Reactivity of mer-hydrido(2-mercaptobenzoyl)tris(trimethylphosphine) cobalt(iii) complex

Article abstract of DOI:10.1039/c3dt52519h

The reactivity of mer-hydrido(2-mercaptobenzoyl)tris(trimethylphosphine) cobalt(iii) complex 1 was intensively studied. A series of sulfur-coordinated organocobalt complexes (2-8) were obtained through the reactions of 1 with RX (RX = HCl, C₂H₅Br and CH₃I), 2-(diphenylphosphanyl)phenol, 2-(diphenylphosphino)benzenethiol, and CO. The reaction of complex 1 with ethynyltrimethylsilane under 1 bar of CO afforded a penta-coordinate cobalt(i) complex 11via insertion reaction of CC bond of ethynyltrimethylsilane into Co-H bond and subsequent C,C-coupling reaction (reductive elimination). The formation mechanism of 11 was proposed and partly-experimentally verified. As an intermediate, the tetra-coordinate cobalt(i) complex 13 was isolated through the reaction of complex 1 with ethynyltrimethylsilane in the absence of CO. The crystal structures of complexes 2-4, 8 and 11 were determined by X-ray diffraction.

Full text of DOI:10.1039/c3dt52519h

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Reactivity of mer-hydrido(2-mercaptobenzoyl)-
tris(trimethylphosphine)cobalt(III) complex†
Cite this: Dalton Trans., 2014, 43,
4059
Qingfen Niu, Hongjian Sun, Lin Wang, Qingping Hu* and Xiaoyan Li*
The reactivity of mer-hydrido(2-mercaptobenzoyl)tris(trimethylphosphine)cobalt(III) complex
1 was
intensively studied. A series of sulfur-coordinated organocobalt complexes (2–8) were obtained through
the reactions of 1 with RX (RX = HCl, C2H5Br and CH3I), 2-(diphenylphosphanyl)phenol, 2-(diphenyl-
phosphino)benzenethiol, and CO. The reaction of complex 1 with ethynyltrimethylsilane under 1 bar of
CO afforded a penta-coordinate cobalt(I) complex 11 via insertion reaction of CuC bond of ethynyl-
trimethylsilane into Co–H bond and subsequent C,C-coupling reaction (reductive elimination). The
formation mechanism of 11 was proposed and partly-experimentally verified. As an intermediate, the
tetra-coordinate cobalt(I) complex 13 was isolated through the reaction of complex 1 with ethynyl-
trimethylsilane in the absence of CO. The crystal structures of complexes 2–4, 8 and 11 were determined
by X-ray diffraction.
Received 13th September 2013,
Accepted 25th November 2013
DOI: 10.1039/c3dt52519h
www.rsc.org/dalton
an excellent catalyst for hydrosilylation of aldehydes and
ketones under mild condition.11
Introduction
The chemistry of thiosalicylaldehydes through the replacement
of an oxygen atom (hard base) in salicylaldehydes by a sulfur
atom (soft base) attracts considerable attention from an
increasing number of researchers. The sulfur atom of thio-
salicylaldehydes can easily coordinate soft acid, such as a low-
valent metal center Co(I), to form stable complexes.1–10 Thio-
salicylaldehydes with two functional groups as pre-chelate
ligands are especially interesting because they are able to
form [C,S]- or [O,S]-chelate complexes or to bridge transition
metals affording multinuclear complexes or clusters. Until
now the research on the chemistry of thiosalicylaldehydes is
limited because it is not easy to prepare the derivatives of
thiosalicylaldehydes. Finally, the unpleasant odor of sulfur-
containing compounds is another reason for this slow
development.
ð1Þ
As a continuation to study the properties of mer-hydrido-
(2-mercaptobenzoyl)tris(trimethylphosphine)cobalt(III) complex
1, the reactivity of complex 1 was intensively studied and
a series of novel sulfur-containing organocobalt complexes
supported by trimethylphosphine ligands were successfully
synthesized.
Experimental
General procedures and materials
Recently we reported the synthesis of sulfur-coordinated
acyl(hydrido)cobalt(III) complex 1 by reaction of thiosalicylalde-
hyde with CoMe(PMe3)4 (eqn (1)). Complex 1 was found to be
All reactions were carried out under an atmosphere of nitrogen
using standard Schlenk techniques. This standard vacuum
technique was used in manipulations of volatile and air-sensi-
tive materials. All the solvents were distilled from Na/benzo-
phenone under nitrogen. Co(PMe3)4Me was prepared from the
literature method.12 Thiosalicylaldehyde was synthesized by
our modified procedure.13 All other chemicals were purchased
from Aldrich or Acros and used as received without further
purification. Infrared spectra, as obtained from Nujol mulls
between KBr disks, were performed within the 4000–400 cm−1
region on a Bruker ALPHA FT-IR Spectrometer. 1H, 13C and
31P NMR spectra (300, 75 and 121 MHz, respectively) were
School of Chemistry and Chemical Engineering, Key Laboratory of Special Functional
Aggregated Materials, Ministry of Education, Shandong University, Shanda Nanlu 27,
250199 Jinan, PR China. E-mail: huqingping@sdu.edu.cn, xli63@sdu.edu.cn;
Fax: +86 531 88361350
†CCDC 910929, 910930, 910932, 910935 and 910939. For crystallographic data
in CIF or other electronic format see DOI: 10.1039/c3dt52519h
This journal is © The Royal Society of Chemistry 2014
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recorded on a Bruker Avance 300 spectrometer with C6D6 as (t, 3J(HH) = 6.0 Hz, 1H, Ar-H), 7.56 (d, 3J(HH) = 6.0 Hz, 1H,
3
the solvent without internal reference at room temperature. Ar-H), 7.75 (d, J(HH) = 6.0 Hz, 1H, Ar-H); 31P NMR (121 MHz,
13C and 31P NMR resonances were obtained with broad band C6D6, 297 K, ppm): δ 1.8 (br s, 1P, PCH3), −14.7 (br s, 2P,
proton decoupling. Elemental analyses were carried out on PCH3). Anal. Calc. for C16H31CoIOP3S (550.24 g mol−1):
Elementar Vario ELIII. Melting points were measured in C, 34.92; H, 5.68. Found: C, 35.11; H, 5.51.
