I1of methyl methacrylate. It is particularly noteworthy that moderate but definite acceleration by visible light was observed also in the block copolymerization reaction (Figure 2). In the block copolymerization of butyl methacrylate initiated from the living poly(methy1 methacrylate) (Mn = 9100) prepared with (TPP)AlMe (100/100/1) at 15 "C for 12 h, the conversion was 75% for the light reaction while 54% in the dark reaction; corresponding to this, Mn = 17 800 (Mw/Mn = 1.1 1) and Mn = 16000 (Mw/Mn = l.lO), respectively.In order to obtain further insight into the nature of the reactive species in polymerization, the reaction mixture (living polymer) was subjected to N M R spectral analysis, which can provide very useful information about the group bound to the metal in a porphyrin ring by the virtue of its strong shielding effect. In the reaction of 5 molar equiv of tert-butyl methacrylate and (TPP)AlMe in C6D6 at 30 "c for 72 h under irradiation, the signal due to A1-CH, (6 -5.8 ppm in C6D6) di~appeared.~ Among the new signals, a strong singlet at -0.3 ppm (-0.8 ppm in CDC1,) was the most characteristic, the intensity relative to pyrrole$ proton of porphyrin being 8.4%. In the reaction of the living poly(methy1 methacrylate) with 5 molar equiv of tert-butyl vinyl ketone, a characteristic signal was observed at -1.5 ppm in CDCl,, which is assigned to tert-butyl group of a (porphinato)aluminum enolate I.6 Therefore, the signal observed at -0.8 ppm in the P\ 1 ' .former reaction is considered due to an aluminum enolate 11, R = t-Bu derived from tert-butyl methacrylate.' These observations indicate that the active species of this polymerization is a (porphinato)aluminum enolate I1 (see Scheme I). The polymerization probably proceeds via the concerted mechanism, where the approach (coordination) of methacrylate to the aluminum atom and the conjugate addition of methyl or enolate group simultaneously take place. (5) Quantitative incorporation of the methyl group into the terminal of poly(methy1 methacrylate) was confirmed by I3C NMR (6 8.4 ppm in CDCIJ. (6) For (TPP)AI-O-C[C(CH,),]=CH-CH,-Et, formed by the reaction of (TPP)AIEt and tert-butyl vinyl ketone, 6 -1.46 ppm in CDCI,: Murayama, H.; Inoue, S . Chem. Lett. 1985, 1377.(7) Other signals at high magnetic field are observed at 6 -0.1 to -0.2 ppm and at 6 -1.8 to -1.9 ppm (in CDC13), which are considered due to either =C-CH2or =C-CH,, respectively.0002-7863/87/l509-4738$01.50/0Thus, not only the addition of (TPP)AlMe to alkyl methacrylate (initiation) but also the addition of (TPP)AI enolate to the methacrylate (every step of propagation) is accelerated by visible light, though to different extents.* Aluminum-alkyl or aluminum-enolate bonds cannot be directly excited by visible light but are considered to be activated indirectly by excitation of the porphyrin ring. Thus, the present reaction is a novel type of photocatalysis with metalloporphyrin. (8) Although there are the examples of photoinduced addition polymerization, light is effective only for the generation...