Synthesis and reactions of binuclear molybdenocene and tungstenocene derivatives

The tetramer [{Mo(η-C5H5)2HLi}4] reacts with N2O giving the yellow dimers cis- and trans-[{Mo(η-C5H5)H}2-(µ-σ : η-C5H4)2]. These thermally rearrange to the green dimer [{Mo(η-C5H5)H}2(µ-η5-C5H4-η5-C5H4)]. Protonation of the latter gives [{Mo(η-C5H5)H}2(µ-H)(µ-η5-C5H4-η5-C5H4)][PF6]. Photolysis of [Mo-(η-C5H5)2H2] or the yellow dimers gives a red dimer [{Mo(η-C5H5)}2(µ-σ : η5-C5H4)2]. Prolonged treatment of the four neutral dimers with aqueous acid gives [{Mo(η-C5H5)}2(µ-H)(µ-OH)(µ-η5-C5H4-η5-C5H4)][PF6]2. The red and yellow dimers react with iodine giving [{Mo(η-C5H5)I}2(µ-σ : η5-C5H4)2] and the corresponding reaction with the green dimer yields [{Mo(η-C5H5)I}2(µ-η5-C5H4-η5-C5H4)]. The red dimer also adds to methyl bromide giving [{Mo(η-C5H5)Me}{Mo(η-C5H5)Br}(µ-σ : η5-C5H4)2], whereas the yellow dimer reacts with methyl iodide to give [{Mo(η-C5H5)}2(µ-σ : η5-C5H4)2]. Photolysis of [W(η-C5H5)2H2] in diethyl ether gives cis- and trans-[{W(η-C5H5)H}2(µ-σ : η5-C5H4)2] and the cation [W(η-C5H5)2(η-C2H4)H]+. Thermal decomposition of [W(η-C5H5)2MeH] in cyclohexane gives isomers of the compound [{W(η-C5H5)2Me}{W(η-C5H5)H}-(µ-σ : η5-C5H4)2].