capillaries sealed under argon and are uncorrected. X-ray
crystallography was performed with a Bruker Smart 1000 of Et2O was combined with 2-(diphenylphosphino)phenol
diffractometer. (0.35 g, 1.30 mmol) in 30 mL of Et2O at −80 °C. The reaction
Synthesis of 5. A sample of 1 (0.55 g, 1.30 mmol) in 30 mL
Synthesis of 2. A sample of 1 (0.70 g, 1.65 mmol) in 30 mL mixture was allowed to warm to ambient temperature and
of Et2O was combined with HCl (2.8 mL, 0.6 mmol mL−1 in stirred for 18 h. During this period, the reaction mixture
Et2O) in 20 mL of Et2O at −80 °C. The reaction mixture was turned dark brown–red in color. After filtering, crystallization
allowed to warm to ambient temperature and stirred for 12 h. from Et2O at −20 °C afforded 5 as yellow needle crystals in
During this period, the reaction mixture turned brown–red in the yield of 65% (0.52 g). Dec. >173 °C. IR (Nujol mull,
color. After being filtered in vacuo, the resulting solid was 4000–400 cm−1): 3058 ν(CAr–H), 1618 ν(CvO), 1570 ν(CvC),
extracted with pentane (40 mL). Crystallization from Et2O at 1535 ν(CvC), 948 ρ(PMe3); 1H NMR (300 MHz, C6D6, 297 K,
−20 °C afforded red crystals suitable for single-crystal X-ray ppm): δ 0.79 (t′, |2J(PH) + 4J(PH)| = 9.0 Hz, 18H, PCH3),
diffraction analysis. Yield: 0.55 g (73%). Dec. >175 °C. 6.88–6.92 (m, 1H, Ar-H), 6.93–6.96 (m, 1H, Ar-H), 6.98–7.02
IR (Nujol mull, 4000–400 cm−1): 3028 ν(CAr–H), 1599 ν(CvO), (m, 2H, Ar-H), 7.05–7.10 (m, 5H, Ar-H), 7.69–7.76 (m, 2H,
1561 ν(CvC), 941 ρ(PMe3); 1H NMR (300 MHz, C6D6, 297 K, Ar-H), 7.95–8.00 (m, 2H, Ar-H), 8.09–8.13 (m, 1H, Ar-H),
4
ppm): δ 1.23 (t′, |2J(PH) + J(PH)| = 6.0 Hz, 18H, PCH3), 1.31 8.28–8.34 (m, 4H, Ar-H); 31P NMR (121 MHz, C6D6, 297 K,
(d, 2J(PH) = 8.4 Hz, 9H, PCH3), 6.77 (t, 3J(HH) = 6.0 Hz, 1H, ppm): δ −6.8 (br s, 2P, PCH3), 40.7 (br s, 1P, PPh); Anal. Calc.
Ar-H), 7.03 (t, 3J(HH) = 6.0 Hz, 1H, Ar-H), 7.54 (d, 3J(HH) = for C31H36CoO2P3S (624.54 g mol−1): C, 59.62; H, 5.81. Found:
