To get a deeper insight into the mechanism of H2 activation by 1 + , DFT computations were carried out at BP86(D3)/def2-TZVP level of theory in CH2Cl2 using the conductor-like polarizable continuum (CPCM) model . These calculations show that the oxidative addition type reaction of H-H bond to P III -center in 1 + producing 1 + -H2 is both exothermic and exergonic (∆H = -16.3 and ∆G = -7.8 kcal•mol -1 ) (Fig. ). Gibbs free energy barrier of ∆G ‡ = 32.6 kcal•mol -1 (TS) of this H2 activation reaction is reasonable and can explain long reaction times and/or heating requirement. The geometry of the transition state (TS) suggests that this activation is most probably an electrophilically driven process, as the H-H σ bond approaches the P-center from the direction in which the LUMO points (Fig. ). The ability of 1 + to transfer hydrogen catalytically was tested with various unsaturated C-C bond containing systems. First the reaction of highly active terminal alkene, 1,1-diphenylethylene (3) with H2 (4 atm) and 10 mol% of [1 + ][B(C6F5)4] was probed. This reaction, however, led to the 1,1-diphenylethylene dimerization product (4) in minutes (~5 min) at room temperature , while the desired 1,1-diphenylethane, a hydrogenation product, was not obtained. Similar reaction was conducted with 1-hexene (5), H2 (4 atm) and [1 + ][B(C6F5)4] (10 mol%) at 40 ºC affording mostly isomerization product (6) (41) after 6 h, and again no hydrogenation of the C=C double bond occurred even after prolonged heating. Importantly, both reactions of 3 and 5 in presence of 10 mol% of [1 + ][B(C6F5)4] without the addition of H2 gave the same results i.e., formation of 4 and 6, respectively (Fig. ). Meaning that the dimerization of 3 as well as isomerization of 5 are catalyzed by 1 + , indicating once again the high Lewis acidity of this cation .