The electroreduction of alkylaryldichlorosilane carried out with Mg cathode and anode in a single compartment cell gave high molecular weight poly(alkylarylsilane) (M(n) = 5200-31000, M(w)/M(n) = 1.4-1.8) in 5-79% yield. The effects of electrode material, monomer concentration, amount of supplied electricity, and ultrasound were investigated. This electroreductive method was also successfully applied to the synthesis of polygermanes, silane-geramane copolymers, and also poly[p-(disilanylene)phenylenes].

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Demetalation kinetics of natural chlorophyll (Chl) d purified from Acaryochloris marina was first studied and compared with those of Chls a and b. The demetalation rate constant of Chl d, which possessed a formyl group at the 3-position, was five-fold smaller than that of Chl a possessing a vinyl group at the same position in aqueous acetone at the proton concentration of 1.2 x 10(-3) M at 25 degrees C. In contrast, the demetalation rate constant of Chl b possessing a formyl group at the 7-position was 26 times smaller than that of Chl a. The activation energy of demetalation reaction of Chl d was larger than that of Chl a, but smaller than that of Chl b. These indicate that the substitution effect of 3-formyl group on the acidic removal of central magnesium in Chls was smaller than that of 7-formyl group.

Demetalation kinetics of bacteriochlorophylls (BChls) c, d and e from green sulfur photosynthetic bacteria were studied under weakly acidic conditions. Demetalation rate constants of BChl e possessing a formyl group at the 7-position were significantly smaller than those of BChls c and d, which had a methyl group at this position. The activation energy of demetalation of 3(1)R-8,12-diethyl([E,E])-BChl e was 1.5-times larger than that of 3(1)R-[E,E]-BChl c. 15N-labeled 3(1)R-[E,E]-BChls c and e were purified from cells of green sulfur bacteria grown in a medium containing 15NH4Cl, and their 15N NMR spectra were measured. The chemical shifts of N21, N22 and N23 atoms of 3(1)R-[E,E]-BChl e were lower-field shifted than those of 3(1)R-[E,E]-BChl c, respectively, and especially the difference in chemical shifts of N22 was significantly large. These results suggest that the electron-withdrawing formyl group at the 7-position of BChl e affected an electronic state of the chlorin macrocycle and caused BChl e to be more tolerant for removal of the central magnesium compared with BChls c and d.

Electroreduction of dichlorosilanes, such as 1 ,I -dichlorodialkylsilanes, I ,2-dichlorotetra-alkyldisilanes, and 1,4-bis(chlorodialkylsilyl)benzenes, with M g electrodes in a single-compartment cell was found to yield the corresponding polysi lanes.We report our new findings that the electroreduction of as 1,l-dichlorosilanes ,I 1,2-dichlorodisilanes,2 and bis(ch1orochlorosilanes with an Mg anode and cathode is effective for silyl)benzenes,3,4 yielded the corresponding polysilanes.1 the formation of Si-Si bonds. The electroreduction of Other metal electrodes were less effective (Pt, Zn, Ni, and trialkylchlorosilanes with Mg electrodes gave disilanes in Cu), The products contained < 2% of the corresponding excellent isolated yields (Scheme 1) , and dichlorosilanes such siloxane.