PMID- 32015807
OWN - NLM
STAT- PubMed-not-MEDLINE
LR  - 20240328
IS  - 2041-6520 (Print)
IS  - 2041-6539 (Electronic)
IS  - 2041-6520 (Linking)
VI  - 10
IP  - 42
DP  - 2019 Nov 14
TI  - Role of torsional strain in the ring-opening polymerisation of low strain 
      [n]nickelocenophanes.
PG  - 9841-9852
LID - 10.1039/c9sc02624j [doi]
AB  - Ring-opening polymerisation (ROP) of strained [1]- and [2]metallocenophanes and 
      related species is well-established, and the monomer ring-strain is manifest in a 
      substantial tilting of the cyclopentadienyl ligands, giving alpha angles of  approximately 14-32 degrees . 
      Surprisingly, tetracarba[4]nickelocenophane [Ni(eta(5)-C(5)H(4))(2)(CH(2))(4)] (2) 
      undergoes ROP (pyridine, 20  degrees C, 5 days) to give primarily insoluble 
      poly(nickelocenylbutylene) [Ni(eta(5)-C(5)H(4))(2)(CH(2))(4)] (n) (12), despite the 
      lack of significant ring-tilt. The exoenthalpic nature of the ROP was confirmed 
      by DFT calculations involving the cyclic precursor and model oligomers (DeltaH0ROP = 
      -14 +/- 2 kJ mol(-1)), and is proposed to be a consequence of torsional strain 
      present in the ansa bridge of 2. The similarly untilted 
      disila-2-oxa[3]nickelocenophanes [Ni(eta(5)-C(5)H(4))(2)(SiMe(2))(2)O] (13) and 
      [Ni(eta(5)-C(5)H(4))(2)(SiMePh)(2)O] (14) were found to lack similar torsional 
      strain and to be resistant to ROP under the same conditions. In contrast, 
      1-methyltricarba[3]nickelocenophane Ni(eta(5)-C(5)H(4))(2)(CH(2))(2)[CH(CH(3))] 
      (15) with a significant tilt angle (alpha  approximately  16 degrees ) was found to undergo ROP to give 
      soluble polymer Ni(eta(5)-C(5)H(4))(2)(CH(2))(2)[CH(CH(3))] (n) (18). The 
      reversibility of the process in this case allowed for the effects of temperature 
      and reaction concentration on the monomer-polymer equilibrium to be explored and 
      thereby thermodynamic data to be elucidated (DeltaH0ROP = -8.9 kJ mol(-1), DeltaG0ROP = 
      -3.1 kJ mol(-1)). Compared to the previously described ROP of the unsubstituted 
      analogue [Ni(eta(5)-C(5)H(4))(2)(CH(2))(3)] (1) (DeltaH0ROP = -10 kJ mol(-1), DeltaG0ROP = 
      -4.0 kJ mol(-1)), the presence of the additional methyl substituent in the ansa 
      bridge appears to marginally disfavour ROP and leads to a corresponding decrease 
      in the equilibrium polymer yield.
CI  - This journal is (c) The Royal Society of Chemistry 2019.
FAU - Musgrave, Rebecca A
AU  - Musgrave RA
AUID- ORCID: 0000-0001-9404-0422
AD  - School of Chemistry , University of Bristol , Bristol BS8 1TS , UK . Email: 
      imanners@uvic.ca.
FAU - Hailes, Rebekah L N
AU  - Hailes RLN
AUID- ORCID: 0000-0001-8895-6426
AD  - School of Chemistry , University of Bristol , Bristol BS8 1TS , UK . Email: 
      imanners@uvic.ca.
FAU - Annibale, Vincent T
AU  - Annibale VT
AUID- ORCID: 0000-0002-0511-4504
AD  - School of Chemistry , University of Bristol , Bristol BS8 1TS , UK . Email: 
      imanners@uvic.ca.
FAU - Manners, Ian
AU  - Manners I
AD  - School of Chemistry , University of Bristol , Bristol BS8 1TS , UK . Email: 
      imanners@uvic.ca.
AD  - Department of Chemistry , University of Victoria , Victoria , BC V8W 3V6 , 
      Canada.
LA  - eng
PT  - Journal Article
DEP - 20190910
PL  - England
TA  - Chem Sci
JT  - Chemical science
JID - 101545951
PMC - PMC6977548
EDAT- 2020/02/06 06:00
MHDA- 2020/02/06 06:01
PMCR- 2019/09/10
CRDT- 2020/02/05 06:00
PHST- 2019/05/29 00:00 [received]
PHST- 2019/07/31 00:00 [accepted]
PHST- 2020/02/05 06:00 [entrez]
PHST- 2020/02/06 06:00 [pubmed]
PHST- 2020/02/06 06:01 [medline]
PHST- 2019/09/10 00:00 [pmc-release]
AID - c9sc02624j [pii]
AID - 10.1039/c9sc02624j [doi]
PST - epublish
SO  - Chem Sci. 2019 Sep 10;10(42):9841-9852. doi: 10.1039/c9sc02624j. eCollection 2019 
      Nov 14.