**Author details**

**Catalyst Substrate Time (h) Conversion (%) TOF (h‐1) Chemoselectivity (%) Regioselective (%)**

2 28 2340 89 n.a.

2 62 4623 95 n.a.

2 39 6404 92 92

2 100 n.a. 85 95

Hence the higher catalytic activity and chemoselectivity of Pd@**L5/6** compared to Pd@**L3/4** were explained in terms of a much easier access of Pd-Nps situated in an amorphous polymer phase. In addition, the easier access of the substrate to the Pd-NPs in Pd@**L5/6** removes more efficiently styrene (i.e., partial hydrogenation product of phenylacetylene) thus avoiding the styrene coordination to the Pd-Nps and hence the hydrogenation to ethylbenzene [37]. The partial hydrogenation of diphenylacetylene to *cis‐*stilbene occurred at 333K. A comparison of the performance of Pd@**L5/6** with other heterogeneous Pd catalysts, such as Pd-Nps supported onto carbon without additional organic modifiers led to much lower chemoselectivities (i.e., styrene <80% and *cis*-stilbene 85%) [38]. The heterogeneous PLA-stereocomplex-based Pd catalysts were easily recovered from the catalytic solution simple by centrifugation of the catalytic THF solution followed by decantation of the solution in air atmosphere. ICP-OES analysis of the THF solution confirmed a very low level of Pd leaching (i.e., >0.5 ppm). HRTEM images acquired of the different recovered heterogeneous catalyst, showed that Pd@**L7/8** is the most promising support for Pd-NPs, avoiding Pd-Nps' stabilization property of **L7/8** is due to interactions between the Pd-Nps' surface and the bipyridine functionality of **L7/8** as shown by

PLA based biopolymers have found to be easily functionalized at the carboxylic acid end. The introduced functional group which is located at the chain end of the polymer chain can be

Pd@**L3/4** Phenylacetylene 1 14 2340 88 n.a.

10 New Advances in Hydrogenation Processes - Fundamentals and Applications

Pd@**L5/6** 1 44 6560 95 n.a.

Pd@ **L3/4** Diphenylacetylene 1 28 9195 90 91.

Pd@ **L5/6** 1 76 11335 90 94

Catalytic conditions: Pd (8.34 × 10-4 mmol), alkyne (4.0 mmol), THF (10.0 mL), and *p* = 0.3 MPa.

**Table 4.** Catalytic performances of different Pd@Lx|y in the partial hydrogenation alkynes.

a

b

c *T* = 298 K. <sup>d</sup>*T* = 333 K.

TOF referred to substrate accessible Pd sites.

IR-spectroscopy [35].

**4. Conclusions**

Chemoselectivity referred to the corresponding alkene.

Marco Frediani1\*, Werner Oberhauser2 , Luca Rosi1 , Elisa Passaglia3 and Mattia Bartoli1

\*Address all correspondence to: marco.frediani@unifi.it

1 Department of Chemistry "Ugo Schiff," University of Florence, Sesto Fiorentino, Italy

2 Institute of Chemistry of Organometallic Compounds (CNR-ICCOM), Sesto Fiorentino, Italy

3 Institute of Chemistry of Organometallic Compounds (CNR-ICCOM), UOS Pisa, Area della Ricerca, Pisa, Italy
