Reaction of the acyl(hydrido)cobalt(III) complex with 2-propyn-1-ol

Article abstract of DOI:10.1002/zaac.200700206

Acyl(hydrido)cobalt(III) complexes mer-[Co^III(O ^∩C=O)(H)(PMe₃)J (1 and 2) stabilized by 2-acylphenolato-chelating ligands and with the support of trimethylphosphine react with 2-propyn-1-ol to generate inserting products of alkyne bond into Co-H bond bearing bis-chelating vinyl cobalt(III) complexes cis[Co ^III(O^∩C=O)(HO^∩C=CH₂) (PMe₃)₂] (3 and 4). In complexes 3 and 4 the vinyl chelating ligands form a novel four-membered chelate ring. Single crystal of complex 3 was analyzed by X-ray diffraction.

Full text of DOI:10.1002/zaac.200700206

DOI: 10.1002/zaac.200700206
Reaction of the Acyl(hydrido)cobalt(III) Complex with 2-Propyn-1-ol
Lei She, Hongjian Sun, and Xiaoyan Li*
Jinan / P. R. China, Shandong University, School of Chemistry and Chemical Engineering
Received April 16th, 2007.
Dedicated to Professor Dieter Fenske on the Occasion of his 65th Birthday
Abstract. Acyl(hydrido)cobalt(III) complexes mer-[CoIII(OʝCϭO)-
(H)(PMe3)3] (1 and 2) stabilized by 2-acylphenolato-chelating
ligands and with the support of trimethylphosphine react with
2-propyn-1-ol to generate inserting products of alkyne bond into
Co-H bond bearing bis-chelating vinyl cobalt(III) complexes cis-
[CoIII(OʝCϭO)(HOʝCϭCH2)(PMe3)2] (3 and 4). In complexes 3
and 4 the vinyl chelating ligands form a novel four-membered
chelate ring. Single crystal of complex 3 was analyzed by X-ray
diffraction.
Keywords: Cobalt; Hydrido ligand; Trimethylphosphine; Alkyne
Introduction
prepared through C-H activation method and most of the
studies are focused on noble metals (Rh, Ru, Ir, etc) [3].
Practically, hydridocobalt complexes play a prominent role
in some homogenous catalyses [4] owing to their low costs
and relatively low environmental impacts, since 1998 Klein
and co-workers have reported a series of acyl(hydrido)-
cobalt(III) complexes obtained via C-H activation of the
aldehyde groups with chelate effect [5].
In this work, bis-chelate acyl enolato vinyl cobalt(III)
complexes (3 and 4) with two chelating ligands are prepared
by the reaction of acyl(hydrido)cobalt(III) complex (1 and
2) with 2-propyn-1-ol.
The coordination chemistry of transition metal hydride
complexes has always shown its attraction to both academe
and industry. Transition metal hydrides are usually believed
as actual active species in many catalytic processes rather
than catalyst precursors in olefin oligomerization/polymer-
ization and organic synthesis [1]. Therefore, the study on
synthesis and properties of transition metal hydrides is one
of the important research fields in organometallic chemistry
[2]. During the last two decades, there have been consider-
able advances in this direction. Some metal hydrides were
Results and Discussion
1. Reaction of acyl(hydrido)cobalt(III) complexes
(1 and 2) with 2-propyn-1-ol
* Dr. Xiaoyan Li
School of Chemistry and Chemical Engineering,
Shandong University,
Addition of 2-propyn-1-ol to the solution of (2-acylphenol-
ato)hydridocobalt(III) complexes 1 or 2 in THF afforded
brown suspensions. The six-coordinate vinyl cobalt(III)
complexes 3 or 4 could be isolated from the reaction solu-
tion (Eq. (1)). In the IR spectra the conspicuous ν(Co-H)
Shanda Nanlu 27,
250100 Jinan /People’s Republic of China
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E-mail: xli63@sdu.edu.cn
Supporting information for this article is available on the
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author
1
absorption of the starting complex is absent. The H NMR
spectrum shows the vinyl signal of the CH2 group at
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Reaction of the Acyl(hydrido)cobalt(III) Complex with 2-Propyn-1-ol
4 ϳ 5 ppm. 31P NMR data present one signal for two trans-
trimethylphosphine ligands. The molecular structure of 3
was confirmed by X-ray diffraction of single crystal.
chelate ring the octahedral coordinarion configuration is
extraordinarily distorted and the double bond C9-C10
(1.499 A) is much longer than the normal CϭC bond in
˚
Cobalt(III) complex 3 was isolated as orange red crystals,
which are facile to be efflorescent. It was air-stable within
several hours at ambient conditions and decomposes above
160 °C. The cobalt atom is in a distorted octahedral coordi-
nation (Fig. 1) bearing two chelate ligands: a five-mem-
bered acyl enolato chelate ligand (OʝCϭO) and a four-
membered vinyl hydroxy chelate ligand (HOʝCϭCH2) [6].
