Cyclopentadienyl ruthenium complexes with naphthalene and other polycyclic aromatic ligands

• Cyclopentadienyl ruthenium complexes with polyarenes are easily accessible from RuCl3.
• Polyarenes can be exchanged for various ligands under mild conditions.
• [CpRu(polyarene)]+ complexes are convenient precursors for synthesis and catalysis.

Synthesis, reactivity and application of cyclopentadienyl ruthenium complexes with naphthalene and other polycyclic aromatic ligands (polyarenes) are reviewed. The parent naphthalene complex [CpRu(C10H8)]+ is readily obtained from ruthenocene while its substituted analog [Cp*Ru(C10H8)]+ is prepared by direct reaction of RuCl3·xH2O with Cp*H and C10H8. More sophisticated polyarene complexes including binuclear species are synthesized from the half-sandwich precursors [Cp*RuCl2]2, [Cp*RuCl]4, and [(C5R5)Ru(MeCN)3]+. Coordinated naphthalene in [CpRu(C10H8)]+ can be exchanged for various 2-electron ligands under thermal or photochemical conditions giving half-sandwich complexes CpRuL2X and [CpRuL3]+ (L = phosphines, N-heterocycles, dienes; X = Cl, Br, I, N3). Similar reactions of [CpRu(C10H8)]+ with cyclopentadienes or arenes produce sandwich compounds CpRu(C5R5) or [CpRu(arene)]+, respectively. The ability of [CpRu(C10H8)]+ to generate the catalytically active species [CpRuLx]+ can be used to promote anti-Markovnikov hydration and cyclotrimerization of alkynes, as well as for enantioselective Carroll rearrangement. In overall it can be concluded that stable and easily accessible [(C5R5)Ru(polyarene)]+ complexes represent convenient precursors for organometallic synthesis and catalysis.

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