Raney-Ni诱导下氯化钴羰化合成Co_2(CO)_8的研究

Studies on Carbonylation of CoCl 2 to Co 2(CO) 8 in the Presence of Raney Ni at Ambient Condition

采用Ｒａｎｅｙ－Ｎｉ（以下称Ｒ－Ｎｉ）为活化剂，在３０～５０℃，０．１ＭＰａ条件下，由ＣｏＣｌ２／ＣＯ／ＣＨ３ＯＨ体系可快速高效地合成Ｃｏ２（ＣＯ）８，２．５ｈ内，氯化钴转化率可达９５％．在甲醇中保存了３～５ｄ的Ｒ－Ｎｉ仍有较高活性．经脱氢处理后的Ｒ－Ｎｉ仍对羰化反应有很好促进作用．说明Ｒ－Ｎｉ促进氯化钴转化为羰基钴，主要是由于超细Ｒ－Ｎｉ粉的作用，而不是Ｒ－Ｎｉ吸附氢的还原作用．合成产物经２５％ＮａＯＨ处理，转变为Ｎａ［Ｃｏ（ＣＯ）４］体系，在一定范围内，转化率可随ｐＨ值的提高而提高．Ｃｏ２（ＣＯ）８／ＣＨ３ＯＨ体系在２０２５ｃｍ－１处有一个强而尖锐的红外吸收峰，经过ＮａＯＨ处理之后，此峰向１８９５ｃｍ－１处发生移动．两峰可分别归属于Ｃｏ２（ＣＯ）８／ＣＨ３ＯＨ及Ｎａ［Ｃｏ（ＣＯ）４］／ＣＨ３ＯＨ体系中Ｍ—ＣＯ的振动吸收．

It is found that Raney Ni (R Ni) can promote the carbonylation of CoCl 2/CO/CH 3OH at ambient conditions. The conversion of CoCl 2 to Co 2(CO) 8 is about 95% in 2.5 h in the presence of R Ni, but the conversion is only a few percent in the absence of R Ni. The reaction temperature,composition of the promoter, and the preparation method of R Ni have great effects on the conversion of CoCl 2. The R Ni catalyst kept in the CH 3OH for 3￣5 days reserves its high activity to promote carbonylation. After desorption of H 2 adsorbed on the surface during preparation at 50 ℃ R Ni shows high activity for the reaction.This result indicates that the high activity of R Ni for carbonylation may come from the active adsorption of CO and cobalt complex on the surface of R Ni microcrystals due to nanometer effect. The IR spectra of the liquid products of carbonylation give a sharp band at 2 025 cm -1 , which may be assigned to the CO vibration in Co 2(CO) 8. When the liquid is treated with 25% NaOH the band at 2 025 cm -1 will shift to 1 895 cm -1 which could be assigned to the CO vibration in complex [Co(CO) 4] -.