Compared with the reactivity of o-Ph2P(C6H4–CH2)BH(NiPr2) with [RuH2(η2-H2)2(PCy3)2], the behavior of the phosphinoborane Ph2P(CH2–C6H4)BH(NiPr2) is radically different. No agostic σ-B–H complex could be observed, the reaction leading to the isolation of a new bis-σ borane aryl-ruthenium complex via B–C bond cleavage and Ru–C bond formation. Reactivity studies of this complex with dihydrogen and/or HBArF4 as a proton source enable the formation of a tethered chiral-at-Ru piano-stool cationic complex.