Living polymerization of novel conjugatively spaced ferrocenylacetylenes

The synthesis and living metathesis polymerization of five different conjugatively spaced ferrocenylacetylenes, (2-ethynylphenyl)ferrocene (3), (Z)-but-1-en-3-ynylferrocene (4), (E)-but-1-en-3-ynylferrocene (5), 2-(4-ethynylphen-1-yl)vin-1-ylferrocene (7), and 1-ferrocenyl-2-(4-ethynylphenyl)diazene (10) is described. Poly-10 represents the first polyacetylene containing ferrocenylazoarylene groups. The X-ray structures of two alkynes, 3 and 7, as well as of one ethynyl precursor, (4-bromophenyl)ferrocenyldiazene (8), are presented. Polymerizations of all terminal alkynes by the well-defined Schrock metathesis catalysts Mo(N-Ar')(CHCMe2Ph)(OCMe(CF3)(2))(2) (Ar' = 2,6-i-Pr2C6H3, 11; Ar' = 2,6-Me2C6H3, 12) start solely via beta-addition of the corresponding monomer to the initiator except for 3, which undergoes alpha-addition with 12. Presumably due to metathesis-type side reactions, 4 and 5 form only low molecular weight polymers. The polymerizations of 3, 7, and 10 proceed in a strongly living manner when either initiator (11, 12) is employed. The polymers are virtually formed via solely head to tail propagation, exhibiting low polydispersities and solubility up to a degree of polymerization (DP) approximate to 60. The influence of the spacer on the final properties of the poylmers with regards to their W-vis absorption spectra and effective conjugation lengths (N-eff) is discussed.