Synthesis and reactions of mono- and dinuclear Ni(I) thiolate complexes

Article abstract of DOI:10.1021/ic802276w

The dinuclear and mononuclear nickel(I) thiolates, [Ni(PPh ₃)(μ-SR)]₂ (1a: R is 2,4,6-triisopropylphenyl (Tip), 1b:R is 1-adamantyl (Ad)), (DxpS)Ni(μ-SDxp)Ni(PPh₃)(2) (Dxp is 2,6-dixylylphenyl), and Ni(SDmp)(PPh₃)(3) (Dmp is 2,6-dimesitylphenyl), have been synthesized by the reaction of the nickel(I) amide Ni{N(SiMe₃)₂}(PPh₃)₂ with the corresponding thiols. The two nickel centers of 1a and 1b are equivalent, and are linked by two thiolato sulfurs and aNi-Ni bond, whereas the two inequivalent nickels of 2 are connected by a SDxp sulfur, a η²/η ³-xylyl group of the other SDxp ligand, and a Ni-Ni bond. A slightly bulkier m-terphenyl thiolate, SDmp, prevents its nickel complex from forming a Ni-Ni bond, and the mononuclear nickel(I) center of 3 is bound to PPh ₃ and SDmp through interactions with the sulfur and a η²-mesityl. The coordinatively unsaturated nickel(I) complex 3 is reactive, and the reaction of 3 with TEMPO generated diamagnetic Ni(SDmp)(PPh₃)(O, N:η²-TEMPO) (4). N-Heterocyclic carbenes, 1,3,4,5-tetramethylimidazolin-2-ylidene (IMe′) and 1,3-bis-(2,4,6-trimethylphenyl)imidazolin-2-ylidene (IMes), also react with 3 to afford a dinuclear nickel(I) complex, [Ni(IMe′)(μ-SDmp)]₂ (5), and a mononuclear nickel(I) complex, Ni(SDmp)(IMes) (6), respectively. The reaction of 3 with 1 equiv of ^tBuNC afforded the dinuclear complex [Ni(CN^tBu)(μ-SDmp)]₂ (7), whereas the analogous reaction with 1 equiv of CO resulted in a mixture of Ni(PPh₃) ₂(CO)₂ and Ni(CO)(SDmp)₂(PPh₃)(8).

Full text of DOI:10.1021/ic802276w

Inorg. Chem. 2009, 48, 2215-2223
Synthesis and Reactions of Mono- and Dinuclear Ni(I) Thiolate
Complexes
Mikinao Ito, Tsuyoshi Matsumoto, and Kazuyuki Tatsumi*
Research Center for Materials Science and Department of Chemistry, Graduate School of Science,
Nagoya UniVersity, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
Received November 27, 2008
The dinuclear and mononuclear nickel(I) thiolates, [Ni(PPh3)(µ-SR)]2 (1a: R is 2,4,6-triisopropylphenyl (Tip), 1b: R
is 1-adamantyl (Ad)), (DxpS)Ni(µ-SDxp)Ni(PPh3) (2) (Dxp is 2,6-dixylylphenyl), and Ni(SDmp)(PPh3) (3) (Dmp is
2,6-dimesitylphenyl), have been synthesized by the reaction of the nickel(I) amide Ni{N(SiMe3)2}(PPh3)2 with the
corresponding thiols. The two nickel centers of 1a and 1b are equivalent, and are linked by two thiolato sulfurs and
a Ni-Ni bond, whereas the two inequivalent nickels of 2 are connected by a SDxp sulfur, a η2/η3-xylyl group of
the other SDxp ligand, and a Ni-Ni bond. A slightly bulkier m-terphenyl thiolate, SDmp, prevents its nickel complex
from forming a Ni-Ni bond, and the mononuclear nickel(I) center of 3 is bound to PPh3 and SDmp through
interactions with the sulfur and a η2-mesityl. The coordinatively unsaturated nickel(I) complex 3 is reactive, and the
reaction of 3 with TEMPO generated diamagnetic Ni(SDmp)(PPh3)(O,N:η2-TEMPO) (4). N-Heterocyclic carbenes,
1,3,4,5-tetramethylimidazolin-2-ylidene (IMe′) and 1,3-bis-(2,4,6-trimethylphenyl)imidazolin-2-ylidene (IMes), also react
with 3 to afford a dinuclear nickel(I) complex, [Ni(IMe′)(µ-SDmp)]2 (5), and a mononuclear nickel(I) complex,
Ni(SDmp)(IMes) (6), respectively. The reaction of 3 with 1 equiv of tBuNC afforded the dinuclear complex [Ni(CNtBu)-
(µ-SDmp)]2 (7), whereas the analogous reaction with 1 equiv of CO resulted in a mixture of Ni(PPh3)2(CO)2 and
Ni(CO)(SDmp)2(PPh3) (8).
Introduction
enzymes such as acetyl-CoA synthase8 and [NiFe] hydro-
genase are scarce.9 Structurally characterized thioether-
coordinated Ni(I) complexes are limited to [Ni(psnet)]+ (psnet
Nickel is recognized as an important element in nature,
and so far, six nickel-containing enzymes have been identi-
fied, which include CO-dehydrogenase, acetyl-CoA synthase,
[NiFe] hydrogenase, methyl-CoM reductase, urease, and Ni-
SOD.1 The protein structures of these nickel enzymes are
available, and various nickel complexes have been synthe-
sized to model the active site structures. Nickel(I) complexes
have attracted attention as potential models for the active
states/forms of some of these nickel enzymes. Whereas there
is a good number of Ni(I) complexes carrying nitrogen and
phosphorus ligands such as porphyrins,2 tetraaza macro-
cycles,3 tetradentate aminopyridines,4 anilidoamines,5 diketim-
inates,6 and phosphines,7 those with sulfur ligands that could
be used for the synthesis of active site models of nickel
(3) (a) Stile, M. J. Org. Chem. 1994, 59, 5381–5385. (b) Stolzenberg,
A. M.; Zhang, Z. Inorg. Chem. 1997, 36, 593–600.
(4) Kryatov, S. V.; Mohanraj, B. S.; Tarasov, V. V.; Kryatova, O. P.;
Rybak-Akimova, E. V.; Nuthakki, B.; Rusling, J. F.; Staples, R. J.;
Nazarenko, A. Y. Inorg. Chem. 2002, 41, 923–930.
(5) Wang, H.-Y.; Meng, X.; Jin, G.-X. Dalton Trans. 2006, 2579–2585.
(6) (a) Kogut, E.; Wiencko, H. L.; Zhang, L.; Cordeau, D. E.; Warren,
T. H. J. Am. Chem. Soc. 2005, 127, 11248–11249. (b) Eckert, N. A.;
Dinescu, A.; Cundari, T. R.; Holland, P. L. Inorg. Chem. 2005, 44,
7702–7704. (c) Bai, G.; Wei, P.; Stephan, D. W. Organometallics
2005, 24, 5901–5908.
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J. Chem. Soc., Chem. Commun. 1972, 872–873. (b) Mindiola, D. J.;
Hillhouse, G. L. J. Am. Chem. Soc. 2001, 123, 4623–4624. (c)
Melenkivitz, R.; Mindiola, D. J.; Hillhouse, G. L. J. Am. Chem. Soc.
