Synthesis, antimicrobial activity, and catalytic activity of rhodium and iridium piano stool complexes: Teaching an old dog new tricks

This dissertation describes the synthesis, antimicrobial properties, and catalytic activity of a variety of eta5-ligand rhodium and iridium complexes. Cp*RM(beta-diketonato)Cl (Cp*R = R-substituted tetramethylcyclopentadienyl ligand) complexes were found to have selective activity against Mycobacterium smegmatis, with activity highly dependent upon the substituents on the Cp*R ligand as well as on the beta-diketonato ligand. These complexes were synthesized in good yield from the reaction of the chloro bridged dimers ([Cp*RMCl2]2) with the desired beta-diketonato ligand under basic conditions. All complexes were fully characterized by 1H and 13C NMR. Twenty single crystal X-ray structures were solved. The success of these syntheses led to investigation of another beta-diketonato ligand: 1,1,1,5,5,5-hexafluoroacetylacetonate (hfac). Though many metal complexes of this ligand are known, reaction with [Cp*MCl2]2 did not yield the desired Cp*M(hfac)Cl complexes. Instead, a variety of products were obtained, three of which were characterized crystallographically. The most interesting structure featured a non-coordinating trifluoroacetate (TFA) anion and a [Cp*Ir]3Na1O4 cubane structure, which is an unprecedented and highly unusual arrangement for iridium. Attempts to synthesize this cluster rationally through reactions of [Cp*IrCl2]2 with TFA yielded instead a chloro bridged [Cp*IrCl(TFA)] dimer. Reaction of [Cp*MCl2]2 with 1,1,1-trifluoroacetylacetonate (tfac) yielded the expected Cp*M(tfac)Cl complex, indicating that the problem lies with using hfac as a ligand for Cp*M(III) complexes. Finally, the indenyl effect was investigated for the oxidative annulation of 2-phenylimidazole with 1-phenyl-1-propyne catalyzed by a series of methyl-substituted [(indenyl)RhCl2] dimers. [(Ind*)RhCl2]2 was found to have significantly greater activity than [Cp*RhCl2]2 (100% vs. 51%). Two plausible catalytic cycles were proposed, one of which invokes a ring slip transition state. Though it is unclear if the "indenyl effect" is responsible for this differing activity, it is certainly apparent that using an indenyl ligand has a notable effect in this catalytic reaction. Cyclometalation was also investigated stoichiometrically for 2-phenyl-1H-imidazole and 1-phenylpyrazole and found to proceed readily for [(Ind*)RhCl2]2. Additionally, the crystallographic structure of a Rh+ /Rh– ionic pair was solved. Ionic pairs such as this are rarely found in the literature.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Chemistry

Department dc:contributor.department

Chemistry

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2019

Author dc:creator

• Duchane, Christine Marie

Chair dc:contributor.committeechair

• Merola, Joseph S.

Committee members dc:contributor.committeemember

• Lowell, Andrew N.
• Falkinham, Joseph O. III
• Long, Gary L.

• rhodium
• iridium
• piano stool complex
• antimicrobial agent
• cluster
• indenyl
• indenyl effect
• ring slip
• catalysis
• C-H activation
• oxidative annulation

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

vt_gsexam:21359

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/101016