Received Jan.14, 2005; Supported by the Natural Science Foundations of China (No. 20242004, 20372012) and Foundations of Key Laboratory of Photochemistry.

Carbonylation is one of the most important reactions in organic chemistry which usually requires high temperatures ( 150-200^oC ) and high pressure ( 10-20 MPa ) or precious metal complex catalysts ( such as Ru, Rh, Ir ), and CO is usually the unique C₁ source . The usage of CO at ambient conditions and CO₂ as C₁ source are promising projects^[1,2]. From our previous work, photopromoted carbonylation of olefins with CO and CO₂ can take place under the catalysis of cobalt complexes^[2,3], most of which are homogeneous catalysts that are difficult to be separated after reaction and reused then. We report herein an efficient method to synthesize nano cobalt, which is reduced from CoCl₂ by NaBH₄, and to use nano cobalt as catalysts for photopromoted carbonylation of olefins with CO and CO₂ at ambient conditions.

1 REAGENT
Carbon monoxide, carbon dioxide, (both of them 99.9%, Dalian Guangming Institute ); CH₃OH, CH₃COCH₃ ( A.R., Dalian Merro Chemical Reagent and Glass Apparatus Co. ); n-decane ( A.R., Beijing Phentex Chemicals Co., Ltd. ); CoCl₂·6H₂O ( A.R., Shenyang Chemical Reagent Co. ); 1-octene ( 97%, Hong Kong Farco Chemical Supplies ), cyclohexene ( Military Medicine Academy of Sciences Material Supplies ).

2 PROCEDURE
A 1.6 mol/L NaBH₄ aqueous solution was made from 1.5038 g NaBH₄ and distilled water , which was purged with N₂. A 1.0 mol/L CoCl₂ aqueous solution was made from 2.0686 g CoCl₂·6H₂O, 1.5 ml polyglycol 600 and distilled water, which was purged with N₂ for 20 minutes. The 1.6 mol/L NaBH₄ aqueous solution was dropwise added to the 1.0 mol/L CoCl₂ aqueous solution with stirring under N₂ , and continued to react for 1 hour after the addition.

    Then filtration was done and the filter cake was successively washed with distilled water, 1M HCl, distilled water and acetone (All of these solution were purged by N₂). After drying under vacuum, 0.506 g nano cabolt was obtained with yield of 98.77％.
    A typical carbonylation procedure was as follows: A quartz test tube with inner magnetic stirring (scheme 1) containing a solution of olefin ( 100 mmol/L ), catalyst ( 10 mmol/L ) and NaOAc(300mmol/L) in CH₃OH-CH₃COCH₃ ( V:V=3:1, 15mL ) was irradiated for 20 hours using a high-pressure mercury lamp of 400W ( Philips & Yaming Corp. ) at room temperature under carbon monoxide or carbon dioxide at atmospheric pressure. The quartz test tube was placed closely against the outer wall of the quartz reactor with a length of 3.3×10^-2m between the center of light and reaction solution, and illuminance of 2.6×10^-2W/m² . The products were detected by GC retention time and GC-MS.

Scheme 1 The quartz test with magnetic stirring for carbonylation of olefins	Scheme 2 TEM picture of nano cobalt

3 RESULTS AND DISCUSSION
Morphology of the obtained particles, which shows black and self-ignites in air, was observed with a JEM-2000EX 400T transmission electron microscopy (TEM) at 120kV and it is shown that the diameter of the particles is less than 20nm (Scheme 2).
    The reactions of cyclohexene and 1-octene with CO and CO₂ are as follows, and the results are shown in Table 1.
　

Table 1 The results of photopromoted carbonylation of olefins under catalysis of nano cobalt in CH₃OH/CH₃COCH₃

Substrates	Carbon sources	Yields (%)
cyclohexene	CO	6
1-octene a	CO	27
cyclohexene	CO2	3
1-octene a	CO2	6

a: n/i=4.4.

    It can be seen that under the catalysis of nano cobalt, photopromoted carbonylation of olefins can take place not only with CO but also with CO₂ at ambient conditions. The reactivity of CO₂ is less than CO.
    According to our previous work, NaOAc is beneficial to the reaction and can improve the reaction activity^[4]. The result of NaOAc as additives is shown in Table 2.

