Synthesis and Structures of 1′,2′,3′,4′,5′-Pentamethylazaferrocene Complexes with Lewis Acidic Boranes

The syntheses, X-ray crystal structures, and electrochemistry of BH3 (2) and BF3 (3) adducts of 1′,2′,3′,4′,5′-pentamethylazaferrocene (1) are reported, together with an improved synthesis, an X-ray crystal structure and the electrochemistry of the known compound, 1. 13C NMR data reveal a similiar dependence of chemical shift on nitrogen lone-pair coordination to that seen for heteroarene analogs. X-ray structural data for 1−3 reveal subtle changes in the binding of the pyrrolyl ring to iron in the Lewis Acid adducts, and intersting short intermolecular contacts in the case of 1 and 3. In cyclic voltammetry studies, 1 displays a reversible metal-based oxidation allowing estimation of the effect of N for −CH− substitution in the oxidation potential of azaferrocenes as compared to ferrocenes. 2 and 3 do not show reversible electrochemistry.