6.0 Hz, 1H, Ar-H), 7.78 (d, 3J(HH) = 6.0 Hz, 1H, Ar-H); 31P NMR C, 59.95; H, 5.68.
(121 MHz, C6D6, 297 K, ppm): δ 3.0 (br s, 1P, PCH3), −5.9 (br s,
2P, PCH3). Anal. Calc. for C16H31ClCoOP3S (458.79 g mol−1): of Et2O was combined with 2-(diphenylphosphino)benzene-
C, 41.89; H, 6.81. Found: C, 41.63; H, 6.72. thiol (0.41 g, 1.40 mmol) in 30 mL of Et2O at −80 °C. The
Synthesis of 6. A sample of 1 (0.60 g, 1.42 mmol) in 30 mL
Synthesis of 3. A sample of 1 (0.65 g, 1.53 mmol) in 20 mL reaction mixture was allowed to warm to ambient temperature
of Et2O was combined with bromoethane (0.17 g, 1.53 mmol) and stirred for 18 h. During this period, the reaction mixture
in 20 mL of Et2O at −80 °C. The reaction mixture was allowed turned dark brown–red in color. After being filtered in vacuo,
to warm to ambient temperature and stirred for 12 h. During crystallization from Et2O at −20 °C afforded 6 as yellow needle
this period, the reaction mixture turned brown–red in color. crystals in a yield of 60% (0.54 g). Dec. >179 °C. IR (Nujol mull,
After being filtered in vacuo, the resulting solid was extracted 4000–400 cm−1): 3052 ν(CAr–H), 1618 ν(CvO), 1569 ν(CvC),
with pentane (30 mL). Crystallization from Et2O at −20 °C 1553 ν(CvC), 946 ρ(PMe3); 1H NMR (300 MHz, C6D6, 297 K,
afforded red crystals suitable for single-crystal X-ray diffraction ppm): δ 0.79 (t′, |2J(PH) + 4J(PH)| = 9.0 Hz, 18H, PCH3),
analysis. Yield: 0.53 g (69%). Dec. >159 °C. IR (Nujol mull, 6.88–6.91 (m, 1H, Ar-H), 6.93–6.96 (m, 1H, Ar-H), 6.97–7.01
4000–400 cm−1): 3044 ν(CAr–H), 1601 ν(CvO), 1564 ν(CvC), (m, 2H, Ar-H), 7.04–7.11 (m, 5H, Ar-H), 7.69–7.76 (m, 2H,
939 ρ(PMe3); 1H NMR (300 MHz, C6D6, 297 K, ppm): δ 1.28 Ar-H), 7.96–8.00 (m, 2H, Ar-H), 8.09–8.13 (m, 1H, Ar-H),
4
2
(t′, |2J(PH) + J(PH)| = 6 Hz, 18H, PCH3), 1.33 (d, J(PH) = 8.7 8.28–8.34 (m, 4H, Ar-H); 13C NMR (75 MHz, C6D6, 297 K, ppm):
Hz, 9H, PCH3), 6.77 (t, 3J(HH) = 6.0 Hz, 1H, Ar-H), 7.03 δ 15.1 (t′, |1J(PC) + 3J(PC)| = 29.3 Hz, PCH3), 119.9–136.7
(t, 3J(HH) = 6.0 Hz, 1H, Ar-H), 7.37 (d, 3J(HH) = 6.0 Hz, 1H, (s, Carom), 201.6 (s, CvO); 31P NMR (121 MHz, C6D6, 297 K,
Ar-H), 7.77 (d, J(HH) = 6.0 Hz, 1H, Ar-H); 31P NMR (121 MHz, ppm): δ −6.5 (br s, 2P, PCH3), 40.4 (br s, 1P, PPh); Anal. Calc.
3
C6D6, 297 K, ppm): δ 3.8 (br s, 1P, PCH3), −9.3 (br s, 2P, PCH3). for C31H36CoOP3S2 (640.60 g mol−1): C, 58.12; H, 5.66. Found:
Anal. Calc. for C16H31BrCoOP3S (503.24 g mol−1): C, 38.19; C, 57.91; H, 5.49.
H, 6.21. Found: C, 37.87; H, 6.18.
Synthesis of 7. A sample of 2 (0.50 g, 1.31 mmol) in 40 mL
Synthesis of 4. A sample of 1 (0.60 g, 1.42 mmol) in 20 mL of Et2O was stirred under 1 bar of CO at room temperature for
of Et2O was combined with iodomethane (0.20 g, 1.42 mmol) 18 h. During this period, the reaction mixture turned clear red
in 20 mL of Et2O at −80 °C. The reaction mixture was allowed in color. After being filtered in vacuo, the resulting solid was
to warm to ambient temperature and stirred for 14 h. During extracted with pentane (40 mL). Crystallization from Et2O at
this period, the reaction mixture turned brown–red in color. −20 °C afforded red crystals of 7. Yield: 0.32 g (58%). Dec.
After filtering in vacuo, the resulting solid was extracted with >197 °C. IR (Nujol mull, 4000–400 cm−1): 3056 ν(CAr–H), 2048
pentane (30 mL). Crystallization from Et2O at −20 °C afforded ν(CO), 1613 ν(CvO), 1569 ν(CvC), 942 ρ(PMe3); 1H NMR
red crystals suitable for single-crystal X-ray diffraction analysis. (300 MHz, C6D6, 297 K, ppm): δ 1.20 (t′, |2J(PH) + 4J(PH)| = 9.0
Yield: 0.52
g
(67%). Dec. >148 °C. IR (Nujol mull, Hz, 18H, PCH3), 6.73 (t, 3J(HH) = 7.5 Hz, 1H, Ar-H), 6.95
4000–400 cm−1): 3050 ν(CAr–H), 1605 ν(CvO), 1565 ν(CvC), (t, 3J(HH) = 7.5 Hz, 1H, Ar-H), 7.43 (d, 3J(HH) = 8.1 Hz, 1H,
940 ρ(PMe3); 1H NMR (300 MHz, C6D6, 297 K, ppm): δ 1.34 Ar-H), 7.58 (d, J(HH) = 7.8 Hz, 1H, Ar-H); 31P NMR (121 MHz,
3
(m, 27 H, PCH3), 6.76 (t, 3J(HH) = 6.0 Hz, 1H, Ar-H), 7.02 C6D6, 297 K, ppm): δ 2.2 (br s, PCH3). Anal. Calc. for
4060 | Dalton Trans., 2014, 43, 4059–4066
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C14H22ClCoO2P2S (410.72 g mol−1): C, 40.94; H, 5.40. Found: mixture was allowed to warm to ambient temperature and
C, 41.17; H, 5.60. stirred for 14 h. During this period, the reaction mixture
Synthesis of 8. A sample of 4 (0.55 g, 1.00 mmol) in 40 mL turned dark purple–red in color. After being filtered in vacuo,
of Et2O was stirred under 1 bar of CO at room temperature for the resulting solid was extracted with pentane (40 mL). Crystal-
18 h. During this period, the reaction mixture turned clear red lization from pentane at −20 °C afforded a purple–red
in color. After being filtered in vacuo, the resulting solid was solid 13. Yield: 0.35 g (58%). Dec. >159 °C. IR (Nujol mull,
extracted with pentane (40 mL). Crystallization from Et2O at 4000–400 cm−1): 3033 ν(CAr–H), 1667 ν(CvO), 948 ρ(PMe3).
