New Vinyl Organometallic Monomers: Synthesis and Polymerization Behavior

Organometallic polymers are useful in a variety of applications such as catalysts, UV absorbers, semiconductors, and antifouling agents.1–3 The construction of organometallic polymers can proceed by derivatizing preformed polymers with organometallic units3 or by preparing monomers with organometallic functions and polymerizing these monomers.2 Monomers 1–3 represent three examples of organometallic monomers which have been polymerized.4–7 In 2 6 and 3,7 the organometallic unit is far removed from the polymerizable vinyl group and does not directly effect the polymerization behavior via electronic effects. However, in vinylferrocene, 1, the organometallic moiety is directly attached to the vinyl group which leads, in turn, to some unusual effects in polymerization. For example, the rate of polymerization of vinylferrocene is first order in both monomer and initiator when initiated by AIBN in benzene (VP = 5.64 × 10−4[1]1.12 [AIBN]1.11).5 This is the result of a monomolecular termination mechanism caused by an electron transfer from iron to the radical center, followed by termination and subsequent decomposition to a paramagnetic Fe(III) center in the polymer. The presence of the transition metal, Fe, in the monomer permits such an unusual redox behavior which is impossible for ‘normal’ organic monomers (equation 1).