Iron carbonyl complexes bearing phenazine and acridine ligands: X-ray structures of Fe(CO)3(η4-C12H8N2), Fe(CO)2{P(OMe)3}(η4-C12H8N2), Fe(CO)2(PPh3) (η4-C13H9N), and Fe(CO)2(κ1-dppm) (η4-C12H8N2)

Abstract

Reactions of Fe3(CO)12 with the heterocycles phenazine and acridine in refluxing benzene afforded the mononuclear complexes Fe(CO)3(η4-C12H8N2) (1a) and Fe(CO)3(η4-C13H9N) (1b), respectively. Treatment of 1a with P(OMe)3 and PPh3 in the presence of Me3NO at room temperature yielded the carbonyl substitution products Fe(CO)2{P(OMe)3}(η4-C12H8N2) (2a) and Fe(CO)2(PPh3) (η4-C12H8N2) (3a), respectively. Similar reactions of 1b yielded Fe(CO)2{P(OMe)3}(η4-C13H9N) (2b) and Fe(CO)2(PPh3) (η4-C13H9N) (3b). Treatment of 1a with the diphosphines dppm and dppf under similar conditions afforded the mononuclear compounds Fe(CO)2(κ1-dppm) (η4-C12H8N2) (4a) and Fe(CO)2(κ1-dppf) (η4-C12H8N2) (4b). Compounds 1a, 2a, 3b, and 4a have been structurally characterized by X-ray crystallography. The ancillary phenazine and acridine ligands in these products adopt an η4-coordination mode by using only the peripheral carbon atoms in one of the carbocyclic rings. Given the rarity of this coordination mode in metal carbonyl complexes, we have performed electronic structure calculations on 1a, and these data are discussed relative to the solid-state structure.