A Comprehensive Theoretical Study on the Reactions of Sc⁺ with C_nH_2n+2 (n=1–3): Structure, Mechanism, and Potential‐Energy Surface

Abstract

The reactions of Sc(+)((3)D) with methane, ethane, and propane in the gas phase were studied theoretically by density functional theory. The potential energy surfaces corresponding to [Sc, C(n), H(2n+2)](+) (n=1-3) were examined in detail at the B3LYP/6-311++G(3df, 3pd)//B3LYP/6-311+G(d,p) level of theory. The performance of this theoretical method was calibrated with respect to the available thermochemical data. Calculations indicated that the reactions of Sc(+) with alkanes are multichannel processes which involve two general mechanisms: an addition-elimination mechanism, which is in good agreement with the general mechanism proposed from earlier experiments, and a concerted mechanism, which is presented for the first time in this work. The addition-elimination reactions are favorable at low energy, and the concerted reactions could be alternative pathways at high energy. In most cases, the energetic bottleneck in the addition-elimination mechanism is the initial C--C or C--H activation. The loss of CH(4) and/or C(2)H(6) from Sc(+)+C(n)H(2n+2) (n=2, 3) can proceed along both the initial C--C activation branch and the Cbond;H activation branch. The loss of H(2) from Sc(+)+C(n)H(2n+2) (n=2, 3) can proceed not only by 1,2-H(2) and/or 1,3-H(2) elimination, but also by 1,1-H(2) elimination. The reactivity of Sc(+) with alkanes is compared with those reported earlier for the reactions of the late first-row transition-metal ions with alkanes.

Amavadin and Other Vanadium Complexes as Remarkably Efficient Catalysts for One‐Pot Conversion of Ethane to Propionic and Acetic Acids

“…In contrast to the extensive theoretical studies that have been undertaken to elucidate the mechanisms of various alkane reactions (hydroxylation, [11] halogenation, [12] dehydrogenation, [13] CH 4 oxidation in sulfuric acid [14] and on an Feexchanged zeolite, [15] C À H bond activation by Re, [16] Pt, [17] Ti, [18] lanthanides, [19] and Rh [20] complexes, by unsaturated Al ions, [21] Sc + [22] or metal oxides, [23] etc. ), only a few papers propose plausible mechanisms of alkane carboxylation, [3a,b,d,g, 4b,c,d, 24] and only two, to our knowledge, report detailed theoretical studies, one of them for a quite different system [25] from ours, and the other one (studied by some of us)…”

Activation of Propane C-H and C-C Bonds by Gas-Phase Pt Atom: A Theoretical Study

“…Last, the molecular complex dissociates into Pt(CH 2 ) 3 + H 2 . The structure of metallacycle Pt(CH 2 ) 3 is similar to that of Sc(CH 2 ) 3 + [6], TiC 3 H 6 + [7], and NiC 4 H 8 + [47]. Alternatively, from cis -3-HPtC 3 H 7 , a 1,2-dehydrogenation process occurs via five-center transition state TS11, producing the dihydrogen propene complex (H 2 )PtC 3 H 6 .…”

“…Of the first-row transition metal series, for the activation of propane, the early members (Sc + [6], Ti + [7], and V + [8]) exhibit efficiency for the dehydrogenation of propane. Co + cation favors H 2 over CH 4 [9,10], whereas Fe + and Ni + cations favor CH 4 over H 2 [9,11].…”

Theoretical study of Ni+ assisted C C and C H bond activations of propionaldehyde in the gas phase

“…The last few decades, the reaction of transition metals with simple organic molecules in the gas phase is one of the important topics [2], [3], [4], [5], [6], [7], [8], [9], [10]. Not only because of the tremendous practical importance to the petroleum industry but also due to the fundamental importance of σ-bonds.…”