Immobilisierung molekularer Katalysatoren und ihre Anwendung in Carbonylierung und Hydrierung

• Immobilization of molecular catalysts and their utilization in carbonylation and hydrogenation

Willms, Andrea; Palkovits, Regina (Thesis advisor); Rose, Marcus Sören (Thesis advisor)

Aachen : RWTH Aachen University (2021)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2021

Abstract

In industry, most chemical conversions are performed with the aid of catalysts. The usage of catalysts strongly facilitates the synthesis of bulk as well as fine chemicals. Functionalized and porous polymers enable the combination of the advantages of both homogeneous molecular and heterogeneous catalysts. Functional groups and high specific surface areas of such polymers allow the immobilization of molecular catalysts. Herein, various porous polyphosphines were synthesized and used to immobilize different rhodium species. The successful immobilization was shown by elemental analyses, and the presence of the coordinative Rh−P bond between the phosphorous center of the respective polyphospine and the rhodium species was proven by 31P MAS NMR spectroscopy. The resulting materials revealed a high activity in the hydroxycarbonylation of cyclohexanol resulting in cyclohexanecarboxlic acid. However, recycling experiments showed a drop in yield, which implies catalyst leaching. The hydroxycarbonylation of cyclohexene through immobilized rhodium catalysts was very successful. By adapting the reaction conditions and using one of the immobilized rhodium catalyst, very good results could be achieved, and there was almost none or no catalyst leaching. This was proven by elemental analysis of the material. Thus, the immobilization of rhodium catalysts in porous polyphosphines led to catalysts showing good activity with regard to the hydroxycarbonylation of cyclohexanol and cyclohexene. Furthermore, novel polyamines were synthesized via polycondensation and characterized with various methods such as physisorption and solid-state NMR spectroscopy. The synthesized polyamines, which showed no porosity in N2-physisorption, were combined with tris(pentafluorophenyl)borane (BCF) to form an in situ frustrated Lewis pair (FLP) and catalyze the hydrogenation of diethylbenzylidene malonate. One of those polyamines combined with BCF exhibited a high catalytic activity in this hydrogenation reaction. Using 10 mol% of BCF and 50 mg of polyamine resulted in full conversion within 6 h. However, both the polyamine/BCF as well as the molecular reference DABCO/BCF are strongly sensitive towards small amounts of moisture in the reaction system. Hydrogen activation was proven via 11B NMR spectroscopy as well as DFT calculations for both polyamine/BCF and DABCO/BCF. Investigations by means of various methods such as liquid-phase as well as solid-state NMR spectroscopy of 11B, FT-IR spectroscopy, and DFT calculations led to the conclusion that those catalyst combinations are no FLPs in the traditional sense. On the contrary, both adduct and FLP exist in equilibrium. However, despite the presence of covalent B−N bonds, the potential for hydrogen activation and the subsequent hydrogenation of diethylbenzylidene malonate was proven.

Institutions

• Department of Chemistry [150000]
• Chair of Heterogeneous Catalysis and Technical Chemistry [155310]