−20 °C afforded 8 as red crystals suitable for single-crystal Anal. Calc. for C21H42CoOP3SSi (522.56 g mol−1): C, 48.27;
X-ray diffraction analysis. Yield: 0.31 g (65%). Dec. >163 °C. H, 8.10. Found: C, 48.57; H, 7.98.
IR (Nujol mull, 4000–400 cm−1): 3064 ν(CAr–H), 2039 ν(CO),
1
X-ray structure determination
1615 ν(CvO), 1574 ν(CvC), 952 ρ(PMe3); H NMR (300 MHz,
4
C6D6, 297 K, ppm): δ 1.27 (t′, |2J(PH) + J(PH)| = 9.0 Hz, 18H,
Intensity data were collected on a Bruker SMART diffracto-
PCH3), 6.71 (t, 3J(HH) = 4.5 Hz, 1H, Ar-H), 6.95 (t, 3J(HH) =
meter with graphite-monochromated Mo-Kα radiation (λ =
4.5 Hz, 1H, Ar-H), 7.47 (d, 3J(HH) = 4.5 Hz, 1H, Ar-H), 7.57
0.71073 Å) at 293 K. The crystallographic data for complexes
2–4, 8 and 11 are summarized in Table 1. The structures were
(d, 3J(HH) = 4.5 Hz, 1H, Ar-H); 31P NMR (121 MHz, C6D6,
297 K, ppm): δ −2.6 (br s, PCH3). Anal. Calc. for C14H22CoIO2P2S
(502.17 g mol−1): C, 33.48; H, 4.42. Found: C, 33.12; H, 4.28.
Synthesis of 9.14 A sample of 1 (0.70 g, 1.65 mmol) in 30 mL
of Et2O was combined with 2-hydroxy-5-phenylcyclohex-1-
enecarbaldehyde (0.33 g, 1.65 mmol) in 20 mL of Et2O at
−80 °C. The reaction mixture was allowed to warm to ambient
temperature and stirred for 14 h. During this period, the reac-
tion mixture turned brown–red in color. After being filtered
in vacuo, the resulting solid was extracted with pentane
(30 mL). Crystallization from Et2O at −20 °C afforded 9 as
yellow powder. Yield: 0.56 g (69%). Dec. >136 °C. IR (Nujol
mull, 4000–400 cm−1): 1883 ν(Co–H), 1583 ν(CvO), 1541
ν(CvC), 938 ρ(PMe3).
solved by direct methods and refined with the full-matrix least-
squares method on all F2 (SHELXL-97) with non-hydrogen
atoms anisotropic.
Results and discussion
Substitutions of the hydrido ligand of 1 by halogen ligands
The reaction of complex 1 with RX (RX = HCl, C2H5Br and
CH3I) afforded three cobalt(III) complexes 2–4 via elimination
of hydrogen or alkane (eqn (2)).
Synthesis of 11. A solution of 1 (0.65 g, 1.53 mmol) in
40 mL of Et2O was combined with trimethylsilylacetylene
(0.15 g, 1.53 mmol) in Et2O (20 mL) at −80 °C. The reaction
mixture was allowed to warm to ambient temperature and
stirred under 1 bar of CO at room temperature for 18 h. During
this period, the reaction mixture turned red in color. After
ð2Þ
The halogenocobalt(III) complexes 2–4 were obtained as red
being filtered in vacuo, the resulting solid was extracted with crystals in high yield by crystallization from Et2O at −20 °C.
pentane (40 mL). Crystallization from Et2O at −20 °C afforded Crystals of 2–4 remain stable at room temperature for more
yellow needle crystals suitable for single-crystal X-ray diffrac- than three days but they quickly decompose when dissolved
1
tion analysis. Yield: 0.31 g (62%). Dec. >175 °C. IR (Nujol mull, and exposed to air. In the H NMR spectra of complexes 2–4
4000–400 cm−1): 3033 ν(CAr–H), 1966, 1899 ν(CO), 1663 two signals of PMe3 ligands were recorded in the integral ratio
1
ν(CvO), 1576 ν(CvC), 943 ρ(PMe3); H NMR (300 MHz, C6D6, of 2 : 1. Two 31P NMR resonances (3.05 and −5.9 ppm (2); 3.8
297 K, ppm): δ 0.087 (s, 9H, Si(CH3)3), 1.17 (t′, |2J(PH) + and −9.3 ppm (3) and 1.8 and −14.7 ppm (4)) were registered
4J(PH)| = 8.4 Hz, 18H, PCH3), 6.92 (dt, 3J(HH) = 7.0 Hz, 4J in the integral ratio of 2 : 1. This indicates a mer-orientation of
3
4
(HH) = 1.5 Hz, 1H, Ar-H), 7.20 (dt, J(HH) = 7.8 Hz, J(HH) = the three phosphine ligands.
3
4
1.5 Hz, 1H, Ar-H), 7.39 (dd, J(HH) = 7.8 Hz, J(HH) = 1.5 Hz,
The molecular structures of complexes 2–4 confirm a hexa-
3
1H, Ar-H), 7.39 (d, J(HH) = 18.6 Hz, 1H, CvC(H)–SiMe3), 7.57 coordinate octahedral geometry in the crystals (Fig. 1–3). Com-
(d, 3J(HH) = 18.9 Hz, 1H, (H)CvCSiMe3), 7.62 (d, 3J(HH) = 9.0 Hz, paring the structures of complexes 2–4 with that of complex
1H, Ar-H); 13C NMR (75 MHz, C6D6, 297 K, ppm): δ 1.79 1,11 we know that a transformation of the configuration of
(s, Si(CH3)3), 17.7 (t′, |1J(PC) + J(PC)| = 34.4 Hz, PCH3), 120.9 these complexes occurs during the ligand substitution.
