Nickel-Mediated Stepwise Transformation of CO to Acetaldehyde and Ethanol

Article abstract of DOI:10.1021/acs.organomet.7b00472

The insertion of CO into the Ni-C bond of synthetic Ni(II)-CH₃ cationic complex ([1-CH₃]⁺) affords a nickel-acetyl complex ([1-COCH₃]⁺). Reduction of resultant [1-COCH₃]⁺ by borohydrides produces CH₃CHO, CH₃CH₂OH, and an Ni(0) compound ([1]⁰), which can react with CH₃I to regenerate [1-CH₃]⁺. By conducting deuterium labeling experiments, we have demonstrated that CH₃CHO is the primary product from CH₃CH₂OH in such CO transformation reactions. In the reduction of [1-COCH₃]⁺, the formation of CH₃CHO competes with the loss of CH₄, which leads to a Ni(0)-CO compound ([1-CO]⁰) as a minor product. Our results establish fundamental steps in the exploration of nickel-mediated CO transformation to valuable chemicals.

Full text of DOI:10.1021/acs.organomet.7b00472

Article
pubs.acs.org/Organometallics
Nickel-Mediated Stepwise Transformation of CO to Acetaldehyde
and Ethanol
Ailing Zhang, Sakthi Raje, Jianguo Liu, Xiaoyan Li, Raja Angamuthu, Chen-Ho Tung,†
†
‡
†
†
‡
,
†
and Wenguang Wang*
†
School of Chemistry and Chemical Engineering, Shandong University, 27 South Shanda Road, Jinan 250100, China
‡
Laboratory of Inorganic Synthesis and Bioinspired Catalysis (LISBIC), Department of Chemistry, Indian Institute of Technology
Kanpur, Kanpur 208016, India
*
S Supporting Information
ABSTRACT: The insertion of CO into the Ni−C bond of synthetic
+
Ni(II)−CH cationic complex ([1-CH ] ) affords a nickel−acetyl
3
3
+
+
complex ([1-COCH ] ). Reduction of resultant [1-COCH ] by
3
3
borohydrides produces CH CHO, CH CH OH, and an Ni(0)
3
3
2
0
compound ([1] ), which can react with CH I to regenerate [1-
CH ] . By conducting deuterium labeling experiments, we have
3
+
3
demonstrated that CH CHO is the primary product from
3
CH CH OH in such CO transformation reactions. In the reduction
3
2
+
of [1-COCH ] , the formation of CH CHO competes with the loss
3
3
0
of CH , which leads to a Ni(0)−CO compound ([1-CO] ) as a minor
product. Our results establish fundamental steps in the exploration of
nickel-mediated CO transformation to valuable chemicals.
4
(SDmp)] (dadtEt = CH (CH N(Et)C H S ) ; Dmp = 2,6-
¯
INTRODUCTION
2
2
2
4
2
■
dimesitylphenyl) has been observed to undergo carbonylation
yielding thioacetate ester CH COSDmp and a [Ni(II)Ni(0)]
species, [Ni(dadt )Ni(COD)]. Monomeric Ni(0)-CO or
Transition-metal-mediated CO transformation into valuable
chemicals is of fundamental importance and is interesting
because it utilizes CO as a C1 source to produce organic
carbonyl substrates or to construct C−C bonds. In addition,
it is relevant to many industrial catalytic reactions such as the
Monsanto process for acetic acid synthesis by catalytic
3
Et
13
1
,2
Ni(I)-CO complexes supported by anionic ligands can be
1
4
methylated to yield Ni-COCH species. The complexes
3
tBu
tBu
t
i
¯
15
16
K [(L )Ni(CO)] (L
= [HC(C( Bu)NC H ( Pr) ) ] )
2
2
6 3 2 2
i
¯
1
g
3
and [(PNP)Ni(CO)] (PNP = N[2-P Pr -4-Me-C H ] )
carbonylation of methanol, hydroformylation, and water−
2 6 3 2
4
react with CH I to afford neutral complexes I and II,
respectively (Chart 1). In contrast, the binding of CO to
Ni(II) center in cationic complexes is usually weak and
reversible. In such cases, transmetalation of a methyl group
from organometallic Grignard reagents such as CH MgX to
Ni(II) precursors is the most commonly used method for the
gas shift reactions. In a natural CO dehydrogenase(CODH)/
3
acetyl-CoA synthase (ACS) complex, CO2 is reduced by
CODH to CO, which combines with a methyl group donated
by the corrinoid iron−sulfur protein (CFeSP) and coenzyme A
CoA) to generate acetyl-CoA. ACS is composed of a dinickel
dithiolate cluster, Ni(II)Ni(II), in a ground state. The proximal
nickel center formed by Fe S cluster allows for its reduction to
Ni(I) for CO binding or to Ni(0) for methylation. The
intermediates of Ni(I)-CO or Ni(II)-CH postulated could
result in two alternative mechanistic routes for the C−C bond
formation (eqs 1 and 2).
17
5
(
3
2
f,18
synthesis of nickel−methyl complexes.
