Investigation of intermetallic communication in novel bimetallic catalysts using cyclic voltammetry: a thesis submitted in partial fulfilment of the requirements for the degree of Masters of Research
thesisposted on 28.03.2022, 12:23 authored by Raphael Hoikin Lam
The first part of this thesis describes the intermolecular hydroalkoxylation of terminal alkynes catalysed by [Rh(CO)₂Phdpm] (18), affording enol ethers with high yield and selectivity. The reactions proceed with optimum conversion and selectivity in the absence of moisture and oxygen and tolerate a range of substituted aryl and allyl acetylene substrates, but do not proceed with internal alkynes. The redox behaviour of complexes 18 and [Rh(CO)₂bpm]BArF₄ (19), probed using cyclic voltammetry, indicate the reaction may proceed via formation of a vinylidene intermediate. In the second part, two novel bimetallic complexes with heteroditopic ligands (16 with bpm/mim motifs; 17 with dpm/mim motifs) were synthesised and characterised. These were tested as catalysts for the intermolecular hydroalkoxylation of phenylacetylene with methanol, and the intramolecular dihydroalkoxylation of alkyne diols 11 and 23. Compared to analogous monometallic complexes, 17 exhibited cooperative rate enhancement in the intermolecular hydroalkoxylation reaction; and both 16 and 17 displayed rate inhibition in the intramolecular dihydroalkoxylation. The redox potentials of 16 and 17, and 10 were compared to those of 18, 19 and [Rh(CO)₂Phmim]BArF₄ (13a). Evidence supports a rate limiting vinylidene formation step for the intermolecular hydroalkoxylation reaction.