3
(s, Carom), 127.2 (s, Carom), 128.8 (s, Carom), 131.2 (s, Carom), Because both hydrido and acyl groups are strong ligands, they
142.8 (s, Carom), 144.4 (s, Carom), 145.5 (s, HCvCHSi), 147.1 are in the cis-arrangement in complex 1. In complexes 2–4, the
(s, HCvCHSi), 196.9 (s, CvO). 31P NMR (121 MHz, C6D6, halogen ligands are the weakest and the acyl group is the
297 K, ppm): δ 25.5 (s, PCH3). Anal. Calc. for C20H33CoO3P2SSi strongest, therefore, the halogen ligands are always located in
(502.48 g mol−1): C, 47.80; H, 6.62. Found: C, 47.52; H, 6.48.
the trans-positions to the acyl group. This transformation is in
Synthesis of 13. A solution of 1 (0.50 g, 1.17 mmol) in line with the trans-influence and therefore this coordination
40 mL of Et2O was combined with trimethylsilylacetylene for complexes 2–4 is a stable configuration. Due to the order of
(0.12 g, 1.17 mmol) in Et2O (20 mL) at −80 °C. The reaction atom size (Cl < Br < I) the order of the bond angle is P1–Co1–
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Table 1 Crystallographic data for complexes 2, 3, 4, 8 and 11
2
3
4
8
11
Empirical formula
FW
Cryst syst.
Space group
a (Å)
b (Å)
c (Å)
α (°)
C
16H31ClCoOP3S
C16H31BrCoOP3S
503.22
C16H31CoIOP3S
550.21
Monoclinic
P2(1)/n
8.7982(18)
15.754(3)
17.424(4)
90.00
C14H22CoIO2P2S
502.15
C20H33CoO3P2Si
502.48
Monoclinic
P2(1)/n
12.503(6)
17.273(8)
13.307(6)
90.00
458.76
Monoclinic
P2(1)/c
8.937(8)
15.682(13)
17.238(13)
90.00
Monoclinic
P2(1)/n
8.859(4)
15.756(7)
16.177(7)
90.00
Orthorhombic
Pna2(1)
18.283(4)
8.5829(17)
12.412(3)
90.00
β (°)
113.86(4)
90.00
2209(3)
4
97.460(7)
90.00
2239.0(17)
4
98.14
90.00
2390.7(8)
4
1.529
90.00
90.00
1947.7(7)
4
1.712
114.85
90.00
2608(2)
4
γ (°)
V (Å3)
Z
Dx (g cm−3
)
1.379
1.493
1.280
No. of rflns collected
No. of unique data
Rint
10 725
3899
0.0569
25.00
12 493
4900
0.0315
27.41
14 113
4216
0.0169
25.00
9171
4338
0.0247
27.55
12 628
4578
0.0562
25.00
θmax (°)
R1 (I > 2σ(I))
wR2 (all data)
0.0539
0.1718
0.0358
0.0951
0.0239
0.0653
0.0353
0.1042
0.0607
0.1783
Fig. 1 Molecular structure of 2, selected distances (Å) and angles (°):
Cl1–Co1 2.436(2), Co1–C7 1.937(5), Co1–S1 2.283(2), Co1–P3 2.272(2),
Co1–P2 2.286(2), Co1–P1 2.271(2), C7–O1 1.218(6), C2–C7 1.402(4);
S1–Co1–P1 86.29(7), P2–Co1–P1 92.72(7), S1–Co1–Cl1 89.27(6),
P3–Co1–P1 169.05(6), S1–Co1–P2 175.11(6), C7–Co1–Cl1 176.4(2),
P1–Co1–Cl1 86.53(8), P2–Co1–Cl1 95.45(6), P3–Co1–Cl1 85.03(9),
S1–Co1–P3 86.63(7), P3–Co1–P2 95.02(6).
Fig. 2 Molecular structure of 3, selected distances (Å) and angles (°):
Br1–Co1 2.5518(9), Co1–C7 1.950(3), Co1–S1 2.288(1), Co1–P3 2.272(1),
Co1–P2 2.293(1), Co1–P1 2.277(1), C7–O1 1.185(4); S1–Co1–P1 86.81(4),
P2–Co1–P1 94.80(4), S1–Co1–Br1 88.43(3), P3–Co1–P1 169.70(3),
S1–Co1–P2 175.34(4), C7–Co1–Br1 176.07(9), C7–Co1–P2 87.6(1),
C7–Co1–S1 88.0(1), C7–Co1–P3 94.4(1), C7–Co1–P1 92.7(1), P1–Co1–
Br1 85.43(4), P2–Co1–Br1 96.05(3), P3–Co1–Br1 86.94(4), S1–Co1–P3
86.07(4), P3–Co1–P2 92.88(4).
P3 (169.05(6)° (2) < P1–Co1–P3 (169.70(3)° (3) < P1–Co1–P2
(170.48(3)° (4). The order of the bond lengths (Co1–C7
(1.937(5)) Å (2) < Co1–C7 (1.950(3)) Å (3) < Co1–C1 (1.996(2))
coordinate bis-chelate cobalt(III) complexes 5 and 6 as yellow
crystals (eqn (3)).
Å (4)) can be explained with the order of trans-influence (I−
>
Br− > Cl−). The extraordinary long Co–X bonds (Co1–Cl1
(2.436(2) Å (2)); Co1–Br1 (2.5518(9) Å (3); Co1–I1 (2.8089(8) Å (4)))
are also caused by the strong trans-influence of the carbon
atom of the acyl group.