2002, 124, 3846–3847. (d) Kitiachvili, K. D.; Mindiola, D. J.;
Hillhouse, G. L. J. Am. Chem. Soc. 2004, 126, 10554–10555. (e)
Adhikari, D.; Mossin, S.; Basuli, F.; Dible, B. R.; Chipara, M.; Fan,
H.; Huffman, J. C.; Meyer, K.; Mindiola, D. J. Inorg. Chem. 2008,
47, 10479–10490. (f) Weng, Z.; Teo, S.; Koh, L. L.; Hor, T. S. A.
Angew. Chem., Int. Ed. 2005, 44, 7560–7564.
* To whom correspondence should be addressed. E-mail: i45100a@
nucc.cc.nagoya-u.ac.jp.
(1) Nickel and Its Surprising Impact in Nature; Sigel, A., Sigel, H., Sigel,
R. K. O., Eds.; John Wiley & Sons, Ltd.: Chichester, U.K., 2007;
Metal Ions in Life Science, Vol. 2.
(2) Arai, T.; Kashitani, K.; Kondo, H.; Sakaki, S. Bull. Chem. Soc. Jpn.
1994, 67, 705–709.
(8) (a) Riordan, C. G. J. Biol. Inorg. Chem. 2004, 9, 509–510. (b)
Ragsdale, S. W. Crit. ReV. Biochem. Mol. Biol. 2004, 39, 165–195.
(c) Evans, D. J. Coord. Chem. ReV. 2005, 249, 1582–1595.
10.1021/ic802276w CCC: $40.75  2009 American Chemical Society
Inorganic Chemistry, Vol. 48, No. 5, 2009 2215
Published on Web 01/27/2009

Ito et al.
and IMes (1,3-bis-(2,4,6-trimethylphenyl)imidazolin-2-ylidene)20
were prepared according to the literature procedures.
is bis(5-(diphenylphosphino)-3-thiapentamethyl)amine)10 and
[PhTttBu]Ni(CO) ([PhTttBu] is phenyltris((tert-butylthio)meth-
yl)borate).11 Reports of nickel(I) thiolates are also rare. The
formation of a Ni(I) thiolate was postulated in the photolysis
of (Ph2P(o-C6H4)SCH3)2Ni, via C-S cleavage of the thio-
ether ligand.12 Thiolato-bridged dinuclear Ni(I) complexes,
[Ni(dadtEt)Ni(dppe)][PF6] (dadtEt is N,N′-diethyl-3,7-diaza-
nonane-1,9-dithiolate)13 and [Et4N][Ni(PhPepS)Ni(dppe)-
(CO)] (PhPepS is N,N′-phenylenebis(o-mercaptobenzamide))
were synthesized in situ.14
We report herein the synthesis and structures of a series
of mono- and dinuclear nickel(I) thiolate complexes, where
the nickel(I) amide, Ni{N(SiMe3)2}(PPh3)2, was used as a
synthon.7a We have also combined the mononuclear Ni(I)
thiolates with such σ donors as N-heterocyclic carbenes,
tBuNC, and CO to synthesize the various Ni(I) thiolates.
Synthesis of [Ni(PPh3)(µ-STip)]2 (1a). At room temperature,
HSTip (32 mg, 0.14 mmol) in toluene (5 mL) was added to a
toluene solution (10 mL) of Ni{N(SiMe3)2}(PPh3)2 (100 mg, 0.134
mmol). A yellowish green precipitate immediately formed. After
being stirred for 2 h, the precipitate was filtrated, washed with
hexane (10 mL), and dried in vacuo to produce 1a (72 mg, 96%
yield) as a yellowish green powder. By layering a hexane solution
of HSTip on a THF solution of Ni{N(SiMe3)2}(PPh3)2, crystals
suitable for X-ray structural analysis grew within 3 days. Anal.
Calcd for C66H76Ni2P2S2: C, 71.24; H, 6.884. Found: C, 71.08; H,
6.509.
Synthesis of [Ni(PPh3)(µ-SAd)]2 (1b). At room temperature, a
solution of HSAd (21 mg, 0.13 mmol) in THF (5 mL) was added
to a THF solution (10 mL) of Ni{N(SiMe3)2}(PPh3)2 (100 mg, 0.134
mmol). The green solution was stirred for 12 h and then evaporated
to dryness to produce a green powder. The product was recrystal-
lized from THF/hexane to produce 28 mg (44% yield) of 1b as
green crystals. Anal. Calcd for C56H60Ni2P2S2: C, 68.88; H, 6.193.
Experimental Section
1
Found: C, 69.12; H, 6.494. H NMR (THF-d8, δ): 7.77-7.60 (m,
General Procedures. All reactions and manipulation were
conducted using standard Schlenk and vacuum line techniques or
in a glovebox under nitrogen atmosphere. Hexane, pentane, ether,
THF, acetonitrile, and toluene were purified according to the method
described by Grubbs, in which the solvents were passed over
columns of activated alumina and a copper catalyst supplied by
Hansen. DME was dried over 4 Å molecular sieves under nitrogen.
Deuterated solvents were dried over potassium (THF-d8) or sodium
(benzene-d6, toluene-d8) under nitrogen. 1H NMR spectra were
recorded on a JEOL ECA-600 apparatus. UV/vis spectra were
recorded in 10 mm quartz glass cells on a JASCO V-560
spectrometer. IR spectra were recorded on a JASCO FT/IR-410
spectrometer or a Perkin-Elmer 2000 FT/IR spectrometer. EPR
spectra were collected on a Bruker EMX-plus spectrometer at
X-band frequencies with liquid helium cryostat. Cyclic voltammo-
grams were recorded on a BSA-660B electrochemical analyzer
using a glassy carbon working electrode and 0.2 M n-Bu4NPF6 as
the supporting electrolyte; potentials are referred to the Ag/AgNO3
electrode. Elemental analyses were performed on a LECO-CHNS-
932 elemental analyzer, where the crystalline samples were sealed
in silver capsules under nitrogen. Ni{N(SiMe3)2}(PPh3)2,7a HSTip
(Tip is 2,4,6-triisopropylphenyl),15 HSAd (Ad is 1-adamantly),16
HSDxp (Dxp is 2,6-dixylylphenyl),17 HSDmp (Dmp is 2,6-
dimesitylphenyl),18 IMe′ (1,3,4,5-tetramethylimidazole-2-ylidene),19
12H, PPh3), 7.36-7.27 (m, 18H, PPh3), 1.54-1.45 (m, 12H,
adamantyl), 1.45-1.39 (m, 6H, adamantyl), 1.32-1.20 (m, 6H,
adamantyl), 1.18-1.09 (m, 6H, adamantyl).
Synthesis of Ni(SDxp)(µ-SDxp)Ni(PPh3) (2). At room temper-
ature, a THF solution (10 mL) of HSDxp (47 mg, 0.15 mmol) was
added to a THF solution (10 mL) of Ni{N(SiMe3)2}(PPh3)2 (100
mg, 0.135 mmol)). The green solution was stirred overnight and
then evaporated to dryness to produce a green solid. This material
was washed with hexane (10 mL) and recrystallized from THF/
hexane to produce 95 mg (70% yield) of 2 as green crystals. Anal.
