Arene Exchange in the Ruthenium–Naphthalene Complex [CpRu(C₁₀H₈)]⁺

Abstract

Abstract Substitution of the naphthalene ligand in [CpRu(C 10 H 8 )] + ( 1 ; Cp = cyclopentadienyl ligand) by other arenes occurs upon heating or visible‐light irradiation and gives complexes [CpRu(arene)] + [arene = C 6 H n Me 6– n , C 6 H 5 OH, C 6 H 5 OMe, C 6 H 4 (OMe) 2 , indene, 2,2‐paracyclophane] in 70–90 % yield. The reaction rate increases with coordinating ability of the solvent, CH 2 Cl 2 < THF/CH 2 Cl 2 < Me 2 CO, and counterion, [B(3,5‐(CF 3 ) 2 C 6 H 3 ) 4 ] – < PF 6 – < BF 4 – < CF 3 SO 3 – . Acceptor or bulky substituents in the incoming arene slow down the exchange. Complexes with acceptor arenes C 6 H 5 COMe, C 6 H 5 COOH, and C 6 H 4 (COOH) 2 were obtained by the exchange reaction in water. Complexes [CpRu(η 6 ‐cycloheptatriene)] + and [CpRu(η 6 ‐cyclooctatetraene)] + were obtained by irradiation of 1 with the corresponding cyclic polyenes. A similar reaction with α‐phellandrene is accompanied by dehydrogenation to give [CpRu(cymene)] + . Cation 1 reacts with 2‐naphthoic acid anion to give the zwitterionic complexes [CpRu] + [C 10 H 7 COO] – in which the [CpRu] + fragment coordinates either at the substituted or unsubstituted ring. Upon protonation and subsequent irradiation, both isomers convert into [CpRu(C 10 H 7 COOH)] + in which the metal atom coordinates only to the unsubstituted ring. The structures of [CpRu( p ‐xylene)][PF 6 ], [CpRu(2,2‐paracyclophane)][PF 6 ], [CpRu(C 6 H 5 COOH)][BF 4 ], and [CpRu(cymene)][BPh 4 ] were determined by X‐ray diffraction.