The addition of (Co-H) functionality to the (CϵC) bond is
in line with the Markovnikov rule. Owing to the coordi-
nation of the O-donor atom of the hydroxyl group, the vinyl
ligand turns to be a chelate ligand. The stability of com-
plexes 3 and 4 is enhanced through the two chelating li-
gands. To the best of our knowledge, only a few examples
of cobalt complexes with four-membered chelate ring had
olefins.
The hydrido ligand in acyl(hydrido)cobalt(III) complexes
bears a partially negative charge [9]. Acyl(phenolato)hydri-
docobalt(III) complexes upon the reaction with acidic hy-
droxyl hydrogen of 2-nitrophenol or 2-nitronaphthol elim-
inate dihydrogen and afford bis-chelate 2-nitrophenolato or
2-nitronaphtholato cobalt(III) compounds [10]. Comparing
with the pKa value of 2-nitrophenol (7.22) most of the ali-
phatic alcohols have the pKa values between 16 and 19.
Therefore, it could be inferred that the neutralization of
acyl(phenolato)hydridocobalt(III) complexes 1 and 2 with
2-proyn-1-ol did not occur and no substituted products
were formed (Eq. (2)) because the acidity of the hydroxyl
hydrogen of 2-proyn-1-ol is too weak.
˚
been published [7]. In addition, Co-O1 bond (1.9763 A) was
˚
significantly shorter than Co-O3 bond (2.205 A) showing
2. The Reaction of complex 3 with CO
the difference between a negatively charged enolato O-do-
nor (O1) and a neutral hydroxyl O-donor atom (O3). The
larger strain of the four-membered ring is another factor,
The reaction of complex 3 with carbon monoxide was car-
ried out under 1 bar of carbon monoxide at room tempera-
ture for several days, complex 3 retained unchanged either
in polar solvents or in non-polar solvents. Because of the
low electronic density at the cobalt(III) atom it is difficult
which makes the (Co-O3) longer. The comparable Co-O(hy-
II
droxyl) distances (2.190 for CoIII and 2.109 A for Co ) were
˚
reported in the literature [8]. Because of the four-membered
Fig. 1 Molecular structure of 3 with the representation of disorder of CH2 groups C2ϪC5. H atomic position on O3 could not be detected.
˚
Selected distances /A and angles /deg: Co1-C7 1.894(3), Co1-C9 1.914(3), Co1-O1 1.9763(19), Co1-O3 2.205(2), Co1-P2 2.2143(11), Co1-P1 2.2226(11), O3-
C10 1.458(3), C9-C10 1.499(4), O1-C1 1.315(3), C1-C6 1.356(4), C6-C7 1.452(4), C7-Co1-C9 106.59(14), C7-Co1-O1 85.92(12), C9-Co1-O1 167.47(11), C7-
Co1-O3 174.80(12), C9-Co1-O3 68.66(11), O1-Co1-O3 98.81(8), C7-Co1-P2 86.47(11), C9-Co1-P2 89.18(11), O1-Co1-P2 92.27(7), O3-Co1-P2 95.46(6), C7-
Co1-P1 86.34(11), C9-Co1-P1 87.09(11), O1-Co1-P1 93.24(7), O3-Co1-P1 91.22(6), P2-Co1-P1 170.60(4).
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L. She, H. Sun, X. Li
for cobalt(III) complex to bear carbonyl ligand to form a
p-back bonding. The examples of carbonyl cobalt(III) com-
plexes were obtained as a result of an equilibrium between
five-coordinated and six-coordinated species in solutions
[11]. Under ambient condition, the unsaturated five-coordi-
nated species with 16 valence electrons tends to combine a
CO molecule to attain stable status with 18 valence elec-
trons, whereas saturated six-coordinate complex 3 could not
accept any CO ligand.
Synthesis of (1-carbonyl-2-oxo-5-phenyl-cyclohexen-
diyl)-(1-ethenyl-2-hydroxy-ethyl)-trans-bis(trimethyl-
phosphan)cobalt(III) (4)
50 mL of THF solution of mer-hydrido(1-carbonyl-2-oxo-5-phenyl-
cyclohexendiyl)tris(trimethylphosphine)cobalt(III) (2) (1.23 g,
2.50 mmol) and 1.76 g (31.4 mmol) of 2-propyn-1-ol in 20 mL of
THF were combined at Ϫ80 °C. Upon warming to ambient tem-
perature the mixture turned brown-red rapidly depositing some
brown solid. After stirring for 18 h the solvent was removed under
vacuum, the residue was extracted with ether and THF,
respectively. Orange-red crystals were afforded at Ϫ27 °C in THF.
Yield 0.33 g of 4 (28 %), m. p.: 130 °C (dec.). C22H35CoO3P2
(468.39 g/mol): C 56.29 (calc. 56.41), H 7.64 (calc. 7.53) %.