Calcd for C66H65Ni2OPS2: C, 72.95; H, 6.029. Found: C, 72.85; H,
1
6.438. H NMR (Tol-d8, δ): 7.35-6.66 (30H, PPh3+Dxp), 4.80
(br s, 2H, m-H of Xyl), 3.73 (br s, 1H, p-H of Xyl), 2.29 (s, 6H,
Me of Xyl), 2.17 (s, 6H, Me of Xyl), 1.86 (s, 6H, Me of Xyl), 1.78
(s, 6H, Me of Xyl).
Synthesis of Ni(SDmp)(PPh3) (3). At room temperature, a
toluene solution (5 mL) of HSDmp (75 mg, 0.22 mmol) was added
to a toluene solution (5 mL) of Ni{N(SiMe3)2}(PPh3)2 (160 mg,
0.215 mmol). The red-brown solution was stirred for 1 h and then
evaporated to dryness to produce a red solid. This material was
washed with pentane (10 mL) and extracted with ether (30 mL).
The solution was concentrated to 2 mL and kept at -30 °C to
produce 99 mg (69% yield) of 3 as orange crystals. Anal. Calcd
for C42H40NiPS: C, 75.69; H, 6.409. Found: C, 76.00; H, 6.010.
µeff ) 1.93µB in C6D6 at 25 °C (Evans NMR method). λmax/nm (ε)
) 314 (sh, 7.9 × 103), 272 (1.6 × 104).
(9) (a) Volbeda, A.; Fontecilla-Camps, J. C. Coord. Chem. ReV. 2005,
249, 1609–1619. (b) Stein, M.; Lubitz, W. J. Inorg. Biochem. 2004,
98, 862–877.
(10) James, T. L.; Cai, L.; Muetterties, M. C.; Holm, R. H. Inorg. Chem.
1996, 35, 4148–4161.
Synthesis of Ni(SDmp)(PPh3)(O,N:η2-TEMPO) (4). At room
temperature, a toluene solution (5 mL) of TEMPO (23 mg, 0.150
mmol) was added to a toluene solution (5 mL) of Ni(SDmp)(PPh3)
(100 mg, 0.150 mmol). The purple solution was stirred for 3 h,
centrifuged, and evaporated to dryness to produce a purple powder.
The product was recrystallized from THF/hexane to produce 67
mg (54% yield) of 4 as pink-purple crystals. Anal. Calcd for
C51H58NNiOPS: C, 74.45; H, 7.105; N, 1.702. Found: C, 74.29;
H, 6.875; N, 1.741. 1H NMR (C6D6, δ): 7.83-7.72 (m, 6H, PPh3),
7.24-7.19 (m, 16H, Dmp+PPh3), 2.59 (s, 6H, p-Me of Mes), 2.50
(s, 12H, o-Me of Mes), 2.01 (s, 6H, Me of TEMPO), 1.12 (s, 6H,
(11) The νCO band of the Ni(I)-CO complex, [PhTttBu]Ni(CO), was
observed at 1995 cm-1. See: (a) Craft, J. L.; Mandimutsira, B. S.;
Fujita, K.; Riordan, C. G.; Brunold, T. C. Inorg. Chem. 2003, 42,
859–867. (b) Fujita, K.; Rheingold, A. L.; Riordan, C. G. Dalton Trans.
2003, 2004–2008.
(12) Kim, J. S.; Reibenspies, J. H.; Darensbourg, M. Y. J. Am. Chem. Soc.
1996, 118, 4115–4123.
(13) Wang, Q.; Blake, A. J.; Davies, E. S.; McInnes, E. J. L.; Wilson, C.;
Schro¨der, M. Chem. Commun. 2003, 3012–3013.
(14) (a) Harrop, T. C.; Olmstead, M. M.; Mascharak, P. K. J. Am. Chem.
Soc. 2004, 126, 14714–14715. (b) Harrop, T. C.; Olmstead, M. M.;
Mascharak, P. K. Inorg. Chem. 2006, 45, 3424–3436.
(15) Blower, P. J.; Dilworth, J. R.; Hutchinson, J. P.; Zubieta, J. A. J. Chem.
Soc., Dalton Trans. 1985, 1533–1541.
(16) Khullar, H. K.; Bauer, L. J. Org. Chem. 1971, 36, 3038–3040.
(17) Luening, U.; Baumgartner, H. Synlett 1993, 8, 571–572.
(18) Ellison, J. J.; Rhulandt-Senge, K.; Power, P. P. Angew. Chem., Int.
Ed. Engl. 1994, 33, 1178–1180.
(19) Hanasaka, F.; Fujita, K.; Yamaguchi, R. Organometallics 2005, 24,
3422–3433.
(20) Arduengo, A. J., III; Krafczyk, R.; Schmutzler, R. Tetrahedron 1999,
55, 14523–14534.
2216 Inorganic Chemistry, Vol. 48, No. 5, 2009

Mono- and Dinuclear Ni(I) Thiolate Complexes
Me of TEMPO), 0.88-0.84 (m, 2H, TEMPO), 0.58-0.52 (m, 2H,
TEMPO), 0.18-0.12 (m, 2H, TEMPO).
6.66 (t, J ) 7.5 Hz, 2H, p-H of Dmp), 2.26 (s, 24H, o-Me of Mes),
2.15 (s, 12H, p-Me of Mes).
Synthesis of [Ni(IMe′)(µ-SDmp)]2 (5). At room temperature, a
toluene solution (5 mL) of IMe′ (20 mg, 0.161 mmol) was added
to a toluene solution (10 mL) of Ni(SDmp)(PPh3) (107 mg, 0.161
mmol). After being stirred for 4 h, the reaction mixture was
centrifuged. The supernatant was evaporated to dryness, and the
residue was washed with hexane (20 mL) to produce 42 mg (49%
yield) of 5 as a dark-yellow powder. Crystallization from THF/
hexane produced crystals suitable for X-ray structural analysis. 1H
NMR (C6D6, δ): 6.92 (t, J ) 7.6 Hz, 2H, p-H of Dmp), 6.74 (d, J
) 7.6 Hz, 4H, m-H of Dmp), 6.71 (s, 8H, m-H of Mes), 3.34 (s,
12H, N-Me), 2.26 (s, 12H, p-Me of Mes), 2.24 (s, 24H, o-Me of
Mes), 1.77 (s, 12H, Me).
Synthesis of Ni(CO)(SDmp)2(PPh3) (8). At room temperature,
a hexane solution (8 mL) of PPh3 (70 mg, 0.27 mmol) was added
to a hexane suspension (10 mL) of Ni(SDmp)2 (200 mg, 0.267
mmol). The reddish brown suspension was stirred for 2 h and then
purged for 5 min with CO at 1 atm. The suspended material
dissolved to produce a reddish brown solution that slowly yielded
a precipitate. After being stirred for 1 h, the precipitate was filtrated,
washed with hexane (10 mL), and dried in vacuo to produce 216
mg (77% yield) of 8 as a reddish brown powder.
