Abstracts Nippon Kagaku Zasshi, 88, 1129^-1137(1967 Chemistry of Tsuzumi ir-Complexes. V Part II. Its Significance in Biochemistry by Minoru TSUTSUI The present article and the preceding Part I deal with a complete review of our published and partially unpublished work concerned with " Tsuzumi type " n-complex chemistry since 1953. I . The significance and the role of the reproduction and the reformulation of Hein'S compounds as " Tsuzumi type " 7rcomplexes in chemistry are described. . The

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... ificance and the role of metal 7r-complex chemistry in catalysis developed by us are described. A new molecular rearrangement, a-ir rearrengement, discovered by us plays an important role in catalysis. Development of interesting catalyses by zerovalent metal complexes initiated by us is described. 111. Our current efforts on studying the possible significance and the role of 7r-complex bonding in biological systems have been rewarded to some extent. New and dynamic developments in this field are expected. Some of our preliminary results are included here. In the solution of carbon tetrachloride, chloroform and acetone, NMR chemical shifts of the ortho-hydroxyl proton of seven thiazolylazophenols have been measured and discussed in relation to their ultraviolet and visible spectra. The latter spectra indicate the existence of quinonhydrazone and azophenol tautomerism in these solutions. The linear relationships were obtained, in which the larger the molar fractions of azophenol tautomers, the lower were the values of the "OH proton" . In this case these molar fractions of azophenol tautomer were estimated by isolated band intensities of absorption spectra in each solution. This fact indicates that the interconversion between the tautomers is rapid. The linear relationship was found between the chemical shifts of "OH proton" and the weighted mean values of vmax attributed to the both tautomers. Also a linear relationship was found between the chemical shifts of the proton adjacent to azo group in benzene ring and v max of the isolated bands of absorption spectra.