A Ru-η6-Arene Complex as a C-Based Lewis Acid in the Activation of Hydrogen and Hydrogenation Catalysis

The PBP ligand (Ph2PC6H4)(2)BPh was used to prepare ((Ph2PC6H4)(2)B(Cl)(eta(6)-Ph)RuCI (1) and subsequently [((Ph2PC6H4)(2)B(eta(6)-Ph))RuCl][B(C6F5)(4)] (2). The latter species exhibited Lewis acidity on the;eta(6)-Ph ring, as reaction with Cy3P gave the donor-acceptor adduct [(Ph2FC6H4)(2)B(eta(5)-C6H5-o-PCy3)RuCl] [B (C6F5)(4)] (3). Steric frustration of this binding was seen with Mes(3)P, and yet the combination of 2 and Mes(3)P reacted with H-2 to give a 2:1 mixture of 5-o and 5-p, two isomers of [(Ph2PC6H4)(2)B(eta(5)-C6H6)RuCl] (5), along with [Mes(3)PH][HB(C6F5)(3)]. Compound 2 behaves as C-. based Lewis acid and thus can also be used for catalytic hydrogenation of aldimines at room temperature via a frustrated Lewis pair mechanism.