Several nickel−
4
4
19
20
21
acetyl complexes (III, IV, and V ) and nickel−acyl
22
intermediate VI are reported to have been formed by the
insertion of CO into the Ni−C bonds of nickel−methyl or
nickel−alkyl complexes. The production of thioacetate has been
3
6
,7
achieved by treatment of [Ni(II)-COCH ] complexes with
3
Ni(I)‐CO + CH + + e → Ni(II)‐COCH3
−
3
(1)
(2)
thiols or thiolates (Chart 1). However, organonickel species
tend to degenerate to elemental nickel and the uncoordinated
protonated ligand.
Ni(II)‐CH + CO → Ni(II)‐COCH
3
3
The reactivity of the synthetic [Ni-COCH ] complexes is
3
Synthetic nickel−acetyl (Ni-COCH ) models are essential to
3
particularly interesting because it not only is relevant to the
biological CO transformation in thioester synthesis but also
provides knowledge that can be used in exploration and
reproduce nickel-mediated CO methylation that the enzymatic
5
d,8
9
10
system does.
heterobimetallic
In this context, monomeric, homo-, or
1
0e,11
synthetic nickel complexes have been
investigated with the aim of reproducing the nickel−acetyl (Ni-
12
COCH ) complexes by methylation of CO. For example, the
Received: June 20, 2017
3
Et
Ni−C bond in trithiolato-dinickel complex [Ni(dadt )Ni(Me)-
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.7b00472
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Chart 1. Examples of Monomeric Nickel−Acetyl Complex
for the Thioacetate Synthesis
Figure 1. Structures of the dications [1]2+ (left) and [1(NCMe)2]2+
(right). Thermal ellipsoids are shown at the 50% probability level, and
hydrogen atoms are omitted for clarity. Selected distances (Å) and
2+
angles (deg): [1] , Ni1−P1 2.196(1), Ni1−P2 2.203(1), Ni1−S1
2
1
.197 (1), Ni1−S2 2.176(1), S1−Ni1−P2 156.83(5), S2−Ni1−P1
2+
50.13(5); [1(NCMe) ] , Ni1−S1 2.4024(9), Ni1−P1 2.4966(8),
2
Ni1−N 2.053(3), P1−Ni1−P1′ 177.86(4).
which features an octahedral geometry. The complex
2
+
[
3
1(NCMe)2] is paramagnetic with a magnetic moment of
development of nickel-based catalysts for manufacturing of
23−25
.01 μ established by the Evans method. This is consistent
B
28
value-added products such as CH CHO or CH CH OH.
3
3
2
with expectations for an uncoupled nickel(II) ion.
In this paper, we describe the production of CH CHO and
3
+
+
2+
+
[(P S )NiH] and [(P S )NiCH ] . The reactivity of [1] or
CH CH OH by reduction of synthetic [Ni-COCH ] cationic
2 2 2 2 3
3
2
3
2+
[
1(NCMe)2] was illustrated by the reaction with pinacolbor-
complexes with borohydride salts (Scheme 1).
ane (HBpin), which results in the formation of cationic
nickel(II) hydride [1-H] (Scheme 2). The H NMR spectrum
+
1
Scheme 1. Reduction of Synthetic Nickel−Acetyl Cationic
¯
Complex by BH Salts
4
Scheme 2. Reactions of [1(NCMe)2]2+ with HBpin and
CH MgBr and Formation of a Nickel−Acetyl Complex
3
RESULTS AND DISCUSSION
■
2
+
2+
[
(P S )Ni] and [(P S )Ni(NCMe) ] . Owing to its soft
2 2 2 2 2
and flexible coordination properties, the phosphine-thioether
ligand has been investigated intensively for group 10 metals
26
+
such as Pd or Pt. In our previous study, we found that the
tetradentate ligand (Ph PC H CH S) (C H ), abbreviated as
of [1-H] in CD CN exhibits a triplet at δ − 13.96 (t, J
=
P
3
P−H
3
1
48.3 Hz) corresponding to the hydride resonance, and the
2
6
4
2
2
2
4
P S , coordinated with iron(II) to form the cationic complex
NMR spectrum exhibits a sharp singlet at δ 28.5. The crystal
2
2
+
+
[
(P S )FeH(CO)] folded in such a way that the hydride and
structure of [1-H] reveals a trigonal-bipyramidal geometry
2
2
27
(Figure S8). The generation of the nickel(II) hydride [1-H]+
CO ligand are in a cis-α disposition. The dicationic complex
2
+
[
Ni(P S )](BF ) ([1] ) was prepared by the straightforward
using a hydroborane such as HBpin has been reported for the
2
2
4 2
tBu
treatment of a solution of P S in THF with a solution of
pincer-type nickel formate complex [( PCP)NiOC(O)H]
2
2
29
Ni(BF ) ·6H O in isopropanol. The molecular structure of
with catecholborane. It is noteworthy that transferring
hydride from typical hydroboranes to the nickel(II) dications
4
2
2
2+
[
1] was established by single-crystal X-ray diffraction, which
+
showed that the Ni(II) center adopts a distorted-tetrahedral
geometry instead of the square-planar geometry common in
four-coordinate nickel(II) complexes (Figure 1). The angle
providing a five-coordinate [Ni(II)-H] cationic complex has
+
not been reported to date, and [1-H] was found to be stable
toward CO or CO gas.
