Reactivity and Electronic Properties of a Ferrocene Molecule Bearing an N,C-Chelated BMes2 Unit

A dimesitylboron-functionalized benzimidazolylferrocene, B(2-ferrocenyl-N-Me-benzimidazolyl)Mes(2) (1), has been synthesized and fully characterized. The B-N bond in 1 was found to undergo a dynamic dissociation/association process in solution, leading to a dynamic exchange of the two mesityls bound to the boron atom and slow hydrolysis of 1 under ambient conditions. The hydrolyzed product 2-BMes(OH)-1-(N-methylbenzimidazol-2-yl)ferrocene (2) was isolated and characterized, in which the boron center has a trigonal-planar geometry with one of the mesityls being replaced by an OH- group. The photoisomerization process of the boron unit in 1 was fully inhibited by the low lying d-d/MLCT states of the ferrocene unit. Compound 1 can be oxidized readily by I-2, forming the ferrocenium species [1(+)]I-3(-) (3). NMR and EPR data for 3 indicated a notable spin delocalization through space from the Fe(III) center to a flanking mesityl group.