X-ray Structure Determinations. Crystal data and refinement
parameters for the structurally characterized complexes are sum-
marized in Table 1. Single crystals were mounted on a loop using
oil (CryoLoop, immersion oil type B: code 1248, Hampton
Laboratories). Diffraction data were collected at -100 °C under a
cold nitrogen stream on a Rigaku AFC8 apparatus equipped with
a Mercury CCD area detector (for 4, 8, and 9), on a Rigaku AFC8
apparatus equipped with a Saturn 70 CCD area detector (for 1a,
1b, 2, 3, 5, and 6), or on a Rigaku RA-Micro007 apparatus with a
Saturn 70 CCD area detector (for 7) equipped with a graphite-
monochromatized Mo KR source (λ ) 0.71070 Å). Data were
collected for 1200 images with an oscillation range of 0.3° (for
1a, 1b, 2, 3, 4, and 6) or for 720 images with an oscillation range
of 0.5° (for 5, 7, 8, and 9). The data were integrated and corrected
for absorption using the Rigaku/MSC CrystalClear program pack-
age. The structures were solved by a direct method (SIR-92 or SIR-
97) and were refined by full-matrix least-squares on F2 using
SHELXL-9721 in the Rigaku/MSC CrystalStructure program pack-
age. Anisotropic refinement was applied to all non-hydrogen atoms
except for disordered atoms, and all hydrogen atoms were put at
the calculated positions. An adamantyl group of 1b was disordered
over two positions in a 1:1 ratio, and two THF crystal solvents of
1b were disordered over two or four positions in 1:1 or 1:1:2:4
ratios, respectively. A xylyl group of 2 was disordered over two
positions in a 55:45 ratio, and the THF crystal solvent of 2 was
disordered over two positions in a 65:35 ratio. A phenyl group of
3 was disordered over two positions in a 1:1 ratio. A THF crystal
solvent of 4 was disordered over three positions in 4:3:3 ratio. A
mesityl group interacting with nickel in 6 was disordered over two
positions in a 1:1 ratio and two methyl groups of an N-heterocyclic
carbene were disordered over two positions in a 1:1 ratio. A tertiary
butyl group of 7 was disordered over two positions in a 60:40 ratio.
A Dmp group of 8 was disordered over two positions in a 1:1 ratio,
and the hexane crystal solvent of 8 was disordered over two
positions in a 1:1 ratio. Additional crystallographic data are given
in the Supporting Information.
Synthesis of Ni(SDmp)(IMes) (6). At room temperature, a
toluene solution (15 mL) of IMes (320 mg, 1.05 mmol) was added
to a toluene solution (50 mL) of Ni(SDmp)(PPh3) (700 mg, 1.05
mmol). After being stirred for 3 h, the reaction mixture was
centrifuged, and the supernatant was evaporated to dryness. The
residue was washed with pentane (70 mL) to produce 450 mg (44%
yield) of 6 as an orange powder. Crystallization from hexane
produced crystals suitable for X-ray structural analysis. Anal. Calcd
for C45H49N2NiS: C, 76.27; H, 6.970; N, 3.953. Found: C, 75.84;
H, 6.593; N, 3.989.
t
Synthesis of [Ni(CNtBu)(µ-SDmp)]2 (7). At -80 °C, BuNC
(0.5 M toluene solution, 0.15 mL, 0.075 mmol) was added to a
toluene solution (5 mL) of Ni(SDmp)(PPh3) (50 mg, 0.075 mmol).
The solution became reddish purple and then orange-yellow upon
warming to r.t. After being stirred for 30 min at r.t., the solution
was evaporated to dryness, and the residue was washed with hexane
(5 mL) to produce 23 mg (63% yield) of 7 as a yellow-brown
powder. Crystallization from THF/hexane produced crystals suitable
for X-ray structural analysis. Anal. Calcd for C58H68N2Ni2S2: C,
71.47; H, 7.032; N, 2.874. Found: C, 71.45; H, 6.477; N, 2.478.
1H NMR (C6D6, δ): 7.84-7.76 (m, 2H, p-H of Dmp), 7.01 (s, 8H,
m-H of Mes), 6.95-6.86 (m, 4H, m-H of Dmp), 2.45 (s, 12H, p-Me
of Mes), 2.30 (s, 24H, o-Me of Mes), 0.86 (s, 18H, tBu). IR (Tol):
ν(CN)/cm-1 2180.
Reaction of Ni(SDmp)(PPh3) with CO. At -80 °C, CO gas
(2.0 mL, 0.090 mmol) was injected by syringe into the head space
above a toluene solution (3 mL) of Ni(SDmp)(PPh3) (60 mg, 0.090
mmol). The solution became bright purple. An IR spectrum of this
solution displayed a band at 2000 cm-1. The purple solution turned
reddish brown within 15 min at -80 °C with νCO bands in the IR
spectrum at 1943 and 2001 cm-1 [Ni(PPh3)2(CO)2] and at 2069
cm-1 [Ni(CO)(SDmp)2(PPh3) (8)]. The solution was covered by a
hexane layer to produce Ni(PPh3)2(CO)2 and 8 as colorless and
reddish brown crystals, respectively. For 8: Anal. Calcd for
C67H65NiOPS2: C, 77.37; H, 6.300. Found: C, 77.32; H, 6.185. 1H
NMR (C6D6, δ): 7.83-7.76 (m, 6H, PPh3), 7.46-7.42 (m, 2H, p-H
of Dmp), 7.11-7.02 (m, 10H, m-H of Dmp + PPh3), 6.84-6.77
(m, 3H, PPh3), 6.71 (s, 8H, m-H of Mes), 2.22 (s, 24H, o-Me of
Mes), 2.06 (s, 12H, p-Me of Mes). IR (KBr): ν(CO)/cm-1 2069.
Synthesis of Ni(SDmp)2 (9). At 0 °C, a DME solution (50 mL)
of LiSDmp, prepared from HSDmp (1.00 g, 2.89 mmol) and n-BuLi
(1.8 mL of a 1.65 M solution in hexane), was added to a DME
suspension (50 mL) of Ni(dme)Cl2 (317 mg, 1.44 mmol). After
being stirred for 2 h at room temperature, the red solution was
evaporated to dryness, extracted with toluene (100 mL), and
concentrated to 10 mL. The solution was kept at -30 °C to produce
510 mg (47% yield) of 9 as red crystals. Anal. Calcd for C55H58NiS2:
Results and Discussion
Dinuclear Nickel(I) Bis-µ-thiolate Complexes. The reac-
tion of transition-metal amides with thiols has been recog-
nized as a convenient route to the corresponding metal
thiolate complexes.22,23 Our strategy to synthesize Ni(I)
thiolate complexes follows this line, and the nickel(I) amide
complex, Ni{N(SiMe3)2}(PPh3)2,7a was reacted with sterically
demanding arene- and alkanethiols.