2
∠
P2−Ni1−S1, 156.83(5)°, is comparable to that of 150.13(5)°
The reaction of [[1(NCMe) ](BF ) with CH MgBr in THF
2
4 2
3
observed for ∠P1−Ni1−S2. Interestingly, dissolving [1](BF )
at 0 °C produced [1-CH ]BF , which was isolated in 79% yield
3 4
1 +
4
2
in MeCN led to the formation of an uncommon 20-electron
as a red solid. The H NMR spectrum of [1-CH ] in CD Cl
3 2 2
bis-acetonitrile complex [1(NCMe) ](BF ) , the structure of
displays a triplet at δ −0.04 (t, JP−H = 10.5 Hz, 3H)
2
4 2
B
DOI: 10.1021/acs.organomet.7b00472
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
1
corresponding to Ni(II)-CH . This is consistent with the H
C H SH, but it reacted with NBu BH salts producing
3
2
5
4
4
NMR spectra of related cationic nickel(II)−methyl complex-
CH CHO and releasing CH (Scheme 3). Treatment of a
3 4
1
8e,30
¯
¯
es.
Exchanging the BF counteranion for BPh4 allowed
4
growth of single crystals of [1-CH ]BPh , suitable for X-ray
diffraction. Crystallographic analysis revealed that the nickel(II)
Scheme 3. Formation of Acetaldehyde, Ethanol, and
3
4
+
¯
Methane from the Reaction of [1-COCH ] with BH Salts
3 4
center is coordinated with both the folded P S and the methyl
2
2
ligand with a pseudo-trigonal-bipyramidal geometry (Figure 2).
CD CN solution (1 mL) of [1-COCH ]BPh (18.8 mM) with
3
3
4
1
equiv of NBu BH led to color change from orange to red
4 4
within 5 min with concurrent formation of red precipitate. The
red solid was isolated by filtration and identified as [(P S )Ni]
2
2
0
(
2
[1] , 63% yield) with the phosphorus resonance signal at δ
1.4 in its 31P NMR spectrum. Alternatively, [1] could be
0
prepared by the reaction of P S ligand with [Ni(COD) ] in
2
2
2
31
+
MeCN; as shown by P NMR spectroscopic studies, it is
identical to [1] generated from [1-COCH ]BPh .
The filtrate from the reaction mixture of [1-COCH ] with
Figure 2. Solid-state structures of the cations [1-CH ] (left) and [1-
3
0
+
COCH ] (right). Thermal ellipsoids are shown at the 50% probability
3 4
3
+
level, and hydrogen atoms are omitted for clarity. Selected distances
3
+
(
Å) and angles (deg): [1-CH ] , Ni1−S1 2.253(1), Ni1−S2 2.264(1),
NBu BH was further analyzed by NMR and IR spectroscopy.
The H NMR spectrum exhibits a characteristic quartet at δ
4
4
3
1
Ni1−P1 2.278(1), Ni1−P2 2.178 (1), Ni1−C1 2.042(4), P2−Ni1−S2
1
Ni1−S2 2.278(1), Ni1−P1 2.198(1), Ni1−P2 2.228(1), Ni1−C1
1
+
30.07(5), P2−Ni1−P1 129.71(4); [1-COCH ] , Ni1−S1 2.349(1),
9.71 corresponding to the aldehyde proton of CH CHO (q,
3
3
31
JH−H = 2.8 HZ, Figure 4a). The P NMR spectrum indicated
.922(4), P1−Ni1−P2 153.82(4), O1−C1−Ni1 123.0(3), O1−C1−
the presence of another organonickel product, distinct from
C2 120.1(4), C2−C1−Ni1 116.9(3).
0
31
that of [1] and exhibiting a P signal at δ 30. The molecular
structure of this new nickel(0) compound [(P S )Ni(CO)], [1-
2
2
CO]0 (νCO = 1907 cm ), was characterized crystallo-
graphically. [1-CO] is a four-coordinate neutral compound
−1
The Ni−C distance 2.042(4) Å is very close to 2.02(2) Å which
+
0
was observed in [(NP )Ni-CH ] (NP3 = N-
3
3
1
+
8e
(
[
CH CH PPh ) )
and slightly longer than 1.94(2) Å in
with an tetrahedral geometry (Figure 3). One of the S atoms is
2
2
2 3
iPr
iPr
3
iPr
19b
(NS3 )Ni-CH ] (NS = N(CH CH S ) ) and 1.92 (2)
3
2
2
3
3
0
Å in [(CH SiMe )(PMe ) Ni-CH ]BF .
2
3
3 2
3
4
Insertion of CO into Ni−C Bond. [1-CH ]BPh reacts
3
4
readily with CO, affording the Ni(II)−acetyl complex [1-
COCH ]BPh in 86% yield. Exposure of a CH Cl solution of
3
4
2
2
+
[
1-CH ] to CO gas at atmospheric pressure resulted in a rapid
3
color change from red to orange. The IR spectrum of the
reaction mixture displays a ν band at 1663 cm for Ni(II)-
COCH3. The acyl group was also identified in the C NMR
−1
CO
2
0
13
spectrum, which features a characteristic Ni-COCH resonance
3
15a,31
at δ 242.6 (t, JP−C = 15 Hz),
while the Ni-CH resonance
3
+
1
was observed at δ 4.1 (t, JP−C = 17.2 Hz) for [1-CH ] . The H
3
NMR spectrum displayed a distinct signal for Ni-COCH at δ
3
1.74.
