C-H bond activation and S-atom transfer from cobalt(iii) thiolate and isothiocyanate complexes

Article abstract of DOI:10.1039/c4dt01823k

The cobalt phenylthiolate complex, cis,mer-(PMe₃)₃Co(CH₃)₂SPh, was found to undergo competitive two-electron ethane reductive elimination and C-H bond cyclometallation. The thiophenolato bound cobaltacycle was generated via C-H bond oxidative addition to a five-coordinate intermediate followed by rapid methane elimination. A related cobalt isothiocyanate complex, cis,mer-(PMe₃)₃Co(CH₃)₂NCS, was also prepared and found to perform ethane elimination and S-atom transfer to yield trimethylphosphine sulfide. This rare example of S-atom donation from a isothiocyanate was characterized by NMR and GC-MS analysis, with cis,mer-(PMe₃)₃Co(CH₃)₂CN identified as one of the cobalt based products. This journal is

Full text of DOI:10.1039/c4dt01823k

Dalton
Transactions
View Article Online
View Journal | View Issue
PAPER
C–H bond activation and S-atom transfer from
cobalt(III) thiolate and isothiocyanate complexes†
Cite this: Dalton Trans., 2014, 43,
14696
Hongwei Xu, Paul G. Williard and Wesley H. Bernskoetter*
The cobalt phenylthiolate complex, cis,mer-(PMe3)3Co(CH3)2SPh, was found to undergo competitive
two-electron ethane reductive elimination and C–H bond cyclometallation. The thiophenolato bound
cobaltacycle was generated via C–H bond oxidative addition to a five-coordinate intermediate followed
by rapid methane elimination. A related cobalt isothiocyanate complex, cis,mer-(PMe3)3Co(CH3)2NCS,
was also prepared and found to perform ethane elimination and S-atom transfer to yield trimethylphos-
phine sulfide. This rare example of S-atom donation from a isothiocyanate was characterized by NMR and
GC-MS analysis, with cis,mer-(PMe3)3Co(CH3)2CN identified as one of the cobalt based products.
Received 18th June 2014,
Accepted 12th August 2014
DOI: 10.1039/c4dt01823k
www.rsc.org/dalton
(PMe3)3Co(CH3)3 and (PMe3)3Co(CH3)2I were prepared as pre-
viously reported.4 Solvents were dried and deoxygenated using
Introduction
Over the past few decades, the mechanism of carbon–carbon literature procedures.5
bond reductive elimination at platinum group metals has been
1H, 13C and 31P NMR spectra were recorded on Bruker DRX
1
extensively studied owing to its crucial role in many catalytic 600 and 400 Avance MHz spectrometers. H and 13C chemical
processes, such as cross-coupling.1,2 More recently, our labora- shifts are referenced to residual solvent signals; 31P chemical
tory has been examining the less well understood mechanism shifts are referenced to an external standard of H3PO4. Spectra
for selective two-electron C–C bond elimination at base-metal were obtained at ambient temperature unless otherwise indi-
centers such as cobalt.3 The rare, selective ethane elimination cated. Due to strong 31P–31P coupling for trans-PMe3 ligands,
1
reactivity of cis,mer-(PMe3)3Co(CH3)2I (1) has been central to some H signals appear as virtual triplets (vt) and are reported
our preliminary studies.3 In efforts to further probe the many as such with the apparent coupling noted. IR spectra were
factors influencing this reaction, a series of cobalt(III) cis,mer- recorded on a Jasco 4100 FTIR. Elemental analyses were per-
(PMe3)3Co(CH3)2X species has been targeted, including X = formed at Robertson Microlit Laboratories, Inc., in Ledgewood,
SPh (2) and X = NCS (3). These complexes serendipitously NJ or Atlantic Microlab, Inc., in Norcross, GA. X-ray crystallo-
demonstrated an interesting alternative pathway to C–C bond graphic data were collected on a Bruker Smart Apex I diffracto-
elimination, including C–H bond activation of the phenylthio- meter. Samples were collected in inert oil and quick transfer
late and a rare S-atom transfer from the isothiocyanate. The to a cold gas stream. The structures were solved from direct
detailed characterization and reactivity of these two sulfur con- methods and Fourier syntheses and refined by full-matrix
taining cobalt(III) complexes are presented here.
least-squares procedures with anisotropic thermal parameters
for all non-hydrogen atoms. Crystallographic calculations were
carried out using SHELXTL. The crystal data for complexes 2, 3
and 3A are summarized in Table 1.