Table 2 The Effect of NaOAc on Photopromoted Carbonylation of Olefins under the Catalysis of Nano Cobalt in CH₃OH/CH₃COCH₃^a

Substrates	Gas	Yields (%)
cyclohexene	CO	51
1-octeneb	CO	78
cyclohexene	CO2	32
1-octeneb	CO2	38

a: NaOAc 300mmol/L. b: n/i=1.44.

    In Table 2 it is shown that the yields of carbonylation of olefins is much higher after adding NaOAc. It has been postulated that NaOAc as additives can modulate the pH of the reaction and thus can improve the reactivity of carbonylation of olefins^[4].
    The research is also done of the carbonylation of olefins with CO and CO₂ in CH₃OH under the catalysis of nano cobalt. The result is shown in Table 3.
    It can be seen from Table 3 that the yields of carbonylation of olefins is lower in CH₃OH than that in CH₃OH-CH₃COCH₃, and the carbonylation of olefins with CO₂ can not take place in CH₃OH, which means that CH₃COCH₃ is necessary to the carbonylation of olefins with CO₂ but not necessary for carbonylation of olefins with CO, which is not coincident with the references^[5].

Table 3 The Results of Photopromoted Carbonylation of Olefins under the catalysis of nano cobalt in CH₃OH

Substrates	Carbon sources	Yields (%)
cyclohexene	CO	12
1-octenea	CO	51

a: n/i=1.

    The preliminary research is made of the recycle of nano cobalt as catalysts through the carbonylation of cyclohexene with CO₂ in CH₃OH-CH₃COCH₃. The comparison is made with solvent containing a small amount of water and with dried solvent. The result is shown in table 4.

Table 4 The Yields of Recycle of Nano Cobalt as Catalysts for Carbonylation of cyclohexene in CH₃OH/CH₃COCH₃

Run	1st	2nd	3rd	4th	5th
1a	23	23	8	0	0
2b	32	32	26	23	19

a: Solvent (not removing water). b: Solvent (removing water)

    It can be seen that the existence of a small amount of water is harmful to the recycle of nano cobalt in photopromoted carbonylation of cyclohexene.
    IR and TCD are used to study carbonylation of olefins with CO₂ in CH₃OH-CH₃COCH₃. CO is found by IR in CH₃OH-CH₃COCH₃, but not in CH₃OH. ¹³CO₂ isotope experiment shows that CO₂ takes part in the reaction, which is supposed that CH₃COCH₃ is beneficial to activate CO₂^[6].

Acknowledgment
We are indebted to the National Natural Science Foundations of China (No. 20242004, 20372012) and Foundations of Key Laboratory of Photochemistry, Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences for the generous financial support.

REFRENCES
[1] Othman H, Arab E, Patrick M H. J. Org. Chem., 2001, 66: 180.
[2] Yin J M, Gao D B, Wang R et al.. Chinese Chem. Lett., 2000, 11 (3): 223.
[3] Gao D B, Yin J M, Guo M et al.. Chinese Chem. Lett., 1998, 9: 423.
[4] Gao D B, Yin J M, Guo M et al.. Chinese Journal of Catalysis, 1999, 20 (3): 290.
[5] Tao Y T, Yeh W L, Tu C L, Chow Y L. J. Mol. Catal., 1991, 67 (1):105.
[6] Yin J M, Gao D B, Hu J H et al.. Chinese Science Bulletion, 2003, 48 (20): 2180-2182.

光促进下纳米钴催化的烯烃羰基化反应
周广运 尹静梅 高大彬 贾颖萍 王锐¹
(大连大学生物有机省重点实验室，辽宁大连， 116622)
摘要 用液相法合成了纳米钴。研究了纳米钴在光促进常温常压下催化烯烃与一氧化碳或二氧化碳的羰基化反应。实验结果表明，纳米钴的催化效果较好，反应后催化剂纳米钴易于分离，可重复使用。
关键词  光促进 羰基化反应 纳米钴 烯烃 一氧化碳 二氧化碳