DFT Study of Small Palladium Clusters Pd_n and Their Interaction with a CO Ligand (n = 1–9)

Abstract

This paper presents a theoretical study of palladium clusters Pd n of low nuclearity, ranging from 1 to 9, completed by their interactions with a carbonyl ligand (Pd n CO). The simulations were performed at the DFT (B3LYP-Lanl2DZ) level. Small palladium clusters are deltahedral structures characterized by a triplet ground state (Pd 2 to Pd 7 ) or a quintet ground state for larger nuclearities (Pd 8 and Pd 9 ). Various electronic states relatively close in energy are present. These states have close geometries but differ by their electron density distribution. A significant electronic population of the 5s orbital is needed to explain the existence and cohesion of palladium-palladium bonds. These latter are formed by the combination of sd hybrid orbitals and get stronger as the 5s character increases. The relative stability of palladium clusters increases with their nuclearity and the study of fragmentation reactions

Density functional study of CO binding on small AgnPdm clusters

“…The PW91PW91 results indicated that Ag clusters bind CO only on top site while Pd 2 binds CO on bridge site and both Pd 3 and Pd 4 bind CO on 3-fold face site, which agrees well with previous reports [5][6][7][8]11]. For alloying dimer, it is found that CO prefers binding on top-Pd site with the C-Pd-Ag angle of 106.6°.…”

“…As one of the key factors to understand the catalytic mechanism, the adsorption behavior of CO on Pd clusters has been extensively studied [5][6][7][8][9][10]. The infrared multiple photo dissociation (IR-MPD) spectroscopy studies on CO adsorption on group 10 (Ni, Pd, Pt) clusters has showed that both Ni and Pt clusters adsorb CO only in atop positions while Pd clusters exhibit a variety of binding sites [5].…”

Oxidative Carbonylierungen: Organometallverbindungen (RM) oder Kohlenwasserstoffe (RH) als Nucleophile

“…B. Pd 0 -Verbindungen relativ elektronenarm und erschwert somit die oxidative Addition von Organohalogenverbindungen an die Pd 0 -Spezies. [9] Infolgedessen sind normalerweise strenge Reaktionsbedingungen wie z. B. hohe Temperaturen und hoher CO-Druck nçtig (siehe Schema 1, Pfad A).…”

Synthesis of Functionalized Heterocycles via Oxidative Carbonylation

“…In this work, the oxidative addition of organohalides to Pd(0) takes place firstly followed by coordination and insertion of CO, and finally reductive elimination occurs giving the carbonylated product. However, the π acidity of CO renders the CO-coordinated low-valence metal electron deficient, which makes oxidative addition of organohalides to Pd(0) difficult [28]. As a result, harsh conditions are often required for this kind of carbonylation.…”