４族メタロセン錯体を用いたＮ２とＣＯ２からヒドラジン類の合成

概要

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Activation of atmospheric dinitrogen under mild conditions has remained a challenge to chemists for more than a century. In addition to the fixation of dinitrogen to ammonia, direct elaboration of inert atmospheric N2 into more value-added organic molecules is also attractive for the evolution of ammonia-independent synthetic pathways. Chirik et al. have found the rich chemistry of substituted bis(cyclopentadienyl)zirconium and hafnium complexes (metallocenes) bearing side-on coordinated dinitrogen ligands. As extension of this chemistry, syntheses of substituted hydrazines from N2 and CO2, which are both abundant chemical feedstocks, promoted by hafnocene and zirconocene were discovered. Addition of 2 equiv of carbon dioxide to the hafnocene and the ansa-zirconocene dinitrogen complexes resulted in insertion into M-N bonds, forming dicarboxylated diazenido complexes, where their insertion patterns are different. Subsequent treatments with Me3SiI liberated dicarboxylated silyl-substituted hydrazines. Moreover, for the zirconocene type, new N-C bonds were also assembled by addition of methyl triflate before liberation of hydrazines by treatments with electrophiles.