Transformations of hydrazines RNHNH2 (R = Me, Ph) at a sulfur-rich bimetallic site: Diazene-diazenido-isodiazene/hydrazido(2-) interconversions

Abstract : The bis(nitrile) compound [Mo2Cp2(μ-SMe)3 (MeCN)2](BF4) (1) (Cp = C5H5) reacted with substituted hydrazines RNHNH2 (R = Me, Ph) in acetonitrile at room temperature to give the stable diazene species [Mo2Cp2 (μ-SMe)3(μ-η2-HN=NR)](BF4) [R= Me (2), Ph (3)]. Compounds 2 and 3 could be readily deprotonated with BuLi to produce neutral diazenido species [Mo2Cp2(μ-SMe)3 (μ-η2-N=NR)] [R = Me (4), Ph (5)]. Photolysis of 4 in THF induced isomerization of the diazenide bridge, affording the complex [Mo2Cp2(μ-SMe)3 (μ-η1-N=NMe)] (8). This species underwent protonation at the outer nitrogen atom (Nβ) to give the stable isodiazene/ hydrazido(2-) complex [Mo2Cp2(μ-SMe)3 (μ-η1-N=NHMe)](BF4) (9) which isomerised slowly back into 2 on warming. The molecular structure of the μ-η2-methyldiazenido complex 4 was established by an X-ray diffraction study.