When 2,4,6-triisopropylbenzenethiol (HSTip) was added
to Ni{N(SiMe3)2}(PPh3)2 in toluene, a large amount of a
yellow-green powder immediately precipitated. Although
1
C, 78.47; H, 6.94. Found: C, 78.82; H, 7.18. H NMR (C6D6, δ):
(21) Sheldrick, G. M. SHELX97; University of Go¨ttingen: Go¨ttingen,
6.91 (d, J ) 7.5 Hz, 4H, m-H of Dmp), 6.74 (s, 8H, m-H of Mes),
Germany, 1997.
Inorganic Chemistry, Vol. 48, No. 5, 2009 2217

Ito et al.
Scheme 1
spectroscopic characterization of the product was not possible
because of its insolubility in common organic solvents, slow
diffusion between two layers of a hexane solution of HSTip
and a THF solution of Ni{N(SiMe3)2}(PPh3)2 produced
crystals suitable for X-ray analysis, which revealed a
dinuclear structure for [Ni(PPh3)(µ-STip)]2 (1a). A similar
reaction of Ni{N(SiMe3)2}(PPh3)2 with 1-adamantanethiol
(HSAd) afforded [Ni(PPh3)(µ-SAd)]2 (1b). Better solubility
1
of 1b allowed us to characterize it by H NMR in THF-d8,
and the crystal structure was determined by X-ray analysis.
The spectrum indicates that the complex is diamagnetic, and
thus the two Ni(I) centers are magnetically coupled through
the Ni-Ni bond.
The molecular structures of 1a and 1b are very much alike,
and Figure 1 shows a perspective view of 1a. Selected metric
parameters are compared in Table 1. With crystallographic
Ci symmetry, complex 1a has an inversion center at the
center of the Ni2S2 rhombus. Although 1b has no crystal-
lographic inversion center, the Ni2S2 ring is also nearly
planar, as indicated by the sum of the four interior angles of
358.3°. Each nickel assumes a trigonal-planar coordination
geometry with two thiolato sulfurs and one phosphorus, and
the sum of the bond angles at nickel is 359.6° for 1a and
358.5 and 358.9° for 1b. The Tip groups of the two
µ-thiolates of 1a orient above and below the Ni2S2 plane,
whereas the Ad groups of 1b are both on the same side of
the Ni2S2 plane. The four Ni-S bond distances in each Ni2S2
rhombus are approximately the same, where the mean values
are 2.179 Å for 1a and 2.183 Å for 1b. The short
metal-metal distances are consistent with strong Ni(I)-Ni(I)
bonding. These distances are somewhat shorter than those
for the analogous dinuclear Ni(I) complexes such as [Ni(µ-
PCy2)(PCy2Me)]2 (2.3910(8) Å)24a and [Ni(µ-Cl)(IiPr)]2
(2.5194(5) Å) (IiPr is 1,3-bis(2,6-diisopropylphenyl)imidazol-
2-ylidene).24b
Unsymmetric Dinuclear Nickel(I) Thiolate Complex.
A similar reaction of Ni{N(SiMe3)2}(PPh3)2 with 2,6-
dixylylbenzenethiol (HSDxp) in THF resulted in isolation
of the dinuclear nickel(I) complex Ni(SDxp)(µ-SDxp)Ni(P-
Ph3) (2) in 70% yield as green crystals (Scheme 2). The X-ray
derived structure of 2 is shown in Figure 2. Interestingly,
this dinuclear Ni(I) complex with bulkier SDxp ligands has
a structure that is quite different from those of 1a,b. Complex
2 consists of two inequivalent nickel centers, one bound to
a SDxp sulfur and the other bound to a PPh3 ligand, and
(22) Ellison, J. J.; Ruhlandt-Senge, K.; Power, P. P. Angew. Chem., Int.
Ed. Engl. 1994, 33, 1178–1180.
(23) (a) Ohki, Y.; Ikagawa, Y.; Tatsumi, K. J. Am. Chem. Soc. 2007, 129,
10457–10465. (b) Ohta, S.; Ohki, Y.; Ikagawa, Y.; Suizu, R.; Tatsumi,
K. J. Organomet. Chem. 2007, 692, 4792–4799.
2218 Inorganic Chemistry, Vol. 48, No. 5, 2009

Mono- and Dinuclear Ni(I) Thiolate Complexes
Figure 2. ORTEP drawing of Ni(SDxp)(µ-SDxp)Ni(PPh3) (2). Thermal
ellipsoids are shown at 50% probability. The xylyl ring that does not
coordinate to the nickels was modeled with two disordered components in
a 55:45 ratio, and the major component is shown. Distances (Å) and angles
(deg): Ni(1)-Ni(2) 2.4238(4), Ni(1)-P 2.2043(6), Ni(1)-S(2) 2.1666(5),
Ni(2)-S(1) 2.1718(6), Ni(2)-S(2) 2.1276(5), Ni(1)-C(49) 2.217(2),
Ni(1)-C(50) 2.0489(19), Ni(2)-C(47) 1.9979(19), Ni(2)-C(48) 2.328(6),
Ni(2)-C(52) 2.2342(19), C(47)-C(48) 1.441(3), C(48)-C(49) 1.402(3),
C(49)-C(50) 1.420(3), C(50)-C(51) 1.403(3), C(51)-C(52) 1.399(3),
C(47)-C(52) 1.432(3), P-Ni(1)-S(2) 113.99(2), Ni(2)-Ni(1)-P 167.159-
(17), S(1)-Ni(2)-S(2) 110.23(2), Ni(1)-Ni(2)-S(1) 165.403(18), Ni(2)-
Ni(1)-S(2) 54.879(16), Ni(1)-Ni(2)-S(2) 56.399(18), Ni(1)-S(2)-Ni(2)
68.721(17).
Figure 1. ORTEP drawing of [Ni(PPh3)(µ-STip)2]2 (1a). Thermal ellipsoids
are shown at 50% probability.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for 1a and 1b
1aa
1b
Ni(1)-Ni(2)
2.3353(4)
2.1784(6)
2.1793(5)
2.3510(3)
2.1821(5)
2.1881(6)
2.1859(6)
2.1766(5)
2.1432(6)
2.1481(6)
113.85(2)
124.82(2)
119.85(2)
114.16(2)
121.33(2)
123.45(2)
65.127(17)
65.184(17)
Scheme 3
Ni(1)-S(1)
Ni(1)-S(2)
Ni(2)-S(1)
Ni(2)-S(2)
Ni(1)-P(1)
2.1392(6)
Ni(2)-P(2)
S(1)-Ni(1)-S(2)
S(1)-Ni(1)-P(1)
S(2)-Ni(1)-P(1)
S(1)-Ni(2)-S(2)
S(1)-Ni(2)-P(2)
S(2)-Ni(2)-P(2)
Ni(1)-S(1)-Ni(2)
Ni(1)-S(2)-Ni(2)
115.19(2)
126.08(2)
118.36(2)
2.4240(5) Å compares well to the reported Ni(I)-Ni(I) bond
distances described above and is slightly longer than those
of 1a and 1b.
