Pyrolysis of Poly(ferrocenylsilanes): Synthesis and Characterization of Ferromagnetic Transition Metal-Containing Ceramics and Molecular Depolymerization Products
Pyrolysis of Poly(ferrocenylsilanes): Synthesis and Characterization of Ferromagnetic Transition Metal-Containing Ceramics and Molecular Depolymerization Products
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DOI：
10.1021/cm00059a010
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发表时间：
1995-11
影响因子：
8.6
通讯作者：
R. Petersen;D. Foucher;B. Tang;A. Lough;N. P. Raju;J. Greedan;I. Manners
中科院分区：
文献类型：
--
作者：
R. Petersen;D. Foucher;B. Tang;A. Lough;N. P. Raju;J. Greedan;I. Manners
用热重分析法（TGA）研究了一系列高分子量聚二茂铁基硅烷[Fe（r-C5 H &·3 iRR）在2a-d（a：R = R = Me; B：R = R = Ph; c：R = Me，R = H; d：R = Me，R =乙烯基）中表明这些材料热稳定至约100 ℃。300-350 ℃下在二氮（加热速率10 ℃/min）和更高的温度下得到陶瓷产品3a-d。通过TGA测得的陶瓷产率在600 ℃时在18%（对于2b）至66%（对于2d）的范围内，在1000 ℃时在17%（2b）至45%（2c，2d）的范围内。a 1的热解：聚合物2c和2d的共混物在600 ℃下以62%的产率得到陶瓷3e，并且在1000 ℃下通过TGA得到最高的陶瓷产率（56%）。在N2下在管式炉中的受控热解实验允许分离黑色发光陶瓷3a-e以及几种分子解聚产物。陶瓷3a（在600和1000 ℃下形成）和3b和3e（在600 ℃下形成）通过扫描电子显微镜（SEM）、能量色散X射线显微分析（EDX）和背散射电子成像（BEI）表征。这些技术表明，这些材料是铁碳化硅。通过粉末X射线衍射（XRD）发现，在t600“C下形成的陶瓷3a是无定形的，而在t1000“C下形成的相应陶瓷显示含有α-Fe微晶。对陶瓷3a、3b和3e进行的穆斯堡尔和磁化测量表明，这些材料是软铁磁体。在热解过程中产生的几种挥发性分子副产物的鉴定为不寻常的分解/解聚途径的操作提供了证据。在2a的热解过程中，生成了不对称的二聚体Fe（r-C5 H4）2（~-SiMe 2）2（r-C5 H3）Fe（11-C5 H5）（4a），并通过单晶X射线衍射对其进行了表征。循环伏安法研究表明，4a在CH 2Cl 2中经历了两个可逆的和连续的单电子氧化（分离A E 12 = 0.26 V）与铁中心之间的氧化还原偶联一致。三苯基硅基二茂铁，Fe（r-C~ H_5）（r-C_5 H_4SiPh_3），是从Mo_2b中分离出来的挥发性热解产物之一。4a 0的晶体为单斜晶系，空间群为P21/n，a = 9.3842（2）A，B = 15.455（2）A，c = 15.6630（12）A; a = 91.092（6）"; 2 = 4; V = 2271.2（11）A3。
Thermogravimetric analysis (TGA) of a series of high molecular weight poly(ferroceny1silanes) [Fe(r-C5H&!3iRR)In 2a-d (a: R = R = Me; b: R = R = Ph; c: R = Me, R = H; d : R = Me, R = vinyl) indicated that these materials are thermally stable to ca. 300-350 "C under dinitrogen (heating rate 10 "C/min) and at more elevated temperatures yield the ceramic products 3a-d. Ceramic yields by TGA were in the range of 18% (for 2b) to 66% (for 2d) a t 600 "C and in the range of 17% (2b) to 45% (2c, 2d) a t 1000 "C. Pyrolysis of a 1 : l blend of the polymers 2c and 2d afforded the ceramic 3e in 62% yield a t 600 "C and the highest ceramic yield by TGA a t 1000 "C (56%). Controlled pyrolysis experiments in a tube furnace under N2 permitted the isolation of the black, lustrous ceramics 3a-e together with several molecular depolymerization products. The ceramics 3a (formed a t 600 and 1000 "C) and 3b and 3e (formed a t 600 "C) were characterized by scanning electron microscopy (SEM) with energy-dispersive X-ray microanalysis (EDX) and back-scattered electron imaging (BEI). These techniques indicated that these materials were iron silicon carbides. The ceramic 3a formed a t 600 "C was found to be amorphous, whereas the corresponding ceramic formed a t 1000 "C was shown to contain a-Fe crystallites by powder X-ray diffraction (XRD). Mossbauer and magnetization measurements carried out on the ceramics 3a, 3b, and 3e indicated that the materials were soft ferromagnets. Identification of several volatile molecular byproducts produced during pyrolysis provided evidence for the operation of unusual decompositioddepolymerization pathways. The unsymmetrical dimer Fe(r-C5H4)2(~-SiMe2)2(r-C5H3)Fe(ll-C5H5) (4a) was formed during the pyrolysis of 2a, and this species was characterized by single-crystal X-ray diffraction. Cyclic voltammetry studies of 4a in CH2C12 showed that this species undergoes two reversible and sequential one-electron oxidations (separation A E 1 / 2 = 0.26 V) consistent with redox coupling between the iron centers. Triphenylsilylferrocene, Fe(r-C~H5)(r-C5H4SiPh3), was isolated as one of the volatile pyrolysis prodvcts derived fromo2b. Crystals of 4aoare monoclinic, space group P21/n, with a = 9.3842(2) A, b = 15.455(2) A, c = 15.6630(12) A; = 91.092(6)"; 2 = 4; V = 2271.2(11) A3.