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Ab initio dynamics trajectory study of the heterolytic cleavage of H2 by a Lewis acid [B(C6F5)3] and a Lewis base [P(tBu)3]
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10.1063/1.4799932
/content/aip/journal/jcp/138/15/10.1063/1.4799932
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/15/10.1063/1.4799932

Figures

Image of Scheme 1.
Scheme 1.

By definition, Θ is the angle between the planes drawn through the boron- and phosphorous-bound carbons (a); φ is the angle between the direction of the lone pair of P and the direction of the empty p-orbital of B, φ ≈ 180° − Θ. Dashed lines in (b) and (c) indicate the phosphorous-carbon and boron-carbon distances involved in the calculation of χ.

Image of FIG. 1.
FIG. 1.

Illustrations and structural details of the fully optimized gas phase conformations of the B(C6F5)3/P(tBu)3 pair with (a) the face-to-face orientation of P(tBu)3 with respect to B(C6F5)3, and (b) with P(tBu)3 facing one of the three C6F5 groups of B(C6F5)3. The upper and lower planes are drawn through the carbon atoms bound to phosphorous and boron, respectively; the corresponding normal vectors are drawn from P and B atoms.

Image of FIG. 2.
FIG. 2.

An illustration of the dynamics of the B(C6F5)3/P(tBu)3 pair based on the two representative trajectories with 50 ps duration per trajectory. (A) The face-to-face orientation of P(tBu)3 with respect to B(C6F5)3, and (B) configurations with P(tBu)3 facing one of the three C6F5 groups of B(C6F5)3.

Image of FIG. 3.
FIG. 3.

An illustration of the variation of R(B-P) versus time in the dynamical simulations of the B(C6F5)3/P(tBu)3 pair initiated from the optimized structure min 1 . Graphs show (a) the first 33 ps from the beginning of representative simulation and (b) the magnification of the selected time-interval.

Image of FIG. 4.
FIG. 4.

(a) Top and (b) side views on the persistent face-to-face conformational evolution of the B(C6F5)3/P(tBu)3 pair. Both images include the every 3rd snapshot from the first 33 ps of the trajectory in red from Figure 2 .

Image of FIG. 5.
FIG. 5.

Structural aspects of the selected face-to-face encounters complexes between B(C6F5)3 and P(tBu)3 and the resultant trimolecular dynamical near attack conformers NAC1–NAC4 in which H2 was optimized “inside” the frozen {B(C6F5)3 + P(tBu)3}aimd “hosts”. All distances are in Å.

Image of FIG. 6.
FIG. 6.

(a)–(c) The time-evolution of R(B–P), R(B–H), R(P–H) and R(H–H) according to the reaction trajectories calculated from the initial structures NAC1–NAC3 (Figure 5 ); the secondary vertical axis (to the right) corresponds to R(H–H) versus time. All distances are in Å.

Image of FIG. 7.
FIG. 7.

The optimized geometries of (a) an open form of the frustrated complex composed of the H2, B(C6F5)3 and P(tBu)3 molecules, (b) the product ion pair, and (c) the TS structure; all bond distances are in Å. (d) All NEB-images from the TS to the product merged together; all hydrogen and fluoride atoms of B(C6F5)3 and P(tBu)3 are removed for clarity of the presentation.

Image of FIG. 8.
FIG. 8.

(a) The potential energy profile and (b) the variation of selected distances along MEP.

Image of FIG. 9.
FIG. 9.

The R(B–P)/R(H–H) plots of 40 successful reaction trajectories simulating the reaction B(C6F5)3 + P(tBu)3 + H2 → (tBu)3PH(+)…(−)HB(C6F5)3 at 300 K. The black lines with the circular and square markers correspond to ⟨AIMD cleavage-path⟩ and MEP, respectively. Also shown are the projections of the transition state along MEP and the geometry-optimized product. Values along the horizontal and vertical axis, i.e., R(B–P) and R(H–H), are in Å.

Image of FIG. 10.
FIG. 10.

An illustration of the observed phases of the dynamics based on all reaction trajectories: the H–H cleavage segments of the trajectories (in red), the after-cleavage product evolution (in grey) and the pre-cleavage reactants evolution (in green). The relative potential energy values (in kcal/mol) are shown along MEP; ⟨AIMD cleavage-path⟩ corresponds to ⟨R(B–P)⟩/⟨R(H–H)⟩ from Table I .

Image of FIG. 11.
FIG. 11.

The variation of (a) R(H–H), (b) R(B–P) with the dashed trend line, (c) dihedral angles of B and P in B(C6F5)3 and P(tBu)3; (d) R(P–H) and R(B–H). Distances are in Å.

Image of FIG. 12.
FIG. 12.

Structural details of the selected snapshots from the reaction dynamics as described in the text. All distances are in Å.

Image of FIG. 13.
FIG. 13.

The variation of the dipole moment (in Debye) along the reaction trajectory.

Image of FIG. 14.
FIG. 14.

HOMOs and LUMOs of representative snapshots with (a) R(H–H) close to the equilibrium value, and (b) with R(H–H) in the range of 0.86 Å–0.9 Å.

Image of FIG. 15.
FIG. 15.

(a)–(c) An illustration of the three major phases of the reaction dynamics. All hydrogen and fluoride atoms of B(C6F5)3 and P(tBu)3 are removed for clarity of the presentation.

Tables

Generic image for table
Table I.

The ensemble averaged representation of the H–H bond cleavage dynamics.

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/content/aip/journal/jcp/138/15/10.1063/1.4799932
2013-04-18
2014-04-18
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Ab initio dynamics trajectory study of the heterolytic cleavage of H2 by a Lewis acid [B(C6F5)3] and a Lewis base [P(tBu)3]
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/15/10.1063/1.4799932
10.1063/1.4799932
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