ð3Þ
Reactions of complex 1 with 2-(diphenylphosphino)phenol
and 2-(diphenylphosphino)benzenethiol
Complexes 5 and 6 are stable in the air for more than one
The reactions of complex 1 with 2-(diphenylphosphino)phenol week. This stability might be supported by the bis-chelate
and 2-(diphenylphosphino)benzenethiol afforded two hexa- effect. In the IR spectra of 5 and 6 the conspicuous ν(Co–H)
4062 | Dalton Trans., 2014, 43, 4059–4066
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Fig. 3 Molecular structure of 4, selected distances (Å) and angles (°):
I1–Co1 2.8089(8), Co1–C1 1.996(2), Co1–S1 2.2749(8), Co1–P3 2.2840(8),
Co1–P2 2.328(1), Co1–P1 2.331(1), S1–C7 1.796(3), C1–O1 1.224(3),
C2–C7 1.402(4); S1–Co1–P3 174.83(3), C1–Co1–I1 175.34(7), P2–Co1–P1
170.48(3), C1–Co1–P2 88.82(8), S1–Co1–P2 86.26(3), P3–Co1–P2
94.94(3), C1–Co1–P1 97.08(8), P3–Co1–I1 96.63(2), P2–Co1–I1 89.22(3),
P1–Co1–I1 84.33(2), S1–Co1–P1 86.56(3), P3–Co1–P1 92.76(3).
Fig. 4 Molecular structure of 8, selected distances (Å) and angles (°):
I1–Co1 2.6845(6), Co1–C1 1.921(4), Co1–C11 1.781(4), Co1–S1 2.2425(9),
Co1–P2 2.249(1), Co1–P1 2.258(1), S1–C7 1.796(3), C1–O1 1.234(5),
C11–O2 1.131(4); S1–Co1–I1 91.94(3), C11–Co1–S1 179.4(1), C1–Co1–P1
91.2(1), C1–Co1–P2 87.6(1), C11–Co1–P1 90.9(1), S1–Co1–P2 87.77(4),
P3–Co1–P2 94.94(3), C11–Co1–P2 92.7(1), C1–Co1–I1 178.5(1),
P2–Co1–I1 91.28(3), C1–Co1–S1 89.0(1), S1–Co1–P1 88.57(4), P2–Co1–P1
176.17(4), C11–Co1–I1 88.5(1), C11–Co1–C1 90.6(2), Co1–C11–O2 177.9(3).
absorption of the complex 1 is absent. The carbonyl vibrations
are found at 1618 (5) and 1617 cm−1 (6). In the 1H NMR
spectra, the 18 protons of two trimethylphosphine ligands
appear at 0.79 ppm as a triplet with |2J(PH) + 4J(PH)| = 9.0 Hz,
which suggests that the two trimethylphosphine ligands are in
axial orientation. Complexes 5 and 6 have similar structures to
the reported organocobalt(III) complexes, which were obtained
from the reactions of acyl(hydrido)cobalt(III) complexes with
2-(diphenylphosphanyl)phenol.14
It must be noted that two signals for complexes 2–6 in the
31P NMR spectra should be one doublet and one triplet in the
ratio of 2 : 1 because of the meriodal-orientation of the three
trimethylphosphine ligands.14 Two singlets indicate some
dynamic equilibrium in the solution.
triplet at 1.20 (7) and 1.27 (8) ppm. All of the spectroscopic
information implies that complexes 7 and 8 have hexa-coordi-
nate geometry.
The molecular structure (Fig. 4) of 8 shows a hexa-coordi-
nate octahedral geometry with two trans-phosphine ligands
and one equatorial [C,S]-chelate ring. This is consistent with
the observation from the spectroscopic data. The Co1–I1 dis-
tance (2.6845(6) Å) is shorter than that (2.8089(8) Å) in
complex 4. It is suggested that the Co1–I1 bond in 8 is
reinforced through the increase of the positive charge at the
cobalt center. This increase is caused by the π-backbonding
between cobalt and CO in complex 8. The shorter distance of
C11–O2 (1.131(4) Å) compared to that of C1–O1 (1.234(5) Å)
suggests that the coordination of the terminal carbonyl group
is enhanced by the π-backbonding. For the same reason Co1–
C1 (1.921(4) Å) is longer than Co1–C11 (1.781(4) Å).
Reactions of complexes 2 and 4 with carbon monoxide
Complex 2 or 4 in a diethyl ether solution under 1 bar of CO at
room temperature slowly transformed to complex 7 or 8
through the replacement of a PMe3 ligand by a CO ligand
(eqn (4)). Complexes 7 and 8 were obtained as red crystals.
They begin to decompose above 197 °C (7) and 163 °C (8).
Reaction of complex 1 with 2-hydroxy-5-phenylcyclohex-1-
enecarbaldehyde
The reaction of complex 1 with 2-hydroxy-5-phenylcyclohex-1-
ð4Þ
enecarbaldehyde afforded
a hydrido(acyl)enolatocobalt(III)
complex 915 as yellow powder in the yield of 69% and thiosali-
cylaldehyde16 confirmed by IR (Scheme 1). This chelate ligand
exchange shows that hydrido(acyl)enolatocobalt(III) complex 9
The red crystals of 7 and 8 are very stable in the air for is more stable than hydrido(2-mercaptobenzoyl)cobalt(III)
several days. The IR bands of the terminal carbonyl group are complex 1. Under reaction conditions the expected bis-chelate
recorded at 2048 (7) and 2039 (8) cm−1 while the acyl CvO complex [10] was not formed via the escape of one molecule
vibrations are registered at 1613 (7) and 1615 (8) cm−1. The of dihydrogen. This indicates that the enol-OH hydrogen of
difference between complex 7 and 8 is caused by the change of 2-hydroxy-5-phenylcyclohex-1-enecarbaldehyde is not acidic
1
Cl atom in 7 to I atom in 8. In the H NMR spectra of the two enough to react with the hydridic hydrogen of complex 1. This
complexes, the resonance of PMe3 ligands was recorded as a experimental result can also be understood according to the
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Scheme 1 Reaction of 1 with 2-hydroxy-5-phenylcyclohex-1-enecarbaldehyde.