1
The H NMR spectrum confirms the diamagnetism of 2,
64.810(19)
consistent with the formation of a Ni-Ni bond. Two broad
signals observed at δ 4.80 and 3.73 in a 2:1 intensity ratio
are assignable to the m- and p-protons of the η2:η3-
coordinated xylyl group, respectively. These signals are
shifted upfield by more than 2 to 3 ppm from those of
HSDxp, which is consistent with the bonding of the xylyl
group to the nickels. Because the broadness of the m-proton
signal at δ 4.80 suggests a fluxional process, and considering
the attachment of Ni(1) to only the C(49) meta site observed
in the crystalline state, we carried out a variable temperature
1H NMR analysis. At -60 °C, the signal at δ 4.80 splits
into two broad signals at δ 5.14 and 4.48, and the two signals
further broaden as the temperature rises to coalesce at -25
°C. We attribute this fluxional process to Ni(1) migration
between the η2-C(49)-C(50) and η2-C(50)-C(51) bonds of
the xylyl group, which accompanies the synchronous shift
of the Ni(2) position that is asymmetrically η3-coordinated
to C(48)-C(47)-C(52).
a For 1a, Ni(2), S(2), and P(2) correspond to Ni(1)*, S(1)*, and P(1)*,
respectively.
Scheme 2
they are bridged by a µ-SDxp sulfur and a µ-η2:η3-xylyl
group of the terminal SDxp. The µ-η2:η3-xylyl coordination
mode can be seen in the Ni-C(η-xylyl) distances, namely,
Ni(1)-C(49) ) 2.217(2), Ni(1)-C(50) ) 2.0489(19),
Ni(2)-C(47) ) 1.9979(19), Ni(2)-C(48) ) 2.328(6), and
Ni(2)-C(52) ) 2.2342(19). This coordination mode is
further evident in the significant bond localization of the xylyl
C-C bonds. Three C-C bonds coordinating to Ni(1) and
Ni(2), C(47)-C(48), C(49)-C(50), and C(47)-C(52), are
longer (1.420(3) to 1.441(3) Å) than the other three C-C
bonds (1.399(3) to 1.402(3) Å). Ni(1) sits in a trigonal plane
composed of µ-sulfur, phosphorus, and the midpoint of the
η2-arene carbons C(49) and C(50). Ni(2) also assumes a
trigonal planar geometry coordinated by two thiolato sulfurs
and the η3-xylyl at C(47), C(52), C(48). The Ni-Ni distance
Mononuclear Nickel(I) Complex with SDmp. The
mononuclear nickel(I) thiolate complex Ni(SDmp)(PPh3) (3)
was synthesized by the reaction of the nickel(I) amide (vide
(24) (a) Kriley, C. E.; Woolley, C. J.; Krepps, M. K.; Popa, E. M.; Fanwick,
P. E.; Rothwell, I. P. Inorg. Chim. Acta 2000, 300, 200–205. (b) Dible,
B. R.; Sigman, M. S.; Arif, A. M. Inorg. Chem. 2005, 44, 3774–
3776.
Inorganic Chemistry, Vol. 48, No. 5, 2009 2219

Ito et al.
Figure 4. Cyclic voltammogram of a 2 mM THF solution of 3 and 0.2 M
n-Bu4NPF6 at a scan rate of 100 mV/s.
Figure 3. ORTEP drawing of Ni(SDmp)(PPh3) (3). Thermal ellipsoids are
shown at 50% probability. One phenyl group of the PPh3 was modeled
with two disordered components in a 1:1 ratio, and only one component is
shown. Distances (Å) and angles (deg): Ni-S 2.2378(7), Ni-P 2.2034(9),
Ni-C(16) 2.129(3), Ni-C(17) 2.147(2), C(16)-C(17) 1.418(4), C(17)-C(18)
1.404(4), C(18)-C(19) 1.392(4), C(19)-C(20) 1.382(4), C(20)-C(21)
1.391(3), C(16)-C(21) 1.419(3), S-Ni-P 107.30(3), P-Ni-C(16) 164.38(7),
P-Ni-C(17) 126.50(9).
Scheme 4
supra) with 2,6-dimesitylbenzenethiol (HSDmp) (Scheme 3).
Although Dmp has just one additional methyl group on each
of the two xylyl groups of Dxp at the p-position, it prevents
the molecule from dimerizing interaction. Complex 3 was
obtained in 69% yield as orange crystals, and the mono-
nuclearity of 3 was confirmed by X-ray crystallography, as
shown in Figure 3. The nickel is coordinated by PPh3, the
thiolate, and an η2-mesityl of Dmp to form a considerably
distorted trigonal planar geometry. The mesityl coordination
can be described as η2 because the Ni-C(16) and Ni-C(17)
distances, 2.129(3) and 2.147(2) Å, respectively, are notably
shorter than the other four Ni-C(mesityl) distances ranging
from 2.529 to 2.907 Å.25 Note that the C(16)-C(17) bond
distance of 1.418(4) Å is slightly longer than those of the
other C-C bonds in the mesityl ring because of the nickel
coordination.
Electron Paramagnetic Resonance and Cyclic Volta-
mmogram of Ni(SDmp)(PPh3) (3). Complex 3 is paramag-
netic (µeff ) 1.93µB in C6D6 at 25 °C), and the EPR spectrum
in toluene exhibits a broad isotropic signal with giso ) 2.18
at 298 K attributable to the nickel unpaired electron.26
The cyclic voltammogram of 3 exhibits two quasi-
reversible redox waves with peak separations of 0.2 V, a
reductive NiI/Ni0 wave at E1/2 ) -1.80, and an oxidative
NiII/NiI wave at E1/2 ) -0.41 V (vs Ag/Ag+) (Figure 4).
These values exhibit an understandable negative shift
compared with those of thioether-coordinated nickel(II)
complexes such as [(Ph2PCH2CH2SEt)2Ni]2+ (E1/2 ) -0.78
for NiI/Ni0, -0.09 V for NiII/NiI) and [(Ph2P(o-C6H4)-
SMe)2Ni]2+ (E1/2 ) -0.90 for NiI/Ni0, -0.35 V for NiII/
NiI)12 because these complexes are cationic, whereas 3 is
charge neutral. Greater electron donation of the thiolate
ligand of 3 compared with that of thioethers also may
contribute.
Reaction of 3 with TEMPO. Hillhouse et al. reported
that the Ni(I) dimer [(dtbpe)Ni(µ-Cl)]2 reacted with TEMPO
to afford the diamagnetic adduct (dtbpe)Ni(Cl)(O,N:η2-
TEMPO) (dtbpe is 1,2-bis(di-tert-butylphosphino)ethane,
TEMPO is 2,2,6,6-tetramethyl-1-piperidine-N-oxyl).27 Treat-
ment of 3 with 1 equiv of TEMPO in toluene produced a
similar mononuclear Ni(II) complex, Ni(SDmp)(PPh3)(O,N:
1
η2-TEMPO) (4), in 54% yield (Scheme 4). The H NMR
spectrum confirms the diamagnetism of 4, in which all of
the aromatic protons of Dmp resonate in the normal region
δ 7.14 to 7.09, suggesting the absence of π coordination of
(25) The Ni-C(18) and Ni-C(21) distances, 2.529(2) and 2.538(2) Å,
are substantially longer than those of the Ni-C(16) and Ni-C(17)
bonds.
