The N‐Methylpyrrolidone (NMP) Effect in Iron‐Catalyzed Cross‐Coupling with Simple Ferric Salts and MeMgBr

The use of N‐methylpyrrolidone (NMP) as a co‐solvent in ferric salt catalyzed cross‐coupling reactions is crucial for achieving the highly selective, preparative scale formation of cross‐coupled product in reactions utilizing alkyl Grignard reagents. Despite the critical importance of NMP, the molecular level effect of NMP on in situ formed and reactive iron species that enables effective catalysis remains undefined. Herein, we report the isolation and characterization of a novel trimethyliron(II) ferrate species, [Mg(NMP)₆][FeMe₃]₂ ( 1 ), which forms as the major iron species in situ in reactions of Fe(acac)₃ and MeMgBr under catalytically relevant conditions where NMP is employed as a co‐solvent. Importantly, combined GC analysis and ⁵⁷Fe Mössbauer spectroscopic studies identified 1 as a highly reactive iron species for the selective formation generating cross‐coupled product. These studies demonstrate that NMP does not directly interact with iron as a ligand in catalysis but, alternatively, interacts with the magnesium cations to preferentially stabilize the formation of 1 over [Fe₈Me₁₂]^? cluster generation, which occurs in the absence of NMP.     

Synthesis and gas transport properties of ODPA-TAP-ODA hyperbranched polyimides with various comonomer ratios

A series of hyperbranched copolyimides (HBPI)s based on commercially available monomers 4,4′-oxydiphthalic anhydride (ODPA), 2,4,6-triaminopyrimidine (TAP) and 4,4′-oxydianiline (ODA) were prepared. The synthesis involved the formation of hyperbranched polyamic acid (PAA) precursors in the first step and the thermal imidization of cast thin PAA films in the second step. Two basic types of HBPIs were prepared by controlling the molar ratio of ODPA and an amine mixture of TAP and ODA. When the molar ratio was 1:1, the amine-terminated HBPIs were obtained; with the molar ratio of 2:1 anhydride-terminated HBPIs were prepared. Degree of branching was estimated by ¹H and ¹³C NMR analysis. It was found that approximately 48% of TAP units presented in ODPA:TAP:ODA = 1:0.75:0.25 HBPI macromolecules create the branching unit. Amine-terminated HBPIs showed moderate weight-average molecular weights and these values rather higher than for the anhydride-terminated HBPIs. With increasing ODA comonomer content in amine-terminated HBPIs increased their molecular weight and thermal and mechanical stability, whereas in anhydride-terminated HBPIs these trends were opposite. Amine-terminated HBPIs generally exhibited higher thermal stability than the anhydride-terminated ones. Gas permeability coefficients of both HBPIs types increased with increasing content of ODA comonomer. Prepared membranes exhibited high separation performance and have a potential to be utilized in industrial gas separation applications.     

超声萃取/气相色谱-质谱联用法同时测定皮革及其制品中21种有害有机溶剂的残留量

建立了气相色谱-质谱/选择离子监测方法,对皮革及其制品中21种有害有机溶剂的残留量进行了同时测定。该方法以乙酸乙酯为萃取溶剂,45℃下超声萃取皮革及其制品中残留的有害有机溶剂,萃取液经固相萃取柱净化后进行气相色谱-质谱/选择离子监测法分析,外标法定量。结果表明,在信噪比(S/N)为10的条件下,乙二醇二丁醚(EGDBE)、三乙二醇二甲醚(TEGDME)、二乙二醇单丁醚(DEGBE)和三乙二醇单乙醚(TEGEE)的定量下限均为50μg/kg,N-甲基乙酰胺(MA)和N-甲基甲酰胺(MF)的定量下限均为150μg/kg,甲酰胺的定量下限为300μg/kg,其余14种组分的定量下限均为100μg/kg。在3个不同加标水平下,方法的平均加标回收率为82.1%~94.9%,相对标准偏差(RSD,n=9)为1.6%~4.8%。该方法简单快捷,灵敏度高,可用于皮革及其制品中有害有机溶剂残留量的测定。     

N-甲基吡咯烷酮与HnXMo12O40·mH2O(X=P,Si,Ge)电荷转移盐的合成、表征及非线性光学性质

由 N-甲基吡咯烷酮 (NMP)和 Hn XMo1 2 O40 · m H2 O(X=P,Si,Ge)合成了具有非线性光学性质的电荷转移盐 ,(NMPH ) 3PMo1 2 O40 · CH3CN ( ) ,(NMPH) 4Si Mo1 2 O40 · CH3CN ( )和(NMPH) 4Ge Mo1 2 O40 · CH3CN( ) ,并以元素分析 ,红外光谱 ,漫反射电子光谱进行了表征 .结果表明 ,杂多酸形成电荷转移盐后其阴离子结构未变 ;N-甲基吡咯烷酮通过 N原子与酸中的质子H 结合成阳离子而成盐 ,在高压汞灯照射下阴阳离子之间可以发生电荷转变 .非线性光学性质研究表明 ,电荷转移盐的倍频效应强度分别为 I2ω =0 .3IKDP,I2ω =0和 I2ω =0 .0 2 IKDP,三阶非线性系数分别为χ( 3) =5 .0× 10 - 1 4 esu,χ( 3) =3.1× 10 - 1 3esu和χ( 3) =4.3× 10 - 1 3es     

H3PMoxW12-xO40·nH2O和N-甲基吡咯烷酮电荷转移盐的合成、表征和非线性光学性质

杂多酸;H3PMoxW12-xO40·nH2O和N-甲基吡咯烷酮电荷转移盐的合成、表征和非线性光学性质