Scheme 2 proposed mechanism of formation of 9.
HSAB rule. Complex 9 formed through hard/(O)–hard/(Co(III)) cobalt(I) complex 11 as yellow needle crystals via C,C-coupling
combination is more stable than complex 1 and 10 with soft/ (eqn (5)). The yellow needle crystals of complex 11 are stable in
(S)–hard/(Co(III)) combination.
air and decompose above 175 °C.
The proposed mechanism of the formation of complex 9 is
suggested in Scheme 2. The first step is the substitution of a
trimethylphosphine ligand by the oxygen atom of the aldehyde
group of 2-hydroxy-5-phenylcyclohex-1-enecarbaldehyde to
form intermediate a. With this coordinated aldehyde group as
the anchoring group, the reductive elimination between Co–H
and Co-acyl occurs to afford the penta-coordinated cobalt(I)
intermediate b with the recovery of the aldehyde group of the
thiosalicylaldehyde ligand. The other hexa-coordinate hydrido
cobalt(III) species c is produced from b via oxidative addition
of the O–H bond of coordinated 2-hydroxy-5-phenylcyclohex-1-
enecarbaldehyde at the cobalt center. The reductive elimin-
ation between Co–S and Co–H bonds in the presence of tri-
methylphosphine delivers intermediate d. The end product 9
can be obtained by oxidative addition of the C–H bond of the
aldehyde group of 2-hydroxy-5-phenylcyclohex-1-enecarbaldehyde.
ð5Þ
In the IR spectra of complex 11 two strong absorptions at
1966 and 1899 cm−1 belong to the two terminal carbonyl
ligands. The acyl ν(CvO) and ν(CvC) bands are found at 1663
and 1576 cm−1 respectively. In the H NMR spectra, the reson-
1
ance of –SiMe3 was recorded as a singlet at 0.087 ppm while
one triplet for two PMe3 ligands at 1.17 ppm was recorded
with |2J(PH) + J(PH)| = 8.4 Hz. The resonances of two vinyl-
4
protons of CHvCH–SiMe3 were recorded as two doublets at
7.39 ppm (3J(HH) = 18.6 Hz, CHvCH–SiMe3) and 7.57 ppm
(3J(HH) = 18.9 Hz, CHvCHSiMe3) respectively, which are com-
parable with the related compounds reported by Pawluc.17
Complex 11 was further studied by X-ray diffraction.
Insertion reaction of complex 1 with ethynyltrimethylsilane in
the presence of carbon monoxide
The reaction of complex 1 with ethynyltrimethylsilane under 1 Complex 11 (Fig. 5) shows a trigonal bipyramidal configuration
bar of CO in diethyl ether gave rise to a penta-coordinate with two trans-phosphine ligands and three atoms (S1, C7 and
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Scheme 3 Proposed mechanism of formation of 11.
Fig. 5 Molecular structure of 11, selected distances (Å) and angles (°):
O1–C8 1.143(6), O2–C7 1.136(6), O3–C15 1.205(6), C13–C15 1.471(6),
C16–C17 1.291(7), Co1–C8 1.723(6), Co1–C7 1.741(6), Co1–P2 2.176(2),
Co1–P1 2.176(2), Co1–S1 2.296(2), Si1–C17 1.841(6), C15–C16 1.481(7);
C8–Co1–C7 128.1(3), C8–Co1–S1 108.8(2), C7–Co1–S1 123.1(2),
P2–Co1–P1 176.80(6), C14–S1–Co1 115.9(2), C13–C15–C16 117.2(4),
C17–C16–C15 125.5(5), C16–C17–Si1 127.0(5), C18–Si1–C17 110.2(3),
C20–Si1–C17 107.2(3), C17–Si1–C19 109.9(3).
1589 cm−1. Because intermediate 13 is paramagnetic, there are
no reasonable NMR spectra to be observed. It could be con-
cluded that no π-coordination of the olefin group to the cobalt
center occurred because penta-coordinate cobalt(I) complex is
antimagnetic. The comparable cobalt(I) complexes with acyle-
nolato ligand was structurally characterized.18 Possibly, the
electron-withdrawing property of the –SiMe3 group and steric
effect make the π-coordination of the olefin group to the
cobalt(I) center in 13 difficult. Under reaction conditions inter-
mediate 12 could not be isolated. According to the HSAB rule19
intermediate 12 formed through soft/(S)–hard/(Co(III)) combi-
nation is more unstable than the corresponding acylenolato-
cobalt(III) with O-coordination.18 The tetra-coordinate 13 under 1
bar of CO in diethyl ether solution transformed to penta-coordi-
nate complex 11 through the replacement of PMe3 by CO. The
molecular structure of 11 confirmed by X-ray single crystal diffr-
action is a strong evidence for the formation of intermediate 13.
