Building C(sp³ ) Molecular Complexity on 2,2'-Bipyridine and 1,10-Phenanthroline in Rhenium Tricarbonyl Complexes

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Synthetic Chemistry

Background:

• Rhenium complexes with N-N chelates are versatile synthetic platforms.
• Understanding nucleophilic addition to coordinated ligands is crucial for developing new synthetic methodologies.

Purpose of the Study:

• To explore the reactivity of [Re(N-N)(CO)3(PMe3)]OTf complexes with tert-butyllithium (tBuLi) and lithium triethylborohydride (LiHBEt3).
• To investigate the site-selectivity of nucleophilic addition to 2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen) ligands.
• To synthesize novel rhenium complexes with modified bipyridine and phenanthroline ligands.

Main Methods:

• Reaction of [Re(N-N)(CO)3(PMe3)]OTf with tBuLi and LiHBEt3.
• Analysis of reaction products using spectroscopic techniques.
• Protonation and methylation of resulting complexes.

Main Results:

• Nucleophilic addition to the N-N chelate showed varying site-selectivity based on the ligand and nucleophile.
• Unprecedented addition to the C5 position of coordinated bipyridine was observed with tBuLi.
• Hydride addition to bipyridine induced intermolecular cyclodimerization, while phenanthroline underwent partial ring reduction.
• Subsequent reactions with HOTf and MeOTf yielded cationic rhenium complexes.

Conclusions:

• Developed novel synthetic routes to functionalized rhenium complexes.
• Demonstrated controlled regioselectivity in nucleophilic additions to coordinated bipyridine and phenanthroline.
• Expanded the scope of organometallic synthesis using rhenium-based catalysts.