Experimental section
Preparation of cis,mer-(PMe3)3Co(CH3)2SPh (2)
All air- and moisture-sensitive manipulations were carried out
using standard vacuum line, Schlenk, cannula or glovebox
techniques. Volatile chemicals were dried with 4 Å molecular
sieves and distilled prior to use. All chemicals were purchase
from Aldrich, VMR, Strem or Cambridge Isotope Laboratories.
A 50 mL Schlenk flask was charged with 0.057 g (0.172 mmol)
of (PMe3)3Co(CH3)3 and approximately 10 mL diethyl ether. On
a Schlenk line, 1 equiv. (18 μL) of thiophenol was added by
microsyringe. The solution was stirred for 30 min at ambient
temperature changing color from yellow to dark red. The
solvent was removed in vacuo to afford 45 mg (62%) 2 as red
powder. The material may be recrystallized from pentane at
−35 °C to obtain material of analytical purity. Anal. Calcd for
C17H38P3SCo: C 47.88; H 8.98. Found: C 47.67; H 8.84.
1H NMR (C6D6): δ −0.82 (bs, 3H, Co–CH3), 0.76 (bs, 3H, Co–
Department of Chemistry, Brown University, Providence, RI 02912, USA.
E-mail: wb36@brown.edu
†Electronic supplementary information (ESI) available: Variable temperature
NMR spectrum of complex 2. CCDC 1007027–1007029. For ESI and crystallo-
graphic data in CIF or other electronic format see DOI: 10.1039/c4dt01823k
14696 | Dalton Trans., 2014, 43, 14696–14700
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
change from orange to dark red was observed immediately fol-
lowing the thiophenol addition and red crystals of 2 were pre-
cipitated in moderate yield from a pentane extraction at
−35 °C. Complex 2 was characterized by NMR spectroscopy
and combustion analysis as well as X-ray diffraction. The 1H
NMR spectrum of 2 in benzene-d6 displays features similar to
the iodide congener, 1, with two distinct cobalt–methyl reson-
ances at 0.76 and −0.82 ppm.6 Both cobalt–methyl peaks are
broad at ambient temperature due to rapid intramolecular site
exchange.3 At 0 °C, the cobalt–methyl signals resolve into a
triplet of doublets and doublet of triplets, consistent with
coupling to three 31P nuclei (see Fig. S1†). The X-ray diffraction
study confirmed the molecular structure of 2. A depiction of
one of two molecules of complex 2 found in the asymmetric
unit is shown in Fig. 1. The metrical parameters of the two
molecules are nearly identical. Complex 2, which has an octa-
hedral geometry with phenylthiolate ligand bound trans to one
of the cobalt–methyl bonds, is similar in structure to previous
reported cis,mer-(PMe3)3Co(CH3)2X congeners.4b,6 The strong
trans influence of the methyl ligand does lead to a slightly
Table 1 Crystal data for compounds 2, 3 and 3A
Compound
Formula
2
3
3A
C
17H38P3SCo
C12H33NP3SCo C18H48N2P4S2Co2
Formula weight 426.40
375.32
Monoclinic
P21/c
8.828(1)
13.596(1)
15.992(1)
90
598.48
Triclinic
ˉ
P1
Crystal system
Space group
a (Å)
b (Å)
c (Å)
Monoclinic
P21/c
18.100(1)
15.500(1)
16.368(1)
90
8.212(1)
8.603(1)
11.443(1)
103.448(5)
102.311(5)
105.632(4)
723.5(2)
2
α (°)
β (°)
103.642(2)
90
4462.2(5)
8
91.602(1)
90
1918.5(1)
4
γ (°)
V (Å3)
Z
T (K)
183
183
183
Radiation
2θmax (°)
F (000)
R1
Mo Kα 0.71073 Mo Kα 0.71073 Mo Kα 0.71073
20.92
1824
0.0234
0.0580
29.27
800
0.0209
0.0590
24.41
284
0.0336
0.0850
wR2 (all data)
CH3), 1.05 (bs, 27H, P–CH3), 7.01 (m, 1H, C6H5), 7.12 (m, 2H,
1
C6H5), 7.79 (m, 2H, C6H5). H NMR (0 °C, Tol-d8): δ −0.88 (dt,
longer Co(1)–P(2) distance of 2.254(1)
Å in comparison
11.0 Hz, 6.8 Hz, 3H, Co–CH3), 0.68 (td, 10.2 Hz, 2.5 Hz, 3H,
Co–CH3), 1.03 (vt, 3.2 Hz, 18H, P–CH3), 1.03 (d, 6.0 Hz, 9H,
P–CH3), 6.98 (m, 1H, C6H5), 7.07 (m, 2H, C6H5), 7.71 (m, 2H,
C6H5).31P NMR (C6D6): δ −3.02 (bs, 1P), 5.78 (bs, 2P). 13C NMR
(C6D6): δ −10.77 (Co–CH3), 2.75 (Co–CH3), 14.75 (P–CH3),
17.18 (P–CH3), 122.13, 127.72, 136.09, 149.72 (Ar).
