Palladium Acetate Trimer: Understanding Its Ligand-Induced Dissociation Thermochemistry Using Isothermal Titration Calorimetry, X-ray Absorption Fine Structure, and ³¹P Nuclear Magnetic Resonance

Abstract

Palladium acetate trimer, Pd 3 (OAc) 6 , is a common precursor for Pd nanoparticle synthesis and an important precatalyst for homogeneous catalysis reactions. Added ligands (L, e.g., phosphines) are well-known to dissociate the Pd 3 (OAc) 6 trimer into Pd(OAc) 2 monomers and form Pd(OAc) 2 (L) 2 complexes. Despite the importance of the trimer dissociation and ligand− monomer binding thermodynamics on the properties of the resulting Pd complex, little is known about either reaction. Using a combination of isothermal titration calorimetry (ITC), X-ray absorption fine structure (XAFS), and 31 P nuclear magnetic resonance ( 31 P NMR) on trimer samples containing monomer impurities, we developed a methodology and a trimer−monomer ITC model to obtain the Gibbs free energy, enthalpy, and entropy for both reactions in toluene and quantify the monomer content. The results provide the following, previously inaccessible, quantitative insights on the reactions. Trioctylphosphine (TOP)-monomer binding reaction is enthalpically driven (ΔH = −187 ± 8 kJ/mol), but the entropy loss due to binding (−TΔS = 84 ± 8 kJ/mol) was significant. However, while the trimer dissociation is enthalpically uphill (ΔH = 323 ± 35 kJ/mol), the increase in entropy due to the formation of monomers was very large (−TΔS = −266 ± 35 kJ/mol). The entropy gains and losses for both reactions have major contributions to each reaction Gibbs free energy and almost compensate for each other, making the overall reaction (i.e., Pd 3 (OAc) 6 + 6 TOP ↔ 3 Pd(OAc) 2 (TOP) 2 ) enthalpically driven. The results show the importance of determining the relative enthalpy and entropy contributions to the free energies for the complete thermochemical cycle of Pd acetate trimer dissociation and reaction with TOP. The methodology can be generalized to other ligands and metal or nonmetal homopolymers to obtain detailed thermochemistry of thermodynamically or kinetically unfavorable reactions.

Membrane-based downhole oil–water separation (DOWS) technology: an alternative to hydrocyclone-based DOWS

“…As complex and delicate hydrocyclone-based DOWS equipment will be fitted in very small cross-sectional area and as they are exposed to very high flow rate, risk of corrosion/erosion increases (Ogunsina and Wiggins 2005;Gao et al 2007). PTFE can be manufactured using electrospinning and sintering from the colloidal nanoparticle of PTFE-PVA emulsion via nucleation and growth of thin fibrous membrane (Mozaffari et al 2017(Mozaffari et al , 2018Li et al 2018). The proposed membrane-based DOWS is simple to construct and its working configuration gives us plenty of options to employ sand filters which could address sand issues.…”

Thermo-Diffusion and Multislip Effects on MHD Mixed Convection Unsteady Flow of Micropolar Nanofluid over a Shrinking/Stretching Sheet with Radiation in the Presence of Heat Source

“…Also, by using the in situ SAXS to measure the evolution of size, size distribution and concentration of Pd colloidal nano-particles during synthesis and population balance modeling (PBM). Li et al [35] developed a methodology and a trimer-monomer ITC model to obtain the Gibbs free energy, enthalpy, and entropy for toluene and quantify the monomer content. Mozaffari et al [36] focused on using continuum calculations to simulate the Stokes flow movement of (neutral) self-diffusiophoretically driven, spherical, and catalytic Janus locomotors in the vicinity of a planar wall to understand the fundamentals of boundary guidance.…”

A Study on Exfoliation of Expanded Graphite Stacks in Candelilla Wax

“…It has a porous and accordion-like structure composed of hundreds of stacks of graphene nanosheets with an enormous surface area, good adsorption properties, high stability, and high thermal conductivity [20,21]. EG is an attractive filler for composites with various matrices and for colloidal suspensions of nanoparticles, which are extensively studied in the field of nanoscience and nanotechnology [22,23]. Pre-exfoliation of graphite is the most economical way to achieve large quantities of nanographite stacks, and a lot of methods for achieving exfoliation of graphite have been developed, each with advantages and disadvantages [24].…”