Reactions of Fe₂(CO)₉ with Azine Derivatives: Discovery of New Coordination Modes and Reactivity of New Bimetallic Compounds

Reaction of N,N‘-bis-(3-phenyl-allylidene)-hydrazine (1) with Fe2(CO)9 was studied. When the reaction was carried out in refluxing THF, the three mononuclear compounds (3), (4), and (5; R = −CHCHPh) were obtained. In refluxing toluene, the novel dinuclear compound Fe(CO)3[PhCHCHCHNNCHCHCHPh]Fe(CO)3 (2) was obtained. Further treatment of 3−5 with Fe2(CO)9 in refluxing toluene eventually led to 2. A detailed study of the reaction of 3−5 with/without Fe2(CO)9 allowed us to establish an overall reaction sequence from 1 to 2. Reaction of the alkyl analogue MeCHCHCHNNCHCHCHMe (10) with Fe2(CO)9 yielded the two dinuclear compounds (11 and 11‘) or the two mononuclear compounds (12) and Fe(CO)3[MeCHCHCHNNCHR‘] (13; R‘ = −CHCHMe) and the dinuclear compound (14), respectively, depending upon the reaction conditions. Treatment of 2 with MeLi yielded the dimeric compound [PhCHCHCHNNCHCHCHPh]2Fe4(CO)12 (16), containing four iron atoms, and treatment with MeLi followed by MeI afforded the dimethyl adduct (17). The molecular structures of 3−5, 8, 11, 11‘, 14, and 16 were confirmed by X-ray diffraction studies.