with the Co(1)–P(1) and Co(1)–P(3) distances of 2.226(1) and
2.219(1) Å.
ð1Þ
Preparation of cis,mer-(PMe3)3Co(CH3)2NCS (3)
A
20 mL scintillation vial was charged with 0.082 g
Unlike 1, the phenylthiolate complex 2 afforded competitive
ethane elimination and cyclometallation products during
thermolysis at 50 °C in benzene-d6 (Fig. 2).
Each reaction pathway likely initiates from trimethylphos-
phine dissociation at the position trans to a methyl group to
form a five-coordinate intermediate, which has been impli-
cated in a range of other reactions.1b,d,3,7 Following C–C bond
(0.185 mmol) of (PMe3)3Co(CH3)2I (1), 0.021 g (0.259 mmol) of
NaSCN and approximately 8 mL of THF. The solution was
stirred at ambient temperature for 3 h resulting in a color
change from orange to yellow. The reaction solution was then
transferred to a 25 mL round bottom flask with a vacuum
adapter. On a high vacuum line, one equivalent of PMe3
(0.185 mmol) was added into the mixture at −196 °C via cali-
brated gas bulb. The reaction mixture was then stirred at
ambient temperature for 20 min. The volatiles were removed
in vacuo and the residue was extracted with diethyl ether, fil-
tered through filter paper, concentrated to approximately 3 mL
and recrystallized at −35 °C to afford 42 mg (61%) of 3 as a
yellow powder. Anal. Calcd for C12H33NP3SCo: C 38.40; H 8.86;
N 3.73. Found: C 38.62; H 8.93; N 3.77. 1H NMR (C6D6):
δ −1.24 (dt, 9.9 Hz, 9.3 Hz, 3H, Co–CH3), 0.36 (td, 10.0 Hz, 3.0
Hz, 3H, Co–CH3); 0.88 (d, 6.5 Hz, 9H, P–CH3), 0.91 (vt, 3.3 Hz,
18H, P–CH3). 31P NMR (C6D6): δ −1.34 (bs), 13.00 (bs).
13C NMR (C6D6): δ −15.00 (Co–CH3), 4.78 (Co–CH3), 13.59
(P–CH3), 16.94 (P–CH3), 139.47 (NvCvS). IR (KBr): νNvCvS
2091 cm−1
.
Fig. 1 Molecular structure of 2 at 30% probability ellipsoids. All hydro-
gen atoms and a second molecule in the asymmetric unit are omitted
for clarity. Select bond distances (Å) and angles (°): Co(1)–C(1) 2.033(3),
Co(1)–C(2) 2.033(3), Co(1)–P(1) 2.226(1), Co(1)–P(2) 2.254(1), Co(1)–P(3)
2.219(1), Co(1)–S(1) 2.356(1), C(1)–Co(1)–P(2) 167.47(9), C(2)–Co(1)–S(1)
Results and discussion
Complex 2 was prepared by protonation of (PMe3)3Co(CH3)3 in
diethyl ether using 1 equiv. of thiophenol (eqn (1)).4a A color 173.4(1), P(1)–Co(1)–P(3) 165.85(3).
