The B-phenylborole complex CpRh(η 5 -C 4 H 4 BPh) (1) reacts with [ML] + fragments to give the arene-type cationic complexes [CpRh(μ-η 5 :η 6 -C 4 H 4 BPh)ML] + (ML=RuCp ∗ (3), Co(C 4 Me 4 ) (4), Rh(cod) (5), and Ir(cod) (6)). Cation 4 undergoes a reversible rearrangement into the triple-decker complex [CpRh(μ-η 5 :η 5 -C 4 H 4 BPh)Co(C 4 Me 4 )] + (7) under visible light irradiation in CH 2 Cl 2 solution. DFT calculations revealed greater stability of arene-type complexes over triple-decker isomers. The structure of [3]BF 4 was determined by X-ray diffraction.