sample preparation conditions. Therefore, these values obtained should be
used as an estimation only.
(29) Feret diameter is the diameter of a circle having the same area as
the object. It was computed as (4 × area/PI)1/2, where area is the area of
the object.