UROP Proceedings 2020-21

School of Science Department of Chemistry 5 Synthesis, Reactivity and Catalytic Properties of Transition Metal Carbyne Complexes Supervisor: JIA Guocheng / CHEM Student: HO Tung Ho / SSCI Course: UROP1100, Summer The non-d0 carbyne complexes are difficult to undergo alkyne metathesis. We aim to find an active rhenium carbyne catalyst for alkyne metathesis and test for their activities. We are using an organometallic compound (Rhenium) to have alkyne metathesis with different catalysts. This work demonstrates the complex Re(≡CH2Ph) (PO2) (PMePh2) 2 to react with PhC≡CMe to produce Re(≡CPh) (PO2) (PMePh2) 2 and also Re(≡CH2Ph) (SO2) (PMePh2) 2 to react with PhC≡CMe to produce Re(≡CPh) (SO2) (PMePh2) 2 to check whether they are suitable rhenium carbyne catalysts. It will also show how we synthesis different reactants needed for the metathesis. We will check the correct structure by using Nuclear Magnetic Resonance (NMR) using phosphorus-31 due to the large molecule containing phosphorus. Tetravalent Cerium Complexes Containing Oxygen Donor Ligands Supervisor: LEUNG Wa Hung / CHEM Student: WANG Lily Ueh-hsi / CHEM Course: UROP1100, Spring A tetravalent cerium sulfamate complex supported by the Kläui tripodal ligand [CpCo{P(O)(OEt)2}3]- (LOEt - ) has been synthesized and its redox reactivity toward 2,6-di-tertbutylphenol was studied. The reaction of [CeIV(LOEt)2Cl2] and AgSO3NH2 afforded [CeIV(LOEt)2(OSO2NH2) 2], whose crystal structure was determined. Plausible synthetic routes to tetravalent cerium selenite and tellurite complexes are still under investigation. Reactions starting from Ag2CO3 seemed to be an issue since the carbonate residue in salt preparation led to the formation of [CeIV(LOEt)2(OCO2)] which is a previously reported complex. The reactions between [CeIV(LOEt)2(OAc)2] (OAc- = acetate) and [CeIV(LOEt)2X2] (X = Cl- , NO3 - , OTs- ) were investigated by NMR spectroscopy and preliminarily results showed that ligand exchange between these complexes occurred. Application of Molecular Orbital Theory to Transition-Metal Complexes Supervisor: LIN Zhenyang / CHEM Student: WONG Wing Hei Marco / CHEM Course: UROP1100, Summer With reference to the work of Yang, Sheong and Lin, this work studied coordination of different ligands to (MesCCC)CoN2 (MesCCC=bis(mesityl-benzimidazol-2-ylidene)phenyl) and (PCP)CoN2. The relative cis-trans stabilities of (MesCCC)Co(H)2 and (PCP)Co(H)2 were also systematically evaluated. Coordination of ligands having strong π accepting and weak σ donating abilities at the apical site of square pyramidal Co(I) pincer complexes was found to be favourable. Phosphine coordination to (MesCCC)CoN2 is more favourable than that to (PCP)CoN2. The empty 2p orbitals of carbenes and empty 4p(Co) orbital of (MesCCC)CoN2 together stabilize phosphine coordination. The delocalized MO formed among the aforementioned orbitals accounts for the higher stability of trans-(MesCCC)Co(H)2 than its cis-isomer, too. In contrast, cis-(PCP)Co(H)2 is more stable than its trans-isomer. It is anticipated that this work may enhance our understanding on the chemistry of carbene pincer ligands.

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