In:
European Journal of Inorganic Chemistry, Wiley, Vol. 2007, No. 25 ( 2007-09), p. 3988-4000
Abstract:
Four chiral, enantiomerically pure monomers, exo , exo ‐ N , N ‐(norborn‐5‐ene‐2,3‐dicarbimido)‐ L ‐valine ethyl ester ( exo ‐ 1 ), endo , endo ‐ N , N ‐(norborn‐5‐ene‐2,3‐dicarbimido)‐ L ‐valineethyl ester ( endo ‐ 1 ), exo , exo ‐ N , N ‐(norborn‐5‐ene‐2,3‐dicarbimido)‐ L ‐valine‐ tert ‐butylamide ( exo ‐ 2 ), and endo , endo ‐ N , N ‐(norborn‐5‐ene‐2,3‐dicarbimido)‐ L ‐valine‐ tert ‐butylamide ( endo‐ 2 ), were subjected to ring‐opening metathesis polymerization (ROMP) with Ru(CF 3 CO 2 ) 2 (IMesH 2 )( p ‐cymene) ( 3 ), Ru(CF 3 CO 2 ) 2 (IMes)( p ‐cymene) ( 4 ), RuCl 2 (IMes)( p ‐cymene) ( 5 ), Ru(PCy 3 )(CF 3 CO 2 ) 2 ( p ‐cymene) ( 6 ), Ru(CF 3 CO 2 ) 2 ( p ‐cymene) · CF 3 COOAgPCy 3 ( 6a ), Ru(CF 3 CO 2 ) 2 (PPh 3 )( p ‐cymene) ( 7 ), Ru(CF 3 CO 2 ) 2 (IMes)(PhNC) 3 ( 8 ), and Ru(CF 3 CO 2 ) 2 (IMesH 2 )(PhNC) 3 ( 9 ) (IMes = 1,3‐dimesitylimidazol‐2‐ylidene, IMesH 2 = 1,4‐dimesityl‐4,5‐diyhdroimidazolin‐2‐ylidene, PCy 3 = tricyclohexylphosphane). X‐ray structures of precatalysts 3 and 6 – 9 are presented. Compounds 3 and 4 displayed significant ROMP activity, allowing for the controlled, yet nonliving synthesis of the corresponding polymers with polydispersity indices (PDIs) in the range of 1.17–2.14. In all cases the exo isomers of compounds 1 and 2 were polymerized by preference. While poly( endo ‐ 1 ) was formed in an all‐ trans form, poly( exo ‐ 1 ) and poly( exo ‐ 2 ) were produced in their cis / trans forms with a cis content of around 40 %. Calculations carried out at the B3LYP/LACVP* level suggest two possible mechanisms for the increased reactivity of the 2,3‐R 2 ‐ exo , exo isomers of norborn‐5‐ene‐2,3‐dicarbimido derivatives resulting in the formation of the ROMP‐active Ru IV alkylidene. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Type of Medium:
Online Resource
ISSN:
1434-1948
,
1099-0682
DOI:
10.1002/ejic.v2007:25
DOI:
10.1002/ejic.200700041
Language:
English
Publisher:
Wiley
Publication Date:
2007
detail.hit.zdb_id:
1475009-0
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