The structure of [1-COCH ]+ was confirmed by X-ray
3
0
Figure 3. Solid-state structure of tetrahedral [1-CO] . Selected
crystallographic analysis (Figure 2). The overall stereo-
+
+
distances (Å) and angles (deg): Ni1−S1 2.2456(8), Ni1−P1
chemistry of [1-COCH ] is similar to that of [1-CH ] , and
3
3
2
.1947(8), Ni1−P2 2.2005(8), Ni1−C1 1.750(2), O1−C1 1.154(2),
the acyl group was unambiguously coordinated with the metal
center. Carbonylation of the Ni-CH3 bond decreased the
distortion of the trigonal-bipyramidal geometry, and this was
reflected in the increase of ∠P2−Ni1−P1 from 129.71(4)° in
P1−Ni1−S1 95.59(3), P1−Ni1−P2 121.06(3), P2−Ni1−S1
102.98(3), C1−Ni1−S1 117.32(7), C1−Ni1−P1 117.31(7), C1−
Ni1−P2 102.46(7), O1−C1−Ni1 173.4(2).
+
+
[
1-CH ] to 153.82(4)° in [1-COCH ] . The Ni−C bond
3
3
+
length in [1-COCH ] is 1.922(4) Å, which is 0.12 Å shorter
not coordinated to the nickel(0) center, revealing the
coordination versatility of P S . We have also found that the
3
+
than the Ni−C bond length in [1-CH ] . The angles ∠Ni1−
3
2 2
+
+
¯
C1−C2 and ∠Ni1−C1−O1 in [1-COCH ] are 116.9(3) and
reaction of [1-COCH ] with BH salts releases CH (yield:
3
3 4 4
1
23.0(3)°, respectively, compared to ∠Ni−C−CH = 118(1)°
28.6 ± 4%), which was identified and quantified by GC
3
and ∠Ni−C−O = 123 (1)° for III.
analysis.
−
2e,19
Reduction of Nickel−Acetyl Complex by BH Salts. In
In the cases of nickel-mediated thioester formation,
the
4
contrast to the previously discussed Ni(II)−acetyl complexes,
reaction of nickel−acetyl complexes with thiols was proposed
to occur via nucleophilic attack of the thiolate on the acetyl
+
[
1-COCH ] failed to react with thiols such as C H SH and
3
6
5
C
DOI: 10.1021/acs.organomet.7b00472
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
3
2
+
¯
ligand. It has also been reported that exposure of (bpy)Ni-
CH )(SR) to CO atmosphere resulted in reductive elimi-
For the reduction of [1-COCH ] by BH salts, the yield of
3 4
0
(
[1-CO] was 32%, which is comparable to the yield of 28.6 ±
4% for CH . The formation of [1-CO] should be along with
the release of CH . Surprisingly, the C−C bond of acetyl
moiety undergoes cleavage in the reduction of [1-COCH ] by
3
22
0
nation of CH C(O)SR. In our case, the formation of two
types of the carbonyl products, CH CHO and [1-CO] indicate
the existence of two different pathways (Scheme 4). [1-
3
4
0
3
4
+
3
¯
0
0
BH4 salts. Although both [1] and [1-CO] are nickel(0)
0
Scheme 4. Nickel-Mediated Stepwise Transformation of CO
to CH CHO and C H OH
species, their reactivities differ significantly. For example, [1]
+
+
reacts with CD I affording [1-CD ] , from which [1-COCD ]
3
2
5
3
3
3
is formed through CO insertion. However, there is no reaction
observed between [1-CO] and CH I. The inactivity of [1-
CO] is due to Ni(0) center ceding electron density to the
0
3
0
carbonyl group through back-donation.
CONCLUSIONS
■
A nickel−acetyl complex has been successfully obtained by the
insertion of CO into the Ni−C bond of a nickel−methyl
cationic complex. Reducing the resultant nickel−acetyl complex
with borohydrides produces CH CHO, CH CH OH, and a
3
3
2
0
Ni(0) compound ([1] ). The formation of CH CHO competes
3
+
with the loss of CH which leads to Ni(0)-CO compound ([1-
CO] ) rather than [1] as a minor product. Notably,
COCH ] could undergo nucleophilic attack by the hydride
4
3
0
0
¯
ligand of BH forming a hydrido−acyl intermediate, [Ni(H)-
4
regeneration of [1-CH ]I could be achieved through the
(
COCH )]. The reductive elimination of CH CHO from the
3
3
3
0
0
22
reaction of [1] with CH I.
Hydrido−acyl species can generate [1] . The production of
CD CHO for [1-COCD ] with NBu BH was verified by H
NMR and H NMR spectra with the signals at δ 9.72 (br) for
CHO and δ 2.05 for CD group (Figures 4b and S28). When
3
+
1
The reductive elimination of acetyl iodide (CH COI) from
3
3
3
4
4
−
2
six-coordinate decarbonyl complex [Rh(COCH )(CO) I ]
3
2 3
−
regenerating [Rh(CO)2I2] catalyst, is one of elementary
3
33,34
steps in acetic acid synthesis.
