Correlation of metal spin-state in α-diimine iron catalysts with polymerization mechanism
Correlation of metal spin-state in α-diimine iron catalysts with polymerization mechanism
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DOI：
10.1021/ic701500y
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发表时间：
2007-10-15
影响因子：
4.6
通讯作者：
Gibson, Vernon C.
中科院分区：
文献类型：
--
作者：
Allan, Laura E. N.;Shaver, Michael P.;Gibson, Vernon C.
α-二亚胺铁络合物(R‘，R’‘)[N，N]FeCl2((R’，R‘’)[N，N]=R‘-N=CR“-CR’‘=N-R’，其中R‘=叔丁基(Tbu)、环己基(Cy)和R’‘=苯基(Ph)、对氟苯基(F-Ph)、对溴苯基(BrPh)、对甲基苯基(Me-Ph)或对甲氧基苯基(MeO-Ph))通过链转移(CCT)机理聚合.磁矩测量表明，含有这些配体的Fe(III)络合物具有中等自旋态的铁中心(S=3/2)。相反，含有质子(R‘’=H)和对二甲氨基苯基(R‘’=NMe2-Ph)取代基的Fe(III)络合物是高自旋的，是有效的原子转移自由基聚合(ATRP)催化剂。Hammett图显示取代基常数sigma分别与聚合速率和聚合物相对分子质量呈线性相关。
The alpha-diimine iron complexes, (R',R '')[N,N]FeCl2 ((R',R '')[N,N] = R'-N=CR"-CR ''=N-R', where R' = tert-butyl (tBu), cyclohexyl (Cy) and R '' = phenyl (Ph), para-fluorophenyl (F-Ph), para-bromophenyl (Br-Ph), para-methylphenyl (Me-Ph), or para-methoxyphenyl (MeO-Ph)), are found to polymerize styrene through a catalytic chain transfer (CCT) mechanism. Magnetic moment measurements indicate that Fe(III) complexes containing these ligands possess intermediate (S = 3/2) spin-state iron centers. In contrast, Fe(III) complexes bearing proton (R '' = H) and paradimethylaminophenyl (R '' = NMe2-Ph) substituents are high-spin and are efficient atom transfer radical polymerization (ATRP) catalysts. Hammett plots show a linear correlation of the substituent constant, sigma, with polymerization rate and polymer molecular weight, respectively.