(26) Only a poor simulation for the complicated hyperfine coupling
appearing at 77 K could be attained, even considering the interactions
of the unpaired electron with only the other nuclei of the ligands
including the phosphorous and the protons in the η-mesityl group. It
may suggest substantial delocalization of the unpaired Ni d electron
over the ligands. The EPR spectrum is shown in the Supporting
Information.
Figure 5. ORTEP drawing of Ni(SDmp)(PPh3)(O,N:η2-TEMPO) (4).
Thermal ellipsoids are shown at 50% probability. Distances (Å) and angles
(deg): Ni-S 2.1780(8), Ni-P 2.1697(7), Ni-N 1.949(2), Ni-O 1.832(2),
P-Ni-S 93.51(3), P-Ni-N 118.41(7), S-Ni-O 104.84(6), N-Ni-O
43.24(8).
2220 Inorganic Chemistry, Vol. 48, No. 5, 2009

Mono- and Dinuclear Ni(I) Thiolate Complexes
Scheme 5
Figure 7. ORTEP drawing of [Ni(IMes)(SDmp)] (6). Thermal ellipsoids
are shown at 50% probability. A mesityl ring interacting with nickel was
modeled with two disordered components in a 1:1 ratio, and only one
position of the disordered atoms is shown here. Distances (Å) and angles
(deg): Ni-S 2.2424(7), Ni-C(1) 1.935(2), Ni-C(39) 2.090(5), Ni-C(44)
2.098(5), S-Ni-C(1) 106.55(7), C(1)-Ni-C(39) 163.27(16), C(1)-Ni-
C(44) 136.98(15).
the mesityl group to the nickel, as was observed for 3. The
X-ray-derived structure of 4 shown in Figure 5 confirms that
nickel is not bound to the mesityl group that resides in a
plane composed of O,N:η2-TEMPO, phosphorus, and the
thiolato sulfur. The respective Ni-N and Ni-O bond
distances compare well to those of the reported (dtbpe)Ni-
(Cl)(O,N:η2-TEMPO).27
Scheme 6
Reactions of 3 with N-Heterocyclic Carbenes. Complex
3 smoothly reacts with σ donors to afford the corresponding
adducts via ligand substitution. The addition of 1,3,4,5-
tetramethylimidazolin-2-ylidene (denoted as IMe′) to 3 at
room temperature afforded the dinuclear Ni(I) complex
[Ni(IMe′)(µ-SDmp)]2 (5) similar to 1a and 1b (Scheme 5).
The short Ni-Ni distance of 2.3941(13) Å confirms Ni-Ni
bond formation (Figure 6). The formation of the dinuclear
complex 5 suggests that the IMe′ ligand is too small to
prevent dimerization. Accordingly, the employment of the
bulkier N-heterocyclic carbene, 1,3-bis-(2,4,6-trimethylphe-
nyl)imidazolin-2-ylidene (IMes), afforded the mononuclear
Ni(IMes)(SDmp) (6) in 60% yield. The structure of 6
revealed by X-ray analysis is shown in Figure 7. The mesityl
group capping the nickel is disordered over two positions in
a 1:1 ratio, and only one set is depicted here.28 The nickel
assumes a similar coordination geometry to that of 3, and
the Ni-S distance of 2.2424(7) Å also compares well to that
of 3.
t
Reaction of 3 with BuNC or CO. Similarly, treatment
t
of 3 with 1 equiv of BuNC at room temperature produced
the thiolato-bridged dinuclear Ni(I) complex [Ni(CNtBu)-
(µ-SDmp)]2 (7) in 63% yield as a yellow-brown powder
(Scheme 6). The substitution of PPh3 with the sterically less
t
demanding BuNC allows the formation of the thiolato-
bridged dimer 7 with a Ni-Ni bond. Note that the dinuclear
Ni(I) complex 7 again has a Ni-Ni bond of 2.3354(8) Å
1
(Figure 8), and the H NMR spectrum in C6D6 confirms its
diamagnetism, as was observed for 1a, 1b, and 5. The IR
spectrum of 7 displays a CN stretching band at 2180 cm-1.
The reaction of 3 with CO produced a somewhat different
adduct from those described above for N-heterocyclic car-
benes and tBuNC. When 1 equiv of CO gas was charged to
the toluene solution of 3, the reddish orange solution
immediately turned reddish brown, and the IR spectrum of
this solution shows three νCO bands at 1943 (s), 2001 (s),
and 2069 (m) cm-1. The bands at 1943 and 2001 cm-1 are
coincident with those of Ni0(PPh3)2(CO)2, and recrystalliza-
tion of the products from hexane produced Ni0(PPh3)2(CO)2
(27) Mindiola, D. J.; Waterman, R.; Jenkins, D. M.; Hillhouse, G. L. Inorg.
Chim. Acta 2003, 345, 299–308.
Figure 6. ORTEP drawing of [Ni(IMe′)(µ-SDmp)]2 (5). Thermal ellipsoids
are shown at 50% probability. Distances (Å) and angles (deg): Ni(1)-Ni(2)
2.3941(13), Ni(1)-S(1) 2.1663(16), Ni(2)-S(1) 2.1935(16), Ni(1)-C(25)
1.912(6), Ni(2)-C(29) 1.920(9), S(1)-Ni(1)-S(1)* 114.48(6), S(1)-Ni(2)-
S(1)* 112.30(6), Ni(1)-S(1)-Ni(2) 66.61(5), S(1)-Ni(1)-C(25) 122.76(4),
S(1)-Ni(2)-C(29) 123.85(4).
(28) See the Supporting Information for the structural details of 6.
(29) (a) Chen, J.; Huang, S.; Seravalli, J.; Gutzman, H.; Swartz, D. J.;
Ragsdale, S.; Bagley, K. A. Biochemistry 2003, 42, 14822–14830.
(b) Seravalli, J.; Kumar, M.; Ragsdale, S. W. Biochemistry 2002, 41,
1807–1819. (c) George, S. J.; Seravalli, J.; Ragsdale, S. W. J. Am.
Chem. Soc. 2005, 127, 13500–13501.
Inorganic Chemistry, Vol. 48, No. 5, 2009 2221

Ito et al.
Figure 9. ORTEP drawing of Ni(CO)(SDmp)2(PPh3) (8). Thermal ellipsoids
are shown at 50% probability. One phenyl and one mesityl ring of a Dmp
group were modeled with two disordered components in a 1:1 ratio, and
only one set of disordered atoms is shown here. Distances (Å) and angles
(deg): Ni-S(1) 2.2087(14), Ni-S(2) 2.2009(14), Ni-P 2.2480(10), Ni-C(78)
1.761(3), C(78)-O 1.123(4), S(1)-Ni-P 90.36(4), S(2)-Ni-P 86.59(4),
S(1)-Ni-C(78) 91.14(19), S(2)-Ni-C(78) 92.91(19), Ni-C(78)-O
178.4(3).