C8) in the triangular plane. The acyl and –SiMe3 groups are in
E-configuration of the olefin CvC bond. Interestingly, the
plane of the conjugated acyl and olefin group is not coplanar
with the phenyl ring. This might be caused by the packing
effect. C16–C17 distance (1.291(7) Å) is a little bit shorter than
the normal olefin CvC bond. The sum (360.0°) of the three
bond angles (C8–Co1–C7 128.1(3), C8–Co1–S1 108.8(2) and
C7–Co1–S1 123.08(17)°) around the central cobalt atom proves
that the four atoms (Co1, S1, C7 and C8) are in the same
plane. The angle P2–Co1–P1 (176.80(6)°) close to 180° bends to
the direction of the Co1–S1 bond. A similar reaction of
hydrido(acylenolato)cobalt(III) complex with ethynyltrimethyl-
silane gave rise to a penta-coordinate π-olefin cobalt(I) complex
in the absence of CO.16 It is proposed that the bulky –SiMe3
group makes the coordination of the olefin group to the cobalt
Conclusions
center impossible. In addition, the π-backbonding between the In summary, the reactivity of sulfur-coordinated acyl(hydrido)-
two carbonyl ligands and cobalt(I) center also lead to difficulty cobalt(III) complex 1 was intensively studied. Complex 1 has
of the coordination of the olefin group to the cobalt(I) center. In similar reaction properties to those of its oxo analogues, the
addition, hexa-coordinate cobalt(I) complex (20 VE) is rare.
hydrido(acylphenolato)cobalt(III) complexes, but the former is
The proposed mechanism of formation of complex 11 is more reactive than the latter. This can be easily understood
suggested in Scheme 3. The first step is insertion of an ethynyl from the viewpoint of HSAB theory. For the reactions (2)–(4),
group into the Co–H bond to give rise to a vinyl cobalt(III)
no significant difference of the chemical properties between
intermediate 12. The analogous cobalt(III) complexes with acy- these two kinds of complexes could be perceived. From
lenolato ligand to 12 was structurally characterized.18 Reduc- Schemes 1 and 2 it can be seen that reactive complex 1 was
tive elimination of both coordinated Co–C bonds of 12 delivers
more easily converted into a more stable oxo complex 9. Reac-
a tetra-coordinate cobalt(I) intermediate 13 via C,C-coupling. tion (5) was so fast that intermediate 12 could not be isolated
Substitution of PMe3 by CO and coordination of CO lead to the or detected, while the similar intermediate of the corres-
ponding oxo complex could possibly be separated.18 In
transformation of 13 to end product, complex 11.
In order to verify the proposed mechanism of formation of addition, the experiments proved that complex 1 is an excel-
complex 11 in Scheme 3 experiments to isolate intermediates lent catalyst for hydrosilylation of aldehydes and ketones
under mild conditions,11 while its oxo analogues do not
12 and 13 were carried out. The reaction of complex 1 with
ethynyltrimethylsilane in the absence of CO gave rise to red have catalytic activity for this transformation. The reason
solid of 13, which was isolated from diethyl ether solution. is that complex 1 as a cobalt(III) compound with a softer S
The band of ν(CvO) at 1667 cm−1 in the IR spectra of 13 indi-
coordination atom is more unstable than the corresponding
cated that the C,C-coupling occurred while the ν(CvO) of 1 is cobalt(III) complex with a harder O coordination atom. This
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instability is the driving force for a catalytic cycle. We think
that this instability of complex 1 may cause the following
results: (1) Complex 1 is more prone to ligand dissociation to
generate an unsaturated coordinate intermediate which is
necessary for starting a catalytic cycle. (2) The hydrido hydro-
gen in complex 1 is more nucleophilic than that of its oxo ana-
logue. (3) The unstable alkoxy cobalt(III) intermediate of
complex 1 means the reductive elimination reaction is more
likely to occur. All these factors indicate that complex 1 is a
potential catalyst.11
6 H.-F. Klein, A. Bickelhaupt, M. Lemke, H. Sun, A. Brand,
T. Jung, C. Röhr, U. Flörke and H.-J. Haupt, Organo-
metallics, 1997, 16, 668–676.
7 H.-F. Klein, X. Li, H. Sun, R. Beck, U. Flörke and
H.-J. Haupt, Inorg. Chim. Acta, 2000, 298, 63–74.
8 P. A. Stenson, A. M. Becerra, C. Wilson, A. J. Blake,
J. McMaster and M. Schöder, Chem. Commun., 2006,
317–319.
9 R. C. Elder, L. R. Florian, K. E. Lake and A. M. Yacynych,
J. Chem. Soc., Chem. Commun., 1973, 2690.
10 (a) C. J. Weschler and E. Deutsch, Inorg. Chem., 1976, 15,
139–145; (b) R. C. Elder and M. Trkula, J. Am. Chem. Soc.,
1974, 96, 2635; (c) J. M. Palmer and E. Deutsch, Inorg.
Chem., 1975, 14, 17–25.
11 Q. Niu, H. Sun, X. Li, H.-F. Klein and U. Flörke, Organo-
metallics, 2013, 32, 5235–5238.
12 (a) H.-F. Klein and H. H. Karsch, Inorg. Chem., 1975, 14,
473–478; (b) H.-F. Klein and H. H. Karsch, Chem. Ber.,
1975, 108, 944–955.
Acknowledgements
We gratefully acknowledge the financial support by NSF China
no 21372143 and the support from Prof. Dr Dieter Fenske
(Karlsruhe Nano-Micro Facility) on the determination of the
crystal structures.
13 Q. Niu, X. Xu, H. Sun and X. Li, Chin. J. Chem., 2012, 30,
2495–2500.
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4066 | Dalton Trans., 2014, 43, 4059–4066
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