Allan Laura E N, Shaver Michael P, White Andrew J P, Gibson Vernon C
Contribution from the Department of Chemistry, Imperial College London, South Kensington, London, SW7 2AZ, UK.
Inorg Chem. 2007 Oct 15;46(21):8963-70. doi: 10.1021/ic701500y. Epub 2007 Sep 14.
The alpha-diimine iron complexes, (R',R'')[N,N]FeCl(2) ((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 para-dimethylaminophenyl (R' ' = NMe(2)-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.
α-二亚胺铁配合物，(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）且R'' = 苯基（Ph）、对氟苯基（F-Ph）、对溴苯基（Br-Ph）、对甲基苯基（Me-Ph）或对甲氧基苯基（MeO-Ph）），被发现通过催化链转移（CCT）机理使苯乙烯聚合。磁矩测量表明，含有这些配体的Fe(III)配合物具有中间（S = 3/2）自旋态铁中心。相比之下，带有质子（R'' = H）和对二甲基氨基苯基（R'' = NMe₂-Ph）取代基的Fe(III)配合物是高自旋的，并且是高效的原子转移自由基聚合（ATRP）催化剂。哈米特图分别显示了取代基常数σ与聚合速率和聚合物分子量的线性相关性。