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 14696–14700 | 14697

View Article Online
Paper
Dalton Transactions
Fig. 2 Thermolysis of complex 2.
coupling to generate ethane, two (PMe3)2CoSPh moieties (eqn (2)).13 A few crystals of 3A were isolated from the mixture
bridge the thiolate ligands to form a dinuclear complex 2A, permitting X-ray determination of its structure (Fig. 3) which
similar to the observations of Li and co-workers (Fig. 2).8 Inter- was consistent with the observed 1H NMR spectrum. The NMR
estingly, the presence of a phenyl substituent in proximity to spectrum displays a virtual triplet at 1.24 ppm and two multi-
the cobalt in 2 also creates an alternative cyclometallation plets at −0.13 and −0.56 ppm, respectively, with an integration
route for the reaction. Given access to the same five-coordinate ratio of 18 : 3 : 3.
intermediate proposed for reductive elimination, the close
contact of the ortho C–H bond and the ability to extrude
methane from
a cobalt–methyl ligand, cyclometallation
becomes a highly favorable process. The sequence of reactions
that eliminate methane, be it C–H bond oxidative addition to a
transient cobalt(V) species or a σ-bond metathesis/protonation
transition structure,9 is not discernable with the observations
in hand.10 Notably, when 2-d5 is heated, the degree of cyclo-
metallation was reduced, comprising only 60% of the cobalt
products. The identity of the cyclometallation product, 2B
(Fig. 2) may be firmly established by solution spectroscopy,
and analogy to a previous report from Beck and co-workers
observed this complex from a C–S bond cleavage reaction.11
ð2Þ
Additional evidence for the identity of 3A came from treat-
ment of the mixture with PMe3 which led to exclusive conver-
1
The H NMR spectrum of complex 2B in benzene-d6 shows a
Co–CH3 signal at −0.74 ppm as a doublet of triplets and two
PMe3 peaks.11 Though the dual reaction pathways from 2 com-
plicated efforts to study C–C bond elimination, the C–H bond
activation reaction observed is nevertheless intriguing given its
analogy to several highly studied reactions on platinum with
relevance to methane and other C–H bond activations.7h,12
In addition to the protonolysis pathways our laboratory has
often employed to obtain congeners of 1, salt elimination reac-
tions have also proven to be a useful synthetic method. During
preliminary investigations, NaSCN was one of several alkali
metal salts which successfully replaced the iodide ligand of 1.
However, NMR spectroscopy revealed that more than one
product was obtained. Analysis of the NMR spectra as well as
the X-ray diffraction data suggested formation of a mono-
nuclear cis,mer-(PMe3)3Co(CH3)2NCS (3) as the major product
and a minor dimeric analogue 3A resulting from PMe3 loss
Fig. 3 Molecular structure of 3 (left) and 3A (right) at 30% probability
ellipsoids. All hydrogen atoms are omitted for clarity. Select bond dis-
tance (Å) and angles (°). Complex 3: Co(1)–C(1) 2.037(1), Co(1)–C(2)
2.017(1), Co(1)–P(1) 2.248(1), Co(1)–P(2) 2.234(1), Co(1)–P(3) 2.229(1),
Co(1)–N(1) 1.970(1), C(12)–N(1) 1.162(2), C(12)–S(1) 1.639(1), C(1)–Co(1)–
P(1) 168.89(4), C(2)–Co(1)–N(1) 177.24(5), P(2)–Co(1)–P(3) 165.18(2),
Co(1)–N(1)–C(12) 168.2(1), N(1)–C(12)–S(1) 179.2(1). Complex 3A: Co(1)–
C(1) 1.997(4), Co(1)–C(2) 2.019(3), Co(1)–P(1) 2.216(1), Co(1)–P(2)
2.221(1), Co(1)–N(1) 1.952(3), Co(1)–S(1a) 2.416(1), C(9)–N(1) 1.163(4),
C(9)–S(1) 1.647(4), C(1)–Co(1)–N(1) 175.9(1), C(2)–Co(1)–S(1a) 179.77(9),
P(1)–Co(1)–P(2) 171.01(4), Co(1)–N(1)–C(9) 164.6(2), N(1)–C(9)–S(1)
176.8(3), C(9)–S(1)–Co(1a) 102.9(1).
14698 | Dalton Trans., 2014, 43, 14696–14700
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
sion to 3. Notably, 3A did not reappear following removal of
the free PMe3 even at elevated temperature. This suggested 3A
Acknowledgements
was created by a deficiency of PMe3 during the synthesis. We gratefully acknowledge funding by the National Science
Indeed, in situ NMR experiments confirmed the formation of Foundation (CHE-1350047) and the American Chemical
small amounts of SPMe3 during the reaction (vide infra). The Society Petroleum Research Fund (52066-DNI3).
