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Molecular Physics
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3.C. Extended Basis Set (sdd/TZVP/DZVP) Results
In this section, we discuss the results obtained at the extended sdd/TZVP/DZVP level
for the following critical points: (a) M3, TS2, M4, M5, TS3, M12 and TS8 for the
conversion and reduction mechanism of Pd(OAc) 2 to Pd(0) complexes (Figure 1 and
Figure 2); (b) M17 and TS11 for the carbonylation along the σ-pathway (Figure 4);
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(c) M20, TS14, TS16, TS18, M22, M23, M24 and TS19 for the carbonylation
occurring along the π η 3 -pathway (Figure 5); (d) TS21 i.e. the transition state for the
carbonylation along the π η 3 -channel. The energy values obtained at the
sdd/TZVP/DZVP level are reported in square brackets in Figure 1, 2, 4 and 5.
The most important aspects evidenced by these computations (compared to the
DZVP/3-21G* energetics) can be summarized as follows:
(i) The Pd(II) Pd (0) reduction remains an easy process and the general
pattern of the energy profile does not change appreciably. The trans pathway is still
favored over the cis one being TS8 15.9 kcal mol -1 higher in energy than TS3. Also
the corresponding intrinsic energy barrier is higher for the cis pathway (55.2
kcal mol -1 ) than for the trans pathway (43.3 kcal mol -1 ). The energy difference
between TS3 and TS8 and the starting reagents becomes larger at the
sdd/TZVP/DZVP level: thus both critical points are now (more realistically) above
the AL
(ii) The mechanistic pattern describing the possible reaction channels for the
carbonylation of allyl chloride catalyzed by Pd(PPh 3 ) 4 does not change significantly.
The values of the intrinsic energy barriers for the most important transition states of
the π-η 3 pathway (TS14, TS16, TS18 and TS19) are very similar to those obtained
with the DZVP/3-21G* basis set. The most significant difference has been found for
the M22 → TS16 energy barrier, which is now 3.7 kcal mol -1 lower. Therefore. the
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