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Ruthenium–Triazene Complexes as Latent Catalysts for UV‐Induced ROMP
Author(s) -
Wang Dongren,
Unold Jörg,
Bubrin Martina,
Elser Iris,
Frey Wolfgang,
Kaim Wolfgang,
Xu Guangjuan,
Buchmeiser Michael R.
Publication year - 2013
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201301048
Subject(s) - triazene , chemistry , romp , ruthenium , norbornene , metathesis , medicinal chemistry , photochemistry , polymer chemistry , catalysis , polymerization , organic chemistry , polymer
Three novel ruthenium(II) complexes, RuX 2 (IMesH 2 )[ N , N ‐diethyl‐ N′ ‐(2‐benzylidene)triazene] [IMesH 2 = 1,3‐dimesitylimidazolin‐2‐ylidene; X = Cl – ( 2 ), CF 3 COO – ( 3 ), C 6 F 5 COO – ( 4 )] are described. Single‐crystal X‐ray structure analysis of compounds 2 – 4 revealed that the triazene ligand exists in the trans form and that the aryl‐connected nitrogen atom of the triazene binds to the ruthenium atom to form a five‐membered chelate ring. Compounds 2 – 4 were applied to the UV‐induced ring‐opening metathesis polymerization (ROMP) of cis ‐cyclooctene ( 5 ) and dicyclopentadiene ( 6 ). Whereas all three precatalysts show pronounced thermal latency in the presence of 5 or 6 , only compound 2 displays significant photo‐ROMP activity. The photoreactivity of precatalysts 2 – 4 , which decreases with increasing electron‐withdrawing character and with decreasing p K a of the X groups, is discussed and correlated with the X‐ray data of 2 – 4 , with low‐temperature 1 H NMR measurements as well as with cyclovoltammetric measurements.