By contrast, [1-COCH ]I is
3
too stable to undergo CH COI reductive elimination. However,
3
our results illustrate the important steps in the exploration of
nickel-based catalysts for reductive transformation of CO to
useful commodity chemicals.
EXPERIMENTAL SECTION
Materials and Methods. All manipulations were conducted under
N atmosphere using standard Schlenk techniques or in a glovebox,
■
2
unless otherwise stated. All reagents were purchased from Sigma-
Aldrich and used as received. (Ph PC H CH S) (C H ) was prepared
2
6
4
2
2
2
4
2
7
according to our previous methods. Et O, pentane, THF (dried by
2
distillation over sodium), MeCN (dried by distillation over CaH ), and
2
CH Cl for general use were of analytical (AR) grade and stored under
2
2
N2 atmosphere. CD Cl2 and CD CN were dried using activated
2
3
molecular sieves (4 Å) and degassed with three thaw−freeze cycles.
C D and THF-d were dried over CaH and purified by vacuum
6
6
8
2
transfer. NMR spectra were recorded on Bruker Avance 500, Avance
1
13
4
00, Avance 300 spectrometers in J. Young NMR tubes. H, C, and
3
1
P NMR chemical shifts are referenced to the proton signal of the
deuterated solvent and external H PO , respectively. Single-crystal X-
3
4
¯
1
ray diffraction data were collected using a Bruker SMART APEX II
diffractometer with a CCD area detector (graphite monochromatic
Mo Kα radiation) at 173 K. Infrared spectra were recorded on a
PerkinElmer FT-IR Spectrometer Spectrum Two and reported for the
Figure 4. Reduction of nickel−acetyl complexes by BH salts. H
4
+
NMR spectra: (a) CH CHO for the [1-COCH ] /NBu BH system
and (b) CD CHO for the [1-COCD ]/NBu BH system in CD CN.
H NMR spectra: (c) CD CH OH from [1-COCD ] with excess
NBu BH , (d) CH CD OD from [1-COCH ] with excess NaBD ,
and (e) CD CD OD from [1-COCD ] with excess NaBD in MeCN.
Conditions: 2 μL of H O was added to c, and D O to d and e to
3
3
4
4
3
3
4
4
3
2
+
3
2
3
+
νCO region only. Cyclic voltammetry was performed under N at room
2
4
4
3
2
3
4
temperature using a CHI 760e electrochemical workstation (Shanghai
Chen Hua Instrument Co., Ltd.) with a glassy carbon working
electrode, Pt wire counter electrode, and the pseudo-reference
3
2
3
4
2
2
quench the reactions prior to NMR analysis.
electrode Ag wire. CH was identified by a Techcomp 7890 II gas
4
chromatograph (GC) equipped with a 5 Å molecular sieve column
using argon as carrier gas and a thermal conductivity detector.
2
+
[
(P S )Ni](BF ) ([1] ). To a solution of Ni(BF ) ·6H O (0.15 g,
2 2 4 2 4 2 2
excess of NaBH was used, CH CH OH was obtained as the
4
3
2
2
0.44 mmol) in 5.0 mL of 2-propanol was added the solution of
Ph PC H CH S) (C H ) (0.28 g, 0.44 mmol) in 10.0 mL of THF
over the course of 5 min. The mixture was stirred at room temperature
for 2.0 h and gave red precipitates. The product was isolated by
filtration and rinsed with 3.0 mL of 2-propanol followed by 2.0 mL of
THF, then dried under vacuum. Yield: 0.23 g (74%). Single crystals
suitable for X-ray diffraction were obtained by layering pentane into
major product. Furthermore, the H NMR spectra observed for
(
+
+
2
6
4
2
2
2
4
the systems of [1-COCD ] /NBu BH , [1-COCH ] /NaBD ,
3
4
4
3
4
+
and [1-COCD ] /NaBD demonstrate the production of
3
4
CD CH OH, CH CD OD, and CD CD OD (Figure 4, spectra
3
2
3
2
3
2
c−e). These results suggest the pathway of reductive
elimination of CH CHO is possible.
3
D
DOI: 10.1021/acs.organomet.7b00472
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Organometallics
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1
CH Cl at −30 °C. H NMR (500 MHz, CD Cl ): δ 7.56−7.17 (m,
orange. By layering the resultant solution with hexane, orange
2
2
2
2
1
2
8 × ArH), 4.28−3.95 (br, 4H, SCH Ph), 3.30−2.91 (br, 4H,
SCH CH S). P NMR (202 MHz, CD Cl ): δ 32.62 (br), 17.04 (br).
microcrystals were obtained at −30 °C. Yield: 0.22 g (86%). H
2
31
NMR (500 MHz, CD Cl ) δ 7.64−6.86 (m, 48 × ArH), 3.82 (br, 4H,
2
2
2
2
2
2
3
1
Anal. Calcd for C H NiP S B F : C, 54.90; H, 4.15. Found: C, 54.98;
SCH Ph), 2.07 (br, 4H, SCH CH S), 1.74 (s, 3H, Ni-COCH ).
