A series of 1,10-phenanthroline derivatives bearing multi(aryl)methyl substituents was synthesized and applied to the Ir-catalyzed C(sp3)–H borylation of alkanes using HBpin. Some Ir complexes bearing the developed 1,10-phenanthroline ligands exhibited superior catalytic activity compared with those containing conventional 1,10-phenanthroline ligands, such as 3,4,7,8-tetramethyl-1,10-phenanthroline and 2-methyl-1,10-phenanthroline. These studies revealed that 3,8-multi(aryl)methyl-substituted 1,10-phenanthrolines are crucial for catalytic activity, and that the steric bulk of the multi(aryl)methyl groups significantly influences the catalytic performance.
Takeuchi et al. (Fri,) studied this question.