Iron carbonyl complexes of heterocyclic α-diimines: systematic synthesis, crystal structures of [Fe(CO) 3(L)] and [Fe 2(CO) 7(L)] (L=2,2′-bipyridine and 1,10-phenantroline), and their AIM analysis

• Published in: Journal of organometallic chemistry Vol. 677; no. 1; pp. 101 - 117
• Main Authors: DelaVarga, Meritxell, Costa, Ramon, Reina, Roser, Núñez, Alberto, Ángel Maestro, Miguel, Mahı́a, José
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-07-2003
• Subjects: AIM; Carbonyl; Complexes; Iron; α-Diimines; Iron; Carbonyl; AIM; Complexes; α-Diimines
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/S0022-328X(03)00381-4

Heterocyclic α-diimines {2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (4,4′-Me
2bpy), 1,10-phenantroline (phen), 4,7-dimethyl-1,10-phenantroline (4,7-Me
2phen) and 2,9-dimethyl-1,10-phenantroline (2,9-Me
2phen)} react, in a wide range of conditions, with iron clusters of nuclearity one, two or three. Two kinds of compounds, [Fe(CO)
3(α-diimine)] (type
1) and [Fe
2(CO)
7(α-diimine)] (type
2), are afforded in all cases. We propose a reaction mechanism to explain this behaviour. The crystal structures of compounds [Fe(CO)
3(bpy)] (
1a), [Fe(CO)
3(phen)] (
1b), [Fe
2(CO)
7(bpy)] (
2a) and [Fe
2(CO)
7(phen)] (
2b) at 173 K were determined by single-crystal X-ray diffraction methods. In contrast, reaction of the pentanuclear iron cluster [Fe
5C(CO)
15] with bpy led to the tetranuclear salt [Fe(bpy)
3][(μ-H)Fe
4C(CO)
12]
2 (
3). The electronic structures of the mono- and di-iron derivatives with bpy and phen were analysed using the atoms in molecules (AIM) theory. Their comparative study seems to rule out the existence of FeFe bond in the dinuclear complexes.
We investigated the reaction of [Fe(CO)
5], [Fe
2(CO)
9] and [Fe
3(CO)
12] in tetrahydrofuran with 2,2′-bipyridine (bpy), 1,10-phenantroline (phen) and their commercial dimethyl derivatives. In all cases, mixtures containing both mono-iron [Fe(CO)
3(NN)] and di-iron [Fe
2(CO)
7(NN)] derivatives (NN=α-diimine) were obtained. A reaction mechanism is proposed to explain this behaviour. The crystal structures of compounds [Fe(CO)
3(bpy)], [Fe(CO)
3(phen)], [Fe
2(CO)
7(bpy)] and [Fe
2(CO)
7(phen)] at 173 K were described, and a comparative theoretical study was performed on them in order to determine the existence of FeFe bond in the dinuclear complexes.