NMR (202 MHz, CD Cl ) δ 14.91 (s), 10.75 (s). C NMR (126
P
40
36
2
2
2
8
2
2
2
3
2
+
13
H, 4.50. ESI-MS: calcd for [1] : 350.0544; found: 350.0533.
2 2
2
+
[
(P S )Ni(MeCN) ](BF ) ([1(NCMe) ] ). By dissolving 175 mg of
MHz, CD Cl ): δ 242.63 (t, J
= 15.1 Hz, Ni-COCH ). Anal. Calcd
P−C 3
2
2
2
4 2
2
2
2
[
1](BF ) in 10 mL of MeCN, a yellow solution was obtained. The
for C H BNiOP S : C, 74.52; H, 5.59. Found: C, 74.77; H, 5.96.
4
2
66 59 2 2
+
product was precipitated by the addition of 10 mL of Et O. The yellow
solid was collected by filtration. Yield: 0.18 g (92%). Crystals were
grown via slow diffusion of Et O into a MeCN solution. μ = 3.01 μB.
ESI-MS: calcd for [1-COCH ] : 743.1271; found: 743.1251. FT-IR
3
2
−1
(CH Cl ): ν = 1663 cm .
2 2 CO
+
[(P S )Ni-COCD ]BPh ([1-COCD ] ). Complex [1-COCD ]BPh
4
2
eff
2
2
3
4
3
3
Anal. Calcd for C H N NiP S B F : C, 55.21; H, 4.42; N, 2.93.
was prepared by using [1-CD
3
]BPh
4
following the same procedure
P NMR (202 MHz, CD Cl ) δ 14.82
Cl ): δ 1.69 (br, Ni-COCD
): δ 242.95 (t, JP−C = 15.1 Hz, Ni-COCD
44
42
2
2 2 2 8
2+
31
Found: C, 55.31; H, 4.70; N, 2.75. ESI-MS: calcd for ([1] -2MeCN):
50.0544; found: 350.0545.
as that for [1-COCH
3
]BPh
(s), 10.72 (s). H NMR (CH
(126 MHz, CD Cl
(CH Cl ): νCO = 1660 cm . Anal. Calcd for C66
74.31; H, 5.86. Found: C, 74.52; H, 6.13. ESI-MS: calcd for [1-
4
.
2
2
2
2
13
3
2
3
). C NMR
). FT-IR
BNiOP : C,
+
[
(P S )NiH]BF ([1-H] ). Treatment the CH Cl solution of
2
2
3
2
2
4
2
2
−
1
[
0
1](BF ) (0.15 g, 0.21 mmol) with excess pinacolborane (HBpin,
.1 mL) resulted in the color of solution changing from red to orange.
2
2
H
D
56
3
S
2 2
4
2
+
The solvent was removed under vacuum. The residue, an orange solid,
was filtered and rinsed with 2.0 mL of benzene followed by 3 × 5.0 mL
of diethyl ether and dried under vacuum. Yield: 0.13 g (86%). Single
COCD
Reduction of [1-COCH
experiment, treatment of a solution of [1-COCH
μmol) in CD CN (2 mL) with 7.3 mg (28 μmol) of NBu
3
] : 746.1459; found: 746.1437.
]BPh by NBu
3
BH
4 4
Salts. In a typical
]BPh (30 mg, 28
BH
4
4
3
4
crystals suitable for X-ray diffraction were obtained by layering pentane
3
4
1
into DCM at −30 °C. H NMR (300 MHz, CD CN): δ 7.78−6.82
resulted in a color change from orange to red within 5 min and the
3
(
(
4
m, 28 × ArH), 4.02 (d, 2H, SCH Ph) 3.15 (d, 2H, SCH Ph), 2.72
formation of red precipitate. The red solid was isolated by filtration
2
2
and identified as (P
filtrate was further analyzed by NMR and IR spectra. The production
of CH CHO was signaled by the characteristic peak of CH CHO at δ
9.71 (q, JH−H = 2.8 HZ). The same procedure was used for analysis of
S
)Ni by 31P NMR spectroscopic analysis. The
2 2
m, 2H, SCH CH S), 0.47 (m, 2H, SCH CH S), −13.96 (t, J
=
2
2
2
2
P−H
3
1
8.3 Hz, Ni-H). P NMR (121 MHz, CD CN): δ 28.5 (s). Anal.
3
Calcd for C H BF NiP S : C, 60.87; H, 4.73. Found: C, 60.99; H,
3
3
4
0
37
4
2 2
+
4
.92. ESI-MS: calcd for [1-H] : 701.1165; found: 701.1156.
P S )Ni ([1] ). A 50 mL Schlenk flask was charged with
0
1
2
(
CD
3
CHO ( H NMR: δ 9.72; H NMR: δ 2.05, CD
3
), CD
OD ( H NMR: δ 3.52, CD2, δ 2.60,
OD ( H NMR: δ 3.50, CD2, δ 2.60, OD, δ 1.07,
2
CH OH
3 2
2
2
2
2
(
(
Ph PC H CH S) (C H ) (0.47 g, 0.73 mmol) and Ni(COD)
0.20 g, 0.73 mmol) in a nitrogen box. Addition of 30 mL of
( H NMR: δ 1.08, CD
OD), and CD CD
CD ).