Conclusion
IR (Nujol, cmϪ1): ν(CϭO) 1613 s; ν(CϭC) 1567 s. 1H NMR (300 MHz,
THF-d8, 294 K, ppm): δ ϭ 1.40 (tЈ, 18H, Η4JP,Hϩ2JH,HΗ ϭ 9.3 Hz, PCH3),
1.50-2.09 (m, 7H, CH2), 4.66 (s, 2H, C-CH2-OH), 4.77 (s, 1H, CϭCH2), 4.89
(s, 1H, CϭCH2), 6.98-7.37 (m, 5H, Harom). 31P NMR (121 MHz, THF-d8,
294 K) δ ϭ 2.25 (s, PCH3).
In conclusion, acyl(hydrido)cobalt(III) complexes 1 and 2
react with 2-propyn-1-ol forming bis-chelating vinyl-
cobalt(III) complexes 3 and 4 via the addition of Co-H
bond to CϵC bond. X-ray diffraction analysis of complex
3 indicates that the vinyl chelating ligand form a four-
membered chelating ring. Under the experimental con-
ditions no reaction of complexes 3 with carbon monoxide
was observed.
Crystallographic data for 3
C16H31CoO3P2, Mr ϭ 392.3, crystal dimensions: 0.32 x 0.28 x
0.20 mm, monoclinic, space group P21/n, a ϭ 9.8187 (18), b ϭ
3
˚
˚
13.735 (2), c ϭ 14.760 (3) A, β ϭ 95.058(3), V ϭ 1982.9 (6) A ,
T ϭ 294(2) K, Z ϭ 4, Dc ϭ 1.311 g cmϪ3, µ ϭ 1.035 mmϪ1. Bruker
AXS SMART APEX. A total of 10937 reflections was collected,
4046 unique (Rint ϭ 0.0391), θmax ϭ 26.42°, multi-scan absorption
correction. R1 ϭ 0.0404 (for 6678 reflections with I > 2σ(I)),
wR2 ϭ 0.1146 (all data). The structure was solved by direct meth-
ods and refined with full-matrix least-squares on all F2(SHELXL-
97) with non-hydrogen atoms anisotropic.
Experimental Section
General Procedures and Materials
All air-sensitive and volatile materials were handled either in vacuo
or under argon by using standard Schlenk techniques. Literature
methods were applied in the preparation of (2-acylphenolatohydri-
do)cobalt(III) complexes 1 and 2 [9], 2-propyn-1-ol was used as
purchased after distillation. All solvents were dehydrated and de-
gassed by known procedures and used freshly distilled. Melting
points/decomposition temperatures: Sealed capillaries, uncorrected
values. IR: Nujol mulls between KBr disks, Bruker spectrophoto-
meter type VECTOR 22. 1H NMR, 31P NMR and 13C NMR
spectra were recorded with Bruker AVANCE 400 and 300 spec-
trometers, respectively; 13C and 31P NMR resonances were
obtained with broad-band proton decoupling.
Crystallographic data have been deposited with the Cambridge
Crystallgraphic Data Centre CCDC No 645481. These data can
be obtained free of charge via www.code.cam.ac.uk/const/
retrieving.html or from Cambridge Crystallographic Centre, 12,
Union Road Cambridge CB2 1EZ, Uk; fax: ϩ44 1223 336033; or
deposit@ccdc.cam.ac.uk
Acknowdlegment. We gratefully acknowledge support by NSFC No.
20572062 and the Doctoral Program of Ministry of Education of
China (MOE) Nos. 20050422010 and 20050422011 as well as Shan-
dong Scientific Plan 032090105, Natural Science Foundation of
Shandong (Y2006B18) and cordially thank Prof. Dr. Dieter Fenske
(Technische Universität Karlsruhe, Germany) for the crystal struc-
ture determination.
Synthesis of (1-carbonyl-2-oxo-cyclohexenediyl)-
(1-ethenyl-2-hydroxy-ethyl) -trans-bis(trimethyl-
phosphan)cobalt(III) (3)
mer-Hydrido(1-carbonyl-2-oxo-cyclohexenediyl)tris(trimethylphos-
phine)cobalt(III) (1) (2.40 g, 5.81 mmol, dissolved in 50 mL THF)
was added 1.07 g (19.1 mmol) of 2-propyn-1-ol in 20 mL of THF
at Ϫ80 °C. The mixture was warmed to ambient temperature and
turned brown-red rapidly. After stirring for 18 h the solvent was
evaporated under vacuum, the residue was extracted with THF.
Orange-red crystals were afforded at Ϫ27 °C in THF, which was
found suitable for X-ray diffraction: yield 0.81 g of 3 (30 %), m.p.:
158 °C (dec.). C16H31CoO3P2 (392.3 g/mol): C 49.10 (calc. 48.99),
H 7.84 (calc. 7.96) %.
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