Efficient Access to 5‐Bromo‐ and 5,6‐Dibromophenanthroline Ligands

Abstract

Bromo-functionalized precursor molecules are essential for generating desired target compounds through crosscoupling reactions. Herein we show an improved synthetic route, feasible at low temperatures and affording high yields, to the ligands 5-bromo-1,10-phenanthroline (1) and 5,6-dibromo-1,10-phenanthroline (2). The corresponding ruthenium complexes, containing various equivalents of ligand 2, are easily accessible in high yields, including the analogue of tris-homoleptic [Ru(bpy) 3 ] 2+ (bpy = 2,2′-bipyridine), [Ru (2) 3 ] 2+ . X-ray dif- [a]

Phenanthroline‐Fused Pyrazinacenes: One‐Pot Synthesis, Tautomerization and a RuII(2,2′‐bpy)2 Derivative

“…The photochemical properties of 6 might be improved by a variety of means that have already been addressed by other workers . In particular, the addition of extended aromatic ligands has been extensively studied for the corresponding Ru II complexes.…”

Stille Expands the Family: Access to 5,6‐Bis‐2‐thienyl‐Substituted Phenanthroline Under Mild Conditions for Luminescent Ruthenium Complexes

“…Stannylated 5‐methylthiophene ( 1 ) and 5,6‐dibromophenanthroline as precursors for the target molecule 2 were prepared according to literature (Scheme ) , . Using standard Stille cross‐coupling conditions with tetrakis(triphenylphosphine)‐palladium(0) {[Pd(PPh 3 ) 4 ]} as catalyst and dry N , N ‐dimethylformamide as solvent, ligand 5,6‐bis(5‐methylthien‐2‐yl)‐1,10‐phenanthroline ( 2 , phenT 2 ) was obtained in 81 % yield after 65 h of reaction time at 85 °C.…”

“…The following chemicals were prepared according to literature procedures: 4,4′‐di‐ tert ‐butyl‐2,2′‐bipyridine, [Ru(tbbpy) 2 Cl 2 ], [Ru(cod)Cl 2 ] n , and 5,6‐dibromo‐1,10‐phenanthroline …”

“…This is mainly due to the demanding synthetic procedures in order to access these positions efficiently. We have recently shown that a high yield, fast and efficient access to 5,6‐dibromophenanthroline is feasible . However, organometallic functionalization of this substrate utilizing Suzuki‐conditions was in our hands only feasible after complexation of a ruthenium center (protection) at the diazadiene sphere.…”

“…As problems had arisen during our attempts to utilize Suzuki‐coupling conditions for the introduction of organic substituents at the 5,6‐positions of phenanthroline, we focused on exploring Stille coupling reactions for the synthesis of bis‐thienyl modified phenanthroline units and their corresponding complexes. Independently, the group of McFarland followed the same strategy for the introduction of substituents at the 5‐position of phenanthroline .…”