Methane Identification by GC. A Pyrex tube was filled with [1-
COCH ]BPh (20 mg, 18.8 μmol) and NBu BH (4.8 mg, 18.8 μmol)
in the glovebox. The tube was sealed with a rubber plug and sealed
with wax. Subsequently, 2 mL of CH CN was injected into the tube.
After stirring for 10 min, H (50 μL) was injected into the tube as an
3 3 2
), CH CD
2
6
4
2
2
2
4
2
2
3
CH CN with vigorous stirring (10 min) gave a dark red solid, which
3
3
was filtered, washed twice with 2 mL of anhydrous diethyl ether, and
1
dried under vacuum to yield 0.41 g (80%) of (P S )Ni. H NMR (500
3
4
4
4
2
2
MHz, C D ): δ 7.94−6.78 (m, 28 × ArH), 3.24 (d, 2H, SCH Ph), 3.06
6
6
2
(
d, 2H, SCH Ph), 2.20 (s, 2H, SCH CH S), 2.07 (s, 2H, SCH CH S).
3
2
2
2
2
2
3
1
P NMR (202 MHz, C D ) δ 21.36 (s). Calcd for C H NiP S : C,
2
6
6
40 36
2 2
internal standard. Next, 120 μL of the gas in the headspace was
sampled by a Hamilton (1750 SL) gas-tight microliter syringe and
then analyzed by a Techcomp 7890 II gas chromatograph (GC), which
is equipped with a 5 Å molecular sieve column using argon as carrier
6
8.49; H, 5.17. Found: C, 68.81; H, 5.41.
+
[
(P S )NiCH ]BPh ([1-CH ] ). Method A. To a slurry of 0.45 g (0.51
2 2 3 4 3
mmol) of [1](BF ) in 50 mL of THF at −78 °C was added dropwise
4
2
0.6 mL (0.6 mmol) of a 1 M solution of CH MgBr in THF. The dark
3
gas and a thermal conductivity detector. The retention time of CH4
red mixture was allowed to warm to room temperature upon stirring,
and 210 mg of NaBPh was added. The solvent was removed under
vacuum, and product was extracted into 5 mL of CH Cl . The extract
produced was compared to that of the standard gas. The amount of
4
3
5
CH was calculated according to the published methods.
(
4
2
2
0
P S )Ni(CO) ([1-CO] ). To a solution of [1-COCH ]BPh (0.19 g,
2 2 3 4
was filtrated through Celite and diluted with 30 mL of hexane to
precipitate a red powder. The resulting powder was recrystallized by
layering a CH Cl solution with hexane at −30 °C. Yield: 0.42 g
0
.18 mmol) in 15 mL of MeCN was added 46 mg of NBu BH (0.18
4 4
mmol). The mixture was stirred for 5 min, during which time the
solution color turned from orange to red with the formation of red
2
2
1
(
3
79%). H NMR (500 MHz, CD Cl ): δ 7.56−6.81 (m, 48 × ArH),
2
2
precipitate. The red solid, (P S )Ni, was isolated by filtration (Yield:
.65 (br, 2H, SCH Ph), 3.35 (d, 2H, SCH Ph), 2.53 (br, 2H,
2 2
2
2
7
9 mg, 63%). The filtrate was dried under vacuum. The residue was
extracted by anhydrous diethyl ether, and the extracts was stored at
30 °C overnight affording (P S )Ni(CO) as micro yellow crystals.
SCH CH S), 1.40 (br, 2H, SCH CH S), −0.04 (t, J = 10.5 Hz, 3H,
2
2
2
2
P−H
31
13
Ni−CH ). P NMR (121 MHz, CD Cl ): δ 12.45 (s). C NMR (126
3
2
2
−
MHz, CD Cl ): δ 4.12 (t, J
= 17.2 Hz, Ni-CH ). Anal. Calcd for
2 2
2
2
P−C
3
1
Yield: 42 mg, 32%. H NMR (500 MHz, CD CN): δ 7.59−6.86 (m,
C H BNiP S : C, 75.38; H, 5.74. Found: C, 75.68; H, 5.93. ESI-MS:
calcd for [1-CH ] : 715.1322; found: 715.1307.
3
65
59
2 2
+
28 × ArH), 4.09 (br, 2H, SCH Ph), 3.73 (br, 2H, SCH Ph), 2.32(br,
2 2
31
3
2
H, SCH CH S), 2.18 (d, 2H, SCH CH S). P NMR (202 MHz,
2 2 2 2
Method B. To a solution of (P S )Ni (0.27 g, 0.39 mmol) in
2
2
CD CN): δ 30.01 (s). Anal. Calcd for C H NiP S O: C, 67.51; H,
toluene was added CH I (26 μL, 0.42 mmol). After the reaction
solution stirred for 30 min, solvent was removed under vacuum. The
residue was redissolved in CH Cl , which was then treated with a
3
41 36
2 2
3
−1
4
.97. Found: C, 67.62; H, 5.24. FT-IR (CH CN): ν = 1907 cm .
