In this work the synthesis of new potentially trans-chelating biphosphine ligands is described and their value in rhodium catalysed hydroformylation evaluated. The reactions of biphosphine diolefin rhodium complexes with hydrogen in methanol, monitored by ¹H- and ³¹P-NMR spectroscopy were used to determine trans-chelating ability. Complexes of 1,5-bis(diphenylphosphino)-3-oxapentane and 1,3-bis- (4-diphenylphosphinobenzyl)benzene formed rhodium dihydrides solely whereas the more flexible 1,7-bis(diphenylphosphino)-4-oxaheptane gave isomeric rhodium dihydrides and a solvate complex. The reaction of diolefin complexes with hydrogen and carbon monoxide in dichloromethane was also investigated. The 3-oxapentane ligand, readily synthesized from 3-oxapentane-1,5-diol, as its rhodium complex gave a n—/iso aldehyde ratio of 9:1 for 1-octene hydroformylation (100°, 80 psi, 1:1 hydrogen/carbon monoxide). Secondly, reactive intermediates relevant to hydroformylation were identified using ¹³C- and ²H-labelling and ¹H, ¹³C and ³¹P-NMR spectroscopy. Hydridocarbonylbis(triphenylphosphine)rhodium(I), the probable catalytic cycle initiator, was conclusively shown to be the initial product of hydridocarbonyltris(triphenylphosphine)rhodium(I) under hydroformylation conditions. The kinetics of interconversion of these latter two complexes were examined by saturation transfer ³¹P-NMR. On reaction of the dicarbonyl complex with styrene no alky1-rhodium complexes were observed, but an iso-acyl intermediate which isomerizes rapidly at ambient temperature was identified and a structure proposed. A similar n-acyl complex, from 1-octene, shows dynamic NMR behaviour explained in terms of triphenylphosphine isomerization at lower temperature and acyl-alkyl interconversion at high temperature.

Thesis (M.S.)--Rutgers University, 2010. / "Graduate Program in Chemistry." Includes bibliographical references.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2008. / Additional advisors: Houston Byrd, Chris Lawson, Sadanandan Velu, Charles Watkins. Description based on contents viewed Feb. 9, 2009; title from PDF t.p. Includes bibliographical references.

This thesis describes the design, synthesis and application of artificial metalloenzymes for transition metal catalysed reactions not performed by natural enzymes. Unique cysteine containing protein templates were covalently modified with transition metal ligand complexes that generate catalytic activity, which allows for the use of virtually any protein template. SCP-2L was selected as template for the linear hydrophobic tunnel that traverses the protein, which has high affinity for linear aliphatic molecules. The use of catalysts based on this protein to induce increased activity in the biphasic hydroformylation of linear α-olefins is investigated in this work. For this purpose, unique cysteine containing mutants of SCP-2L were modified with phosphine ligands by application of a novel bioconjugation procedure. Application of rhodium adducts of the phosphine modified protein constructs led to up to a 100 fold increase of the turn over numbers was measured compared to a Rh/TPPTS model system which is used in industry. Furthermore, good selectivity towards the linear product was observed. If it can be confirmed that the found catalytic results truly are the result of substrate encapsulation by the protein scaffold, this system represents the first rationally designed artificial metalloenzyme which exploits the shape selectivity of the protein scaffold to direct the outcome of a catalytic reaction. In addition, a study was performed for the development of enantioselective artificial metalloenzymes. Nitrogen ligands were covalently introduced in SCP-2L and the obtained conjugates were applied in the copper catalysed Diels-Alder and Michael addition reaction. A promising 25% ee was found for the Diels-Alder reaction between azachalcone and cyclopentadiene using one of the created constructs. Further development of these catalyst systems with the use of both synthetic (e.g. optimisation of ligand structure) and biomolecular tools (e.g. optimisation of protein environment) for optimisation can lead to very efficient and enantioselective conversions in the future.