1H NMR spectrum of 3 in benzene-d6 also displays two distinct
cobalt–methyl resonances at 0.36 and −1.24 ppm. The mole-
cular structure of complex 3 (Fig. 3) also shows comparable
References
bond distances and angles to its congeners.6,4b The Co(1)–N(1)
distance of 1.970(1) Å is slightly longer than a typical Co(III)–
NCS bond, probably due to the strong trans influence of the
methyl ligand.14,15 The bond distances of C(12)–N(1) and
C(12)–S(1) of 1.162(2) and 1.639(1) Å are typical of cobalt iso-
thiocyante species reported in the literature.14
1 (a) P. K. Byers, A. J. Canty, M. Crespo, R. J. Puddephatt and
J. D. Scott, Organometallics, 1988, 7, 1363–1367; (b) W. De
Graaf, J. Boersma, W. J. J. Smeets, A. L. Spek and G. van
Koten, Organometallics, 1989, 8, 2907–2917; (c) G. S. Hill
and R. J. Puddephatt, Organometallics, 1998, 17, 1478–1486;
(d) B. S. Williams and K. I. Goldberg, J. Am. Chem. Soc.,
2001, 123, 2576–2587; (e) V. P. Ananikov, D. G. Musaev and
K. Morokuma, J. Am. Chem. Soc., 2002, 124, 2839–2852;
(f) P. Espinet and A. M. Echavarren, Angew. Chem., Int. Ed.,
2004, 43, 4704–4734; (g) J. Procelewska, A. Zahl, G. Liehr,
R. van Eldik, N. A. Smythe, B. S. Williams and
K. I. Goldberg, Inorg. Chem., 2005, 44, 7732–7742;
(h) S. Gatard, R. Celenligil-Cetin, C. Guo, B. M. Foxman and
O. V. Ozerov, J. Am. Chem. Soc., 2006, 128, 2808–2809;
(i) R. Ghosh, X. Zhang, P. Achord, T. J. Emge, K. Krogh-
Jespersen and A. S. Goldman, J. Am. Chem. Soc., 2007, 129,
853–866; ( j) J. F. Hartwig, Inorg. Chem., 2007, 46, 1936–
1947; (k) A. T. Luedtke and K. I. Goldberg, Inorg. Chem.,
2007, 46, 8496–8498; (l) B. L. Madison, S. B. Thyme,
S. Keene and B. S. Williams, J. Am. Chem. Soc., 2007, 129,
14523–14523; (m) R. Ghosh, T. J. Emge, K. Krogh-Jespersen
and A. S. Goldman, J. Am. Chem. Soc., 2008, 130, 11317–
11327; (n) J. M. Racowski, A. R. Dick and M. S. Sanford,
J. Am. Chem. Soc., 2009, 131, 10974–10983.
With pure complex 3 in hand, its reactivity under thermo-
lysis was also investigated. After 3 h at 50 °C in benzene-d6, a
small amount of black precipitate was observed along with for-
mation of ethane and a new doublet located at 1.02 ppm in
1H NMR spectrum and a singlet at 28.4 ppm in 31P NMR spec-
trum. Continued heating at 50 °C for 72 h brought this reac-
tion to completion. Collection of the volatile materials and
analysis by NMR spectroscopy and GC-MS analysis revealed a
nearly 90% conversion (based on Co) to trimethylphosphine
sulfide, resulting from a rare S-atom transfer from isothiocya-
nate (eqn (3)).16 The non-volatile materials proved to be mostly
insoluble even in halogenated solvent; however, limited quan-
tities of cis,mer-(PMe3)3Co(CH3)2(CN) (4)6a were detected in
1H NMR spectrum, consistent with a net S-atom transfer from
–NCS. While the poor selectivity between C–C bond elimin-
ation and alternative reaction pathways for 3 is not ideal for
further experimental mechanistic study, the S-atom transfer
reaction of the isothiocyanate is one with little precedent and
is possible interest for oxidative sulfur additions.16a,b,d
2 J. P. Collman, L. S. Hegedus, J. R. Norton and R. G. Finke,
Principles and Applications of Organotransition Metal Chem-
istry, University Science Books, Mill Valley, CA, 1987.
3 H. Xu and W. H. Bernskoetter, J. Am. Chem. Soc., 2011, 133,
14956–14959.
4 (a) H.-F. Klein and H. H. Karsch, Chem. Ber., 1975, 108,
956–966; (b) R. Beck and H.-F. Klein, Z. Anorg. Allg. Chem.,
2008, 634, 1971–1974.
