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Dioxygen affinities and catalytic oxidation performance ofcobalt(II) hydroxamates with benzo-15-crown-5 pendantsHong Bo Lia,*, Chuan Qina, Wen Bing Yanga, Xiao Ping Hua, Sheng Ying QinbaCollege of Material Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, ChinabDepartment of Chemistry, Sichuan University, Chengdu 610064, ChinaReceived 18 April 2006AbstractThe oxygenation constants ðKO2Þ of cobalt(II) hydroxamates ðCoL1measured over the range of ?5 to +20 8C, and the values of thermodynamic parameters (DH0and DS0) were calculated based onthese ðKO2Þ values. Meanwhile, these crowned complexes were employed to the oxidation for p-xylene to p-toluic acid with air at110D under normal atmospheric pressure. The effects of B15C5 pendant and the length of chain bonded to B15C5 in thesecomplexes on the O2-binding capabilities and oxidation for p-xylene were investigated with the comparison of crown-freeanalogues CoL42.# 2006 Hong Bo Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.2?CoL32Þ with benzo-15-crown-5 (B15C5) pendants wereKeywords: Benzo-15-crown-5; Cobalt(II) hydroxamates; Dioxygen affinity; Catalytic oxidation; p-XyleneStudies on dioxygen binding to transition metal complexes are ofintrinsic importance, and provideopportunities toaddress the fundamental issues of biological oxygen carriers and oxygenases. During the past decades, the transitionmetal complexes of porphyrins, Schiff bases and macrocyclic ligands, etc., have been used as artificial model on thestudies on mimic oxygen carrying metalloenzymes and oxygenases [1,2]. Among them, the complexes with crownether components showed much improved O2-binding and catalytic oxidation activities due to the specialconfigurationandfunctionofthecrownetherring[3,4].Buthydroxamicacidcomplex,akindoftetradentatecomplex,as a synthetic oxygen carrier and catalyst for oxidation has been seldom reported [5,6]. Furthermore, studies on theproperties of transition–metal hydroxamates with crown ethers have not been reported up to now.In this paper, a series of novel B15C5-functionalized cobalt(II) hydroxamates CoL1employed in the oxidation reaction of p-xylene to p-toluic acid (PTA) successfully. The effects of B15C5 ringsappended in the ligand and the length of the methylene chain on the oxygenation and catalytic oxidation performancewere investigated with the comparison of uncrowned analogue CoL4Pyridine, p-xylene and diglyme were of analytical grade, among these reagents, pyridine and p-xylene werepurified prior to use. All of the complexes (CoLn2, n = 1–4) were supplied by our laboratory, their structures werecharacterized by IR, FAB-MS, and elemental analysis.2?CoL32were developed and2(see Fig. 1).www.elsevier.com/locate/ccletChinese Chemical Letters 18 (2007) 103–106* Corresponding author.E-mail address: li-honggg@163.com (H.B. Li).1001-8417/$–see front matter # 2006 Hong Bo Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.doi:10.1016/j.cclet.2006.11.011万方数据