Microwave‐Assisted Synthesis and Transformations of Cationic CpRu(II)(naphthalene) and CpRu(II)(naphthoquinone) Complexes

Details of the direct synthesis of cationic Ru(II)(η⁵‐Cp)(η⁶‐arene) complexes from ruthenocene using microwave heating are reported. Developed for the important catalyst precursor [Ru(II)(η⁵‐Cp)(η⁶‐1‐4,4a,8a‐naphthalene)][PF₆] reaction time could be shortened from three days to 15 min. The method was extended to [Ru(II)(η⁶‐benzene)(η⁵‐Cp)][PF₆], [Ru(II)(η⁵‐Cp)(η⁶‐toluene)][PF₆], [Ru(II)(η⁵‐Cp)(η⁶‐mesitylene)][PF₆], [Ru(II)(η⁵‐Cp)(η⁶‐hexamethylbenzene)][PF₆], [Ru(II)(η⁵Cp)(η⁶‐indane)][PF₆], [Ru(II)(η⁵‐Cp)(η⁶‐2,6‐dimethylnaphthalene)][PF₆], and [Ru(II)(η⁵‐Cp)(η⁶‐pyrene)][PF₆]. 1‐methylnaphthalene and 2,3‐dimethylnaphthalene afforded mixtures of regioisomeric complexes. [Ru(Cp)(CH₃CN)₃][PF₆], derived from the naphthalene precursor provided access to the cationic RuCp complexes of naphthoquinone, tetralindione, 1,4‐dihydroxynaphthalene, and 1,4‐dimethoxynaphthalene. Reduction of the tetralindione complex afforded selectively the endo,endo diol derivative. X‐Ray structures of five complexes are reported.