ð3Þ
5 A. B. Pangborn, M. A. Giardello, R. H. Grubbs, R. K. Rosen
and F. J. Timmers, Organometallics, 1996, 15, 1518–1520.
6 (a) H. Xu, P. G. Williard and W. H. Bernskoetter, Organo-
metallics, 2012, 31, 1588–1590; (b) H. Xu, P. G. Williard and
W. H. Bernskoetter, Organometallics, 2013, 32, 798–806.
7 (a) M. P. Brown, R. J. Puddephatt, C. E. E. Upton and
S. W. Lavington, J. Chem. Soc., Dalton Trans., 1974, 1613–
1618; (b) M. P. Brown, R. J. Puddephatt and C. E. E. Upton,
J. Chem. Soc., Dalton Trans., 1974, 2457–2465; (c) S. Roy,
R. J. Puddephatt and J. D. Scott, J. Chem. Soc., Dalton
Trans., 1989, 2121–2125; (d) B. A. Markies, A. J. Canty,
J. Boersma and G. van Koten, Organometallics, 1994, 13,
2053–2058; (e) R. van Asselt, E. Rijnberg and C. J. Elsevier,
Organometallics, 1994, 13, 706–720; (f) K. I. Goldberg,
J. Yan and E. M. Breitung, J. Am. Chem. Soc., 1995, 117,
Conclusion
In summary, two cobalt(III) cis,mer-(PMe3)3Co(CH3)2X species
(X = SPh, NCS) were prepared via protonolysis and salt elimin-
ation methods. Each complex showed unique reactivity upon
thermolysis in benzene giving combinations of C–C bond
reductive elimination, arene ortho-C–H bond activation, and
S-atom transfer chemistry. The phenylthiolate species provided
an unusual example of C–H bond cyclometallation from such
a ligand at a first row transition metal. S-atom transfer from
the isothiocyanate conger appears to be a quite rare example
of a metal bound –NCS ligand acting as an efficient S-atom
donor. Such reactivity could be interest in endeavors to apply
first row transition metals to synthetic methods for oxidative
sulfur transfer.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 14696–14700 | 14699

View Article Online
Paper
Dalton Transactions
6889–6896; (g) G. S. Hill and R. J. Puddephatt, Organometal-
(b) V. De Felice, A. De Renzi, A. Panunzi and D. Tesauro,
J. Organomet. Chem., 1995, 488, C13–C14; (c) G. S. Hill,
L. M. Rendina and R. J. Puddephatt, Organometallics, 1995,
14, 4966–4968; (d) S. S. Stahl, J. A. Labinger and
J. E. Bercaw, J. Am. Chem. Soc., 1995, 117, 9371–9372;
(e) A. J. Canty, A. Dedieu, H. Jin, A. Milet and
M. K. Richmond, Organometallics, 1996, 15, 2845–2847;
(f) S. A. O’Reilly, P. S. White and J. L. Templeton, J. Am.
Chem. Soc., 1996, 118, 5684–5689; (g) P. E. M. Siegbahn and
R. H. Crabtree, J. Am. Chem. Soc., 1996, 118, 4442–4450;
(h) S. S. Stahl, J. A. Labinger and J. E. Bercaw, J. Am. Chem.
Soc., 1996, 118, 5961–5976; (i) U. Fekl, A. Zahl and R. van
Eldik, Organometallics, 1999, 18, 4156–4164; ( j) U. Fekl and
K. I. Goldberg, J. Am. Chem. Soc., 2002, 124, 6804–6805;
(k) H. A. Zhong, J. A. Labinger and J. E. Bercaw, J. Am.