3 CO
2
2
solution of 0.16 g of NaBPh (0.47 mmol) in 10 mL of THF. The
solvent was removed under vacuum, and product was extracted into 5
ASSOCIATED CONTENT
Supporting Information
4
■
*
S
mL of CH Cl . The extract was filtrated through Celite. Hexane (15
2
2
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.7b00472.
mL) was layered on the top of the red solution, which gave red crystals
at −30 °C overnight. Yield: 0.34 g (85%).
+
[
(P S )NiCD ]BPh ([1-CD ] ). Complex [1-CD ]BPh was prepared
2
2
3
4
3
3
4
31
by using CD I and (P S )Ni following method B for [1-CH ]BPh .
P
3
2
2
3
4
1
31
2
X-ray crystallography and NMR ( H, P) spectra (PDF)
NMR (121 MHz, CD Cl ): δ 12.94 (s). H NMR (CH Cl ): δ −0.09
2
2
2
2
(
br, Ni−CD ). Anal. Calcd for C H D BNiP S : C, 75.16; H, 6.02.
3
65 56
3
2 2
Accession Codes
+
Found: C, 75.38; H, 6.37. ESI-MS: calcd for [1-CD ] : 718.1510;
3
CCDC 1548492−1548497 contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge via www.ccdc.cam.ac.uk/data_request/cif, or by email-
ing data_request@ccdc.cam.ac.uk, or by contacting The
found: 718.1492.
+
[
(P S )Ni-COCH ]BPh ([1-COCH ] ). CO (1 atm) gas was bubbled
2
2
3
4
3
through a solution of [1-CH ]BPh (0.25 g, 0.24 mmol) in 30 mL of
3
4
CH Cl . The color of the solution immediately turned from red to
2
2
E
DOI: 10.1021/acs.organomet.7b00472
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
Ragsdale, S. W.; Rauchfuss, T. B.; Reek, J. N. H.; Seefeldt, L. C.;
Thauer, R. K.; Waldrop, G. L. Chem. Rev. 2013, 113, 6621−6658.
(b) Warner, D. S.; Limberg, C.; Oldenburg, F. J.; Braun, B. Dalton
Trans. 2015, 44, 18378−18385. (c) Hegg, E. L. Acc. Chem. Res. 2004,
7, 775−783. (d) Webster, C. E.; Darensbourg, M. Y.; Lindahl, P. A.;
Hall, M. B. J. Am. Chem. Soc. 2004, 126, 3410−3411.
7) Can, M.; Giles, L. J.; Ragsdale, S. W.; Sarangi, R. Biochemistry
2017, 56, 1248−1260.
(8) (a) Denny, J. A.; Darensbourg, M. Y. Chem. Rev. 2015, 115,
AUTHOR INFORMATION
Corresponding Author
E-mail: wwg@sdu.edu.cn.
ORCID
Raja Angamuthu: 0000-0002-5152-0837
Chen-Ho Tung: 0000-0001-9999-9755
Wenguang Wang: 0000-0002-4108-7865
■
3
*
(
5
248−5273. (b) Sellmann, D.; Hau
Am. Chem. Soc. 1996, 118, 5368−5374.
9) (a) Harrop, T. C.; Olmstead, M. M.; Mascharak, P. K. J. Am.
̈
ssinger, D.; Knoch, F.; Moll, M. J.
(
Notes
Chem. Soc. 2004, 126, 14714−14715. (b) Mathrubootham, V.;
Thomas, J.; Staples, R.; McCraken, J.; Shearer, J.; Hegg, E. L. Inorg.
Chem. 2010, 49, 5393−5406. (c) Hatlevik, O.; Blanksma, M. C.;
Mathrubootham, V.; Arif, A. M.; Hegg, E. L. JBIC, J. Biol. Inorg. Chem.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
2
(
4
004, 9, 238−246.
10) (a) Krishnan, R.; Riordan, C. G. J. Am. Chem. Soc. 2004, 126,
484−4485. (b) Dougherty, W. G.; Rangan, K.; O’Hagan, M. J.; Yap,
G. P. A.; Riordan, C. G. J. Am. Chem. Soc. 2008, 130, 13510−13511.
c) Harrop, T. C.; Olmstead, M. M.; Mascharak, P. K. Chem. Commun.
We gratefully acknowledge the financial support from the “1000
Youth Talents Plan”, the Natural Science Foundation of China
and Shandong Province (21402107, 91427303, and
ZR2014M011). We also thank Prof. Di Sun for assistance
with the X-ray crystallography. S.R. acknowledges the CSIR,
India, for senior research fellowship. R.A. thanks the IIT
Kanpur for funding.
(
2
004, 1744−1745. (d) Harrop, T. C.; Olmstead, M. M.; Mascharak, P.
K. Inorg. Chem. 2006, 45, 3424−3436. (e) Rao, P. V.; Bhaduri, S.;
Jiang, J.; Holm, R. H. Inorg. Chem. 2004, 43, 5833−5849.
(
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Organometallics XXXX, XXX, XXX−XXX

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DOI: 10.1021/acs.organomet.7b00472
Organometallics XXXX, XXX, XXX−XXX