Figure 8. ORTEP drawing of [Ni(CNtBu)(µ-SDmp)]2 (7). Thermal
ellipsoids are shown at 50% probability. One tert-butyl group was modeled
with two disordered components in a 6:4 ratio, and the major component
is shown. Distances (Å): Ni(1)-Ni(2) 2.3354(8), Ni(1)-S(1) 2.2047(16),
Ni(1)-S(2) 2.1775(12), Ni(1)-C(49) 1.817(5), Ni(2)-S(1) 2.2070(14),
Ni(2)-S(2) 2.1810(15), Ni(1)-C(54) 1.815(5).
obtained as a minor product in the former reaction, it can be
synthesized in a good yield via an alternative pathway;
Ni(SDmp)2 (9), synthesized from Ni(dme)Cl2 and 2 equiv
of LiSDmp,32 reacts with PPh3 under a CO atmosphere to
produce 8 in 77% yield (Scheme 8). As shown in Figure 9,
the nickel sits in a square plane composed of the two
thiolates, CO, and PPh3. The two Dmp groups of the thiolates
occupy positions that are cis to the CO and are tipped toward
the CO side because of steric repulsion with the PPh3 located
trans to the CO. As a result, the CO is completely covered
by the Dmp groups, which stabilizes the CO adduct 8. The
Ni-C(78) distance (1.761(3) Å) is within the range of
reported Ni(II)-CO complexes (1.728 to 1.80 Å),33 and the
Scheme 7
Scheme 8
ν
CO band of 8 at 2069 cm-1 is comparable to those of Ni(II)-
CO complexes ranging from 2003 to 2162 cm-1.33
as a major product. The recrystallization also produced a
small amount of NiII(CO)(SDmp)2(PPh3) (8) in crystalline
form, which has a νCO band at 2069 cm-1 (Scheme 7). To
provide insight into this reaction that affords both Ni(0) and
Ni(II) carbonyl complexes, the reaction of 3 with 1 equiv of
CO was conducted at -80 °C in toluene. The red-orange
solution of 3 immediately turned bright purple, and the IR
spectrum of the solution shows only one strong νCO band at
2000 cm-1. Because this value is reasonable for a Ni(I)-CO
species, the formation of a CO adduct of 3 (3-CO) is
indicated. However, IR analysis also shows the formation
of a significant amount of Ni0(PPh3)2(CO)2 and 8 within 15
min, even at -80 °C, and thus the characterization of the
3-CO is limited by its instability.
Conclusions
Mono- and dinuclear nickel(I) thiolates have been syn-
thesized by acid-base reactions of the Ni(I) amide,
Ni{N(SiMe3)2}(PPh3)2, and the corresponding thiols. Whereas
(31) Ogata, H.; Mizoguchi, Y.; Mizuno, N.; Miki, K.; Adachi, S.; Yasuoka,
N.; Yagi, T.; Yamauchi, O.; Hirota, S.; Higuchi, Y. J. Am. Chem.
Soc. 2002, 126, 11628–11635.
(32) (a) The structure of Ni(SDmp)2 (9) was confirmed by X-ray structural
analysis. The structural details are described in the Supporting
Information. Power and coworkers have reported a similar Ni(II)
thiolate. See: (b) Nguyen, T.; Panda, A.; Olmstead, M. M.; Richards,
A. F.; Stender, M.; Brynda, M.; Power, P. P. J. Am. Chem. Soc. 2005,
127, 8545–8552.
(33) (a) Saint-Joly, C.; Mari, A.; Gleizes, A.; Dartiguenave, M.; Dart-
iguenave, Y.; Galy, J. Inorg. Chem. 1980, 19, 2403–2410. (b)
Miedanger, A.; Curtis, C. J.; Wander, S. A.; Goodson, P. A.; DuBois,
D. L. Organometallics 1996, 15, 5185–5190. (c) Nguyen, D. H.; Hsu,
H. F.; Millar, M.; Koch, S. A. J. Am. Chem. Soc. 1996, 118, 8963–
8964. (d) Liaw, W.-F.; Horng, Y.-C.; Ou, D.-S.; Ching, C.-Y.; Lee,
G.-H.; Peng, S.-M. J. Am. Chem. Soc. 1997, 119, 9299–9300. (e) Liaw,
W.-F.; Chen, C.-H.; Lee, C.-M.; Lee, G.-H.; Peng, S.-M. J. Chem.
Soc., Dalton Trans. 2001, 138–143. (f) Fornie´s, J.; Mart´ın, A.; Mart´ın,
L. F.; Menjo´n, B.; Kalamarides, H. A.; Rhodes, L. F.; Day, C. S.;
Day, V. W. Chem.sEur. J. 2002, 8, 4925–4934. (g) Wilson, A. D.;
Fraze, K.; Twamley, B.; Miller, S. M.; DuBois, D. L.; Rakowsky
DuBois, M. J. Am. Chem. Soc. 2008, 130, 1061–1068.
Here the chemical significance of 8 is worth mentioning.
Although the Ni(II)-CO complexes carrying thiolato ligands
have been found in the active sites of nickel enzymes such
as CO-dehydrogenase29a,30 and [NiFe] hydrogenase,31 Ni(II)-
CO complexes are rather rare.33,34 Whereas complex 8 was
(30) (a) Darnault, C.; Volbeda, A.; Kim, E. J.; Legrand, P.; Vernede, X.;
Lindahl, P. A.; Fontecilla-Camps, J. C. Nat. Struct. Biol. 2003, 10,
271–279. (b) Jeoung, J.-H.; Dobbek, H. Science 2007, 318, 1461–
1464.
(34) Macgregor, S. A.; Lu, Z.; Eisenstein, O.; Crabtree, R. H. Inorg. Chem.
1994, 33, 3616–3618.
2222 Inorganic Chemistry, Vol. 48, No. 5, 2009

Mono- and Dinuclear Ni(I) Thiolate Complexes
the reaction with each of HSTip, HSAd, and HSDxp results
in each case in the formation of a dinuclear Ni(I) thiolate
with a Ni-Ni bond, the bulkier Dmp ligand prevents the
molecule from being dimerized to afford the mononuclear
Ni(I) thiolate, Ni(SDmp)(PPh3) (3). Complex 3 smoothly
reacts with σ donors such as N-heterocyclic carbenes and
tBuNC to form the mono- and dinuclear Ni(I) complexes in
which the nuclearity depends on the steric bulk of the donors.
The reaction of 3 with CO produced the corresponding Ni(I)-
CO adduct of 3, which is further converted to Ni(0) and
Ni(II) carbonyl complexes because of the thermodynamic
instability of the CO adduct of 3. The complexes reported
here are rare examples of Ni(I) thiolates and are expected to
be useful precursors of active site models of nickel enzymes.
Acknowledgment. This research was financially supported
by Grant-in-Aids for Scientific Research (nos. 18GS0207 and
18065013) from the Ministry of Education, Culture, Sports,
Science, and Technology, Japan. We are grateful to Prof.
Ryo Miyamoto (Hirosaki University) for discussions on EPR
spectra. We also thank Prof. Roger E. Cramer for discussions
and careful reading of the manuscript.
Supporting Information Available: EPR spectra for 3, molec-
ular structures for 6 and 9, and X-ray crystallographic data for 1a,1b,
and 2-9 in CIF format. This material is available free of charge
via the Internet at http://pubs.acs.org.
IC802276W
Inorganic Chemistry, Vol. 48, No. 5, 2009 2223