Chem. Soc., 2002, 124, 1378–1399; (l) A. F. Heyduk,
J. A. Labinger and J. E. Bercaw, J. Am. Chem. Soc., 2003, 125,
6366–6367; (m) E. Khaskin, P. Y. Zavalij and
A. N. Vedernikov, J. Am. Chem. Soc., 2006, 128, 13054–
13055; (n) J. M. Villalobos, A. J. Hickman and
M. S. Sanford, Organometallics, 2010, 29, 257–262.
lics, 1997, 16, 4522–4524; (h) U. Fekl, A. Zahl and R. van
Eldik, Organometallics, 1999, 18, 4156–4164; (i) G. S. Hill,
G. P. A. Yap and R. J. Puddephatt, Organometallics, 1999,
18, 1408–1418; ( j) K. L. Bartlett, K. I. Goldberg and
W. T. Borden, J. Am. Chem. Soc., 2000, 122, 1456–1465;
(k) D. M. Crumpton and K. I. Goldberg, J. Am. Chem. Soc.,
2000, 122, 962–963; (l) D. M. Crumpton-Bregel and
K. I. Goldberg, J. Am. Chem. Soc., 2003, 125, 9442–9456;
(m) Y. Fu, Z. Li, S. Liang, Q.-X. Guo and L. Liu, Organometal-
lics, 2008, 27, 3736–3742; (n) A. Ariafard, Z. Ejehi,
H. Sadrara, T. Mehrabi, S. Etaati, A. Moradzadeh,
M. Moshtaghi, H. Nosrati, N. J. Brookes and B. F. Yates,
Organometallics, 2011, 30, 422–432.
8 G. Jiao, X. Li, H. Sun and X. Xu, J. Organomet. Chem., 2007,
692, 4251–4258.
9 R. H. Crabtree, The Organometallic Chemistry of the Tran-
sition Metals, John Wiley & Sons, Inc., New Jersey, 2009.
10 (a) S. Murahashi, J. Am. Chem. Soc., 1955, 77, 6403–6404;
(b) H.-F. Klein, M. Helwig, U. Koch, U. Florke and
H.-J. Haupt, Z. Naturforsch., B: J. Chem. Sci., 1993, 48, 778–
784; (c) H.-F. Klein, S. Schneider, M. He, U. Floerke and 13 (a) U. A. Gregory, J. A. J. Jarvis, B. T. Kilbourn and
H.-J. Haupt, Eur. J. Inorg. Chem., 2000, 2295–2301;
(d) A. Wang, H. Sun and X. Li, Organometallics, 2008, 27,
5434–5437; (e) P.-S. Lee, T. Fujita and N. Yoshikai, J. Am.
Chem. Soc., 2011, 133, 17283–17295; (f) N. Yoshikai,
Synlett, 2011, 1047–1051; (g) E. R. King, G. T. Sazama and
P. G. Owston, J. Chem. Soc. A, 1970, 2770–2774;
(b) J.-M. Shi, Z. Liu, Y.-M. Sun, L. Yi and L.-D. Liu, Chem.
Phys., 2006, 325, 237–242; (c) S. Wöhlert, T. Fic,
Z. Tomkowicz, S. G. Ebbinghaus, M. Rams, W. Haase and
C. Näther, Inorg. Chem., 2013, 52, 12947–12957.
T. A. Betley, J. Am. Chem. Soc., 2012, 134, 17858–17861; 14 O. Alnaji, Y. Peres, F. Dahan, M. Dartiguenave and
(h) B. Punji, W. Song, G. A. Shevchenko and L. Ackermann, Y. Dartiguenave, Inorg. Chem., 1986, 25, 1383–1386.
Chem. – Eur. J., 2013, 19, 10605–10610; (i) K. Gao and 15 M. R. Snow and R. F. Boomsma, Acta Crystallogr., Sect. B:
N. Yoshikai, Acc. Chem. Res., 2014, 47, 1208–1219; Struct. Crystallogr. Cryst. Chem., 1972, 28, 1908–1913.
( j) S. P. Semproni, C. C. H. Atienza and P. J. Chirik, Chem. 16 (a) H. Werner, S. Lotz and B. Heiser, J. Organomet. Chem.,
Sci., 2014, 5, 1956–1960; (k) D. Tilly, G. Dayaker and
P. Bachu, Catal. Sci. Technol., 2014, 4, 2756.
11 R. Beck, M. Frey, S. Camadanli and H.-F. Klein, Dalton
Trans., 2008, 4981–4983.
12 (a) N. F. Goldshle, V. V. Eskova, A. E. Shilov and
A. A. Shteinma, Zh. Fiz. Khim., 1972, 46, 1353–1354;
1981, 209, 197–210; (b) H. Werner and B. Juthani, J. Organo-
met. Chem., 1981, 209, 211–218; (c) A. Ibdah,
J. H. Espenson and W. S. Jenks, Inorg. Chem., 2005, 44,
8426–8432; (d) J. P. Donahue, Chem. Rev., 2006, 106, 4747–
4783; (e) Q. X. Dai, H. Seino and Y. Mizobe, Dalton Trans.,
2011, 40, 11822–11830.
14700 | Dalton Trans., 2014, 43, 14696–14700
This journal is © The Royal Society of Chemistry 2014