Hailes Rebekah L N, Musgrave Rebecca A, Kilpatrick Alexander F R, Russell Andrew D, Whittell George R, O'Hare Dermot, Manners Ian
School of Chemistry, University of Bristol, Bristol, BS8 1TS, UK.
Chemistry Research Laboratory, Department of Chemistry, University of Oxford, 12 Mansfield Rd, Oxford, OX1 3TA, UK.
Chemistry. 2019 Jan 18;25(4):1044-1054. doi: 10.1002/chem.201804326. Epub 2018 Nov 26.
Polymetallocenes based on ferrocene, and to a lesser extent cobaltocene, have been well-studied, whereas analogous systems based on nickelocene are virtually unexplored. It has been previously shown that poly(nickelocenylpropylene) [Ni(η -C H ) (CH ) ] is formed as a mixture of cyclic (6 ) and linear (7) components by the reversible ring-opening polymerisation (ROP) of tricarba[3]nickelocenophane [Ni(η -C H ) (CH ) ] (5). Herein the generality of this approach to main-chain polynickelocenes is demonstrated and the ROP of tetracarba[4]nickelocenophane [Ni(η -C H ) (CH ) ] (8), and disila[2]nickelocenophane [Ni(η -C H ) (SiMe ) ] (12) is described, to yield predominantly insoluble homopolymers poly(nickelocenylbutylene) [Ni(η -C H ) (CH ) ] (13) and poly(tetramethyldisilylnickelocene) [Ni(η -C H ) (SiMe ) ] (14), respectively. The ROP of 8 and 12 was also found to be reversible at elevated temperature. To access soluble high molar mass materials, copolymerisations of 5, 8, and 12 were performed. Superconducting quantum interference device (SQUID) magnetometry measurements of 13 and 14 indicated that these homopolymers behave as simple paramagnets at temperatures greater than 50 K, with significant antiferromagnetic coupling that is notably larger in carbon-bridged 6 /7 and 13 compared to the disilyl-bridged 14. However, the behaviour of these polynickelocenes deviates substantially from the Curie-Weiss law at low temperatures due to considerable zero-field splitting.
基于二茂铁的多金属茂，以及在较小程度上基于二茂钴的多金属茂，已经得到了充分研究，而基于二茂镍的类似体系实际上尚未被探索。此前已经表明，聚（二茂镍基丙烯）[Ni(η -C₅H₅)(CH₂)₃]是由三环[3]二茂镍环戊二烯[Ni(η -C₅H₅)(CH₂)₃]（5）通过可逆开环聚合（ROP）形成的环状（6）和线性（7）组分的混合物。在此，展示了这种制备主链聚二茂镍的方法的通用性，并描述了四环[4]二茂镍环戊二烯[Ni(η -C₅H₅)(CH₂)₄]（8）和二硅[2]二茂镍环戊二烯[Ni(η -C₅H₅)(SiMe₂)₂]（12）的ROP，分别得到主要为不溶性均聚物聚（二茂镍基丁烯）[Ni(η -C₅H₅)(CH₂)₄]（13）和聚（四甲基二硅基二茂镍）[Ni(η -C₅H₅)(SiMe₂)₂]（14）。还发现8和12的ROP在高温下是可逆的。为了获得可溶性高摩尔质量材料，进行了5、8和12的共聚反应。对13和14的超导量子干涉装置（SQUID）磁力测量表明，这些均聚物在温度高于50 K时表现为简单顺磁体，具有显著的反铁磁耦合，与二硅桥联的14相比，碳桥联的6 /7和13中的反铁磁耦合明显更大。然而，由于相当大的零场分裂，这些聚二茂镍在低温下的行为与居里 - 外斯定律有很大偏差。
