New synthesis of Fischer-type hydrazino(alkyl) complexes. First x-ray characterisation of a chelate hydrazino derivative

The first Fischer-type hydrazino(methyl)carbene complex has been synthesized from the appropriate acetylhydrazine and Na2Cr(CO)5; the new complex has some peculiar features in comparison with aminocarbene complexes: (i) the E rotamer can be completely transformed into the Z rotamer through the formation of its anion, and (ii) as a result of a thermal reaction, the Z isomer affords a new unusual chelate hydrazino(methyl)carbene complex that can be mono- or dialkylated.